RU2817540C2 - Modular package of electrolytic cell and method of conversion of carbon dioxide into gaseous products under high pressure and with high degree of conversion - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to package (100', 100'') electrolysis cell for conversion of gaseous carbon dioxide (CO₂) into at least one gas-phase product leaving package (100', 100'') electrolysis cell containing: end unit (26) on the cathode side with gas inlet (21), fluid inlet (23), fluid outlet (24) and an electrical outlet; end unit (27) on the anode side with gas outlet (22) and an electrical outlet; at least two electrolysis cells (40) located between end unit (26) on the cathode side and end unit (27) on the anode side, wherein each electrolysis cell (40) comprises: cathode current collector (5; 5a, 5b, 5c, 5d); anode current collector (10); membrane electrode assembly containing: ion-exchange membrane (7) with a first side and a second side, a cathode catalyst layer (6b) located on said first side in contact with membrane (7), gas diffusion layer (6a) on the cathode side, located on the cathode catalyst layer (6b) in contact with cathode catalyst (6b), anode catalyst layer (8b) located on said second side in contact with membrane (7), gas diffusion layer (8a) on anode side located on anode catalyst layer (8b) in contact with anode catalyst (8b); spacer element (9a, 9b) located between cathode current collector (5; 5a, 5b, 5c, 5d) and anode current collector (10), wherein said spacer element (9a, 9b) is configured to: fixing the membrane electrode assembly between the cathode current collector (5; 5a, 5b, 5c, 5d) and the anode current collector (10) in the position between the cathode current collector (5; 5a, 5b, 5c, 5d) and anode current collector (10), wherein: gas diffusion layer (6a) on cathode side is in partial contact with cathode current collector (5; 5a, 5b, 5c, 5d), thereby forming in-plane flow structure (5'') on cathode side between them, and gas diffusion layer (8a) on side of anode is in partial contact with anode current collector (10), thereby forming an intraplanar flow structure (5') on the anode side between them; cathode current collector compartment (5; 5a, 5b, 5c, 5d) and anode current collector (10) from each other; sealed continuous gas path of the cell passing between gas inlet (46) into the cell and gas outlet (47) from the cell within cell (40) through flow structure (5'') on cathode side; sealed continuous fluid path of the cell passing between fluid inlet (48) into the cell and fluid outlet (49) of the cell within cell (40) through flow structure (5') on the anode side; wherein the electrical terminal of end unit (26) on the cathode side, said at least two electrolysis cells (40) and the electrical terminal of end unit (27) on the anode side are electrically connected in series; and gas paths of electrolysis cells (40) with gas transfer channels (34, 35) passing between adjacent cells (40) through cathode current collector (5; 5a, 5b, 5c, 5d), spacer element (9a, 9b) and anode current collector (10) form a continuous gas path passing from gas inlet (21) to gas outlet (22) for supplying CO₂ to each gas diffusion layer (6a) on the cathode side for conversion of CO₂ into a gas-phase product by carrying out at least one cathodic electrolysis reaction in flow structure (5'') on the cathode side of each electrolysis cell (40) and for discharge of product through said gas outlet (22), and fluid paths of electrolysis cells (40) with channels (38, 39) for movement of fluid medium passing between adjacent cells (40) through cathode current collector (5; 5a, 5b, 5c, 5d), spacer element (9a, 9b) and anode current collector (10) form a continuous fluid path passing from fluid inlet (23) to fluid outlet (24) for supplying liquid anolyte to each flow structure (5') on anode side to perform said cathode electrolysis reaction, wherein at least one anodic electrolysis reaction takes place in flow structure (5') on the anode side of each electrolysis cell (40), and for discharging liquid-phase anolyte and one or more reaction products obtained during said anodic electrolysis reaction through said fluid outlet (24). Invention also relates to an electrolytic apparatus and a method for converting gaseous carbon dioxide.

EFFECT: use of the proposed invention enables to produce a product with the highest possible selectivity, and also to produce products that are easily amenable to separation.

24 cl, 8 ex, 24 dwg

Description

Field of technology to which the invention relates

The present invention relates to the field of obtaining gas-phase products under high pressure and with a high degree of conversion by electrolysis of carbon dioxide gas. The invention also relates to a new modular electrolyser package for carrying out said electrolysis and thereby converting carbon dioxide into a variety of gas-phase products, preferably ready for further use as raw materials for production processes.

State of the art

Carbon dioxide (CO ₂ ) is a greenhouse gas; Therefore, an approach that uses renewable energy to convert it into transportation fuels and commodity chemicals offers the benefit of simultaneously producing products and mitigating the environmental impact of carbon emissions. The potential to produce large quantities of chemicals worldwide through electrochemical reduction (and hydrogenation) of CO ₂ increases the importance of this strategy. Electrochemical synthesis of chemicals using energy from renewable sources (such as solar or wind) helps reduce the harmful environmental impact of the chemical industry and increase its compliance with the principles of sustainable development. The variety of products that can be obtained from CO ₂ using electrolyzers based on polymer electrolyte membranes (PEMs) makes the latter extremely promising. Industrial enterprises interested in such technologies range from energy/utility companies to cement manufacturers, manufacturing and oil and gas sectors.

Similar to PEM-based electrolyzers for water decomposition (i.e., H ₂ /O ₂ generators), a PEM-based CO ₂ electrolyzer in a conventional configuration contains two flow channels - one for the anolyte and the other for the catholyte, separated by an ion exchange membrane located in direct contact with catalysts. The cathode electrocatalyst is immobilized on a porous gas diffusion layer (GDL), usually in contact with a flow of liquid catholyte, while the supply of gaseous CO ₂ also occurs through the GDL. This circuit overcomes some of the disadvantages known in the art, namely: (i) current limitation due to the low concentration of CO ₂ at the electrode; (ii) transition of H ⁺ from the anode through the membrane with subsequent oxidation of the catholyte and, as a consequence, increased selectivity for the release of _H2 ; (iii) diffusion of products to the anode, where they are oxidized (transition of products). Currently, there is no mass industrial production of such devices, but most of their components (i.e., HDS and catalysts), as well as laboratory-scale installations (with electrodes measuring ~5 cm ² ) are already available. At the same time, the design of CO ₂ electrolyzers based on FEM and their operating modes require careful optimization for CO ₂ electrolysis.

A comprehensive analysis of CO ₂ electrolysis based on TEM is given, for example, in the journal “Progress in Energy and Combustion Science”, No. 62 (2017), pp. 133-154, with a detailed description of the parameters influencing on the performance of CO ₂ flow electrolyzers. The analysis covers the basic design principles of the electrochemical cell (microfluidic or membrane-based), the materials used (e.g. catalysts, substrates, etc.), and operating conditions (e.g., type of electrolyte, influence of pressure, temperature, etc.) .

Published European Patent Application No. 3,375,907 A1 discloses a carbon dioxide electrolysis apparatus in the form of a single-cell electrolyzer comprising an anode portion including an anode that oxidizes water or hydroxide ions to produce oxygen; a cathode portion including a cathode that reduces carbon dioxide to form a carbon compound, a cathode solution path through which the cathode solution is supplied to the cathode, and a gas path through which carbon dioxide is supplied to the cathode; a separator separating the anode portion from the cathode portion; and a differential pressure control device for controlling the pressure difference between the cathode solution and carbon dioxide to control the amount of carbon dioxide produced by the reduction reaction in the cathode portion.

Published US patent application No. 2018/0274109 A1 relates to a single-cell carbon dioxide electrolysis device equipped with a regenerant supply unit, including a gas supply unit capable of supplying a gaseous substance to at least an anode or a cathode; a regeneration control unit that stops the supply of current from the power source and the supply of carbon dioxide and electrolytic solution and a control unit for supplying the regenerant in accordance with the criteria for the required power of the electrolytic cell.

Published US patent application No. 2013/0105304 A1 relates to methods and systems for the electrochemical conversion of carbon dioxide into organic products, including formates and formic acid. An embodiment of the system comprises a first electrochemical cell comprising a cathode compartment comprising a surface-developed cathode and a liquid bicarbonate-based catholyte saturated with carbon dioxide. The system also contains an anode compartment containing an anode and liquid acidic anolyte. The first electrochemical cell is configured to create a product flow by creating an electrical voltage between the anode and the cathode. Another embodiment of the system may comprise a separate second electrochemical cell similar to and fluidly coupled to the first.

US Patent Application Published No. 2016/0369415 A1 discloses catalyst layers for use in electrochemical devices, particularly electrolysers, the feedstock of which includes at least CO ₂ or H ₂ O. The catalyst layers contain a catalytically active element and ion-conducting polymer. The ion-conducting polymer contains positively charged cyclic amino groups. The ion-conducting polymer contains at least one of the following compounds: imidazolium, pyridinium, pyrazolium, pyrrolidinium, pyrrolium, pyrimidium, piperidinium, indolium, triazinium, and polymers thereof. The catalytically active element includes at least one of the following elements: V, Cr, Mn, Fe, Co, Ni, Cu, Sn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Ir, Pt, Au, Hg, Al, Si, In, Tl, Pb, Bi, Sb, Te, U, Sm, Tb, La, Ce and Nd.

Published US Patent Application No. 2017/0321334 A1 discloses a membrane electrode assembly (MEA) for use in a CO ₂ reduction reactor. The MES comprises a cathode layer containing a reduction catalyst and a first ion-conducting polymer, as well as an anode layer containing an oxidation catalyst and a second ion-conducting polymer. Between the anode and cathode layers there is a PEM containing a third ion-conducting polymer. TEM creates an ion bond between the anode layer and the cathode layer. The assembly also contains a cathode buffer layer containing a fourth ion-conducting polymer between the cathode layer and the TEM. There are also three classes of ion-conducting polymers: anion-conducting, cation-conducting, and conducting cations and anions. At least two of the first, second, third and fourth ion-conducting polymers belong to different classes of ion-conducting polymers.

International publication No. WO 2017/176600 A1 refers to the electrocatalytic method for CO ₂ conversion. The method involves the use of a new catalytic combination, the purpose of which is to overcome one or more limitations, including low conversion rates, high overvoltages and low electron conversion efficiencies (namely selectivity indicators), low rates of catalytic reactions and high energy demands of sensors . The catalytic combination or mixture contains at least one catalytically active element in the form of supported or unsupported particulates having an average particle size of from about 0.6 nm to 100 nm, preferably from 0.6 nm to 40 nm, and most preferably from 0.6 nm to 10 nm . The catalytic combination also contains an auxiliary polymer, which may contain, for example, positively charged cyclic amino groups, for example imidazolium or pyridinium. The catalytic combination of a catalytically active element and an auxiliary polymer is very effective when using a single electrochemical cell in the cathode catalyst bed to convert CO ₂ into a variety of reaction products.

US Patent No. 10,208,385 B2 discloses a carbon dioxide electrolysis apparatus with a single electrolysis cell for converting CO ₂ into a variety of products, in particular CO, the cell including a cathode, an anode, a carbon dioxide supply unit, an electrolytic solution supply unit and a separator for separating the specified cathode and anode from each other. In addition to the cell, the carbon dioxide electrolysis device further comprises a power source; a reaction control unit that initiates a reduction reaction and an oxidation reaction by passing an electrical current from a power source to the anode and cathode. Said cell is supplied with CO ₂ gas to the cathode and liquid electrolyte to at least one side of the anode. The distribution of gas and one or more liquids in the cell occurs, respectively, along gas and liquid paths formed in the cathode and anode current collectors.

