Nano-carbide tungsten hydrogen evolution catalyst, and preparation method and application thereof

Abstract

The application provides a preparation method of a nano tungsten carbide hydrogen evolution catalyst, which comprises the following steps: S1, configuring a first mixed slurry of conductive carbon black, a tungsten salt precursor and a first solvent; S2, adding a solution of a self-polymerizable polymer monomer into the first mixed slurry, and then performing a solvothermal treatment to obtain a second mixed slurry; S3, performing a solid-liquid separation on the second mixed slurry to obtain a solid material; and S4, calcining the solid material and grinding to obtain the nano tungsten carbide hydrogen evolution catalyst; wherein the calcining process comprises a heating stage, a holding stage and a cooling stage which are sequentially performed; the heating stage and the cooling stage are performed under a reducing atmosphere, and the holding stage is performed under a mixed atmosphere of a reducing atmosphere and water vapor. The application provides a non-noble metal catalyst which can replace a 20% Pt / C catalyst and has good hydrogen evolution activity, and is of great significance for reducing the cost of a proton exchange membrane electrolytic cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen evolution catalyst, in particular to a nano tungsten carbide hydrogen evolution catalyst and a preparation method and application thereof. BACKGROUND

[0002] The hydrogen evolution catalyst is located at the cathode position of the proton exchange membrane electrolyzer, and is an important component of the proton exchange membrane electrolyzer. The proton exchange membrane electrolyzer can produce hydrogen and oxygen under the action of electric current. The hydrogen evolution catalyst can reduce the cathode overpotential in the process of producing hydrogen by water electrolysis of the proton exchange membrane, thereby reducing the energy consumption in the process of producing hydrogen. At present, the cathode catalyst used in the proton exchange membrane electrolyzer is mainly a 20% Pt / C catalyst. Since a noble metal is used as the hydrogen evolution catalyst, the initial investment cost of the proton exchange membrane electrolyzer is high, which limits the large-scale application of the proton exchange membrane electrolyzer in the field of producing hydrogen. And the current amount of noble metal is only enough to support the production of 3-7.5 GW / year of the proton exchange membrane electrolyzer.

[0003] Based on the problem of high cost of the proton exchange membrane electrolyzer at present, it is necessary to develop a non-noble metal catalyst with good hydrogen evolution activity which can replace the 20% Pt / C catalyst. SUMMARY

[0004] The main purpose of the present application is to provide a nano tungsten carbide hydrogen evolution catalyst and a preparation method and application thereof, so as to solve the problem of high cost of the proton exchange membrane electrolyzer caused by using non-noble metal catalyst as the hydrogen evolution catalyst in the prior art, and to provide a non-noble metal catalyst with good hydrogen evolution activity which can replace the 20% Pt / C catalyst.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a preparation method of a nano tungsten carbide hydrogen evolution catalyst is provided, and the preparation method comprises the following steps:

[0006] S1, configuring a first mixed slurry of conductive carbon black, tungsten salt precursor and a first solvent;

[0007] S2, adding a solution of a self-polymerizable polymer monomer into the first mixed slurry, and then performing a solvothermal treatment to obtain a second mixed slurry;

[0008] S3, performing a solid-liquid separation on the second mixed slurry to obtain a solid material;

[0009] S4, calcining and grinding the solid material to obtain a nano tungsten carbide hydrogen evolution catalyst;

[0010] The calcination process comprises a heating stage, a holding stage and a cooling stage which are performed in sequence; the heating stage and the cooling stage are performed in a reducing atmosphere, and the holding stage is performed in a mixed atmosphere of the reducing atmosphere and water vapor.

[0011] Further, the temperature of the solvothermal treatment is 20-100°C, preferably 40-80°C; the time of the solvothermal treatment is 3-24h, preferably 6-12h.

[0012] Further, the volume concentration of the self-polymerizable polymer monomer in the second mixed slurry is 0.1-5μL / mL, preferably 1-2μL / mL.

[0013] Further, the temperature of the holding stage is 600-1200°C, preferably 800-1000°C; the time of the holding stage is 5-60min, preferably 10-30min.

[0014] Further, the gas flow rate of the mixed atmosphere of the reducing atmosphere and water vapor in the holding stage is 20-200ml / min.

[0015] Preferably, the gas flow rate of the reducing atmosphere in the heating stage and the cooling stage is 100-1000ml / min.

[0016] Further, the volume ratio of water vapor to the reducing atmosphere in the holding stage is (0.5-9):1.

[0017] Further, the mass concentration of the conductive carbon black in the first mixed slurry is 0.1-5%, preferably 0.5-1.5%.

