CN111330619B - Ru/WNO catalyst for wide pH value and high-efficiency hydrogen evolution and preparation method thereof - Google Patents

Ru/WNO catalyst for wide pH value and high-efficiency hydrogen evolution and preparation method thereof Download PDF

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CN111330619B
CN111330619B CN202010171235.2A CN202010171235A CN111330619B CN 111330619 B CN111330619 B CN 111330619B CN 202010171235 A CN202010171235 A CN 202010171235A CN 111330619 B CN111330619 B CN 111330619B
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孟歌
崔香枝
施剑林
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Shanghai Institute of Ceramics of CAS
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Abstract

The invention provides a Ru/WNO catalyst for wide pH value and high-efficiency hydrogen evolution and a preparation method thereof, and the nano catalyst comprises: porous WNO nanosheets, and Ru nanoparticles doped in the porous WNO nanosheets. According to the invention, Ru is doped in the porous WNO nanosheet, the electronic structure of the WNO material is adjusted while the specific surface area is enlarged, and the Ru @ WNO nano catalytic material with excellent HER performance in full-pH electrolyte is obtained.

Description

Ru/WNO catalyst for wide pH value and high-efficiency hydrogen evolution and preparation method thereof
Technical Field
The invention relates to a high-efficiency hydrogen evolution Ru @ WNO catalyst with a wide pH value and a preparation method thereof, belonging to the technical field of inorganic nano materials.
Background
The hydrogen production (HER) by water electrolysis can realize high-efficiency preparation of pure hydrogen by virtue of the characteristic of no pollution of the product, and is a key link for developing green hydrogen energy in the future. WNO nanomaterials (W) compared to low inventory, expensive commercial Pt catalysts0.62(N0.62O0.38) Are a promising alternative to Pt-based catalysts due to their similar density of d-band electronic states as Pt. At present, however, HER performance research on WNO materials shows that the adsorption capacity of tungsten to H is too strong, and a skillful design of doping the structure and phase of tungsten is required to expand the specific surface area of tungsten and change the electronic structure of tungsten to weaken hydrogen adsorption, so that a hydrogen evolution material with catalytic activity equivalent to that of a noble metal Pt catalyst is obtained.
However, while the specific surface area of the material is enlarged, WNO is doped by selecting appropriate elements and dosage to skillfully adjust the electronic structure of WNO, so that the adsorption and desorption energy of H on WNO is moderate, the hydrogen evolution catalytic performance is improved, and the requirement on experimental design is higher. And in preparation and experiments, elements doped in WNO can generate agglomeration and the like, and the hydrogen evolution performance and stability of the prepared material are seriously influenced, so that the WNO nano hydrogen evolution electrocatalyst has certain difficulty in the appearance design and phase doping of the WNO nano material, and the WNO nano hydrogen evolution electrocatalyst applicable to the full pH value is not reported at present.
Disclosure of Invention
In view of the above problems, the present invention aims to provide a WNO nano hydrogen evolution electrocatalyst applicable to a full pH value and a preparation method thereof.
In a first aspect, the present application provides a nanocatalyst comprising: porous WNO nanosheets, and Ru nanoparticles doped in the porous WNO nanosheets.
According to the invention, Ru is doped in the porous WNO nanosheet, the specific surface area is enlarged, and meanwhile, the electronic structure of the WNO material is adjusted, so that the Ru @ WNO nano catalytic material with excellent HER performance in full-pH electrolyte is obtained.
Preferably, the length of the porous WNO nano sheet is 150-300 nm.
Preferably, the doping amount of the Ru nanoparticles is 0.5-1 wt.%.
In a second aspect, the present application provides a method for preparing any one of the above nanocatalysts, comprising the steps of:
(a) uniformly mixing a solution containing a tungsten source, a nitrogen source and a pore-forming agent, and separating out a solid;
(b) carrying out heat treatment on the solid obtained in the step (a) at 800-1000 ℃ for 1-3 h under a protective atmosphere to obtain a porous WNO nanosheet material;
(c) dissolving the obtained porous WNO nanosheet material in water, adding a ruthenium source, stirring at 70-90 ℃ for 2-6 h, and separating out a solid;
(d) and (c) carrying out heat treatment on the solid obtained in the step (c) for 1-3 h at 100-200 ℃ in a protective atmosphere to obtain the nano catalyst.