From the above review of the prior art, the focus in the field of CO ₂ electrolysis is on the development of new catalysts to improve activity and product selectivity when using single-cell designs. At the same time, the maximum reaction rate achievable in a simple periodic electrochemical cell is often limited by the low solubility (~30 mmol) of CO ₂ in water. Similar problems arise when supplying a solution (catholyte) to the cathode of a continuous electrolyzer, so electrolysis cells with a direct supply of CO ₂ gas (i.e. without electrolyte) would be preferable.

Thus, there is a need to increase the degree of CO ₂ conversion to a practically significant level. In other words, to overcome the limitations associated with mass transfer, there is a need for a continuous operation plant with direct supply of gaseous CO ₂ and a method for electrochemical reduction of CO ₂ with a high degree of conversion (for example, with a current density of at least 150 mA cm ^-2 ).

There is a consensus in the technical field that to make the process economically feasible, it is important to produce (i) any product with the greatest possible selectivity; (ii) products having economic value; and (iii) products that can be easily separated. To achieve these goals, there is a need for electrolysis cells/packs that work with:

• high current density (the consequence of which is a high reaction rate);

• high Faraday efficiency for the desired product(s) (i.e. a large proportion of the total current input spent on the formation of the product (j _product ), and, as a consequence, high selectivity for a given product), in this case:

• low overvoltage (determining

energy efficiency of the process, defined as follows:

where E ⁰ _anode and E° _cathode are the standard redox potentials of the anodic and cathodic reactions, respectively, and V _cell is the measured cell voltage; And

• high conversion efficiency (which is reflected by the ratio of converted CO ₂ and raw CO ₂ ), defined as follows:

If an electrolysis cell/pack does not meet any of these points, it cannot practically compete with other non-electrochemical technologies.

Therefore, there also exists a need for a new CO ₂ electrolyser package and method with package configuration and operating parameters optimized to achieve the above objectives.

There is also a need to create, in particular for industrial applications, a large-sized and modular package of CO ₂ electrolyzer cells, i.e. a multi-cell electrolyzer stack consisting of more than one, preferably several, electrolysis cells, said cells being relatively simple and inexpensive to manufacture.

In most cases, CO ₂ gas is obtained from industrial sources at high pressures. In addition, for industrial processes using a variety of gas-phase carbon-based substances, such as synthesis gas, carbon monoxide, methane, ethane, ethylene, etc., as raw materials for the production of other products, it is necessary that the raw materials also be under high blood pressure; Hereinafter, the term “high pressure” means differential pressure values in the range from approximately 0 bar to no more than approximately 30 bar.

With this in mind, there is an obvious need for a CO ₂ electrolyser package capable of withstanding high pressures, particularly on its cathode side.

It is yet another object of the present invention to provide a CO ₂ electrolyser package that can be conveniently and easily redesigned if there is a need to change the capacity or even the type of product being produced.

Additional objects, as well as aspects, features and advantages of the present invention will be set forth in the description that follows.

The essence of the invention

The above goals are achieved in a multi-cell or multi-layer package of a continuous electrolyzer according to claim 1 of the formula. Additional preferred embodiments of the proposed package are set forth in claims 2-14. The above problems are also solved by means of a CO ₂ electrolysis unit according to claim 15 for converting the initial gaseous carbon dioxide into one or more final gas-phase products.

Preferred embodiments of the proposed CO ₂ electrolysis installation are described in paragraphs 14-21 of the formula.

The above problems are also solved by the method of converting gaseous carbon dioxide (CO ₂ ) into at least one gas-phase product according to claim 22 of the formula. Preferred variants of the method are set out in paragraphs 23 and 24 of the formula.

In particular, the invention relates to new components and a new carbon dioxide electrolyser package assembly capable of operating at high differential pressures with high conversion rates. It is based on the electrochemical reduction of carbon dioxide gas to gas-phase products (see Table 1 below) and the oxidation reaction (for example, water H ₂ O - 2e ^- = 2H ⁺ + 0.5 O ₂ ) respectively on the cathode and anodic sides; The carbon dioxide used is preferably humidified before entering the electrolyser package.

Thanks to the proposed technological innovations and modular structure, the proposed electrolyzer package configuration is highly variable in size and adaptable. The size of the package can be easily varied, both in terms of size/dimensions and the number of cells used, without exceeding the permissible pressure limits. Thus, in accordance with the idea of a multilayer configuration, new to the field of CO ₂ electrolysis, a CO ₂ electrolyzer package is created, the number of cells in which can be up to ten or more, preferably from two to seven, more preferably from three to six, and most preferably three, or four, or five, or six.

In addition, the configuration of the package allows individual electrolysis cells to be connected in parallel, or in series, or in combination in terms of gas control. Unexpectedly, it was found that changing only one element of the electrolyzer package (and rearranging others) makes it possible to switch from a series to a parallel circuit. This allows the package to be operated in such a way as to achieve an unusually high conversion rate or conversion efficiency depending on the needs. The catalysts, gas diffusion layers and ion exchange membranes used provide the possibility of adaptation to obtain different gas-phase products. Due to this, the proposed CO ₂ electrolyzer package can find application in many industries, such as chemical, petroleum and energy. It should be noted that the present invention is not limited to packages exclusively for a CO ₂ electrolyser, but after suitable conventional modifications it can also find application in other electrochemical installations (for example, as packages for N ₂ recovery for ammonia production).

According to the present invention, multiple cells (electrocatalyst layers and membranes) are connected in series (electrically) and are delimited by assembled bipolar plates functioning as the anode of one cell on one side and as the cathode for the next cell on the other side (similar to FEM fuel cells or decomposition electrolyzers). water).

This special multi-cell stack configuration is achieved by using two component prefabricated bipolar plates to form said individual electrolysis cells. Here, the first component of said bipolar plate assembly forms the anode portion of the cell, and the second component of said bipolar plate assembly forms the cathode portion of the cell located downstream of said cell. In this way, it is possible to form a series of electrolysis cells, with some elements of the flow structure of the cathode/anode paths in the package, i.e. cavities and channels for gas flow in the cathode part, as well as cavities and channels for liquid flow in the anode part of the package, are created on/in opposite side surfaces and between opposite side surfaces of the first and second components of the prefabricated bipolar plates.

In addition, the series/parallel flow channel configuration is created by selectively forming ring-shaped spacer elements, i.e. anode side spacer elements upon which the subsequent prefabricated bipolar plates in the electrolyzer stack are substantially supported when the stack is assembled, with through channels; in particular, in accordance with the modular structure, two types of spacer elements are provided - the first type with a single internal gas movement channel in the peripheral part of the spacer element and the second type with two gas movement channels located diametrically opposite to each other in the peripheral part of the spacer element. When assembling an electrolyzer package, the use of a spacer element of the first type between successive prefabricated bipolar plates allows the formation of a continuous gas path in the package (i.e., individual cells are connected in series from the point of view of gas control in the package), and the result of the use of a spacer element of the second type is between successive prefabricated bipolar plates is the formation of a gas path with parallel sections in the package (ie, the gas paths of the cells in each of the individual cells are connected in parallel from the point of view of controlling the gas in the package). The use of these special spacer elements also makes it possible to create an ordered gas path within a multilayer cell stack, which can contain both serial and parallel sections.

Thus, prefabricated bipolar plates and end blocks perform a complex function:

(i) they form current collectors in contact with the catalyst layers, (ii) when reactants are supplied to the catalyst layer through channels formed in said plates, they ensure the supply of reactants to the active zone of the stack and the proper removal of products, (iii) they contribute in the mechanical strength of the package. In addition, they also play an important role in regulating the heat transfer of the electrolyser package. For this purpose, a system of in-plane flow channels has been formed in the surface of each of these elements to increase the surface area and facilitate movement processes. These flow channels are ordered to form a variety of flow distribution patterns of special geometries, specially optimized for the first time.

Another component used in the proposed CO ₂ electrolyser package is a specially designed and assembled anode side structural member made of titanium (Ti) frit (Ti-frit). This Ti frit is made of titanium powder with different average particle sizes. In practice, a Ti frit is made by pressing titanium particles. The anode catalyst is either placed directly on the Ti frit by, for example, wet chemical synthesis, or synthesized separately and then immobilized on the Ti frit.

The cathode catalyst used in the proposed CO ₂ electrolyzer package is immobilized on a carbon substrate with a developed surface (i.e., GDS), which is in direct contact with the prefabricated bipolar plate. The supply of CO ₂ gas to the catalyst occurs through this GDS. In this case, the catalyst is in direct contact with the PEM, which facilitates ion transfer.

Another component used in the proposed CO ₂ electrolyzer package is a pressure chamber formed in special end blocks located at both ends of the package - i.e. on the cathode side and on the anode side. These pressure chambers provide adaptive pressure control on the cells on both sides and thereby uniform pressure distribution across the cells. This structure prevents deformation of the package body and, thereby, a reduction in the contact area between the internal components. The result is constant stability of the bag even under high pressure. It is important to note that the use of end blocks eliminates the need for moving parts (such as pistons or valves) or elasto-plastic elements as means of regulating the pressure in the stack. In addition, unlike external pressure control, the use of pressure chambers in these end blocks is essentially safe, since the pressure in the pressure chambers can never exceed the pressure occurring in the electrolysis cells. To ensure pressure-independent electrochemical performance, pressure chambers are used in pairs, i.e. one on the cathode side and the other on the anode side of the proposed electrolyser package.

Brief description of drawings

The invention will be further described using the accompanying drawings as examples, where:

- Fig. 1 simplifies the operation of the proposed carbon dioxide electrolysis plant with the supply of (humidified) CO ₂ gas on the cathode side and the supply of the prepared anolyte on the anode side of the electrolysis cell/package used in it;

- Fig. 2A is a schematic cross-sectional view of a single-layer electrolysis cell suitable for use in the carbon dioxide electrolysis plant of FIG. 1;

- Fig. 2B is a perspective view of a portion of the example cell of FIG. 2A;

- Fig. 3A and 3B are complete top and bottom axonometric views, respectively, of a particular example of the implementation of the proposed electrolyzer package with three cells for the conversion of carbon dioxide into a variety of gas-phase products;

- Fig. 4 is a partially disassembled image of the proposed multi-cell electrolyzer package containing n cells, with one electrolysis cell in disassembled form;

- Fig. 5 is a bottom view of a preferred two-component bipolar plate assembly used as the first (anodic) component of the intermediate electrolysis cell (cell i+1) of the stack, as well as the second (cathode) part of the adjacent intermediate electrolysis cell (cell i) of the stack (in this case: 0<i<n-1, /, n - integers);

- Fig. 5A is a view of the bipolar plate in FIG. 5 in a cross section of the assembly along the A-A axis;

- Fig. 5B is a view of the bipolar plate assembly of FIG. 5 in cross section along the B-B axis;

- Fig.6 is a cross-sectional view of a 3-cell package along the axis A-A in Fig. 3A assembled to form a parallel flow configuration in terms of supplying CO ₂ to the stack; in this case, the system of flow channels and cavities, indicated in gray, represents the flow path of the gas in the package from the CO ₂ inlet to the CO ₂ and product outlet;

- Fig. 7 is a cross-sectional view of a 3-cell package along axis AA in FIG. 3A, assembled to form a sequential configuration in terms of supplying CO ₂ to the package; in this case, the system of flow channels and cavities, indicated in gray, represents the flow path of the gas in the package from the CO ₂ inlet to the CO ₂ and product outlet;

