Preparation method and application of n atom doped carbon-molybdenum-cobalt composite material

Abstract

The application discloses a preparation method of N atom doped carbon molybdenum cobalt composite material and application thereof. Co(NO3)2.6H2O and citric acid are fully dissolved in deionized water, then sodium molybdate crystals are added and stirred uniformly to obtain solution A; the obtained solution A is poured into a hydrothermal kettle for hydrothermal reaction; after reaction, standing is carried out at room temperature, then suction filtration, washing and vacuum drying are sequentially carried out to obtain cobalt molybdate CoMoO4; the obtained CoMoO4 and dicyandiamide are mixed and ground, then are placed in a quartz boat A; additionally, dicyandiamide is weighed, ground and placed in a quartz boat B; the quartz boat A and the quartz boat B are placed in a tube furnace, annealing treatment is carried out under an argon atmosphere, and grinding is carried out after the treatment to obtain a product N atom doped carbon molybdenum cobalt composite material. The N-Mo6Co6C / C composite material prepared by using the application has the advantages of simple preparation method and remarkable hydrogen evolution effect of the obtained N-Mo6Co6C / C composite material in an alkaline medium.

Description

I. Technical Field:

[0001] This invention relates to the field of hydrogen energy technology, and in particular to a method for preparing an N-doped carbon-molybdenum-cobalt composite material and its application. II. Background Technology:

[0002] Electrolysis of water for hydrogen production offers advantages such as high efficiency and zero pollution, but it suffers from the problem of excessively high hydrogen evolution overpotential, consuming a significant amount of electrical energy. Platinum is currently the most active hydrogen evolution catalyst, but its high price limits its large-scale application. Therefore, there is an urgent need to develop transition metal hydrogen evolution catalysts with low hydrogen evolution overpotential, low catalyst cost, and good stability to reduce costs.

[0003] Transition metal compounds such as sulfides, carbides, nitrides, and phosphides have attracted widespread attention due to their potential to replace noble metal catalysts. Among them, molybdenum carbide, due to its platinum-like d-band electronic structure, exhibits platinum-like performance in electrocatalysis. However, when exposed molybdenum atoms serve as hydrogen evolution active sites, excessive adsorption of H* makes hydrogen desorption difficult, thus affecting the catalyst's hydrogen evolution activity. Furthermore, excessive calcination during annealing can lead to sintering of molybdenum carbide, resulting in the loss of active sites.

[0004] In recent years, research by technicians has revealed that the combination of Mo₂C with Fe, Co, and Ni can effectively reduce the electron density of the unoccupied d-band of Mo and decrease the excessive hydrogen binding energy of Mo₂C. Meanwhile, the cobalt center is widely considered an excellent active site for hydrolysis. Furthermore, N atom doping can be used to adjust the catalyst structure and increase the number of active sites, thereby improving catalyst performance. III. Summary of the Invention:

[0005] The technical problem this invention aims to solve is to address the shortcomings of current hydrogen evolution catalyst preparation processes by providing a two-step method for preparing high-performance hydrogen evolution catalysts and its application. Specifically, this invention provides a method for preparing N-doped carbon-molybdenum-cobalt composite materials and their application in electrocatalytic hydrogen evolution. This invention enables the preparation of high-performance hydrogen evolution catalysts through simple operations. The equipment used in the overall preparation process is simple and readily available, and the operation is straightforward.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing a carbon-molybdenum-cobalt composite material doped with nitrogen atoms, the method comprising the following steps:

[0008] a. Dissolve cobalt nitrate hexahydrate Co(NO3)2·6H2O and citric acid CA in deionized water. After complete dissolution, add sodium molybdate crystals Na2MoO4·2H2O and stir until homogeneous to obtain solution A.

[0009] b. Pour the obtained solution A into a hydrothermal reactor and react it using a hydrothermal method. The reaction temperature is 180-240℃ and the reaction time is 5-13h. After the reaction, cool it to room temperature and let it stand. Then, filter, wash and vacuum dry it in sequence to obtain cobalt molybdate CoMoO4.