[0018] Further, the mass ratio of the tungsten salt precursor to the conductive carbon black is (8:1)-(1:8), preferably (4:1)-(1:4).

[0019] Further, the tungsten salt precursor is one or more of phosphotungstic acid, ammonium phosphotungstate, and sodium phosphotungstate.

[0020] Further, the self-polymerizable polymer monomer is pyridine and / or pyrrole.

[0021] Further, the self-polymerizable polymer monomer is added to the first mixed slurry in the form of dropwise addition, preferably the dropwise addition rate in the dropwise addition process is 0.2-2ml / min.

[0022] Further, the reducing atmosphere is a mixed gas of a reducing gas and an inert gas; wherein the volume concentration of the reducing gas in the reducing atmosphere is 1-30%; preferably the reducing gas is one or more of carbon monoxide, hydrogen, and methane.

[0023] Further, the first solvent is water; preferably the solvent in the solution of the self-polymerizable polymer monomer is water.

[0024] Further, the time of the calcination process is 1-6h; preferably 2-4h, the time of the temperature rising stage is 120-240min, and the time of the temperature decreasing stage is 120-240min.

[0025] Further, the way of the solid-liquid separation is suction filtration; preferably, the solid material obtained after the suction filtration is washed with the first solvent; more preferably, the washed solid material is dried at a temperature of 60-120℃ for 6-24h.

[0026] Further, the water vapor is introduced through a humidification bottle, and the temperature of the humidification bottle is room temperature to 80℃, preferably 30-60℃.

[0027] In order to achieve the above-mentioned purpose, according to one aspect of the present application, there is provided a nano tungsten carbide hydrogen evolution catalyst prepared according to the above-mentioned preparation method.

[0028] According to another aspect of the present application, there is provided an application of the above-mentioned nano tungsten carbide hydrogen evolution catalyst in catalyzing the water electrolysis of proton exchange membrane.

[0029] By using the technical solution of the present application, a nano tungsten carbide hydrogen evolution catalyst is obtained. In the nano tungsten carbide hydrogen evolution catalyst, the conductive carbon black provides a larger specific surface area, which provides a sufficient reaction platform for the catalytic reaction and enhances the electrical conductivity between the electrode and the catalyst. The polymer monomer undergoes self-polymerization during entering the system and forms an organic layer covering on the surface of the tungsten salt precursor and the conductive carbon black. During the subsequent calcination process, the organic layer will be carbonized, further forming a carbon layer covering the surface of the tungsten carbide catalyst. A part of the carbon layer in contact with the tungsten reacts to form tungsten carbide, and a part of the carbon layer close to the surface reacts to form water gas due to the contact of water vapor, so that the carbon layer is thinned to a more appropriate thickness, and sufficient oxygen vacancies are introduced, further improving the performance of the hydrogen evolution catalyst. Based on the above physical characteristics, the wrapped nano tungsten carbide catalyst not only reduces the surface activation energy of the tungsten compound, but also improves the electron transfer speed between the wrapping layer and the conductive particles, which further improves the overall activity of the nano tungsten carbide catalyst. In addition, in the preparation method designed in the present application, the thickness of the carbon layer can be controlled by the parameters in the process. In actual operation, due to the fast polymerization reaction, simply using monomer polymerization and calcination often forms an excessively thick carbon layer, therefore the present application specially introduces a water vapor participating holding stage in the subsequent calcination process, which can achieve the purpose of thinning the carbon layer, so that the thickness of the carbon layer is more appropriate. At the same time, the water vapor participating holding process can also increase the surface oxygen vacancies. The above reasons make the hydrogen evolution performance of the tungsten carbide catalyst significantly improved, and the ability of the catalyst surface to transfer electrons, absorb hydrogen ions and desorb hydrogen gas during the hydrogen evolution reaction is better.

[0030] Based on the above reasons, the present application provides a non-noble metal catalyst with good hydrogen evolution activity, which can replace 20% Pt / C catalyst, and is of great significance for reducing the cost of proton exchange membrane electrolysis cell. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The embodiments of the present application, and their

[0032] Figure 1 shows the hydrogen evolution overpotential diagram of Example 3 and Comparative Example 1 according to the preparation method of the present application; and

[0033] Figure 2 shows the scanning electron microscope image of the nanometer carbide hydrogen evolution catalyst prepared according to the present application. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] In order to solve the problems in the prior art as described above, according to an aspect of the present application, a preparation method of a nanometer tungsten carbide hydrogen evolution catalyst is provided, which comprises the following steps: S1, configuring a first mixed slurry of conductive carbon black, tungsten salt precursor and a first solvent; S2, adding a solution of a self-polymerizable polymer monomer into the first mixed slurry, and then performing a solvothermal treatment to obtain a second mixed slurry; S3, performing a solid-liquid separation on the second mixed slurry to obtain a solid material; S4, calcining the solid material, and grinding to obtain the nanometer tungsten carbide hydrogen evolution catalyst; wherein the calcination process comprises a heating stage, a holding stage and a cooling stage performed in sequence; the heating stage and the cooling stage are performed in a reducing atmosphere, and the holding stage is performed in a mixed atmosphere of a reducing atmosphere and water vapor.