- Fig. 8 is a cross-sectional view of a 3-cell package along the B-B axis in FIG. 3A in serial/parallel configuration; in this case, the system of flow channels and cavities, indicated in gray, represents the flow path of the fluid (i.e., anolyte) in the package from the anolyte inlet to the outlet of the anolyte and anode product (in particular - O ₂ if the anolyte is water);

- Fig. 9 illustrates various flow patterns formed on the surface of a cathode current collector used in the proposed electrolyser package; in this case, Fig. 9(a) - (c) show some examples of a design with CO ₂ supplied to the cell in the center and CO ₂ withdrawn from the cell along the outer peripheral ring, and FIG. 9(d) depicts another example of a design with CO ₂ supplied to the cell along the perimeter of the cathode susceptor and CO ₂ withdrawn from the cell also along the perimeter of the cathode susceptor, but in a place located opposite the point where CO ₂ is introduced, after passing along the double helical scheme;

- Fig. 10A illustrates a possible preferred embodiment of an anode side spacer element used to create a series gas flow pattern between two adjacent cells/bipolar plate assemblies in a multi-cell cell stack after assembly;

- Fig. 10B illustrates a possible preferred embodiment of an anode side spacer element used to create a parallel gas flow configuration between two adjacent cells/bipolar plate assemblies in a multi-cell cell stack after assembly;

- Fig. 11A and 11B depict a possible preferred embodiment of the anode current collector, i.e. the anode part of the assembled bipolar plate in Fig. 5, top and bottom respectively, with a flow pattern formed in one of its side surfaces, highlighting the cavities formed for the ring seals;

- Fig. 12A and 12B are exploded views of one cell in a multilayer cell stack assembled to form a series or parallel gas flow configuration, respectively;

- Fig. 13 illustrates the effects of increasing the number of individual electrolysis cells in an inventive electrolyzer stack assembled to form a series or parallel gas flow configuration; in particular, graph (a) shows CO ₂ conversions during electrolysis at ΔU = -2.75 V / cell, possible when using a 1-cell and 3-cell electrolyzer with a series connection at different CO ₂ supply flow rates, and graph (b ) the conversion of CO ₂ during electrolysis at different cell voltages is presented, which is possible when using an electrolyzer package containing one cell or three parallel-connected cells (with an identical normalized gas supply to the cells);

- Fig. 14 depicts a graph of current density depending on the operating voltage of the cell of the proposed 3-cell package of a CO ₂ electrolyzer used to produce synthesis gas (H ₂ /CO mixture on a silver catalyst) or hydrocarbon (CH ₄ and C ₂ H ₄ on a copper catalyst) , obtained by voltammetry with linear potential scan (VAMLRP) with a scan rate v=10 mV/s ^-1 , with negative gas diffusion electrodes (GDE) containing different catalysts;

- Fig. 15 - chronoamperometric curve obtained at ΔU=-3 V / cell for the proposed 3-cell CO ₂ electrolyzer package, using negative GDE containing 1 mg/cm ^-2 silver, immobilized on carbon paper “Sigracet39BC” by sputtering;

- Fig. 16 shows gas chromatograms obtained from a chronoamperometric measurement at ΔU=-2.75 V/cell performed using the proposed 3-cell CO ₂ electrolyzer stack with silver [graph (a)] or copper [graph (b) catalysts];

- Fig. 17 depicts the partial current densities for the formation of CO and H ₂ (ordinates on the left), as well as the ratio of partial current densities (ordinates on the right) at different stack voltages (obtained by chronoamperometric and gas chromatographic measurements);

- Fig. 18 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the amount of silver catalyst in the negative GDE;

- Fig. 19 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU=-2.75 V depending on the intercathode distance used;

- Fig. 20 represents partial current densities for H ₂ and CO production (left ordinates) and CO ₂ conversion (right ordinates) during electrolysis at ΔU=-2.75 V as a function of the depth of the flow pattern on the cathode side of the proposed electrolyzer stack;

- Fig. 21 illustrates the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the consumption of carbon dioxide (normalized by surface area) in the cathode compartment of the proposed electrolyzer package ;

- Fig. 22 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the temperature of the anolyte (potassium hydroxide (KOH) in a concentration of 1 M) (at a flow rate feed ~9 cm ³ cm ^-2 min ^-1 ) in the proposed electrolyzer package;

- Fig. 23 presents VAMLRP curves obtained at a scan speed v=10 mV/s ^-1 at various differential pressures of CO ₂ during electrolysis in the proposed electrolyzer package; And

- Fig. 24 depicts the current densities at different stack voltages (graph A) and the ratio of partial current densities (graph B) during electrolysis at ΔU=-2.75 V, both depending on the differential pressure of CO ₂ .

Carrying out the invention

Fig. 1 illustrates an exemplary embodiment of a CO ₂ electrolysis plant 200 comprising an (electrochemical) CO ₂ electrolyzer package 100 configured to generate gaseous products under high pressures with high conversion rates by electrolyzing CO ₂ gas supplied to the package 100 containing a cathode 101 on the cathode side. , an anode 103 on the anode side and a separator 102 for separating said cathode 101 and anode 102 from each other; in this case, the separator 102 is preferably a PEM-based element (for example, an anion exchange membrane, or a cation exchange membrane, or a bipolar membrane). Said stack 100 includes at least one gas inlet 101a and at least one gas outlet 101b, both gas-connected to the cathode side of stack 100. Said stack 100 also includes at least one fluid inlet 103a and at least one outlet 103b fluid, both fluidly coupled to the anode side of the stack 100. The unit 200 further comprises a CO ₂ gas source 201, a humidifier 203 for humidifying the CO ₂ gas, a power source 220 for supplying energy to the electrochemical stack 100, an anolyte regeneration unit 211 for regenerating the anolyte 213 applied on the anode side of the stack 100, a water separator 208 to remove moisture from one or more gaseous products obtained by electrolysis of CO ₂ gas on the cathode side of the stack 100, a back pressure regulator 209 to pressurize the stack 100 to maintain a high pressure (up to 30 bar inclusive, preferably up to 20 bar inclusive) in the package 100, as well as a gaseous product outlet 216 leading to a gaseous product receptacle (not shown). The CO ₂ source 201 can be either a source of pure CO ₂ gas or a source from which CO ₂ is supplied as a gas mixture. The installation 200 optionally further includes a mass flow controller 202 for accurately controlling the mass flow rate of CO ₂ gas supplied to the cathode side of the stack 100, and associated pressure gauges 210, 210' for determining the pressure prevailing in the stack 100. The CO ₂ source 201 is connected to the gas inlet 101a package 100 by a corresponding pipe 204, and the product outlet 216 is connected to the gas outlet 101 b of the package 100 by a pipe 207. The result is the formation of a continuous flow path from the specified CO ₂ source 201 to the product outlet 216 through the cathode side of the package 100. The mass flow controller 202 is preferably installed in pipe 204 downstream of the CO ₂ source 201. A humidifier 203 is preferably installed in a pipe 204 downstream of the mass flow controller 202 to humidify the CO ₂ gas before it enters the package 100. The humidifier 203 is preferably a thermostatic bubble type humidifier, but any other type of humidifier may also be used. A pressure gauge 210 is also optionally installed in the pipe 204 to continuously monitor the inlet pressure of the stack 100. A water separator 208 is mounted in a pipe 207 downstream of the stack 100. A back pressure regulator 209 is installed in the pipe 207 downstream of said water separator 208. One skilled in the art It will be appreciated by those skilled in the art that the water separator 208 and back pressure regulator 209 can be any type of water separator and pressure regulator. An additional pressure gauge 210' is optionally installed in the pipe 207 between the stack 100 and the backpressure regulator 209 to continuously monitor the pressure at the outlet of the stack 100. This also allows the pressure drop across the stack 100 to be determined by the pressure gauges 210, 210'.

The anode side of the stack 100 is fluidly coupled through its fluid outlet SW and pipe 205 to the inlet 211a of the anolyte regeneration unit 211. In addition, the anode side of the stack 100 is in fluid communication through its fluid inlet 103a and the pipe 206 to the outlet 211b of the anolyte regeneration unit 211. Thus, a closed continuous flow path is formed on the anode side of the stack 100 between said anode side and the anolyte regeneration unit 211. This closed flow path circulates the anolyte 213 by means of a pump 215, preferably mounted in the anode side pipe 206, through a suitable fluid channel system formed in the anode, and a regeneration unit 211 for regenerating (if necessary) the anolyte spent at one or more electrochemical reactions on the anode side of the package 100. In addition, to allow ventilation of the specified anolyte regeneration block 211, the specified block also contains ventilation means 214 with the ability to remove through them excess gas accumulating in the regeneration block 211 after separation from the spent anolyte 213 during the regeneration process of the anolyte 213. To ensure optimal operation of the CO ₂ electrolysis unit 200 and, in turn, the package 100, the anolyte regeneration unit 211 is thermally coupled to the corresponding conditioning means 212 to regulate the temperature of the anolyte 213, that is, its cooling/heating. One skilled in the art will appreciate that it is possible to use conditioning agents for this purpose, i.e. cooler/heater, any type.

With respect to the power supply of the stack 100, the negative pole of the power supply 220 is electrically coupled to the cathode side of the stack 100, specifically the cathode side contact plate, and the positive pole of the power supply 220 is electrically coupled to the anode side of the stack 100, specifically the contact plate. on the anode side (as will be discussed in detail below). The power source 220 can be either an electrical network or some local source of electrical power, i.e. solar, wind, nuclear. The power source 220 may also be a disposable or rechargeable battery.

In operation, carbon dioxide (pure or as a gas mixture) is first humidified at a controlled temperature (preferably in the range of about 20° C. to about 70° C.) and then applied to the cathode side of the stack 100. In this case, the cathode is not some solution is supplied. In the case of supplying only humidified CO ₂ gas to the cathode side, the concentration of the reactant on the catalyst remains very high, which allows for high reaction rates (currents). In addition, due to the lack of solution supply, the unreacted reagent is not washed out with the solution flow. Since this type of reagent has an important and complex effect on the performance of the package, this modification in terms of the type of supply represents an important difference from most known solutions. During the electrolytic reactions in the proposed CO ₂ electrolysis unit 200, only gas-phase products are formed in the package 100. Depending on the catalysts used in the package 100 and the CO ₂ electrolysis reactions carried out (see Table 1), a variety of products are obtained; Examples here include: (i) synthesis gas (a CO/H ₂ mixture of controlled composition) and (ii) ethylene. Gaseous products formed in the cathode part, i.e. in a system of flow channels formed in the cathode side structures (disclosed below), leaving the package 100 and then entering the water separator 208 to remove moisture. Anolyte 213 (applied as an aqueous solution, the type of which depends on the type of separator 102 used, i.e., the ion exchange membrane used) is directly and continuously supplied to the anode side of the package 100 using a pump 215. The specified anolyte 213 then flows through the package 100 in the system flow channels formed in the structural elements on the anode side, and collects gaseous oxygen generated during the CO ₂ electrolysis reaction along its path.