[0010] c. Mix and grind the CoMoO4 and dicyandiamide obtained in step b, and place them in quartz boat A. Separately weigh the same amount of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace and anneal them under an argon atmosphere. After annealing, grind them to obtain the N-atom-doped carbon-molybdenum-cobalt composite material, i.e., N-Mo6Co6C / C composite material.

[0011] According to the above-described method for preparing N-doped carbon-molybdenum-cobalt composite material, in step a, the molar ratio of Co(NO3)2·6H2O to CA is 1:0–10; the molar ratio of Co(NO3)2·6H2O to Na2MoO4·2H2O is 1:0.5–5; and the ratio of Co(NO3)2·6H2O to deionized water is 1 mol:10–30 L (the stirring time during the dissolution and stirring processes is 10–100 min).

[0012] According to the above-mentioned method for preparing N-atom-doped carbon-molybdenum-cobalt composite materials, the specific process of cooling to room temperature in step b is as follows: after the hydrothermal reaction, 30-60 minutes later, the reaction product is taken out and cooled at room temperature of 0-20°C.

[0013] According to the above-described method for preparing N-doped carbon-molybdenum-cobalt composite materials, the settling time in step b is 20–30 h.

[0014] According to the above-described method for preparing N-doped carbon-molybdenum-cobalt composite materials, the washing in step b involves sequential washing with deionized water and anhydrous ethanol; the vacuum drying process involves a vacuum degree of -0.07 MPa, a drying temperature of 60–80 °C, and a drying time of 6–10 h.

[0015] According to the above-described method for preparing N-atom-doped carbon-molybdenum-cobalt composite materials, in step c, the mass ratio of CoMoO4 and dicyandiamide added during the mixing and grinding process is 1:5 to 30; the mass of dicyandiamide used in quartz boat A and quartz boat B is equal; and the distance between quartz boat A and quartz boat B is 5 to 20 cm.

[0016] According to the above-mentioned method for preparing N-atom-doped carbon-molybdenum-cobalt composite material, during the annealing treatment in step c, the first stage temperature is 300-500℃ and the holding time is 30-80 min, and the second stage temperature is 700-1000℃ and the holding time is 0.5-5 h.

[0017] In addition, an application of the N-doped carbon-molybdenum-cobalt composite material prepared above in electrocatalytic hydrogen evolution is provided.

[0018] In the technical solution of this invention, Na2MoO4·2H2O is used as the molybdenum source, Co(NO3)2·6H2O is used as the cobalt source, and citric acid is used as the structure directing agent; alternatively, (NH4)6Mo7O can also be used. 24 ·4H2O, MoCl5 or H2MoO4 were used as the molybdenum source, and CoCl2·6H2O or CoC2O4·2H2O were used as the cobalt source; ethylenediaminetetraacetic acid, pyromellitic acid or butanetetracarboxylic acid were used as the structure directing agent.

[0019] The positive and beneficial effects of this invention are:

[0020] 1. In the N-Mo6Co6C / C composite material prepared by this invention, Mo and Co atoms are connected by Co-Mo bonds, which effectively reduces the electron density of the unoccupied d orbitals of Mo, thereby reducing the excessively high hydrogen binding energy of Mo2C. Ultimately, the prepared N-Mo6Co6C / C composite material exhibits better catalytic activity, and the N-doped graphite substrate also significantly improves the hydrogen evolution activity of the catalyst.

[0021] 2. The precursor CoMoO4 of the N-Mo6Co6C / C composite material prepared in this invention is composed of nanorods of varying sizes stacked together, and has a large number of semi-circular pores on its surface. After simultaneous nitrogen doping and high-temperature carbonization, a large number of small spheres grow on its surface. This special structure can effectively expose active sites and provide sufficient electrochemical active area, thereby significantly improving the electrocatalytic activity of the prepared composite material.