[0036] The conductive carbon black provides a larger specific surface area, which provides a sufficient reaction platform for the catalytic reaction and enhances the conductivity between the electrode and the catalyst. The polymer monomer undergoes self-polymerization during entering the system, and forms an organic layer covering on the surface of the tungsten salt precursor and the conductive carbon black. During the subsequent calcination process, the organic layer will be carbonized to further form a carbon layer covering the surface of the tungsten carbide catalyst. A part of the carbon layer in contact with the tungsten reacts with the tungsten to form tungsten carbide, and a part of the carbon layer close to the surface reacts with water vapor to generate water gas, so that the carbon layer is thinned to a more suitable thickness, and sufficient oxygen vacancies are introduced, which further improves the performance of the hydrogen evolution catalyst. Based on the above physical characteristics, the wrapped nano tungsten carbide catalyst not only reduces the surface activation energy of the tungsten compound, but also improves the electron transfer speed between the wrapping layer and the conductive particles, which further improves the overall activity of the nano tungsten carbide catalyst. In addition, in the preparation method designed in the present application, the thickness of the carbon layer can be controlled by various parameters in the process. In actual operation, due to the fast polymerization reaction, simply using monomer polymerization and calcination often forms a too thick carbon layer, so the present application specially introduces a water vapor participating holding stage in the subsequent calcination process, which can achieve the purpose of thinning the carbon layer, so that the thickness of the carbon layer is more suitable. At the same time, the water vapor participating holding process can also increase the surface oxygen vacancies. The above reasons can significantly improve the hydrogen evolution performance of the tungsten carbide catalyst, and the ability of electron transfer, hydrogen ion adsorption and hydrogen desorption on the surface of the catalyst during the hydrogen evolution reaction is better.

[0037] The thickness of the carbon layer in the nano tungsten carbide hydrogen evolution catalyst provided by the present application can be about 10 nm through the above-mentioned means of regulation, and the overpotential can be as low as -208 mV, as shown in Figure 2 and Figure 1 .

[0038] In the actual operation of the present application, the conductive carbon black can be VXC-72R, Ketjen black, BP2000 and the like, but is not limited to the above-mentioned types.

[0039] For the purpose of further promoting the solvothermal reaction, in a preferred embodiment, the temperature of the solvothermal treatment is 20-100℃, preferably 40-80℃; the time of the solvothermal treatment is 3-24h, preferably 6-12h. Under the preferred conditions, the self-polymerizable polymer monomer can form a covering layer with a more suitable thickness range on the surface of the tungsten salt precursor and the conductive carbon black, which is beneficial to better improve the hydrogen evolution activity of the tungsten carbide catalyst through the mechanism as described above, and at the same time provides a basis for controlling the thickness of the carbon layer through the subsequent calcination process.

[0040] In order to further make the polymerization of monomers occur uniformly and avoid the agglomeration phenomenon caused by high concentration of monomers, in a preferred embodiment, the volume concentration of the self-polymerizable polymer monomer in the second mixed slurry is 0.1-5 μL / L, preferably 1-2 μL / mL. Controlling the monomer concentration in the above range, on the one hand, the slurry viscosity is suitable, and the polymerization reaction is more stable, on the other hand, it is also more conducive to the full coating of the generated polymer on the surface of the tungsten salt precursor and the conductive carbon black, and has a better promoting effect on the coating effect of the carbon layer, thereby more conducive to improving the hydrogen evolution performance of the final catalyst.

[0041] In a preferred embodiment, the temperature of the holding stage is 600-1200 °C, preferably 800-1000 °C; the time of the holding stage is 5-60 min, preferably 10-30 min. Preferably, the above holding stage conditions are more conducive to forming a carbon layer with a suitable thickness.