When the flow of anolyte 213 leaves the package 100 and before it begins to recirculate into the specified package 100, the oxygen contained in the anolyte 213 is released in the anolyte regeneration unit 211 and discharged through the specified ventilation means 214. It should be noted that, in conjunction with the conversion of CO _2, other reasonable electrolytic processes (other than water oxidation, for example, production of chlorine or oxidation of alcohols), as will be understood by one skilled in the art; The configuration of the specified installation 200 / package 100 is suitable not only for water oxidation. In addition, during operation of the plant 200, the back pressure regulator 209 continuously regulates the pressure in the stack 100. Thus, unlike most prior art solutions, the electrolyser stack 100 operates at a substantially constant differential pressure.

Fig. 2A is a schematic cross-sectional view of an example of one FEM-based electrolysis cell for use in the CO ₂ electrolyzer stack 100/installation 200 of FIG. 1; Fig. 2B is a perspective view of a portion of the cell close to the bb-axis in FIG. 2A. Said cell contains a PEM, in particular an ion exchange membrane 7, 102, held in place (i.e. on the cathode side and on the anode side) by spacer elements 9(a, b) located on opposite sides of said membrane 7 along its outer edge parts. The membrane 7 functions as a separating element, separating the cathode 101 and anode 103 (ie, the cathode and anode sides) of the cell from each other. On the cathode side, a (cathode) catalyst layer 6b is located adjacent to and in direct contact with the membrane 7. On the catalyst layer 6b, namely on its surface facing away from the membrane 7, a gas diffusion layer 6a is located in direct contact with said catalyst layer 6b. On the gas diffusion layer 6a there is a plate of the cathode current collector 5 in direct contact with the specified gas diffusion layer 6a.

In this case, membrane 7 is an anion exchange membrane, commercially available under the trade names ''Fumasep'', ''Selemion'' and ''Sustanion'', to name but a few examples, which operates to allow the transfer of hydroxide ions (OH ions). ^- ; charges and, therefore, current) between the cathode and anode sides of the cell through its main part, while water (H ₂ O), diffusing through it from the anode to the cathode side, participates in the electrolytic reduction of CO ₂ on the cathode side. Since in this case there is no transfer of electrons through the membrane 7, said membrane 7 essentially acts as an electrical insulation layer between the cathode and anode sides of the cell. One skilled in the art will appreciate that, depending on what electrolytic reaction is to be carried out on the cathode side, it is also possible to use cation exchange membranes commercially available under trade names such as "Nafion" and "Aquivion" or additional bipolar membranes. membranes (for example, "Fumasep FBM") as a membrane 7.

The cathode current collector 5, on the one hand, functions as a current distribution element, i.e. uniformly distributes the electric current received from the external power supply through the cathode side contact plate (disclosed below) over the cathode side gas diffusion layer 6a, and on the other hand forms a corresponding space for compressing said cathode side gas diffusion layer 6a. The cathode pantograph 5 contains a system of in-plane flow channels 5'' with a height M formed on/in the surface of the cathode pantograph 5 facing the membrane 7; said flow channel system 5'' corresponds to various geometric structures (see, for example, Fig. 9). The flow channels 5'' formed in the form of an ordered system ensure uniform distribution of gaseous CO ₂ over the gas diffusion layer 6a on the cathode side. The cathode current collector 5 also contains, in the form of through holes, an inlet for supplying gaseous CO ₂ to the gas diffusion layer 6a and an outlet for releasing the gaseous product formed on the cathode side of the cell during the electrolysis (reduction) reaction of CO ₂ .

In operation, the gas diffusion layer 6a on the cathode side allows CO ₂ to be transferred to the cathode catalyst layer 6b in contact with the membrane 7, where a reduction reaction of CO ₂ gas occurs to form the desired product. The gas diffusion layer 6a also allows said gaseous product (as a mixture also containing some unconverted CO ₂ ) to be transferred through a flow channel system on the cathode side to the CO ₂ and product outlet of the cell. To ensure effective transfer properties, any of carbon cloth, carbon felt or carbon film, preferably modified with a microporous layer, as known to one skilled in the art, can be used as the gas diffusion layer 6a on the cathode side. A variety of catalysts can be used as cathode catalyst 6b, in this case preferably silver-carbon (Ag/C) and copper-carbon (Cu/C) catalysts. The total thickness of the gas diffusion layer 6a and the cathode catalyst layer 6b is H, as shown in FIG. 2B, and represents the distance between the cathode compartments.

In turn, on the anode side, a layer of anode catalyst 8b is located next to and in direct contact with the membrane 7; in this case, the most preferred are anodic catalysts based on 1 IrO _x , RuO _x , NiΟ _x and TiO _x . On the anode catalyst layer 8b, on its surface facing away from the membrane 7, a gas diffusion layer 8a is located on the anode side in direct contact with said anode catalyst layer 8b. Said gas diffusion layer 8a on the anode side is formed from a layer of titanium frit (Ti-frit) in the form of pressed titanium powder with different average particle sizes (preferably in the range of 50-200 μm) or a layer of nickel frit (Ni-frit) in the form of pressed nickel powder with different average particle sizes (preferably in the range of 50-200 μm), titanium mesh (Ti-mesh) or nickel mesh (Ni-mesh), the range of wire thickness and hole size of both meshes being, for example, 50-200 μm. On the gas diffusion layer 8a on the anode side, an anode current collector plate 10 is located in direct contact with the gas diffusion layer 8a. The anode current collector 10 also contains a system of flow channels 5' formed in the surface of the anode current collector 10 facing the membrane 7.

The anode current collector 10, on the one hand, functions as a current distribution element, i.e. uniformly distributes the electric current received from the external power supply through the anode side contact plate (disclosed below) over the anode side gas diffusion layer 8a, and on the other hand forms a corresponding space for compressing the anode side gas diffusion layer 8a. The anode current collector 10 also contains, in the form of through holes, an inlet for supplying liquid anolyte to the gas diffusion layer 8a on the anode side and an outlet for releasing a mixture of liquid anolyte with anode products (for example, gaseous O ₂ if the anolyte also contains water) formed at the anode side of the cell during the electrolysis (oxidation) of anolyte reactions occurring on the anode side.

One skilled in the art will appreciate that the cathode side gas diffusion layer 6a, the cathode catalyst layer 6b, the membrane 7, the anode catalyst layer 8b and the anode side gas diffusion layer 8a can be combined to form a single unit, i.e. membrane-electrode assembly and applied in the form of the specified assembly for constructing a modular electrolysis cell by placing the membrane-electrode assembly between the cathode current collector 5 and the anode current collector 10 with the possibility of electrical connection and gas / fluid communication between them and installing the specified assembly in the correct position using spacer elements 9a, 9b on the anode side. It should also be noted that the electrolysis cell thus obtained, shown in FIG. 2 is a substantially zero-gap electrolysis cell and, as discussed below, may find use in constructing multi-cell CO ₂ electrolyzer stacks 100'' of a modular design.

Fig. 3 and 4 illustrate examples of multi-cell electrolyzer stacks 100', 100'' with more than one electrolysis cell module. In particular, FIG. 3A and 3B are perspective views, respectively, from above and below an electrolyzer package 100' containing three electrolysis cells configured to convert CO ₂ gas into gaseous products under high pressures and high conversion rates by electrolysis. Fig. 4 is an exploded view of a proposed multi-cell electrolyzer package 100'' containing n cells 40 (n is a positive integer), with one electrolysis cell from a series of cells 40 in an exploded view. In this case, it is advisable to select the number n from the range from at least one to ten or more; in particular, the number n of cells used is preferably two to seven, more preferably three to six, and most preferably three or four or five or six in one electrolyzer stack 100''.

As can be seen from FIG. 3A, 3B and 4, the packages 100', 100'' of the electrolyser have a modular structure, the components used to build the packages 100', 100'' are made in the form of plate elements for different functional purposes. The plate components can be of any flat shape; in the exemplary embodiments of FIGS. Components 3A, 3B and 4 are substantially circular in shape. In addition, to speed up the assembly and/or reassembly of these components into packages 100', 100'', each of the plate components is provided with an assembly-facilitating recess 52 formed in its outer edge. The assembly-facilitating indentations 52 clearly indicate how to properly assemble the components into a package; When the components are correctly placed/orientated, said recesses 52 are aligned with each other.

Upon completion of the assembly of these components into a package, the package thus obtained contains individual electrolysis cells located side by side in the longitudinal direction. Hereinafter, the term “longitudinal” characterizes a direction substantially perpendicular to the planes of the surfaces of said plate components. In FIG. 3A, 3B and 4 show that the plate components are configured with a plurality of through holes in said longitudinal direction. Part of these holes are bores 1a for screws 1 with heat-shrinkable tubes and gaskets for assembling these components into packages 100', 100'' with subsequent tight connection of these components by screwing screw nuts 14 with gaskets onto screws 1 inserted into the corresponding bores 1a. The remaining holes formed in said plate components, configured to be properly aligned with each other and sealed by special channel sealing means (disclosed in detail below), which can be placed around the circumference of each hole and between the plate components, serve to form the longitudinal flow path of the channel systems. movements on the cathode and anode sides within the packages 100', 100''. In particular, on the cathode side, one of said holes serves as a gas inlet 21 for introducing CO ₂ gas into electrolysis cells 40 assembled to form a series or parallel (or mixed) configuration in terms of supply of CO ₂ and its movement in the package, and two The other of these openings serve as: (i) a fluid inlet 23 for introducing liquid anolyte into electrolysis cells 40 assembled in a series/parallel configuration, and (ii) a fluid outlet 24 for discharging spent anolyte with gaseous anode products (e.g. , O ₂ ), formed in individual cells 40 of one or more electrolysis reactions on the anode side. In turn, on the anode side, one of these holes serves as a gas outlet 22 for releasing unreacted CO ₂ in excess of the gaseous cathode products formed in the cells 40 during the electrolysis of CO ₂ on the cathode side.

In the example in FIG. 4, the proposed multi-cell package 100'' of a CO ₂ electrolyzer is used for the decomposition of gaseous CO ₂ by electrolysis and the production, depending on the catalysts and anolyte used, of various gaseous products. For this purpose, the package 100'' contains a number n of electrolysis cells 40 located adjacent to each other and with the possibility of a sealed fluid/gas connection to each other through the longitudinal portion of the travel channel systems on the cathode and anode sides. In addition, said electrolysis cells 40 are electrically connected to each other and to the electrical terminals of the stack 100'', i.e. with contact plates 4, 11 in series on the cathode side and on the anode side. Thus, the stack 100'' contains a series of electrolysis cells 40 consisting of interconnected intermediate cells located between the cathode side end block 26 and the anode side end block 27 at opposite ends of the said series in the longitudinal direction.