[0022] 3. The N-Mo6Co6C / C composite material prepared using the technical solution of this invention has a simple preparation method; the obtained N-Mo6Co6C / C composite material exhibits good hydrogen evolution performance in alkaline media at a current density of 10 mA cm⁻¹. -2 At this time, the basic hydrogen evolution potential of N-Mo6Co6C / C is as low as -10mV, and the Tafel slope is 80mV dec. -1 At a current density of 400 mA cm⁻¹ -2 At this point, the alkaline hydrogen evolution potential is -272 mV. After 2000 CV cycles, the catalyst still exhibits high catalytic activity. IV. Description of the attached drawings:

[0023] Figure 1 XRD image of the N-Mo6Co6C / C composite material prepared in Example 1 of this invention;

[0024] Figure 1 In the diagram, the horizontal axis represents 2Theta, and the vertical axis represents the diffraction intensity; from Figure 1 It can be seen that the material is basically compared with Mo6Co6C (PDF#03-065-8115C (PDF#97-008-8818) on the standard card, indicating that the material is Mo6Co6C supported on carbon material.

[0025] Figure 2 Raman image of the N-Mo6Co6C / C composite material prepared in Example 1 of this invention;

[0026] Depend on Figure 2 It can be seen that at 1341cm -1 1571cm -1 and 2682cm -1 Nearby, D peaks, G peaks, and 2D peaks, characteristic of graphene, appeared respectively; by calculating I... D / I G =0.77, which proves that the loaded C in the N-Mo6Co6C / C composite material is graphite carbon material, which helps to improve the hydrogen evolution performance.

[0027] Figure 3 SEM image of CoMoO4 prepared in Example 1 of this invention;

[0028] Depend on Figure 3 It is known that CoMoO4 is composed of nanorods with a certain orientation. When these nanorods are assembled into a blocky material of a certain size, the varying sizes, misaligned arrangement, and surface pits of the nanorods provide a large number of possible defects.

[0029] Figure 4 SEM image of the N-Mo6Co6C / C composite material prepared in Example 1 of this invention;

[0030] Depend on Figure 4 It is known that N-Mo6Co6C / C generates a large number of particles on the surface based on the CoMoO4 structure, which significantly increases the electrochemical surface area of ​​the composite material and promotes the penetration of electrolyte and the exposure of active sites.

[0031] Figure 5 Linear sweep voltammetric curves of CoMoO4 and N-Mo6Co6C / C prepared in Example 1 of this invention in 1 mol KOH solution;

[0032] Depend on Figure 5 It can be seen that at a current density of 10 mA cm⁻¹ -2 At this time, the basic hydrogen evolution potential of CoMoO4 is -374 mV, while the basic hydrogen evolution potential of N-Mo6Co6C / C is as low as -10 mV, at a current density of 400 mA cm⁻¹. -2 At this point, the alkaline hydrogen evolution potential is -272 mV. After 2000 CV cycles, the catalyst still exhibits high catalytic activity.

[0033] Figure 6 Tafel curve of N-Mo6Co6C / C prepared in Example 1 of this invention in 1 mol KOH solution;

[0034] Depend on Figure 6 It can be seen that the Tafel slope of N-Mo6Co6C / C is 80 mV dec. -1 .

[0035] Figure 7 Cyclic voltammetry curves of N-Mo6Co6C / C prepared in Example 1 of this invention in 1 mol KOH solution.

[0036] Depend on Figure 7 It can be seen that N-Mo6Co6C / C has a large electrochemically active surface area. V. Detailed Implementation Methods:

[0037] The present invention will be further illustrated below with reference to the embodiments, but this does not limit the scope of protection of the technical solution of the present invention.

[0038] Example 1:

[0039] The detailed steps of the method for preparing the N-doped carbon-molybdenum-cobalt composite material of the present invention are as follows:

[0040] a. Dissolve 0.002 mol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.004 mol of citric acid CA in 50 mL of deionized water and stir for 20 min to fully dissolve. Then add 0.002 mol of sodium molybdate crystals Na2MoO4·2H2O and stir for 30 min. After stirring evenly, solution A is obtained.