[0042] In order to better control the thickness of the carbon layer, in a preferred embodiment, the gas flow rate of the mixed atmosphere of reducing atmosphere and water vapor in the holding stage is 20-200 ml / min; preferably, the gas flow rate of the reducing atmosphere in the heating stage and the cooling stage is 100-1000 ml / min. Preferably, the gas flow rate of the holding stage is controlled, which is conducive to making the reaction of the carbon layer with water vapor more easily controllable and increasing the surface oxygen vacancies of the tungsten carbide catalyst. Controlling the reducing atmosphere in the heating and cooling stages is conducive to obtaining a tungsten carbide catalyst with higher hydrogen evolution activity. In order to make the calcination process more controllable, preferably, the gas flow rate of each stage is a constant value in each stage.

[0043] In a preferred embodiment, the volume ratio of water vapor to reducing atmosphere in the holding stage is (0.5-9):1. Under this preferred atmosphere, the reaction of water and carbon is more conducive to proceeding.

[0044] In actual operation, preferably, the calcination process is carried out in a tube furnace.

[0045] In order to better provide sufficient high specific surface area carriers, in a preferred embodiment, the mass concentration of the conductive carbon black in the first mixed slurry is 0.1-5%, preferably 0.5-1.5%. Preferably, the above-mentioned addition amount of conductive carbon black can better provide sufficient reaction platform and improve the hydrogen evolution activity of the tungsten carbide catalyst.

[0046] In order to provide sufficient tungsten source, in a preferred embodiment, the mass ratio of the tungsten salt precursor to the conductive carbon black is (8:1)-(1:8), preferably (4:1)-(1:4).

[0047] In the technical solution of the present application, the tungsten salt precursor is preferably one or more of phosphotungstic acid, ammonium phosphotungstate, and sodium phosphotungstate, but is not limited to the above-mentioned types.

[0048] In the technical solution of the present application, the self-polymerizable monomer is preferably pyridine and / or pyrrole.

[0049] In order to keep the self-polymerizable monomer mixed uniformly and react sufficiently in the slurry, in a preferred embodiment, the self-polymerizable monomer is added to the first mixed slurry in the form of dropwise addition, and the dropwise addition speed in the dropwise addition process is preferably 0.2-2 ml / min.

[0050] In order to further improve the hydrogen evolution activity of the tungsten carbide catalyst, in a preferred embodiment, the reducing atmosphere is a mixed gas of a reducing gas and an inert gas; the volume concentration of the reducing gas in the reducing atmosphere is 1-30%; and the reducing gas is preferably one or more of carbon monoxide, hydrogen, and methane.

[0051] In order to make the polymer coating process more controllable, in a preferred embodiment, the first solvent is water; and preferably, the solvent in the self-polymerizable monomer solution is water.

[0052] In order to make the calcination more sufficient, in a preferred embodiment, the calcination time is 1-6 h, preferably 2-4 h; and preferably, the temperature rising time is 120-240 min, and the temperature falling time is 120-240 min.

[0053] In order to further improve the concentration of the product, in a preferred embodiment, the solid-liquid separation method is suction filtration; preferably, the solid material obtained after suction filtration is washed with the first solvent; and more preferably, the washed solid material is subjected to drying treatment at a temperature of 60-120℃ for 6-24 h.

[0054] In actual operation, preferably, the above drying process is carried out in a vacuum oven.

[0055] In order to make the operation of passing different atmospheres in the calcination process more convenient, in a preferred embodiment, the water vapor is passed through a humidification bottle, and the temperature of the humidification bottle is room temperature to 80℃, preferably 30-60℃. When switching from the temperature rising stage to the temperature holding stage, the reducing atmosphere is switched to the humidification bottle, and the gas flow is adjusted to calculate the aeration time.

[0056] According to another aspect of the present application, a nano tungsten carbide hydrogen evolution catalyst is provided, which is prepared according to the above preparation method. The nano tungsten carbide hydrogen evolution catalyst has good hydrogen evolution activity.

[0057] According to another method of the application, there is provided an application of a nano tungsten carbide hydrogen evolution catalyst in catalytic proton exchange membrane electrolysis of water. The tungsten carbide catalyst in the application is applied to the field of proton exchange membranes, which greatly reduces the cost compared with noble metal-based catalysts and is conducive to realizing large-scale production.

[0058] The application will be further described in detail below in combination with specific embodiments, which should not be construed as limiting the scope of the application.

[0059] Example 1

[0060] (1) 1 g of phosphotungstic acid and 1 g of conductive carbon black VXC-72R were weighed, then 200 mL of deionized water was added, stirred for 0.5 h, the heating temperature of the oil bath electromagnetic stirrer was set to 40℃, and the oil bath reaction hydrothermal reaction time was 12 h, then the mixed slurry beaker was placed in the oil bath electromagnetic stirrer for temperature rising reaction.