According to the invention, the porous loose WNO nano-sheet is prepared by MOF (metal organic framework) assisted synthesis, namely, a metal framework is generated through the action of a nitrogen source and a pore-forming agent, WNO is prepared by utilizing the metal framework, the obtained material is in a uniform porous nanosheet structure, the heat treatment of the material is favorable for controlling non-toxicity and harmlessness under a protective atmosphere (such as an argon atmosphere), then a ruthenium source is added into a WNO nanosheet precursor aqueous solution, reacting for a period of time at a certain temperature to obtain a small amount of ruthenium-doped porous WNO nanosheet hydrogen evolution catalyst with excellent hydrogen evolution performance at full pH, it can have high-efficiency electrocatalytic hydrogen evolution activity in the full pH range, and the catalytic performance can be activated in the circulating process, thereby further increasing performance and maintaining performance during subsequent testing, a phenomenon that is particularly evident under neutral conditions. At present, because the hydrogen ions are easy to dissociate out to generate hydrogen because of the freely moving ions under the acid-base condition, the catalysis of the dissociation of the water molecules has important significance under the neutral condition without the freely moving ions.
In some embodiments, a nitrogen source and a pore-forming agent are added into a precursor solution containing a tungsten source, the precursor solution and the pore-forming agent are uniformly mixed by ultrasonic stirring, and the pore-forming agent is volatilized by heat treatment under a specific atmosphere for a certain time to obtain a loose porous WNO nanosheet material capable of exposing a large number of active sites. And then adding a ruthenium source into the WNO nanosheet-containing aqueous solution, stirring and thermally treating at a certain temperature to dope Ru into the WNO nanosheets, and realizing electronic structure adjustment of the WNO material while enlarging the specific surface area to obtain the Ru @ WNO nano catalytic material with excellent HER performance in the full-pH electrolyte. According to the method, when a ruthenium source is added into a WNO aqueous solution, Ru-based ions are captured by WNO nanosheets in situ, and Ru nanoclusters are doped in the WNO nanosheets in situ through stirring and thermal treatment to form the WNO nanosheet material doped with ultra-small Ru nanoparticles. The method has mild preparation conditions and is easy to operate.
Preferably, the tungsten source is tungstic acid, the nitrogen source is 2-methylimidazole, the pore-forming agent is zinc nitrate, and the molar ratio of the tungsten source to the nitrogen source is controlled to be 1: 0.1-1: and 1, controlling the molar ratio of the nitrogen source to the pore-forming agent to be 1: 2-1: 5.
Preferably, in step (a), the solvent of the solution is methanol.
Preferably, in the step (a), the solution is subjected to ultrasonic treatment for 3 to 10 minutes, and stirred at room temperature for 1 to 6 hours to be uniformly mixed.
Preferably, the ruthenium source is ruthenium chloride.
Preferably, in step (c), the molar ratio of the ruthenium source to the porous WNO nanosheet material is 1: 500-1: 5000.
in a third aspect, the application provides an application of any one of the nano-catalysts in hydrogen production by water electrolysis at a full pH value.
The Ru-doped WNO nano catalyst provided by the application has electron transfer due to the electron action between W and Ru, and the excellent HER catalytic activity and stability in the full pH are shown because the H adsorption energy is reduced. The hydrolysis is promoted to H by strong electron action, especially under neutral and alkaline conditions+The hydrolysis potential barrier is greatly reduced, excellent HER electrocatalytic activity and stability are shown while the usage amount of Ru is low, the cost of the catalyst is greatly reduced, and the catalyst has higher economic benefit and practical value.
Has the advantages that:
(1) according to the preparation method, a WNO nanosheet is successfully prepared by using an MOF pyrolysis method, and meanwhile, rich hole structures are manufactured, and more active sites are exposed;
(2) the Ru @ WNO nanosheet prepared by the method is low in Ru consumption (0.5-1 wt.%), and has extremely high economic benefit;
(3) a strong electron effect exists between Ru and W in the Ru @ WNO nanosheet obtained by the application, the strong hydrogen adsorption energy of the traditional WNO material is reduced, meanwhile, the hydrolysis potential barrier under neutral and alkaline conditions is also reduced, the efficient HER reaction in the full-pH electrolyte can be realized, and the stability is very high.