[0041] b. The obtained solution A was poured into a stainless steel autoclave lined with PTFE for hydrothermal reaction at a temperature of 200℃ for 10 hours. After the reaction, the temperature was lowered to room temperature and allowed to stand for 24 hours. The precipitate was then collected by filtration. The precipitate was washed with deionized water and anhydrous ethanol in sequence. After washing, it was vacuum dried (vacuum degree of -0.07MPa, drying temperature of 60℃, drying time of 6 hours) to obtain cobalt molybdate CoMoO4.

[0042] c. Weigh 20 mg of CoMoO4 obtained in step b and 220 mg of dicyandiamide, mix and grind them, and place them in quartz boat A. Separately weigh 220 mg of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace (the distance between quartz boat A and quartz boat B is 12 cm) and perform annealing treatment under an argon atmosphere. During annealing treatment, the temperature is increased to 500℃ at a heating rate of 2℃ / min and held for 1 h, then increased to 800℃ at a heating rate of 5℃ / min and held for 1 h. After treatment, grind the product N-Mo6Co6C / C composite material.

[0043] Example 2:

[0044] The detailed steps of the method for preparing the N-doped carbon-molybdenum-cobalt composite material of the present invention are as follows:

[0045] a. Dissolve 0.002 mol of cobalt nitrate hexahydrate Co(NO3)2·6H2O in 50 mL of deionized water and stir for 20 min to dissolve completely. Then add 0.002 mol of sodium molybdate crystals Na2MoO4·2H2O and stir for 30 min. After stirring evenly, solution A is obtained.

[0046] b. The obtained solution A was poured into a stainless steel autoclave lined with PTFE for hydrothermal reaction at a temperature of 200℃ for 10 hours. After the reaction, the temperature was lowered to room temperature and allowed to stand for 24 hours. The precipitate was then collected by filtration. The precipitate was washed with deionized water and anhydrous ethanol in sequence. After washing, it was vacuum dried (vacuum degree of -0.07MPa, drying temperature of 60℃, drying time of 6 hours) to obtain cobalt molybdate CoMoO4.

[0047] c. Weigh 20 mg of CoMoO4 obtained in step b and 220 mg of dicyandiamide, mix and grind them, and place them in quartz boat A. Separately weigh 220 mg of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace (the distance between quartz boat A and quartz boat B is 15 cm) and perform annealing treatment under an argon atmosphere. During annealing treatment, the temperature is increased to 500℃ at a heating rate of 2℃ / min and held for 1 h, then increased to 800℃ at a heating rate of 5℃ / min and held for 1 h. After treatment, grind the product N-Mo6Co6C / C composite material.

[0048] Example 3:

[0049] The detailed steps of the method for preparing the N-doped carbon-molybdenum-cobalt composite material of the present invention are as follows:

[0050] a. Dissolve 0.002 mol cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.012 mol citric acid CA in 50 mL of deionized water and stir for 20 min to fully dissolve. Then add 0.002 mol sodium molybdate crystals Na2MoO4·2H2O and stir for 30 min. After stirring evenly, solution A is obtained.

[0051] b. The obtained solution A was poured into a stainless steel autoclave lined with PTFE for hydrothermal reaction at a temperature of 200℃ for 10 hours. After the reaction, the temperature was lowered to room temperature and allowed to stand for 24 hours. The precipitate was then collected by filtration. The precipitate was washed with deionized water and anhydrous ethanol in sequence. After washing, it was vacuum dried (vacuum degree of -0.07MPa, drying temperature of 60℃, drying time of 6 hours) to obtain cobalt molybdate CoMoO4.

[0052] c. Weigh 20 mg of CoMoO4 obtained in step b and 220 mg of dicyandiamide, mix and grind them, and place them in quartz boat A. Separately weigh 220 mg of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace (the distance between quartz boat A and quartz boat B is 10 cm) and perform annealing treatment under an argon atmosphere. During annealing treatment, the temperature is increased to 500℃ at a heating rate of 2℃ / min and held for 1 h, then increased to 800℃ at a heating rate of 5℃ / min and held for 3 h. After treatment, grind the product N-Mo6Co6C / C composite material.