[0061] (2) 20 μL of pyridine was measured with a pipette and added to 20 mL of deionized water for dissolution, then the pyridine aqueous solution was added to the mixed slurry in (1) at a titration rate of 0.5 mL / min for polymerization reaction to obtain a second mixed slurry.

[0062] (3) After the reaction was completed, the second mixed slurry in (2) was filtered, and after filtration, it was washed with deionized water for 5 times, then the filter cake was placed in a vacuum drying oven and dried at 120℃ for 12 h.

[0063] (4) The product in (3) was placed in a ceramic boat and transferred to a tube furnace for high-temperature calcination, the calcination atmosphere was argon-hydrogen mixed gas (5% H2+95% Ar), the gas flow rate was 300 mL / min, the heating time was 160 min, the cooling time was 160 min, the holding stage temperature was 800℃, and the time was 2 h.

[0064] (5) When the calcination temperature in (4) reached 800℃, the argon-hydrogen mixed gas atmosphere was switched to pass through a humidification bottle at 40℃, and the gas flow rate was adjusted to 50 mL / min, the water vapor time was 15 min, then the gas path was switched back to the argon-hydrogen mixed gas atmosphere, and the gas flow rate was adjusted back to 300 mL / min to the end of the reaction.

[0065] (6) The hydrogen evolution catalyst in (5) was subjected to electrochemical test, and when the current density was 10 mA / cm 2 , the overpotential of the catalyst was -232 mV.

[0066] Example 2

[0067] (1) Weigh phosphotungstic acid 2 g, conductive carbon black BP2000 1 g, then add 200 mL of deionized water, stir for 0.5 h, set the heating temperature of the oil bath electromagnetic stirrer to 60°C, and the oil bath reaction hydrothermal reaction time is 24 h, then place the mixed slurry beaker in the oil bath electromagnetic stirrer for temperature rising reaction.

[0068] (2) Use a pipette to take 10 μL of pyridine and add it to 20 mL of deionized water for dissolution, then add the pyridine aqueous solution to the mixed slurry in (1) at a titration rate of 1 mL / min for polymerization reaction to obtain a second mixed slurry.

[0069] (3) After the reaction is completed, filter the second mixed slurry in (2), wash it with deionized water 5 times after filtration, then place the filter cake in a vacuum drying oven and dry it at 120°C for 12 h.

[0070] (4) Place the product in (3) in a ceramic boat and transfer it to a tube furnace for high-temperature calcination, the calcination atmosphere is argon-hydrogen mixed gas (10% H2+90% Ar), the gas flow rate is 300 mL / min, the heating time is 180 min, the cooling time is 180 min, the holding stage temperature is 900°C, and the time is 3 h.

[0071] (5) When the calcination temperature in (4) reaches 900°C, switch the argon-hydrogen mixed gas atmosphere to pass through a humidification bottle at 50°C, and adjust the gas flow rate to 100 mL / min, the water vapor time is 30 min, then switch the gas path back to the argon-hydrogen mixed gas atmosphere, and adjust the gas flow rate back to 300 mL / min to the end of the reaction.

[0072] (6) Electrochemical test of the hydrogen evolution catalyst in (5), when the current density is 10 mA / cm 2 , the overpotential of the catalyst is -236 mV.

[0073] Example 3

[0074] (1) Weigh phosphotungstic acid 2 g, conductive carbon black VXC-72R 0.2 g, then add 200 mL of deionized water, stir for 0.5 h, set the heating temperature of the oil bath electromagnetic stirrer to 80°C, and the oil bath reaction hydrothermal reaction time is 12 h, then place the mixed slurry beaker in the oil bath electromagnetic stirrer for temperature rising reaction.

[0075] (2) Use a pipette to take 20 μL of pyridine and add it to 10 mL of deionized water for dissolution, then add the pyridine aqueous solution to the mixed slurry in (1) at a titration rate of 1 mL / min for polymerization reaction to obtain a second mixed slurry.

[0076] (3) After the reaction is completed, the second mixed slurry in (2) is filtered, washed with deionized water for 5 times after filtration, and then the filter cake is placed in a vacuum drying oven and dried at 120°C for 12h.

[0077] (4) The product in (3) is placed in a ceramic boat and transferred to a tube furnace for high-temperature calcination. The calcination atmosphere is argon-hydrogen mixed gas (5% H2+95% Ar), the gas flow rate is 300mL / min, the heating time is 200min, the cooling time is 200min, the temperature in the holding stage is 1000°C, and the time is 4h.