The cathode side end block 26 terminates a series of electrolysis cells 40 on the cathode side of the stack 100''. The inner surface of the cathode side end block 26 is in direct contact with the first cell 40 of the series, and the outer surface of the cathode side end block 26 is in practice open to the environment. The cathode side end block 26 itself is modular; it comprises a cathode side contact plate 4 with the inner surface in question, a cathode side insulation 3 disposed on said cathode side contact plate 4, and a cathode side end plate 2 with said outer surface disposed on the cathode side insulation 3. The end plate 2 on the cathode side contains holes in gas/fluid communication respectively with the cathode and/or anode channel systems for moving the stack 100'' through corresponding holes formed in the insulation 3 and contact plate 4 and properly aligned with the holes in question, i.e. e. a gas inlet 21 for supplying CO ₂ , a fluid inlet 23 for supplying anolyte, and a fluid outlet 24 for releasing spent anolyte (and anode product). In the assembled state of the stack 100'', the holes formed in the end block 26 on the cathode side on the same axis with each other form continuous longitudinal sealed flow channels, each of which opens into a corresponding hole of the first electrolysis cell 40. In this case, the seal is ensured due to sealing elements of the appropriate size, preferably in the form of sealing rings 15, 16, 17, made of corrosion-resistant plastic (for example, Viton ⁸ ), located between the end plate 2 and the insulation 3, the insulation 3 and the contact plate 4, and between the contact plate 4 and the specified first cell along the circumference of the corresponding holes. The cathode side end plate 2 serves as a mechanical reinforcement element and to increase the pressure tightness of the package 100'' through the through screws 1. The cathode side insulation 3 serves as electrical insulation between the end plate 2 and the cathode side contact plate 4. The cathode side insulation 3 also accommodates a cathode side pressure chamber to prevent possible displacement of the internal components of the stack 100'' towards the cathode side end plate 2 as the pressure of the stack 100'' increases after it begins operation. This pressure chamber is formed as a cavity in the cathode side insulation body 3 and extends to a portion of the cathode side end plate 2 when the stack 100'' is assembled. In such a case, the pressure chamber on the cathode side is sealed by an O-ring 15 placed in an annular groove around the circumference of said cavity in the insulation 3 on the cathode side between the insulation 3 and the end plate 2. In addition, the contact plate 4 on the cathode side provides electrical connection with the external source of electrical power while simultaneously functioning as a current distribution element uniformly distributing the electrical current received from said power source through the inner surface of the cathode side end block 26 to the outermost surface of each first cell in the series of intermediate cells 40. The cathode side contact plate 4 also facilitates the supply gaseous CO ₂ into the first electrolysis cell 40 of the package 100'', as well as the introduction of liquid anolyte into the first electrolysis cell 40 of the package 100'' and the release of spent anolyte from it.

The anode side end block 27 terminates a series of electrolysis cells 40 on the anode side of the stack 100''. The inner surface of the end block 27 on the anode side is in direct contact with the latter, i.e. nth, cell 40 of the specified series, and the outer surface of the end block 27 on the anode side is in practice open to the environment. The anode side end block 27 itself is modular; it comprises an anode side contact plate 11 with the inner surface in question, an anode side insulation 12 disposed on said anode side contact plate 11 and an anode side end plate 13 with said outer surface disposed on the anode side insulation 12.

The anode side end plate 13 contains an orifice in gas communication with the cathode path system of the stack 100'' through corresponding openings formed in the anode side insulation 12 and the anode side contact plate 11 and suitably aligned with the orifice in question, i.e. gas outlet 22 for release of CO ₂ and cathode product. In the assembled state of the package 100'', the holes formed in the end block 27 on the anode side on the same axis with each other form a continuous longitudinal sealed flow channel extending into the corresponding hole of the last electrolysis cell 40. In this case, the seal is ensured by sealing elements of appropriate size, preferably in the form of sealing rings, placed between said last cell and the anode side contact plate 11, the anode side contact plate 11 and the anode side insulation 12, and between the anode side insulation 12 and the anode side end plate 13 anode around the circumference of the indicated holes; The O-rings in question are similar/equivalent to the O-rings used in the cathode side end block 26. In this case, the anode side contact plate 11 provides an electrical connection to an external power source while simultaneously functioning as a current distribution element uniformly distributing the electric current obtained from said power source through the inner surface of the anode side end block 27 to the outermost surface of each latter cells in a series of intermediate cells 40. The contact plate 11 on the anode side also facilitates the release of CO ₂ gas mixed with the electrolysis product from the last electrolysis cell 40 of the stack 100''. The anode side insulation 12 serves as electrical insulation between the anode side contact plate 11 and the anode side end plate 13. The anode side insulation 12 also accommodates an anode side pressure chamber to prevent the internal components of the stack 100'' from moving toward the anode end plate 13 as the pressure of the stack 100' increases after it begins operation. This pressure chamber is formed as a cavity in the anode side insulation body 12 and extends to a portion of the anode side end plate 13 when the stack 100'' is assembled. In such a case, the anode side pressure chamber is sealed by an O-ring 15 placed in an annular groove around the circumference of said cavity in the anode side insulation 12 between the insulation 12 and the anode side end plate 13. In addition, the end plate 13 on the anode side serves as a mechanical strengthening element and to increase the tightness of the package 100'' under pressure due to the screw nuts 14 with spacers screwed onto the screws 1 passing through the entire structure of the package 100'' in the bores 1a from end plate 2 on the cathode side. According to conventional practice, the cathode-side contact plate 4 and the anode-side contact plate 11 are electrically connected to the negative and positive poles of the external power source, respectively.

In the examples in FIGS. 5, 5A and 5B, respectively, showing bottom views of the two-piece bipolar plate assembly 40', in cross section along axis A-A and in cross section along axis B-B, of the first component 40a of the assembly 40' (i.e., the anode current collector 10 V one cell) and the second component 40b of the assembly 40' (ie the cathode current collector 5(a, b, c, d) in one cell) contain on their opposite side surfaces some elements of the cathode and anode side movement channel systems. In particular, the first component 40a includes inlet/outlet openings for flow channel systems on the cathode side and on the anode side within the cell 40'. These openings are: an inlet channel 41 for moving gas into the cell and an outlet channel 42 for moving gas out of the cell to supply and move gas (ie, CO ₂ , the desired product) on the cathode side in the bipolar plate assembly 40', as well as an inlet channel 48 anolyte into the cell, channel 49 for the exit of anolyte from the cell, channel 43 for moving the anolyte in the cell and channel 44 for moving the anolyte and anode product in the cell for supplying and moving a fluid (i.e. anolyte; spent anolyte with an anode product, for example, gaseous 0 ₂ ) on the anode side in the assembled bipolar plate 40'. The first component 40a also contains an in-plane system of fluid flow channels 5' of a certain geometry on/in its side surface, facing, when in the package, towards the end block on the cathode side. Said holes lead from said side surface to the opposite side surface of the first component 40b, where each of said holes leads into a corresponding cavity completely surrounding it, i.e. cavities 33a, 33b, 33c, 33d. These cavities and openings provide fluid communication with corresponding longitudinal fluid flow channels 41', 42', 43', 44' formed in the second component 40b. Said second component 40b also includes a cell gas inlet channel 46 and a cell gas outlet channel 47 for supplying and moving gas (i.e., CO ₂ , the desired product) on the cathode side in the bipolar plate assembly 40', as well as an in-plane flow system gas channels 5'' of a certain geometry (see Fig. 9). These cavities are equipped with appropriate sealing elements, in particular - sealing rings 16, 17, 17', 19, made of corrosion-resistant plastic (for example, Viton ⁸ ) to seal the flow channels when the package is assembled and maintain the prevailing pressure in the package during work.

The first and second components 40a, 40b of the assembly 40' are made of the same electrically conductive composition as the remaining electrical conductive parts of the stack, such as titanium, stainless steel, various alloys and composite materials. Holes and cavities are formed by mechanical processing, in particular milling on a computer numerical control (CNC) machine.

From Fig. 4, it can be seen that after assembly of the proposed CO ₂ electrolyzer package 100'', n substantially identical intermediate electrolysis cells 40 are located between the cathode-side and anode-side end blocks 26, 27, the electrolysis cells 40 being connected to each other (i) in series with from the point of view of controlling the power (electric current) of the package 100'', (ii) in parallel from the point of view of the supply and movement of the anolyte in the package 100'' and (iii) in series, or in parallel, or combined from the point of view of the supply and movement of CO ₂ in a 100'' package. Each cell 40 is formed from two-piece prefabricated bipolar membranes 40' (see FIGS. 5A and 5B). In particular, each cell 40 contains a first (anodic) component 40a/th of the assembled bipolar membrane 40', a second (cathode) component 40b of the adjacent one, i.e. (j-1)-th bipolar membrane assembly 40' (in this case, 1<j<n, an integer), the above-disclosed membrane electrode assembly located between the first and second components 40a, 40b, and the spacer element 9a, 9b on the side an anode inserted between the first and second components 40a, 40b of the bipolar membrane assembly 40' in its peripheral region. Feature (i) results from electrical communication between successive cells 40 in stack 100''. Feature (ii) is a consequence of the physical structure, i.e. the number of longitudinal channels made in the spacer elements 9a, 9b on the anode side for moving gas on the cathode side, and the actual orientation in which a particular spacer element 9a, 9b is located in the package 100''. In particular, in FIG. 10A shows that one longitudinal channel 36 is provided in the spacer elements 9a for use in connecting two adjacent cells to form a serial gas flow channel on the cathode side of the stack 100''; the corresponding cell configuration is illustrated in an exploded view in FIG. 12A. In addition, FIG. 10B shows that two longitudinal channels 36 are provided in the spacer member 9b for use in connecting two adjacent cells to form gas flow channels running parallel on the cathode side of the stack 100''; in this case, longitudinal channels 36 are formed at diametrically opposite positions of the spacer element 9b. A corresponding cell configuration is illustrated in an exploded view in FIG. 12V.

The cathode-side gas control and the anode-side fluid control for a preferred embodiment of a multi-cell electrolyzer stack 100'' comprising three individual cells 40 or bipolar plate assemblies 40' will now be described in more detail. In particular, FIG. 6 shows the 3-cell electrolyzer stack 100' in cross section along axis AA in FIG. 3A with the gas path of the package indicated in gray; in this case, the stack 100' is assembled to form a parallel configuration of gas paths of the individual cells 40 in terms of supply and movement of CO ₂ in the stack 100'. Fig. 7 illustrates a 3-cell electrolyzer stack 100' in cross section along axis AA in FIG. 3A with the gas path of the package, also indicated in gray; in this case, the stack 100' is assembled to form a sequential configuration of gas paths of the individual cells 40 in terms of supply and movement of CO ₂ in the stack 100'. Fig. 8 shows the 3-cell electrolyzer stack 100' in cross section along the B-B axis of FIG. 3A with the fluid path of the package, indicated in gray; in this case, the stack 100' is assembled to form any of series and parallel configurations of individual cells 40 in terms of supply and movement of CO ₂ in the stack 100', with the fluid paths of the cells combined to form a parallel stack fluid path configuration in terms of feeding and moving anolyte in a 100' package.

Fig. 6 illustrates a continuous gas path of the stack extending from the gas inlet 21 to the gas outlet 22 through the cathode side pressure chamber 31 formed in the cathode side end block, in particular in the cathode side insulation 3, then through the bores formed in the cathode side insulation 3 side of the cathode and the contact plate 4 on the cathode side, exiting into the gas inlet 46 into the cell formed in the cathode pantograph, then through the specified gas inlet 46 into the cell 46 into the troughs 45 of the flow circuit 5'' (see Fig. 9) formed in surface of the cathode current collector facing the gas diffusion layer on the cathode side, and into the first electrolysis cell 40 located in the series of applied cells 40. The gas path of the package then extends as inside the planar gas path of the first cell 40 formed between the cathode side current collector and the gas diffusion layer on the cathode side, being in partial contact with each other, and exits the first cell 40 through the gas outlet 47 from the cell, gas-connected with the sealed cavity 33b; said cavity 33b is formed in the surface of the anode current collector. The gas path of the package further passes from the said cavity 33b through the gas transfer outlet 35, then through the bores formed in the anode side contact plate 11 and the anode side insulation 12, into the anode side pressure chamber 32 formed in the anode side end block , in particular - in the insulation 12 on the anode side, then from the specified pressure chamber 32 on the anode side to the gas outlet 22. In this case, the gas moving outlet channel 35 is formed by the cell gas moving output channels 42' (see FIG. 9) formed in the cathode current collector, the internal gas moving channel 36 of the spacer member 9b on the anode side (see FIG. 10B), and an output channel 42 for moving gas from the cell formed in the anode current collector (see, for example, Fig. 11A).