[0053] Example 4:

[0054] The detailed steps of the method for preparing the N-doped carbon-molybdenum-cobalt composite material of the present invention are as follows:

[0055] a. Dissolve 0.002 mol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.004 mol of citric acid CA in 50 mL of deionized water and stir for 20 min to fully dissolve. Then add 0.001 mol of sodium molybdate crystals Na2MoO4·2H2O and stir for 30 min. After stirring evenly, solution A is obtained.

[0056] b. The obtained solution A was poured into a stainless steel autoclave lined with PTFE for hydrothermal reaction at a temperature of 220℃ for 10 hours. After the reaction, the temperature was lowered to room temperature and allowed to stand for 24 hours. The precipitate was then collected by filtration. The precipitate was washed with deionized water and anhydrous ethanol in sequence. After washing, it was vacuum dried (vacuum degree of -0.07MPa, drying temperature of 60℃, drying time of 6 hours) to obtain cobalt molybdate CoMoO4.

[0057] c. Weigh 20 mg of CoMoO4 obtained in step b and 220 mg of dicyandiamide, mix and grind them, and place them in quartz boat A. Separately weigh 220 mg of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace (the distance between quartz boat A and quartz boat B is 16 cm) and perform annealing treatment under an argon atmosphere. During annealing treatment, the temperature is increased to 500℃ at a heating rate of 2℃ / min and held for 1 h, then increased to 800℃ at a heating rate of 5℃ / min and held for 1 h. After treatment, grind the mixture to obtain the product N-Mo6Co6C / C composite material.

[0058] Example 5:

[0059] The detailed steps of the method for preparing the N-doped carbon-molybdenum-cobalt composite material of the present invention are as follows:

[0060] a. Dissolve 0.002 mol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.004 mol of citric acid CA in 50 mL of deionized water and stir for 20 min to fully dissolve. Then add 0.002 mol of sodium molybdate crystals Na2MoO4·2H2O and stir for 30 min. After stirring evenly, solution A is obtained.

[0061] b. The obtained solution A was poured into a stainless steel autoclave lined with PTFE for hydrothermal reaction at a temperature of 200℃ for 8 hours. After the reaction, the temperature was lowered to room temperature and allowed to stand for 24 hours. The precipitate was then collected by filtration. The precipitate was washed with deionized water and anhydrous ethanol in sequence. After washing, it was vacuum dried (vacuum degree of -0.07MPa, drying temperature of 60℃, drying time of 8 hours) to obtain cobalt molybdate CoMoO4.

[0062] c. Weigh 20 mg of CoMoO4 obtained in step b and 200 mg of dicyandiamide, mix and grind them, and place them in quartz boat A. Separately weigh 200 mg of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace (the distance between quartz boat A and quartz boat B is 8 cm) and perform annealing treatment under an argon atmosphere. During annealing treatment, the temperature is increased to 500℃ at a heating rate of 2℃ / min and held for 1 h, then increased to 800℃ at a heating rate of 5℃ / min and held for 5 h. After treatment, grind the mixture to obtain the product N-Mo6Co6C / C composite material.

[0063] Examples of applications of the N-Mo6Co6C / C composite material prepared according to the present invention in electrocatalytic hydrogen evolution.

[0064] Application Example 1:

[0065] Performance testing of the N-Mo6Co6C / C composite material prepared in Example 1 of this invention in alkaline solution:

[0066] (1) The performance of the N-Mo6Co6C / C composite material prepared in Example 1 in alkaline solution was tested using a three-electrode system, which mainly included a working electrode, a reference electrode, and a counter electrode. The working electrode and counter electrode formed a complete circuit loop, and the reference electrode served as the standard for measuring and applying the working electrode. A glassy carbon electrode (3 mm in diameter) with the sample material dropped on it was used as the working electrode. A mercury / mercury oxide electrode (Hg / HgO) was used as the reference electrode, and a platinum sheet electrode was used as the counter electrode. The test was compared at the standard reversible hydrogen electrode voltage (RHE). Therefore, the voltage in the test needed to be converted, and the conversion formula is:

[0067] E (VS.RHE) =E (VS.Hg / HgO) +0.0592×pH+E θ Hg / HgO V

[0068] Where E θ Hg / HgO The value is 0.098V, the pH of 1M KOH is 14, and E (VS.RHE) The voltage of the reversible hydrogen electrode.