[0078] (5) When the calcination temperature in (4) reaches 1000°C, the argon-hydrogen mixed gas atmosphere is switched to a humidification bottle at 60°C, and the gas flow rate is adjusted to 50mL / min. The water vapor time is 15min, and then the gas path is switched back to the argon-hydrogen mixed gas atmosphere, and the gas flow rate is adjusted back to 300mL / min until the reaction is completed.

[0079] (6) The hydrogen evolution catalyst in (5) is subjected to electrochemical test, and when the current density is 10mA / cm 2 , the overpotential of the catalyst is-208mV.

[0080] The overpotential diagram of the hydrogen evolution catalyst of Example 3 is shown in Figure 1 , and the scanning electron microscope image is shown in Figure 2 .

[0081] Example 4

[0082] (1) Weigh 2.5g of sodium tungstophosphate and 1g of conductive carbon black BP2000, then add 200mL of deionized water, stir for 0.5h, set the oil bath electromagnetic stirrer heating temperature to 20°C, and the oil bath reaction hydrothermal reaction time to 12h, then place the mixed slurry beaker in the oil bath electromagnetic stirrer for temperature rising reaction.

[0083] (2) Use a pipette to take 30μL of pyrrole and add it to 20mL of deionized water for dissolution, then add the pyrrole aqueous solution to the mixed slurry in (1) at a titration rate of 0.2mL / min for polymerization reaction to obtain a second mixed slurry.

[0084] (3) After the reaction is completed, the second mixed slurry in (2) is filtered, washed with deionized water for 5 times after filtration, and then the filter cake is placed in a vacuum drying oven and dried at 60°C for 6h.

[0085] (4) The product in (3) was placed in a ceramic boat and transferred to a tube furnace for high-temperature calcination. The calcination atmosphere was a mixture of methane and argon (30% CO + 70% Ar), the gas flow rate was 100 mL / min, the temperature rising time was 120 min, the temperature falling time was 120 min, the temperature in the holding stage was 600°C, and the time was 2 h.

[0086] (5) When the calcination temperature in (4) reached 600°C, the mixed gas atmosphere of methane and argon was switched to a 30°C humidification bottle, the gas flow rate was adjusted to 20 mL / min, the water vapor time was 5 min, then the gas path was switched back to the mixed gas atmosphere of methane and argon, the gas flow rate was adjusted back to 100 mL / min until the end of the reaction.

[0087] (6) The hydrogen evolution catalyst in (5) was subjected to electrochemical test, when the current density was 10 mA / cm 2 , the overpotential of the catalyst was -245 mV.

[0088] Example 5

[0089] (1) 3 g of phosphotungstic acid ammonium and 1.5 g of conductive carbon black were weighed, then 200 mL of deionized water was added, stirred for 0.5 h, the oil bath electromagnetic stirrer heating temperature was set to 100°C, and the oil bath reaction hydrothermal reaction time was 3 h, then the mixed slurry beaker was placed in the oil bath electromagnetic stirrer for temperature rising reaction.

[0090] (2) 20 μL of pyrrole was taken with a pipette and added to 20 mL of deionized water for dissolution, then the pyrrole aqueous solution was added to the mixed slurry in (1) at a titration rate of 2 mL / min for polymerization reaction, to obtain a second mixed slurry.

[0091] (3) After the reaction was completed, the second mixed slurry in (2) was filtered, and after filtration, it was washed with deionized water for 5 times, then the filter cake was placed in a vacuum drying oven and dried at 120°C for 24 h.

[0092] (4) The product in (3) was placed in a ceramic boat and transferred to a tube furnace for high-temperature calcination. The calcination atmosphere was a mixture of methane and argon (30% CO + 70% Ar), the gas flow rate was 100 mL / min, the temperature rising time was 120 min, the temperature falling time was 120 min, the temperature in the holding stage was 600°C, and the time was 2 h.

[0093] (5) When the calcination temperature in (4) is raised to 1200°C, switch the atmosphere of carbon monoxide and nitrogen gas to pass through a humidification bottle at 30°C, and adjust the gas flow rate to 200 mL / min, the water vapor passing time is 60 min, then switch the gas circuit back to the atmosphere of carbon monoxide and nitrogen gas, and adjust the gas flow back to 1000 mL / min to the end of the reaction.

[0094] (6) The hydrogen evolution catalyst in (5) is subjected to electrochemical test, when the current density is 10 mA / cm 2 , the overpotential of the catalyst is -240 mV.

[0095] Example 6

[0096] (1) Weigh 1 g of phosphotungstic acid and 0.125 g of conductive carbon black VXC-72R, then add 200 mL of deionized water, stir for 0.5 h, set the heating temperature of the oil bath electromagnetic stirrer to 40°C, and carry out the oil bath reaction hydrothermal reaction for 12 h, then place the mixed slurry beaker in the oil bath electromagnetic stirrer for temperature rising reaction.