In addition, to supply CO ₂ to the second and any subsequent cells 40, the stack path passes from the pressure chamber 31 on the cathode side through the gas movement inlet channel 34 into the sealed cavities 33a formed in the specified surface of the anode current collector of the individual cells 40, each of the cavities 33a is connected to the gas inlet 46 of the cell of the cell 40. Thus, in operation, all cells 40 are connected by gas to the specified gas movement inlet channel 34, which means that the gas movement configuration of the electrolyzer stack 100' is parallel. The gas moving input channel 34 formed by the cell gas moving input channel 41 formed in the cathode current collector, the additional internal gas moving channel 36 of the spacer member 9b on the anode side and the cell gas moving input channel 41 ends with the end of the gas moving input channel 34a, i.e. e. is a blind gutter.

Fig. 7 illustrates a continuous gas path of the package extending from gas inlet 21 to gas outlet 22. In this case, when the multi-cell electrolyzer package 100' is assembled, due to (D) the use of a spacer element 9a on the anode side with a single internal gas movement channel 36 (instead of two) and the fact that (ii) the specified spacer element 9a is located on the anode side in adjacent cells in an orientation with a rotation of 180° around an axis perpendicular to the spacer element 9a at its center, the package path forms series-connected cell paths as a result of the splitting of the gas movement input channel 34 and the gas movement output channel 35 (see Fig. 6).

Fig. 8 illustrates a continuous stack fluid path extending from fluid inlet 23 to fluid outlet 24 through a continuous input flow path formed by a through channel 43' in the cathode current collector, a through channel 38 in the spacer element, and a through channel 43 in the anode current collector of the electrolysis cells. , then through the sealed cavities 33c, connected in a flow with the inputs 48 of the fluid into the cells, then through the flow circuits 5' and through channels 49 into the sealed cavities 33d, then from the cavities 33d, connected in a fluid medium with a continuous channel for moving the output flow formed through channel 44 in the anode current collector, through channel 39 in the spacer element and through channel 44' in the cathode current collector of the electrolysis cells.

Next, using the examples of Fig. 9-11 will detail the structural components of one electrolysis cell 40, such as that illustrated in FIG. 4 in an exploded view, formed from two-component prefabricated bipolar plates 40'.

In particular, FIG. 9 depicts four possible embodiments of the cathode current collector 5a, 5b, 5c, 5d (forming the second component 40b of the two-component bipolar plate assemblies used), each embodiment comprising some form of in-plane flow channel system or flow pattern 5''. The 5'' flow pattern plays a critical role in ensuring uniform CO ₂ delivery to the cathode side of the cells and efficient product removal from them. In this case, CO ₂ is supplied through the gas inlet channel 46 running longitudinally into the cell, and the product is taken out through the gas exit channel 47 from the cell, also running in the longitudinal direction. Between the specified input and output channels 46 and 47, gaseous CO ₂ moves and its continuous participation in the electrolysis reaction at the cathode and, as a consequence, conversion into a gaseous product in the gutters 45 of a continuous 5'' flow pattern in contact with the membrane electrode assembly (not shown). As can be seen from FIG. 9, in three flow configuration examples, namely, the flow configurations in FIG. 5(a) to 5(c), corresponding to the labyrinth flow pattern, the offset circle flow pattern and the radial double helical flow pattern, CO ₂ gas is supplied at the center, i.e. channel 46 of gas entry into the cell is located in the center of the cathode current collector, and is taken along the entire circumference of the outer ring, i.e. channel 47 for gas exit from the cell is located in the peripheral part of the cathode current collector. Fig. 5d) illustrates an additional flow configuration in which CO ₂ is supplied around the perimeter of the cathode pantograph and is withdrawn, for example, at a diametrically opposite location of the cathode pantograph after passing through a double helical pattern, i.e. both the gas entry channel 46 into the cell and the output channel 47 are located in the peripheral region of the cathode current collector. Surprisingly, it was found that, unlike fuel cells, the best performance in all cases was demonstrated by flow patterns with CO ₂ supplied at the center of the flow pattern.

It should be noted that for the use of cathode current collectors 5a, 5b, 5c, 5d of other flow circuits 5'' together with the same anode current collector 10 in a multilayer stack, in other words - for the use of the second component 40b of various flow circuits 5'' of a two-component bipolar plate 40' with a single type of first component 40a (ie, a unique flow pattern 5'), the gas inlet passage 41 is formed in a special manner. Specifically, the shape of said gas inlet passage 41 is circular on the side of the second component 40b with flow pattern 5'' and narrow oblong on the opposite side of the second component 40b for covering the cell gas inlet passage 46, whether it is formed at the center or in the peripheral region of the second component 40b.

Fig. 10A and 10B depict possible embodiments of anode-side spacer members 9a, 9b for placement between a cathode current collector and an anode current collector in each electrolysis cell 40 of a multi-cell electrolyzer stack 100', 100'' to create a respectively series or parallel gas flow path configuration on cathode side. These two types of spacer members 9a, 9b on the anode side are essentially identical except for the number of internal gas movement channels 36 extending in the longitudinal direction. If this unique design is selected, the anode side spacer elements are spacer elements configured to function as a means of selecting a path for connecting the paths of two adjacent cells to each other in the gas path of the cell stack. The spacer elements 9a, 9b on the anode side are made of dielectrics, preferably plastic or Teflon. Thus, said spacer elements 9a, 9b on the anode side are simple and cheap to manufacture, even on an industrial scale and in an automated manner.

Fig. 11 depicts the anode current collector 10 (forming the first component 40a of two-component bipolar plate assemblies) used in the proposed CO ₂ electrolyser packages, wherein FIG. 11A is a top view, and FIG. 11B is a bottom view of the anode current collector 10, highlighting the cavities 33a, 33b, 33c, 33d designed to create a gas/fluid seal for controlling the gas/fluid of the stack, as well as to accommodate the necessary sealing elements, i.e. various o-rings.

And finally, Fig. 12A and 12B illustrate an exploded view of one cell 40 of a multi-cell electrolyser stack assembled to form, respectively, series and parallel cathode-side gas flow configurations. Fig. 12A and 12B also demonstrate the advantage of the modular design used. In particular, the use, instead of a spacer element 9a on the anode side with a single internal gas movement channel 36, of a spacer element 9b on the anode side containing two internal gas movement channels 36, makes it possible to easily change the flow configuration of the cell 40 in question from series to parallel and vice versa. Those. simply by disassembling the electrolyzer stack into cells, and any of the cells into components, replacing the anode side spacer(s) with the anode side spacer(s) needed for the desired cathode side gas flow configuration, then reassembling each cell from components, and then assembling a package of cells, you can obtain a multi-cell electrolyzer package with the desired gas flow control option. Thus, the proposed multilayer electrolyser package can be easily and quickly adapted to production needs and practically without delay.

Next, the invention and its advantages will be further disclosed by the example of experimental measurements carried out on CO ₂ electrolyzer packages made with one or three cells, in the latter case connected in series/parallel.

As stated above, the proposed CO ₂ electrolyser package is made with at least one, preferably more than one, cells, i.e. its main part, carrying out the electrolysis of CO ₂ , is formed by individual electrolysis cells, electrically connected in series, and from the point of view of controlling the gas in the package, forming a series or parallel configuration; the number of cells used to construct the package is ten or more, and preferably ranges from two to seven, more preferably from three to six, and most preferably three, or four, or five, or six.

Example 1 - Work

This example provides a brief comparison of some of the performance characteristics of a 3-cell stack assembled to form a series configuration, then a parallel configuration (from a cathode-side gas control perspective), and a 1-cell stack (i.e., a single cell).

Fig. 13 illustrates the effects of increasing the number of individual electrolysis cells used in an exemplary embodiment of the proposed stack assembled to form a series or parallel gas flow configuration. In particular, graph (a) shows CO ₂ conversions during electrolysis at ΔU = -2.75 V / cell, which are possible when using a 1-cell and 3-cell series-connected package at different CO ₂ supply flow rates. Graph (b) shows the conversion of CO ₂ during electrolysis at different package voltages, which is possible when using one cell or three parallel-connected cells (with identical normalized gas supply to the cells). A series of measurements was carried out with the supply of KOH anolyte in a concentration of 1 M at a temperature of Τ = 50°C to the anode (with a supply flow rate of 1.5 dm ³ min ^-1 ). As a cathode catalyst layer, 3 mg/cm ^-2 silver (Ag) was immobilized on Sigracet39BC carbon paper by sputtering. As an anodic catalyst, 1 mg/cm ^-2 of iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ . In addition, the CO ₂ flow rate was set to 8.3 cm ³ cm ^-2 min ^-1 for the measurements presented in (b).

As can be seen from graph (a), when three electrolysis cells are connected in series (compared to a 1-cell stack under the same conditions):

• CO ₂ conversion improves;

• this effect is more pronounced the higher the flow rate; And

• approximately 40% conversion achieved.

As can be seen from graph (b), when three electrolysis cells are connected in parallel (compared to a 1-cell stack under the same conditions):

• you can increase the number of cells without changing the performance characteristics;

• CO ₂ flow inside the package is evenly divided; And

• conversion and partial CO currents are similar in the 3-cell configuration, which clearly confirms the possibility of changing the scale of the process.

Fig. 14 illustrates the dependence of the current density on the operating voltage of the cell of the proposed 3-cell package of a CO ₂ electrolyzer used to produce synthesis gas (H ₂ /CO mixture on a silver catalyst) or hydrocarbon (CH ₄ and C ₂ H ₄ on a copper catalyst). The curves were obtained by linear potential sweep voltammetry (VAMLRP) at a scan rate v=10 mV/s ^-1 with negative gas diffusion electrodes (GDE) containing different catalysts. A series of measurements was carried out with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of -9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=2.5 cm ³ cm ^-2 min ^-1 . As a cathode catalyst layer, 1 mg/cm ^-2 silver (Ag) was immobilized on Sigracet39BC carbon paper by sputtering. Cu-containing GDE was formed by electrodeposition. As an anodic catalyst layer, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". In addition, the package was equipped with a spacer element 300 microns thick.

The electrochemical performance of the cells confirms the low voltage requirement. Due to the excellent electrical connection between the various components of the package, which increases under pressure, the operating voltage of the package is quite low (from 2.5 to 3.0 V). The consequence of this is good efficiency rates (40-50%). The formation of synthesis gas (H ₂ /CO mixture) has been demonstrated in the presence of a silver-carbon catalyst, and the production of ethylene has been demonstrated in the presence of a copper-carbon catalyst.

Fig. 15 demonstrates the stable operation of the electrolyzer package. The presented chronoamperometric curve was obtained at ΔU=-3 V/cell for the proposed 3-cell CO ₂ electrolyzer package, using negative GDE containing 1 mg/cm ^-2 silver catalyst immobilized on carbon paper "Sigracet39BC" by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The package was equipped with a spacer element with a thickness of 270 microns. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1Μ at a temperature of Τ = 50°C into the anode compartment (with a flow rate of -9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=2.5 cm ³ cm ^-2 min ^-1 .

