A Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material and its preparation method and application

Abstract

The present invention discloses a Ni3S2 / VN-C / C bifunctional electrocatalytic material and its preparation method and application. The preparation method comprises: taking a nickel source, a vanadium source and thioacetamide in proportion, mixing them uniformly, adding them to ethanol, stirring to dissolve them, and obtaining a mixed solution; transferring the mixed solution to a polytetrafluoroethylene liner of an autoclave; placing a pretreated C / C composite material; sealing the autoclave; and finally placing the autoclave in an electric blast drying oven, setting the temperature parameter to 100-170°C, and holding the temperature for 10-16 hours to carry out a solvent thermal reaction. V-Ni3S2-C / C is obtained; the V-Ni3S2-C / C is placed in a porcelain boat, the small porcelain boat is placed at one end of a large porcelain boat, a nitrogen source is placed at the other end to ensure that the molar ratio of the V source to the nitrogen source is 1:(4-6), the nitrogen source is placed at the air inlet end, and a tubular furnace is used to calcine for 1-4 hours under an argon atmosphere at a calcination temperature of 700-1200°C to obtain a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material; the material has good morphology, good electrocatalytic performance, is stable for a long time in a strong alkaline environment, and the preparation method is simple and the product morphology is controllable.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials and relates to electrocatalytic materials, and specifically relates to a Ni / Ni3S2 / VN-C / C dual-functional electrocatalytic material and a preparation method and application thereof. Background Art

[0002] Chemical water splitting to produce hydrogen is a sustainable energy conversion and storage technology that can meet energy needs and mitigate carbon emissions caused by excessive fossil fuel consumption. Water splitting involves two core processes: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Unfortunately, the OER and HER are plagued by sluggish kinetics, which require state-of-the-art electrocatalysts (e.g., Ru- or Ir-based for OER and Pt-based for HER) to promote them [H. Qi, P. Zhang, H. Wang, Y. Cui, X. Liu, X. She, Y. Wen, T. Zhan, Cu2Se nanowires shelled with NiFelayered double hydroxide nanosheets for overall water-splitting, J. ColloidInterface Sci. 599 (2021) 370–380]. However, the low Earth reserves, high cost, and poor long-term stability of noble metals significantly limit their large-scale application. Numerous efforts have been made to develop highly active and durable non-noble metal electrocatalysts for electrochemical water splitting. Reported electrocatalysts include transition metal sulfides, carbides, nitrides, and phosphides for HER electrocatalysis, and transition metal (hydride) oxides for OER electrocatalysis. Among them, Ni3S2, which has multiple valence states, strong chemical adsorption capacity for hydrogen, and metallic properties, is the best choice for OER and HER electrocatalysts [Z. Mamiyev, et al., Metal Sulde Photocatalysts for Hydrogen Generation: A Review of Recent Advances, Catalysts, 2022, 12, 1–36. 40]. However, its disadvantages such as low specific surface area and poor ion transport kinetics are relatively prominent, and the relatively insufficient stability of nickel sulfide has seriously hindered its further improvement.

[0003] Heterostructure engineering is an effective strategy to enhance catalytic activity by leveraging improved electron transfer capabilities and tuned electronic structures. The interfaces within heterostructures are considered to be the actual catalytic active sites. [ S. Tao, G.Zhang, B. Qian, J. Yang, S. Chu, C. Sun, D. Wu, W. Chu, L. Song, Appl. Catal.B: Environ. 2023, 330, 122600.

[12] Q. Wen, K. Yang, D. Huang, G. Cheng, X.Ai, Y. Liu, J. Fang, H. Li, L. Yu, T. Zhai, Adv. Energy Mater. 2021, 11,2102353] Designing heterostructures and combining two or more heterogeneous materials to achieve complementary advantages and improve structural properties is considered to be an effective method to improve catalytic activity [Z.Li,M.Hu,P.Wang,J.Liu,J.Yao,C.Li,Corrd. Chem. Rev. 2021, 439, 213953].

[0004] Existing heterostructured electrocatalysts still suffer from limitations such as limited stability, prone to poisoning and deactivation after prolonged use, and specific requirements for pH, temperature, or electrolyte concentration, limiting their application range. Notably, HER electrocatalysts perform well in acidic electrolytes, while OER electrocatalysts work better under alkaline conditions. The pH mismatch between OER and HER composite electrocatalysts inevitably leads to poor water splitting performance. Although HER and OER bifunctional electrocatalysts have been developed to simplify water splitting systems and reduce costs, they typically exhibit excellent HER activity but relatively poor OER catalytic activity, or vice versa [T. Zhan, X. Liu, S. Lu, W. Hou, Nitrogen doped NiFelayered double hydroxide / reduced graphene oxide mesoporous nanosphere as an effective bifunctional electrocatalyst for oxygen reduction and evolution reactions, Appl. Catal. B Environ. 205 (2017) 551–558]. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material with good morphology, good electrocatalytic performance, and long-term stability in a strong alkaline environment, as well as a preparation method and application thereof. The preparation method is simple and the product morphology is controllable.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material comprises the following steps:

[0008] Step 1: Take a nickel source and a vanadium source at a molar ratio of 0.5 to 3:1, and take thioacetamide at a molar ratio of 1:(1 to 2) to a sulfur source. Mix and grind the above raw materials until uniform, then add them to ethanol and stir on a magnetic stirrer to dissolve them to obtain a mixed solution.