[0097] (2) Use a pipette to take 100 μL of pyridine and add it to 20 mL of deionized water for dissolution, then add the pyridine aqueous solution to the mixed slurry in (1) at a titration rate of 0.5 mL / min for polymerization reaction, to obtain a second mixed slurry.

[0098] (3) After the reaction is completed, filter the second mixed slurry in (2), wash the filter cake with deionized water for 5 times after filtration, then place the filter cake in a vacuum drying oven and dry at 120°C for 12 h.

[0099] (4) Place the product in (3) in a ceramic boat and transfer it to a tube furnace for high-temperature calcination, the calcination atmosphere is argon-hydrogen mixed gas (5% H2+95% Ar), the gas flow is 300 mL / min, the heating time is 160 min, the cooling time is 160 min, the holding stage temperature is 800°C, and the time is 2 h.

[0100] (5) When the calcination temperature in (4) is raised to 800°C, switch the atmosphere of argon-hydrogen mixed gas to pass through a humidification bottle at 40°C, and adjust the gas flow rate to 10 mL / min, the water vapor passing time is 15 min, then switch the gas circuit back to the atmosphere of argon-hydrogen mixed gas, and adjust the gas flow back to 300 mL / min to the end of the reaction.

[0101] (6) The hydrogen evolution catalyst in (5) is subjected to electrochemical test, when the current density is 10 mA / cm 2 , the overpotential of the catalyst is -290 mV.

[0102] Example 7

[0103] (1) Weigh 1 g of phosphotungstic acid and 8 g of conductive carbon black, then add 200 mL of deionized water, stir for 0.5 h, set the heating temperature of the oil bath electromagnetic stirrer to 40℃, and carry out the hydrothermal reaction for 12 h, then place the mixed slurry beaker in the oil bath electromagnetic stirrer for temperature rising reaction.

[0104] (2) Use a pipette to take 5 μL of pyridine and add it to 20 mL of deionized water for dissolution, then add the pyridine aqueous solution to the mixed slurry in (1) at a titration rate of 0.5 mL / min for polymerization reaction, to obtain a second mixed slurry.

[0105] (3) After the reaction is completed, filter the second mixed slurry in (2), wash it with deionized water for 5 times, then place the filter cake in a vacuum drying oven and dry it at 120℃ for 12 h.

[0106] (4) Place the product in (3) in a ceramic boat and transfer it to a tube furnace for high-temperature calcination, the calcination atmosphere is argon-hydrogen mixed gas (5% H2+95% Ar), the gas flow rate is 800 mL / min, the heating time is 160 min, the cooling time is 160 min, the holding stage temperature is 800℃, and the time is 3 h.

[0107] (5) When the calcination temperature in (4) reaches 800℃, switch the argon-hydrogen mixed gas atmosphere to pass through a humidification bottle at 40℃, and adjust the gas flow rate to 500 mL / min, the water vapor time is 15 min, then switch the gas path back to the argon-hydrogen mixed gas atmosphere, and adjust the gas flow rate back to 800 mL / min until the reaction is completed.

[0108] (6) Perform electrochemical testing on the hydrogen evolution catalyst in (5), when the current density is 10 mA / cm 2 , the overpotential of the catalyst is -250 mV.

[0109] Comparative Example 1

[0110] Commercially available nano tungsten (IV) carbide powder, 400 nm, CAS No.: 12070-12-1.

[0111] The overpotential diagram of the hydrogen evolution of Comparative Example 1 is shown in Figure 1 .

[0112] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0113] The nano tungsten carbide hydrogen evolution catalyst prepared by the technical scheme of the present application has good hydrogen evolution activity, especially the process conditions in Example 3 are all within the preferred range, and the overpotential of the prepared hydrogen evolution catalyst is as low as-208 mV, which is significantly improved compared with tungsten carbide nanoparticles (Comparative Example 1). Through Figure 2 It can be seen that the thickness of the carbon layer is about 10 nm, and a suitable carbon layer thickness is conducive to achieving better hydrogen evolution activity. The nano tungsten carbide catalyst provided by the present application has market prospects for replacing platinum-based catalysts and being applied to proton exchange membrane electrolysis cells.