Fig. 16 represents the production of different gaseous CO ₂ reduction products using an electrolyzer stack with different catalysts. Gas chromatograms were obtained from a chronoamperometric measurement at ΔU=-2.75 V/cell performed using the proposed 3-cell CO ₂ electrolyzer stack containing sprayed GDE containing 3 mg/cm ^-2 silver catalyst [graph (a)], and GDE with a copper catalyst formed by electrodeposition of copper nanocubes onto Sigracet39BC carbon paper [graph (b)]. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. The silver-containing GDE and the anodic catalyst layer contained 15 wt. % ionomer "Sustanion". The package was equipped with a spacer element with a thickness of 270 microns. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with a flow rate u ~ 2.5 cm ³ cm ^-2 min ^-1 .

Example 2 - Composition of the total product depending on voltage

This example confirms that the composition of the synthesis gas (H ₂ /CO ratio) can be simply adjusted by changing the voltage of the package. The higher the voltage of the package, the greater the amount of H ₂ received.

Fig. 17 depicts the partial current densities for the formation of CO and H ₂ (ordinates on the left), as well as the ratio of partial current densities (ordinates on the right) at different package voltages (obtained by chronoamperometric and gas chromatographic measurements), when using negative silver containing 3 mg/cm ^-2 GDE immobilized on Sigracet39BC carbon paper by spraying. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The package was equipped with a spacer element 300 microns thick. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of ~ 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=2.5 cm ³ cm ^-2 min ^-1 .

Example 3 - Effect of catalyst content

This example confirms that the rate of carbon dioxide reduction is highly dependent on the amount of immobilized cathode catalyst. The partial current density for CO formation reaches a maximum at medium catalyst content.

Fig. 18 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the amount of silver catalyst in the negative GDE. The silver cathode catalyst layer was immobilized on Sigracet39BC carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of ~ 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=2.5 cm ³ cm ^-2 min ^-1 .

Example 4 - Effect of intercathode distance (GDS compression)

This example demonstrates an additional benefit of the proposed package design. Changing just one plastic element allows you to change the compression of the gas diffusion layer (GDL). It should be noted that this parameter affects both the composition of the total product and the conversion. It is important to note that, if it is necessary to use different GDS, the package can be quickly and easily adapted to them (unlike installations such as fuel cells, where the gas tightness and compression of the GDS is ensured by laying a certain thickness, which must be carefully selected for the GDS used) .

Fig. 19 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the intercathode distance used. For the cathode, a layer of 1 mg/cm ^-2 cathode silver catalyst was immobilized on "Sigracet39BC" carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of ~ 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=1.25 cm ³ cm ² min ^-1 .

Example 5 - Influence of the flow pattern used in the cathode current collector This example clearly confirms that the configuration of the flow pattern (see Fig. 9) has a pronounced impact on the residence time of gaseous CO ₂ in the proposed electrolyzer package and, as a consequence, on the performance of the package. In this case, the effect of the trough depth M (see FIG. 2B) is presented for the flow pattern in FIG. 9(a). According to this example, there is an optimal trough depth and therefore residence time that ensures high conversion rates.

Fig. 20 depicts the partial current densities for H ₂ and CO production (left ordinates) and CO ₂ conversion (right ordinates) during electrolysis at ΔU=-2.75 V as a function of the flute depth Μ of the flow pattern employed on the cathode side of the proposed electrolyzer stack. For the cathode, a layer of 3 mg/cm ^-2 cathode silver catalyst was immobilized on "Sigracet39BC" carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt.% Sustanion ionomer. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=2.5 cm ³ cm ^-2 min ^-1 .

Example 6 - Effect of carbon dioxide flow in the electrolyser package

This example should confirm that the higher the CO ₂ consumption, the higher the degree of conversion (current density) of the proposed electrolyzer package. In this case, the ratio of the converted CO ₂ to the supply flow rate decreases (therefore, it is necessary to find and apply the optimal value for the CO ₂ flow rate).

Fig. 21 illustrates the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the consumption of carbon dioxide (normalized by surface area) in the cathode compartment of the proposed electrolyzer package . In this case, for the cathode, a layer of cathode silver catalyst 3 mg/cm ^-2 was also immobilized on Sigracet39BC carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion". The measurement was performed with a continuous supply of KOH anolyte in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a supply flow rate of ~9 cm ³ cm ^-2 min ^-1 ).

Example 7 - Effect of anolyte (package) temperature

This example should confirm that high reaction rates and selectivity can be achieved at high temperatures, which can be easily controlled by the temperature of the anolyte. It is important to note that the components of the electrolyzer package are made resistant to hot (alkaline) solutions, as in this example.

Fig. 22 depicts the partial current densities for the formation of H ₂ and CO (ordinates on the left) and the conversion of CO ₂ (ordinates on the right) during electrolysis at ΔU = -2.75 V depending on the temperature of the anolyte (KOH at a concentration of 1 M) (with a feed flow rate of ~9 cm ³ cm ^-2 min ^-1 ) in the proposed electrolyzer package. The cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with a flow rate of u=2.5 cm ³ cm ^-2 min ^-1 . In this case, for the cathode, a layer of cathode silver catalyst 3 mg/cm ^-2 was also immobilized on Sigracet39BC carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. Both catalyst layers contained 15 wt. % ionomer "Sustanion".

Example 8 - Effect of pressure in the electrolyzer package

This example should confirm that at lower stack voltages, the predominant cathodic process is CO ₂ reduction, and at higher stack voltages, water reduction predominates. With increasing CO ₂ pressure, the transition from one to the other of these two processes shifts towards higher current densities, allowing the electroreduction of CO ₂ to occur at higher rates. The slope of the VAMLRP curve at lower stack voltages gradually increases with increasing CO ₂ pressure. Thus, when the cell stack is operated under pressure, the same current densities can be achieved at lower stack voltages. This is also evidenced by the oscillogram of the VAMLRP curves obtained for different CO ₂ pressures at given package voltages.

Fig. 23 presents VAMLRP curves obtained at a scan rate of v=10 mV/s ^-1 at various differential CO ₂ pressures ranging from 1 bar to 10 bar during electrolysis in the proposed electrolyzer package. In this case, for the cathode, a layer of cathode silver catalyst 3 mg/cm ^-2 was also immobilized on Sigracet39BC carbon paper by sputtering. For the anode, 1 mg/cm ² iridium black was immobilized on a porous titanium frit. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of ~ 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=12.5 cm ³ cm ^-2 min ^-1 .

In addition, FIG. 24 depicts current densities at different package voltages (graph A) and the ratio of partial current densities (graph B) during electrolysis at ΔU = -2.75 V, while both graphs reflect the dependence on the differential pressure of CO ₂ prevailing in the electrolyzer package during its continuous operation. In this case, for the cathode, a layer of cathode silver catalyst 3 mg/cm ^-2 was also immobilized on Sigracet39BC carbon paper by sputtering. For the anode, 1 mg/cm ^-2 iridium black was immobilized on a porous titanium frit. The measurement was performed with a continuous supply of anolyte KOH in a concentration of 1 M at a temperature of Τ = 50 ° C into the anode compartment (with a flow rate of ~ 9 cm ³ cm ^-2 min ^-1 ), and the cathode compartment was purged with humidified (demineralized water at room temperature) CO ₂ with flow rate u=12.5 cm ³ cm ^-2 min ^-1 .

From Fig. 24 it follows that the selectivity for producing CO increases significantly with increasing CO ₂ pressure. Consequently, it is also possible to regulate the composition of the resulting synthesis gas (H ₂ /CO ratio).

Brief conclusions

As can be seen from the above, the present invention provides/is characterized by the following:

• design of the electrochemical package for efficient electrochemical conversion of carbon dioxide;

• pressure regulation up to and including 30 bar (preferably 20 bar) by means of pressure chambers on the cathode side and on the anode side;

• permissible pressure, i.e. the pressure applied to the electrolyser package improves the coordination of the various components, sealing elements and electrical connections of the package by compensating for the negative consequences of incomplete sizing of components due to manufacturing errors and thereby improves the performance of the package;

• high mechanical strength of components (for example, the use of frames made of stainless steel, titanium, metal alloys or composite materials);

• a special sealing system, including sealing rings installed in the recesses/grooves and the pressure chamber, both on the anode and cathode sides;

• modular structure allows you to easily vary the structure of the package, both in terms of size or physical dimensions, and in terms of the number of cells and product yield;

• multi-cell structure with sequential and parallel gas supply (important from the point of view of scalability), meaning that the initial flow of gaseous CO ₂ is either (i) divided in a package and supplied to all cells (parallel conversion occurs in several cells), or ( ii) all supplied CO ₂ passes one after another through all cells (sequential configuration);

• the above two scenarios (i.e. gas control on the cathode side using a series or parallel circuit) are implemented using the same structural elements due to different assembly, the possibility of which is ensured by the modular structure of the electrolyzer package and the multifunctionality of the elements, in particular the spacer element on the anode side, whose special design makes it possible to control the gas in a series or parallel circuit in the same package;

• the modular structure of the package allows you to combine these two scenarios, that is, connect some of the electrolysis cells in parallel, and the rest in series, in the same package;

• the modular structure also allows the use of different ion exchange membranes, gas diffusion layers and catalysts without changing the overall configuration (while maintaining the permissible pressure);

• high conversion rates as a result:

direct gas supply,

ability to work under high pressure,

adjustable residence time (due to the geometry of the package),

special flow patterns (CO ₂ supply in the center, radial selection of products);

• a new design solution for connecting several individual cells to each other to facilitate the movement of gas and liquid in the electrolyzer package;

• a wide variety of catalysts suitable for use in the electrolyzer, including, but not limited to, those based on Sn, Pb, Ag, Cu, Au, C, Fe, Co, Ni, Zn, Ti, Mn, Mo, Cr, Nb, Pt, Tr, Rh, Ru, various two-component compositions based on them and their oxides;

• many different products forming different compositions, including, but not limited to, hydrogen, carbon monoxide, ethylene, methane;

• the possibility of producing, including on an industrial scale, for example, synthesis gas and ethylene in CO ₂ electrolyzer packages with a silver-carbon catalyst and a copper-carbon catalyst, respectively;

• the ability to optimize operating parameters (input flow rate, humidification, pressure, package temperature, flow pattern and its depth, HDS compression);

• the ability to regulate the composition of the synthesis gas simply by changing the voltage of the package.

One skilled in the art will also understand that the embodiments of the present invention, considered individually or in any combination, are not limited to the disclosed embodiments, i.e. The electrolyzer packages are designed to convert carbon dioxide gas, but they can also find application in other electrochemical plants (for example, the reduction of N ₂ to ammonia).

In view of the above, from a technological point of view, the assembly of multi-cell electrolyzers similar to that illustrated in FIG. 1, instead of many single-cell packages operating in parallel, allows to reduce capital costs, since the frame of the package and the anolyte circulation circuit will need to be built only once, and to include an additional cell, only an additional prefabricated bipolar plate, several sealing elements and additional membrane-electrode assembly.