[0009] Step 2: The mixed solution prepared in step 1 is transferred to the polytetrafluoroethylene liner of the autoclave, and the pretreated C / C composite material is placed to ensure that it is immersed in the mixed solution and sealed. Finally, the autoclave is placed in an electric blast drying oven, the temperature parameters are set to 100-170 ° C, and the holding time is 10-16 h for solvent thermal reaction. After the invention is completed, it is cooled to room temperature, taken out, washed, sealed and dried at room temperature to obtain V-Ni3S2-C / C;

[0010] Step 3: Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source at the other end to ensure that the molar ratio of the V source to the nitrogen source is 1:(4~6). Place the nitrogen source at the air inlet end, and use a tubular furnace to raise the temperature from room temperature to 700~1200℃ under argon atmosphere and calcine for 1~4 h to obtain Ni / Ni3S2 / VN-C / C.

[0011] The present invention also has the following technical features:

[0012] Preferably, the nickel source in step 1 includes any one of nickel dichloride, nickel acetylacetonate and nickel nitrate.

[0013] Preferably, the vanadium source in step 1 includes any one of vanadium trichloride, vanadium acetylacetonate and vanadium sulfate.

[0014] Preferably, the pretreatment method of the C / C composite material described in step 2 includes: ultrasonically cleaning the carbon / carbon matrix with ultrapure water and ethanol alternately for 10 minutes each time, repeated 3 times, and finally placing it in a culture dish and drying it in an electric blast drying oven at 50 ° C for 6 hours.

[0015] Preferably, the filling ratio of the polytetrafluoroethylene liner described in step 2 is 50%.

[0016] Preferably, the washing in step 2 is performed by alternately rinsing with ultrapure water and ethanol 3 to 5 times.

[0017] Preferably, the nitrogen source in step three comprises any one of urea, dicyandiamide and melamine.

[0018] Preferably, the heating rate of the tubular furnace during the calcination process in step 3 is 10° C. / min.

[0019] The present invention also protects a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material prepared by the method as described above and its use as an electrocatalyst for electrolysis of water to produce hydrogen, electrolysis of water to produce oxygen or full water splitting in a strong alkaline environment.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] The present invention uses a simple two-step method to grow uniformly distributed nanotubular Ni / Ni3S2 and nanoparticulate VN on a carbon / carbon substrate, resulting in a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material with multiple exposed active sites and a large specific surface area. The heterogeneous interface formed by Ni3S2 and VN can regulate the redistribution of charge to obtain the adsorption free energy of a suitable intermediate, thereby fastening ion transport and improving the catalytic rate. The use of a C / C self-supporting substrate not only provides more active sites, but also its excellent conductivity facilitates rapid electron transport on the catalyst surface, and its excellent mechanical stability ensures the stability of the catalyst during the reaction. At a current density of 100 in an alkaline solution, the material requires an overpotential of only 165 mV for electrocatalytic hydrogen evolution (HER), only 328 mV for electrocatalytic oxygen evolution (OER), and a voltage of 1.847 V for complete water splitting.

[0022] The present invention prepares a Ni3S2 and VN composite electrocatalyst on a carbon / carbon conductive matrix through hydrothermal and sintering methods, adopts an ammonia-free and nitrogen-free atmosphere, has a simple process, a controllable process, is green and safe, and has a good product morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD pattern of Ni / Ni3S2 / VN-C / C prepared in Example 1;

[0024] Figure 2 This is a SEM image of Ni / Ni3S2 / VN-C / C prepared in Example 1;

[0025] Figure 3The LSV curve of the electrocatalytic hydrogen evolution of Ni / Ni3S2 / VN-C / C prepared in Example 1 is shown;

[0026] Figure 4 The LSV curve of the electrocatalytic oxygen evolution of Ni / Ni3S2 / VN-C / C prepared in Example 1 is shown;

[0027] Figure 5 This is the LSV curve of the electrocatalytic water splitting of Ni / Ni3S2 / VN-C / C prepared in Example 1. DETAILED DESCRIPTION

[0028] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0029] Example 1:

[0030] Step 1: Weigh 206.15 mg of nickel dichloride hexahydrate (NiCl2·6H2O) and 125.84 mg of vanadium trichloride (VCl3), with the molar ratio of nickel to vanadium source being 1:1; weigh 60 mg of thioacetamide, with the molar ratio of nickel to sulfur source being 1:1; mix and grind the above raw materials, add them to 25 mL of ethanol, and stir on a magnetic stirrer for 30 minutes to dissolve them to obtain a mixed solution;

[0031] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 min each time, repeated 3 times, and finally placed in a culture dish and dried in an electric blast drying oven at 50 ° C for 6 h for use;

[0032] The mixed solution prepared in step 1 was transferred to a 50 mL polytetrafluoroethylene-lined autoclave, and a piece of treated C / C composite material was placed to ensure that it was immersed in the solution. The autoclave was sealed and the volume filling ratio was controlled at 50%. Finally, the autoclave was placed in an electric blast drying oven with the temperature parameters set to 120 ° C and the holding time set to 10 h. After the invention was completed and cooled to room temperature, the V-Ni3S2-C / C was removed and rinsed with ultrapure water and ethanol alternately three times, and then sealed and dried at room temperature.