Drawings
Figure 1 is an XRD pattern of Ru @ WNO nanoplatelet material prepared in example 1 of the present application and WNO nanoplatelet prepared in comparative example 1 and Ru — NC material prepared in comparative example 2.
FIG. 2 is a SEM photograph of Ru @ WNO prepared herein, where a is example 1, b is example 2, c is example 3, d is example 4, e is example 5, f is comparative example 1, g is comparative example 2, and h is comparative example 3.
FIG. 3 is a TEM photograph of Ru @ WNO prepared herein, where a (200 nm scale), c (50 nm scale) and d (50 nm scale) are TEM photographs of Ru @ WNO nanoplates prepared in example 1, and b is a selected area electron diffraction pattern.
FIG. 4 is a TEM photograph of a material prepared in comparative example of the present application, wherein a and b are TEM photographs of WNO nanosheets prepared in comparative example 1, and c and d are TEM photographs of Ru-NC prepared in comparative example 2.
FIG. 5 shows Ru @ WNO (designated as Ru @ WNO-C in a, C and RuW-NCO in b) prepared in example 1 of the present application and WNO (designated as WNO-C in a, C and W-NCO in b) prepared in comparative example 1, Ru-NC (designated as Ru @ NO-C in a, C and Ru-NCO in b) prepared in comparative example 2 and RuW NPs (designated as 0.5M H) prepared in comparative example 32SO4(acidic), 1M Na2SO4LSV (Linear voltammetry) curves for hydrogen production by electrolysis of water in (neutral) and 1M KOH (alkaline), where a is 0.5M H2SO4Hydrogen evolution electrocatalysis curve in electrolyte, b is 1M Na2SO4The hydrogen evolution electrocatalysis curve in the electrolyte and the c is the hydrogen evolution electrocatalysis curve in 1M KOH.
FIG. 6 shows the Ru @ WNO concentration at 0.5M H for the compound prepared in example 1 of the present application2SO4，1M Na2SO4And an electrolyzed water hydrogen production LSV curve (showing stability) after 10000 cycles of circulation in 1M KOH, wherein a is 0.5M H2SO4Hydrogen evolution electrocatalysis curve in electrolyte, b is 1M Na2SO4The hydrogen evolution electrocatalysis curve in the electrolyte and the c is the hydrogen evolution electrocatalysis curve in 1M KOH.
FIG. 7 shows the Ru @ WNO concentration at 0.5M H for the compounds prepared in examples 2, 3, 4 and 5 of the present application2SO4，1M Na2SO4And the LSV curve of hydrogen production by water electrolysis in 1M KOH, wherein a is 0.5M H2SO4Hydrogen evolution electrocatalysis curve in electrolyte, b is 1M Na2SO4The hydrogen evolution electrocatalysis curve in the electrolyte and the c is the hydrogen evolution electrocatalysis curve in 1M KOH.
Detailed Description
The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.
In order to overcome the defects of low hydrogen production efficiency and small specific surface area of the existing WNO material, so as to give full play to the active sites of WNO and realize HER performance which is enough to be comparable to Pt, the application provides a Ru @ WNO nano catalyst, wherein Ru nano particles are doped in WNO nano sheets.
The Ru @ WNO nano-catalyst is in the shape of uniformly dispersed nano-sheets, and the surface of the Ru @ WNO nano-catalyst is loose and porous. The nanoplatelets can have a length of about 150 to 300nm, preferably 150 to 250 nm. The thickness of the nano-sheet can be 5-30 nm.
Ru is uniformly doped in WNO, exists in the form of ultra-small nanoparticles (for example, the particle diameter of the nanoparticles is less than 1 nm), and does not form agglomerates. The doping of the ultra-small Ru nano particles can be more uniformly distributed on the WNO nano sheet carrier and interact with the WNO nano sheet carrier, so that the catalytic reaction is promoted to be rapidly and efficiently generated.