[0069] (2) Preparation of the working electrode:

[0070] The working electrode was polished to a mirror finish using alumina polishing powder, ultrasonically washed several times with deionized water and anhydrous ethanol, and then dried at 60°C. 5 mg of the composite material (catalyst) prepared in Example 1 of this invention was dispersed in a mixed solution of 990 μL anhydrous ethanol and 10 μL 5 wt% Nafion, and ultrasonicated for 2 h to form a uniform ink. Then, 12 μL of the ink was dropped into a container with a geometric area of ​​0.0707 cm². -2 On a glassy carbon electrode (GCE) (catalyst loading ≈ 0.84 mg cm⁻¹) -2 Dry and set aside for later use.

[0071] (3) Performance testing of composite materials in alkaline solutions:

[0072] At a current density of 10 mA cm -2 The basic hydrogen evolution potential of N-Mo6Co6C / C is as low as -10mV.

[0073] For detailed spectral analysis of the intermediate and final products obtained in Example 1, please refer to the appendix. Figure 1-7 .

[0074] Application Example 2:

[0075] Performance testing of the N-Mo6Co6C / C composite material prepared in Example 2 of this invention in alkaline solution:

[0076] (1) The performance of the N-Mo6Co6C / C composite material prepared in Example 2 was tested in alkaline solution using a three-electrode system.

[0077] (2) Preparation of the working electrode:

[0078] 5 mg of the composite material (catalyst) prepared in Example 2 of this invention was dispersed in a mixed solution of 990 μL anhydrous ethanol and 10 μL 5 wt% Nafion, and sonicated for 2 h to form a uniform ink; then, 12 μL of the ink was dropped onto a surface with a geometric area of ​​0.0707 cm². -2 The glassy carbon electrode (GCE) is dried and ready for use.

[0079] (3) Performance testing of composite materials in alkaline solutions:

[0080] At a current density of 10 mA cm -2 The basic hydrogen evolution potential of N-Mo6Co6C / C is -45mV.

[0081] Application Example 3:

[0082] Performance testing of the N-Mo6Co6C / C composite material prepared in Example 3 of this invention in alkaline solution:

[0083] (1) The performance of the N-Mo6Co6C / C composite material prepared in Example 3 was tested in alkaline solution using a three-electrode system.

[0084] (2) Preparation of the working electrode:

[0085] 5 mg of the composite material (catalyst) prepared in Example 3 of this invention was dispersed in a mixed solution of 990 μL anhydrous ethanol and 10 μL 5 wt% Nafion, and sonicated for 2 h to form a uniform ink; then, 12 μL of the ink was dropped onto a surface with a geometric area of ​​0.0707 cm². -2 The glassy carbon electrode (GCE) is dried and ready for use.

[0086] (3) Performance testing of composite materials in alkaline solutions:

[0087] At a current density of 10 mA cm -2 The alkaline hydrogen evolution potential of N-Mo6Co6C / C is -194mV.

[0088] Application Example 4:

[0089] Performance testing of the N-Mo6Co6C / C composite material prepared in Example 4 of this invention in alkaline solution:

[0090] (1) The performance of the N-Mo6Co6C / C composite material prepared in Example 4 was tested in alkaline solution using a three-electrode system.

[0091] (2) Preparation of the working electrode:

[0092] 5 mg of the composite material (catalyst) prepared in Example 4 of this invention was dispersed in a mixed solution of 990 μL anhydrous ethanol and 10 μL 5 wt% Nafion, and sonicated for 2 h to form a uniform ink; then, 12 μL of the ink was dropped onto a surface with a geometric area of ​​0.0707 cm². -2 The glassy carbon electrode (GCE) is dried and ready for use.