[0114] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a nano-tungsten carbide hydrogen evolution catalyst, characterized in that, The preparation method includes the following steps: S1, a first mixed slurry of conductive carbon black, tungsten salt precursor and first solvent is prepared; S2, add a solution of self-polymerizable monomers to the first mixed slurry, and then perform solvothermal treatment to obtain a second mixed slurry; S3, the second mixed slurry is subjected to solid-liquid separation to obtain a solid material; S4, calcining and grinding the solid material to obtain the nano-tungsten carbide hydrogen evolution catalyst; The calcination process includes a heating stage, a holding stage, and a cooling stage performed sequentially; the heating stage and the cooling stage are carried out in a reducing atmosphere, and the holding stage is carried out in a mixed atmosphere of reducing atmosphere and water vapor. The temperature during the heat preservation stage is 600~1200℃; the self-polymerizable monomer is pyridine and / or pyrrole.

2. The preparation method according to claim 1, characterized in that, The temperature of the solvent heat treatment is 20~100℃; the time of the solvent heat treatment is 3~24h.

3. The preparation method according to claim 2, characterized in that, The temperature of the solvent heat treatment is 40~80℃; and / or the time of the solvent heat treatment is 6~12h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The volume concentration of the self-polymerizable polymer monomer in the second mixed slurry is 0.1~5 μL / mL.

5. The preparation method according to claim 4, characterized in that, The volume concentration of the self-polymerizable polymer monomer in the second mixed slurry is 1~2 μL / mL.

6. The preparation method according to any one of claims 1 to 3, characterized in that, The temperature during the heat preservation stage is 800~1000℃; the heat preservation stage lasts for 5~60 minutes.

7. The preparation method according to claim 6, characterized in that, The heat preservation stage lasts for 10 to 30 minutes.

8. The preparation method according to any one of claims 1 to 3, characterized in that, The gas flow rate of the mixed atmosphere of reducing atmosphere and water vapor during the heat preservation stage is 20~200 ml / min; And / or, the gas flow rate of the reducing atmosphere during the heating and cooling phases is 100~1000 ml / min.

9. The preparation method according to any one of claims 1 to 3, characterized in that, The volume ratio of water vapor to reducing atmosphere during the heat preservation stage is (0.5~9):

1.

10. The preparation method according to any one of claims 1 to 3, characterized in that, The mass concentration of the conductive carbon black in the first mixed slurry is 0.1-5%.

11. The preparation method according to claim 10, characterized in that, The mass concentration of the conductive carbon black in the first mixed slurry is 0.5~1.5%.

12. The preparation method according to any one of claims 1 to 3, characterized in that, The mass ratio of the tungsten salt precursor to the conductive carbon black is (8:1) to (1:8).

13. The preparation method according to claim 12, characterized in that, The mass ratio of the tungsten salt precursor to the conductive carbon black is (4:1) to (1:4).

14. The preparation method according to any one of claims 1 to 3, characterized in that, The tungsten salt precursor is one or more of phosphotungstic acid, ammonium phosphotungstic acid, and sodium phosphotungstic acid.

15. The preparation method according to any one of claims 1 to 3, characterized in that, The self-polymerizable polymer monomer is added to the first mixed slurry in a dropwise manner, and the dropwise addition rate is 0.2~2 ml / min.

16. The preparation method according to any one of claims 1 to 3, characterized in that, The reducing atmosphere is a mixture of a reducing gas and an inert gas; wherein the volume concentration of the reducing gas in the reducing atmosphere is 1-30%; and the reducing gas is one or more of carbon monoxide, hydrogen, and methane.

17. The preparation method according to any one of claims 1 to 3, characterized in that, The first solvent is water; and / or, the solvent in the solution of the self-polymerizable polymer monomer is water.

18. The preparation method according to any one of claims 1 to 3, characterized in that, The calcination process lasts for 1 to 6 hours; the heating phase lasts for 120 to 240 minutes; and the cooling phase lasts for 120 to 240 minutes.

19. The preparation method according to claim 18, characterized in that, The calcination process takes 2 to 4 hours.

20. The preparation method according to any one of claims 1 to 3, characterized in that, The solid-liquid separation method is vacuum filtration; the solid material obtained after vacuum filtration is washed with the first solvent; the washed solid material is dried at a temperature of 60~120℃ for 6~24h.

21. The preparation method according to any one of claims 1 to 3, characterized in that, The water vapor is introduced through a humidifier bottle, the temperature of which is room temperature to 80°C.

22. The preparation method according to claim 21, characterized in that, The temperature of the humidifier bottle is 30~60℃.

23. A nano-tungsten carbide hydrogen evolution catalyst, prepared by the method according to any one of claims 1 to 22.

24. The application of the nano-tungsten carbide hydrogen evolution catalyst according to claim 23 in catalytic proton exchange membrane electrolysis of water.

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