The doping amount of Ru can be 0.5-1 wt.%. If the doping amount of Ru is too high, on one hand, during the preparation or the subsequent catalysis process, a large amount of loaded Ru particles can obviously agglomerate or fall off, so that the catalysis performance is obviously attenuated; on the other hand, Ru is relatively expensive, and an increase in the amount of Ru leads to an increase in cost, which is not suitable for practical production.
The Ru @ WNO nano-catalyst disclosed by the invention has the current density of 10mA/cm under an acidic condition2The overpotential of HER electrocatalysis is about 172-225 mV, the overpotential under neutral condition is about 295-358 mV, and the overpotential under alkaline condition is about 16-69 mV. The Ru @ WNO nano-catalyst disclosed by the invention has excellent catalytic activity for hydrogen production by water electrolysis in full pH and has good HER electrocatalytic stability.
In some embodiments of the application, WNO electronic structure and morphology can be regulated and controlled by element doping and MOF pyrolysis, so that trace amount of Ru-doped WNO nano catalytic material can be obtained. The preparation method of the Ru @ WNO nanocatalyst is exemplarily described below.
Preparing a precursor solution containing a tungsten source, a nitrogen source and a pore-forming agent. The tungsten source is selected from tungstic acid (H)2WO4) Phosphotungstic acid (12 WO)3·H3PO4) Ammonium metatungstate ((NH)4)6H2W12O40) Among them, tungstic acid is preferredBecause of its simple composition, no other impurity elements except H, O are present. The nitrogen source may be selected from 2-methylimidazole (C)4H6N2) Melamine (C)3H6N6) Urea (NH)2CONH2) And the like, among them, 2-methylimidazole is preferable because 2-methylimidazole can be used as a ligand to synthesize a zeolitic imidazole framework in combination with other elements. The pore-forming agent is selected from zinc nitrate (Zn (NO)3)2·6H2O), ammonium hydrogen carbonate (NH)4HCO3) Etc., among them, zinc nitrate is preferred because it can provide metal ions, and works together with 2-methylimidazole and metal salts to form a zeolite framework, resulting in a material having a uniform morphology. The molar ratio of tungsten source to nitrogen source may be 1: 0.1-1: at this molar ratio, nanosheets having a uniform WNO phase were produced. The molar ratio of the nitrogen source to the pore former may be 1: 2-1: and 5, at the molar ratio, the pore-forming agent can be coordinated with the nitrogen source to generate a stable ligand. The solvent of the precursor solution can be methanol, ethanol, deionized water and the like, wherein methanol is preferred because the methanol is used as the solvent, so that the specific surface area of the material can be effectively increased. The dosage ratio of the tungsten source to the solvent can be as follows: 20-120 mL of solvent is used for 1-5 mmol of tungstic acid. In one example, tungstic acid is dissolved in a solution containing a molar ratio of 1: 2-1: and 5, obtaining a precursor solution from 20-120 mL of methanol solution of 2-methylimidazole and zinc nitrate.
And uniformly mixing the precursor solution, and separating out solids to obtain the tungsten precursor material. In one example, the precursor solution is subjected to ultrasonic treatment for 3-10 min, and then stirred (e.g., magnetically stirred) at room temperature for 1-6 h to mix uniformly. The method for separating out solids may be any method known in the art, such as centrifugation. The separated solid can be washed and dried. The drying temperature can be 50-100 ℃.
Carrying out heat treatment on the tungsten precursor material to obtain porous WNO (W)0.62(N0.62O0.38) ) a nanosheet material. The heat treatment may be performed at 800 to 1000 ℃ for 1 to 3 hours under a protective atmosphere (e.g., argon). If the heat treatment temperature is too low, WNO material cannot be generated; if the heat treatment temperature is too high, the size of the nanosheet is increased, and the morphology is not uniform.