[0093] (3) Performance testing of composite materials in alkaline solutions:

[0094] At a current density of 10 mA cm -2 The alkaline hydrogen evolution potential of N-Mo6Co6C / C is -101mV.

[0095] Application Example 5:

[0096] Performance testing of the N-Mo6Co6C / C composite material prepared in Example 5 of this invention in alkaline solution:

[0097] (1) The performance of the N-Mo6Co6C / C composite material prepared in Example 5 was tested in alkaline solution using a three-electrode system.

[0098] (2) Preparation of the working electrode:

[0099] 5 mg of the composite material (catalyst) prepared in Example 5 of this invention was dispersed in a mixed solution of 990 μL anhydrous ethanol and 10 μL 5 wt% Nafion, and sonicated for 2 h to form a uniform ink; then, 12 μL of the ink was dropped onto a surface with a geometric area of ​​0.0707 cm². -2 The glassy carbon electrode (GCE) is dried and ready for use.

[0100] (3) Performance testing of composite materials in alkaline solutions:

[0101] At a current density of 10 mA cm -2 The alkaline hydrogen evolution potential of N-Mo6Co6C / C is -261mV.

Claims

1. A method for preparing a nitrogen-doped carbon-molybdenum-cobalt composite material, characterized in that, The preparation method includes the following steps: a. Dissolve cobalt nitrate hexahydrate Co(NO3)2·6H2O and citric acid CA in deionized water. After complete dissolution, add sodium molybdate crystals Na2MoO4·2H2O and stir until homogeneous to obtain solution A. b. Pour the obtained solution A into a hydrothermal reactor and react it using a hydrothermal method. The reaction temperature is 180-240℃ and the reaction time is 5-13h. After the reaction, cool it to room temperature and let it stand. Then, filter, wash and vacuum dry it in sequence to obtain cobalt molybdate CoMoO4. c. Mix and grind the CoMoO4 and dicyandiamide obtained in step b, and place them in quartz boat A. Separately weigh the same amount of dicyandiamide, grind it, and place it in quartz boat B. Place quartz boat A and quartz boat B in a tube furnace and anneal them under an argon atmosphere. After annealing, grind them to obtain the N-atom-doped carbon-molybdenum-cobalt composite material, i.e., N-Mo6Co6C / C composite material.

2. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that: In step a, the molar ratio between Co(NO3)2·6H2O and CA is 1:0 to 10; the molar ratio between Co(NO3)2·6H2O and Na2MoO4·2H2O is 1:0.5 to 5; and the ratio between Co(NO3)2·6H2O and deionized water is 1 mol:10 to 30 L.

3. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that, The specific process of cooling to room temperature in step b is as follows: 30 to 60 minutes after the hydrothermal reaction, the reaction product is taken out and cooled at room temperature of 0 to 20°C.

4. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that: The settling time mentioned in step b is 20 to 30 hours.

5. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that: The washing in step b is performed sequentially with deionized water and anhydrous ethanol; the vacuum drying is performed at a vacuum degree of -0.07 MPa, a drying temperature of 60-80°C, and a drying time of 6-10 h.

6. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that: In step c, the mass ratio of CoMoO4 and dicyandiamide added during the grinding process is 1:5 to 30; the mass of dicyandiamide used in quartz boat A and quartz boat B is equal; and the distance between quartz boat A and quartz boat B is 5 to 20 cm.

7. The method for preparing the N-doped carbon-molybdenum-cobalt composite material according to claim 1, characterized in that: During the annealing process described in step c, the first stage temperature is 300–500℃ and the holding time is 30–80 min, while the second stage temperature is 700–1000℃ and the holding time is 0.5–5 h.

8. The application of the N-doped carbon-molybdenum-cobalt composite material prepared according to claim 1 in electrocatalytic hydrogen evolution.

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