Claims (66)

1. An electrolyzer stack (100', 100'') for converting carbon dioxide gas (CO ₂ ) into at least one gas phase product leaving the electrolyzer stack (100', 100''), comprising: - an end block (26) on the cathode side with a gas inlet (21), a fluid inlet (23), a fluid outlet (24) and an electrical outlet; - end block (27) on the anode side with gas outlet (22) and electrical outlet; - at least two electrolysis cells (40) located between the end block (26) on the cathode side and the end block (27) on the anode side, each electrolysis cell (40) containing: cathode current collector (5; 5a, 5b, 5c, 5d); anode current collector (10); membrane-electrode assembly containing: an ion exchange membrane (7) with a first side and a second side, a cathode catalyst layer (6b) located on said first side in contact with the membrane (7), a gas diffusion layer (6a) on the cathode side, located on the cathode catalyst layer (6b) in contact with the cathode catalyst (6b), a layer of anode catalyst (8b) located on said second side in contact with the membrane (7), a gas diffusion layer (8a) on the anode side located on the anode catalyst layer (8b) in contact with the anode catalyst (8b); a spacer element (9a, 9b) located between the cathode pantograph (5; 5a, 5b, 5c, 5d) and the anode pantograph (10), wherein said spacer element (9a, 9b) is configured to: fixing the membrane-electrode assembly between the cathode current collector (5; 5a, 5b, 5 c, 5d) and the anode current collector (10) in the position between the cathode current collector (5; 5a, 5b, 5 c, 5d) and anode current collector (10), and: the gas diffusion layer (6a) on the cathode side is in partial contact with the cathode current collector (5; 5a, 5b, 5c, 5d), thereby forming an in-plane flow structure (5'') on the cathode side between them, and the gas diffusion layer (8a) on the anode side is in partial contact with the anode current collector (10), thereby forming an in-plane flow structure (5') on the anode side between them; separating the cathode current collector (5; 5a, 5b, 5c, 5d) and the anode current collector (10) from each other; a sealed continuous cell gas path extending between the cell gas inlet (46) and the cell gas outlet (47) within the cell (40) through a flow structure (5'') on the cathode side; a sealed continuous cell fluid path extending between the cell fluid inlet (48) and the cell fluid outlet (49) within the cell (40) through a flow structure (5') on the anode side; and • the electrical terminal of the end block (26) on the cathode side, the at least two electrolysis cells (40) and the electrical terminal of the terminal block (27) on the anode side are electrically connected in series; And • gas paths of electrolysis cells (40) with channels (34, 35) for gas movement passing between adjacent cells (40) through the cathode current collector (5; 5a, 5b, 5c, 5d), spacer element (9a, 9b) and anode The current collector (10) form a continuous gas path passing from the gas inlet (21) to the gas outlet (22) for supplying CO ₂ to each gas diffusion layer (6a) on the cathode side for converting CO ₂ into a gas-phase product by conducting at least one cathode an electrolysis reaction in a flow structure (5'') on the cathode side of each electrolysis cell (40) and for releasing the product through said gas outlet (22), and • fluid paths of electrolysis cells (40) with channels (38, 39) for moving the fluid passing between adjacent cells (40) through the cathode current collector (5; 5a, 5b, 5c, 5d), spacer element (9a, 9b) and the anode current collector (10) form a continuous fluid path extending from the fluid inlet (23) to the fluid outlet (24) for supplying liquid anolyte to each flow structure (5') on the anode side to perform said cathodic electrolysis reaction, at wherein at least one anodic electrolysis reaction occurs in a flow structure (5') on the anode side of each electrolysis cell (40), and for discharging a liquid phase anolyte and one or more reaction products obtained from said anodic electrolysis reaction through said outlet ( 24) fluid medium. 2. Package (100', 100'') of the electrolyser according to claim 1, characterized in that: at least part of the gas paths of the electrolysis cells (40) are connected to each other in series; or at least part of the gas paths of the electrolysis cells (40) are connected to each other in parallel. 3. Package (100', 100'') of the electrolyser according to claim 2, characterized in that the spacer element (9a, 9b) contains an internal channel (36) for gas movement passing through it in the first peripheral region of the spacer element (9a, 9b ), wherein said spacer element (9a, 9b) further comprises a second peripheral area located diametrically opposite to the first peripheral area, wherein said second peripheral area is configured to function as a means of selecting a path for connecting paths of two adjacent cells to each other in a gas path of the package (100', 100'') of the electrolyser, wherein said means is made in the form of an additional internal channel (36) for moving gas in the second peripheral region. 4. Package (100', 100'') of the electrolyzer according to any one of paragraphs. 1 - 3, characterized in that in the outer edge of each end block (26) on the cathode side, the end block (27) on the anode side and the cathode current collector (5; 5a, 5b, 5c, 5d), a spacer element (9a, 9b) and the anode current collector (10) of each electrolysis cell (40) of the electrolyser package (100', 100'') is formed with an easy-to-assemble recess (52) to ensure quick and correct assembly/reassembly of the package (100', 100''). 5. Package (100', 100'') of the electrolyzer according to any one of paragraphs. 1 - 4, characterized in that: a cathode-side pressure chamber (31) is formed in a cathode-side end block (26), and a pressure chamber (32) on the anode side is formed in the end block (27) on the anode side, wherein said gas path is directed through a pressure chamber (31) on the cathode side and a pressure chamber (32) on the anode side to enable adaptive pressure control on the electrolysis cells (40) and thereby uniformly distribute pressure across all of said electrolysis cells (40). 6. Package (100', 100'') of the electrolyser according to any one of paragraphs. 1 - 5, characterized in that: a cathode current collector (5; 5a, 5b, 5c, 5d) of each electrolysis cell (40) is formed as a second component (40b) of a two-piece bipolar plate assembly (40'), and an anode current collector (10) of each electrolysis cell (40) is formed as a first component (40a) of a two-piece bipolar plate assembly (40'). 7. Electrolyzer package (100', 100'') according to claim 6, characterized in that the second component (40b) of the two-component bipolar plate assembly (40') contains a system (5'') of flow channels in its surface facing the membrane (7), located with the ability to ensure uniform distribution of gas over the gas diffusion layer (6a) on the cathode side. 8. Package (100', 100'') of the electrolyser according to any one of paragraphs. 6 - 7, characterized in that the first component (40a) of the two-component bipolar plate (40') contains a system of flow channels (5') in its surface facing the membrane (7), located with the ability to ensure uniform distribution of the fluid along the gas diffusion layer (8a) on the anode side. 9. Package (100', 100'') of the electrolyser according to any one of paragraphs. 6-8, characterized in that said first and second components (40a, 40b) of the two-component bipolar plate assembly (40') additionally contain holes (41, 42, 43, 44, 46, 47, 48, 49) and corresponding cavities ( 33a, 33b, 33c, 33d) completely surrounding said openings for fluid/gas communication between opposing side surfaces of said first and second components (40a, 40b). 10. Electrolyzer package (100', 100'') according to claim 9, characterized in that the cavities (33a, 33b, 33c, 33d) are sealed separately when the package (100, 100'') is assembled. 11. Package (100', 100'') electrolyzer according to any one of paragraphs. 1-10, characterized in that the gas diffusion layer (8a) on the anode side of each electrolysis cell (40) is selected from the group consisting of: titanium (Ti-) frits in the form of pressed titanium powder with different average particle sizes, nickel (Ni- ) frits in the form of pressed nickel powder with different average particle sizes, titanium (Ti-) mesh and nickel (Ni-) mesh. 12. Electrolyzer package according to any one of paragraphs. 1-11, characterized in that the cathode catalyst (6b) is selected from the group consisting of: a silver-carbon catalyst and a copper-carbon catalyst. 13. Electrolyzer package according to any one of paragraphs. 1-12, characterized in that the anode catalyst (8b) is selected from the group consisting of: IrO _x , RuO _x , NiO _x and TiO _x . 14. Package (100', 100'') electrolyzer according to any one of paragraphs. 1-13, characterized in that the number of electrolysis cells (40) is no more than ten, preferably from three to seven, more preferably from three to six. 15. An electrolysis unit (200) for converting carbon dioxide gas (CO ₂ ) into at least one gas-phase product, wherein the unit (200) contains: package (100', 100'') of the electrolyser according to any one of paragraphs. 1-14; source (201) of CO ₂ gas; source of liquid anolyte (213); an external power source (220) with a first pole having a first electric charge and a second pole having a second electric charge, the second electric charge being opposite in sign to the first electric charge; wherein the first pole is electrically connected to the electrical terminal of the end block (26) on the cathode side of the stack (100', 100'') of the electrolyzer, and the second pole is electrically connected to the electrical terminal of the end block (27) on the anode side of the stack (100', 100 '') electrolyser; a circulation unit on the cathode side for circulating CO ₂ gas from said CO ₂ gas source (201) through the gas path of the electrolyser package (100', 100'') to at least one product receiver; And a circulation unit on the anode side for circulating liquid anolyte (213) from said source of liquid anolyte (213) through the fluid path of the electrolyzer stack (100', 100''). 16. Electrolysis installation (200) according to claim 15, characterized in that the circulation unit on the cathode side additionally contains a humidifier (203) located upstream of the electrolyzer package for humidifying CO ₂ before it is supplied to the package (100', 100'') electrolyser. 17. Electrolysis installation (200) according to claim 15 or 16, characterized in that the circulation unit on the cathode side additionally contains a back pressure regulator (209) located downstream of the electrolyzer package (100', 100'') to increase the differential pressure , predominant in the package (100', 100'') of the electrolyser. 18. Electrolysis plant (200) according to any one of paragraphs. 15-17, characterized in that the circulation unit on the cathode side additionally contains a water separator (208) located downstream of the electrolyzer package (100', 100'' and upstream of the back pressure regulator (209) to remove moisture from one or several gaseous products. 19. Electrolysis plant (200) according to any one of paragraphs. 15-18, characterized in that the circulation unit on the anode side also contains a liquid anolyte regeneration unit (211) for regenerating the anolyte (213) if necessary and/or separating one or more reaction products formed during one or more anodic electrolysis reactions, from anolyte (213). 20. Electrolysis installation (200) according to claim 19, characterized in that the anolyte regeneration unit (211) is thermally connected to the conditioning means (212) for regulating the temperature of the anolyte (213). 21. Electrolysis plant (200) according to any one of paragraphs. 15-20, characterized in that the anolyte is an aqueous solution of potassium hydroxide (KOH). 22. A method for converting gaseous carbon dioxide (CO ₂ ) into at least one gas-phase product, including the steps of: create a package (100', 100'') of the electrolyzer according to any one of paragraphs. 1-14; using the specified package (100', 100'') of the electrolyzer, assemble the electrolysis installation (200) according to any one of paragraphs. 13-21; circulating gaseous CO ₂ through the package (100', 100'') of the electrolyzer of the electrolysis installation (200); simultaneously with the circulation of CO ₂ , the liquid anolyte (213) is circulated through the package (100', 100'') of the electrolyzer of the electrolysis installation (200); And while continuing to circulate CO ₂ and anolyte, carry out cathodic electrolysis reactions and anodic electrolysis reactions in the electrolyzer stack (100', 100'') to convert CO ₂ gas, in a continuous flow, into at least one gas-phase product; separating said at least one gas-phase product from gaseous CO ₂ ; if necessary, optionally carry out regeneration of the anolyte (213); And said at least one gas-phase product is released from the electrolysis unit (200). 23. The method according to claim 22, characterized in that to obtain a mixture of hydrogen and carbon monoxide, a silver-carbon cathode catalyst (Ag/C) is used as a gas-phase product. 24. The method according to claim 22, characterized in that to produce ethylene, a copper-carbon (Cu/C) cathode catalyst is used as a gas-phase product.

Images