And dissolving the porous WNO nanosheet material and a ruthenium source in a solvent, and uniformly stirring to uniformly load Ru on the WNO nanosheet. The ruthenium source may be selected from ruthenium chloride (RuCl)3·xH2O), ruthenium acetylacetonate (Ru (acac)3) Ruthenium chloride is preferred, because it is soluble in water, a certain amount of solution can be prepared so as to accurately regulate the addition amount, and simultaneously, the components are simple, and impurity elements cannot be introduced. The molar ratio of the ruthenium source to the porous WNO nanoplatelet material may be 1: 500-1: 5000. at this molar ratio, Ru can be uniformly supported on the porous WNO nanosheets, without agglomeration or shedding, nor scattered. The solvent may be water or the like. The dosage ratio of the porous WNO nano sheet material to the solvent can be 0.1-1L of the solvent used per gram of the porous WNO nano sheet material. And during uniform stirring, the temperature can be controlled to be 70-90 ℃, and uniform loading of Ru on the WNO nanosheets can be realized while the WNO phase structure is not damaged by stirring at the temperature. The stirring time can be 2-6 h.
And then, separating a solid material from the solution system, and carrying out heat treatment on the obtained solid material to obtain the Ru @ WNO nanosheet material. The solid material can be separated by methods known in the art, such as centrifugation. The separated solid material can be washed and dried. The drying temperature can be 50-100 ℃. The heat treatment may be heat treatment at 100-200 deg.C under a protective atmosphere (such as argon) for 1-3 h. If the heat treatment temperature is too low, the Ru nano particles cannot be stably loaded on the WNO nano sheet; if the heat treatment temperature is too high, the agglomeration of Ru nano particles is easy to occur, and the catalytic performance is influenced.
As a preparation scheme of the Ru @ WNO nanosheet, the preparation method comprises the following steps:
(1) adding 1-5 mmol of tungstic acid into 20-120 mL of methanol solution containing 2-methylimidazole and zinc nitrate at room temperature, wherein the molar ratio of 2-methylimidazole to zinc nitrate is controlled to be 1: 2-1: 5;
(2) ultrasonically treating the solution obtained in the step (1) for 3-10 min, and magnetically stirring at room temperature for 1-6 h to obtain a uniformly mixed solution;
(3) centrifuging the mixed solution prepared in the step (2), washing the mixed solution for 3-5 times by using methanol, and drying the washed mixed solution in a vacuum drying oven;
(4) carrying out heat treatment on the powder obtained in the step (3) for 1-3 h at 800-1000 ℃ in an argon atmosphere;
(5) taking a certain amount of heat-treated powder, dissolving the heat-treated powder in 15-30 mL of deionized water, and adding 50mg/L RuCl31-4 mL of solution;
(6) placing the mixed solution prepared in the step (5) in a water bath kettle at the temperature of 70-90 ℃, stirring for 2-6 h, centrifuging, washing for 3-5 times by using ethanol, and drying in a vacuum drying oven;
(7) and (3) carrying out heat treatment on the prepared powder for 1-3 h at 100-200 ℃ in an argon atmosphere to obtain the Ru @ WNO nanosheet material.
The trace Ru-doped WNO nanosheet material prepared according to the process flow is characterized in that: the morphology of the nano-sheet is about 200-300 nm, and Ru is uniformly doped in WNO and does not form agglomeration; and the catalytic activity of electrolyzing water to produce hydrogen in the full pH value is high, and the stability is good.
According to some embodiments of the invention, a nitrogen source and a pore-forming agent are added into a precursor solution containing a tungsten source, the precursor solution and the pore-forming agent are uniformly mixed through ultrasound and stirring, and the mixture is subjected to heat treatment in a specific atmosphere for a certain time, so that the pore-forming agent is volatilized to obtain a loose porous WNO nanosheet material capable of exposing a large number of active sites. And then adding a ruthenium source into the WNO nanosheet-containing aqueous solution, uniformly doping Ru into the WNO nanosheets by stirring and heat treatment at a certain temperature, and realizing electronic structure adjustment of the WNO material while enlarging the specific surface to obtain the Ru @ WNO nano catalytic material with excellent HER performance in full-pH (acidic, neutral and alkaline) electrolyte.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
Electrocatalytic activity test method: three-electrode method (using Shanghai Chenghua CHI 760E electrochemical workstation). Pt/C catalysts for performance comparison were purchased from Shanghai HEPHAS energy Inc.
Example 1
0.9466g of tungstic acid was dissolved in 105mL of methanol solution containing 1.1408g of zinc nitrate and 1.2424g of 2-methylimidazole at room temperature, and stirred at room temperature for 4 hours with ultrasound for five minutes to obtain a uniformly mixed solution. And centrifuging the obtained solution, washing the solution for 5 times by using methanol, drying the solution in a vacuum drying oven at 70 ℃ for 12h, and then putting the obtained powder into a tubular furnace to perform heat treatment at 900 ℃ for 3h under the argon atmosphere to obtain a WNO nano-sheet precursor. Dissolving the prepared 100mg WNO nanosheet precursor in 26mL deionized water, and adding 50mg/L RuCl3·xH2And stirring the mixture for 6 hours in a water bath kettle at the temperature of 70 ℃ to ensure that Ru is uniformly loaded on the WNO nano-sheets. And centrifuging, washing with ethanol for 5 times, drying in a vacuum drying oven at 70 ℃ for 12h, and placing in an argon atmosphere for heat treatment at 125 ℃ for 1h to obtain the Ru @ WNO nanosheet material.
The main phase of the prepared material is WNO material, as shown in an XRD (Ru @ WNO-C) of figure 1, the morphology is a nanosheet structure as shown in an SEM (a in figure 2) picture and a TEM (figure 3) picture, and selective area electron diffraction (b in figure 3) is represented by characteristic diffraction of WNO. The current density of the alloy is 10mA/cm under the acidic condition2The HER electrocatalytic overpotential at time of treatment was 172mV (as shown by the LSV curve for Ru @ WNO-C in fig. 5 a), 358mV under neutral conditions (as shown by the LSV curve for RuW-NCO in fig. 5 b), and 16mV under alkaline conditions (as shown by the LSV curve for Ru @ WNO-C in fig. 5C). After 10000 cycles of circulation, the overpotential of HER electrocatalysis is not obviously reduced under acidic, neutral and alkaline conditions, but the performance is slightly increased after 1000 cycles (as shown in figure 6), which indicates that the Ru @ WNO nanosheet electrocatalysis material not only has good HER electrocatalysis activity, but also has good electrocatalysis stability.
Example 2
0.5680g of tungstic acid were dissolved in 63mL of methanol containing 0.6845g of zinc nitrate and 0.7454g of 2-methylimidazole at room temperature as in the process flow of example 1, and the other operating conditions were the same as in example 1 to obtain a catalyst having a sheet structureThe Ru @ WNO electro-catalytic nanomaterial is in a nanosheet structure, and is shown as b in figure 2. The current density of the alloy is 10mA/cm under the acidic condition2HER electrocatalytic overpotential at time of 220mV, overpotential at neutral condition of 315mV, and overpotential at alkaline condition of 60mV (shown as LSV in fig. 7). After 10000 cycles, the HER electrocatalytic overpotential under acidic, neutral and alkaline conditions did not decrease significantly, but rather the performance increased slightly after 1000 cycles.
Example 3
According to the process flow (same as example 1), 0.4544g of tungstic acid is dissolved in 50mL of methanol solution containing 0.5483g of zinc nitrate and 0.5963g of 2-methylimidazole at room temperature, and other operation conditions are the same as example 1, so that the obtained Ru @ WNO nano-material has a nano-sheet structure, as shown in an SEM photograph in c of FIG. 2. The current density of the alloy is 10mA/cm under the acidic condition2The HER electrocatalytic overpotential at time was 205mV, the overpotential under neutral conditions was 295mV, and the overpotential under alkaline conditions was 66mV (shown as LSV in figure 7). After 10000 cycles, the HER electrocatalytic overpotential under acidic, neutral and alkaline conditions did not decrease significantly, but rather the performance increased slightly after 1000 cycles.
Example 4
According to the process flow (same as example 1), the difference from example 1 is that the temperature of the first heat treatment is 800 ℃, and the obtained Ru @ WNO nano-material has a sheet structure, as shown in SEM picture in d of FIG. 2. The current density of the alloy is 10mA/cm under the acidic condition2The HER electrocatalytic overpotential at time of treatment was 225mV, the overpotential under neutral conditions was 300mV, and the overpotential under alkaline conditions was 69mV (shown as LSV in fig. 7). After 10000 cycles, the HER electrocatalytic overpotential under acidic, neutral and alkaline conditions did not decrease significantly, but rather the performance increased slightly after 1000 cycles.
Example 5
According to the process flow (same as example 1), the difference from example 1 is that the temperature of the second heat treatment is 200 ℃, and the obtained Ru @ WNO nano material has a nano-sheet structure assembled by loose nano-particles, as shown in SEM picture in e of FIG. 2As shown. The current density of the alloy is 10mA/cm under the acidic condition2The HER electrocatalytic overpotential at time of treatment was 223mV, the overpotential under neutral conditions was 310mV, and the overpotential under alkaline conditions was 53mV (shown as LSV in fig. 7). After 10000 cycles, the HER electrocatalytic overpotential under acidic, neutral and alkaline conditions did not decrease significantly, but rather the performance increased slightly after 1000 cycles.
Comparative example 1
According to the process flow (same as example 1), ruthenium source is not added, the operation is the same as example 1, the prepared material is WNO nanosheet material, as shown by XRD pattern (WNO-C) in figure 1, and as shown by SEM picture (f in figure 2) and TEM picture (a and b in figure 4), the HER electrocatalytic activity of the WNO nanosheet material is much worse than that of Ru @ WNO prepared in example 1, as shown by LSV curves of WNO-C and W-NCO in figure 5.
Comparative example 2
According to the process flow (same as example 1), a tungsten source is not added, the operation is the same as example 1, the prepared material is a Ru-NC regular dodecahedron nano material, as shown by an XRD (Ru @ NO-C) in figure 1, and as shown by SEM (g in figure 2) and TEM (C and d in figure 4), the HER electrocatalytic activity of the Ru-WNO nano material is much poorer than that of the Ru @ WNO prepared in example 1, as shown by LSV curves of Ru @ NO-C and Ru-NCO in figure 5.
Comparative example 3
According to the process flow (same as example 1), the pore-forming agent is not added, the other operation is the same as example 1, and the prepared material has a polygonal prism-shaped structure, as shown in h in fig. 2. The electrocatalytic activity was much worse than that of Ru @ WNO in example 1, as shown by the LSV curve of RuW NPs in FIG. 5.

Claims (7)

1. A method for preparing a nano catalyst, wherein the nano catalyst comprises the following steps: the preparation method comprises the following steps of preparing porous WNO nano sheets and Ru nano particles doped in the porous WNO nano sheets, wherein the doping amount of the Ru nano particles is 0.5-1 wt%, and the preparation method comprises the following steps:
(a) uniformly mixing a solution containing a tungsten source, a nitrogen source and a pore-forming agent, and separating out a solid;
(b) carrying out heat treatment on the solid obtained in the step (a) at 800-1000 ℃ for 1-3 hours in a protective atmosphere to obtain a porous WNO nanosheet material;
(c) dissolving the obtained porous WNO nanosheet material in water, adding a ruthenium source, stirring at 70-90 ℃ for 2-6 hours, and separating out a solid;
(d) carrying out heat treatment on the solid obtained in the step (c) for 1-3 hours at 100-200 ℃ in a protective atmosphere to obtain the nano catalyst;
the nitrogen source is 2-methylimidazole, and the pore-forming agent is zinc nitrate.
2. The preparation method according to claim 1, wherein the length of the porous WNO nanosheets is 150-300 nm.
3. The production method according to claim 1, wherein the tungsten source is tungstic acid, and the molar ratio of the tungsten source to the nitrogen source is controlled to be 1: 0.1-1: and 1, controlling the molar ratio of the nitrogen source to the pore-forming agent to be 1: 2-1: 5.
4. The method according to claim 1, wherein in the step (a), the solvent of the solution is methanol.
5. The method according to claim 1, wherein in the step (a), the solution is sonicated for 3 to 10 minutes and stirred at room temperature for 1 to 6 hours to be uniformly mixed.
6. The production method according to claim 1, wherein the ruthenium source is ruthenium chloride.
7. The method of any one of claims 1 to 6, wherein in step (c), the molar ratio of ruthenium source to porous WNO nanoplatelet material is 1: 500-1: 5000.
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