[0033] Step 3: Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source, i.e., 334 mg of dicyandiamide, at the other end. The molar ratio of the V source to the nitrogen source is 1:5, and the nitrogen source is placed at the air inlet end. Use a tubular furnace to calcine for 2 h under an argon atmosphere at a calcination temperature of 800 °C and a heating rate of 10 °C / min to obtain a Ni / Ni3S2 / VN-C / C sample.

[0034] Figure 1The XRD pattern of Ni / Ni3S2 / VN-C / C prepared in Example 1 is as follows; Figure 1 As shown, the C peak at 26.3° is attributed to the matrix; the peaks at 44.5°, 51.8°, and 76.3° are attributed to the (111), (200), and (220) crystal planes of Ni (JCPDS Card No. 89-7128); the peaks at 21.76°, 31.101°, 37.795°, 44.349°, 50.112°, and 55.155° are attributed to the (1 0 0), (-1 1 0), (1 1 1), (2 0 0), (2 -1 0), and (2 -1 1) crystal planes of Ni3S2 (JCPDS Card No. 85-1802); the peaks at 37.7°, 43.8°, 63.7°, and 76.5° are attributed to the (JCPDS Card No. Card number 35-0768) (111), (200), (220) and (311) crystal planes.

[0035] Figure 2 The SEM photo of Ni / Ni3S2 / VN-C / C prepared in Example 1; Figure 2 It can be seen that nanotube-shaped Ni / Ni3S2 and nanogranular VN are grown on the carbon / carbon matrix, which are evenly distributed and have a large specific surface area.

[0036] In a standard three-electrode system, the electrocatalytic performance of Ni / Ni3S2 / VN-C / C was tested in 1 M KOH electrolyte solution. Figure 3 In order to evaluate the electrocatalytic hydrogen evolution performance of the prepared samples, the -1 Linear sweep voltammetry (LSV) tests required overpotentials of 165, 389, and 521 mV at current densities of 100, 500, and 1000, respectively. Figure 4 In order to evaluate the electrocatalytic oxygen evolution performance of the prepared samples, the electrocatalytic performance was evaluated at 5 mV·s -1 Linear sweep voltammetry (LSV) tests showed that electrocatalytic hydrogen evolution required overpotentials of 328, 435, and 543 mV at current densities of 100, 500, and 1000, respectively. Figure 5 As shown in the figure, similarly, in order to evaluate the electrocatalytic water splitting performance of the prepared samples, the -1 Linear sweep voltammetry (LSV) tests were performed, and complete water splitting required only a voltage of 1.847 V at a current density of 100.

[0037] Example 2

[0038] Step 1: Weigh 206.15 mg of nickel dichloride hexahydrate (NiCl2·6H2O), weigh 125.84 mg of vanadium trichloride (VCl3), and weigh 120 mg of thioacetamide to ensure that the molar ratio of nickel to sulfur source is 1:2; mix and grind the above raw materials, add them to 25 mL of ethanol, and stir on a magnetic stirrer for 30 minutes to dissolve them to obtain a mixed solution;

[0039] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 min each time, repeated 3 times, and finally placed in a culture dish and dried in an electric blast drying oven at 50 ° C for 6 h for use;

[0040] The mixed solution prepared in step 1 was transferred to a 50 mL polytetrafluoroethylene-lined autoclave, and a piece of treated C / C composite material was placed to ensure that it was immersed in the solution. The autoclave was sealed and the volume filling ratio was controlled at 50%. Finally, the autoclave was placed in an electric blast drying oven, the temperature parameters were set to 120 ° C, and the holding time was 10 h. After the invention was completed and cooled to room temperature, the V-Ni3S2-C / C was taken out, and it was rinsed with ultrapure water and ethanol alternately for 4 times, and then sealed and dried at room temperature.

[0041] Step 3: Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source, i.e., 334 mg of dicyandiamide, at the other end, ensuring a molar ratio of the V source to the nitrogen source of 1:5. Place the nitrogen source at the air inlet end and calcine in a tubular furnace under an argon atmosphere for 2 h at a calcination temperature of 800 °C and a heating rate of 10 °C / min to obtain a Ni / Ni3S2 / VN-C / C sample.

[0042] Example 3:

[0043] Step 1: Weigh 256.91 mg of nickel acetylacetonate (Ni(CH3COCHCOCH3)2), weigh 314.6 mg of vanadium trichloride (VCl3), ensure that the molar ratio of nickel to vanadium source is 1:2, weigh 112.5 mg of thioacetamide, ensure that the molar ratio of nickel to sulfur source is 2:3; mix and grind the above raw materials, add them to 25 mL of ethanol, stir on a magnetic stirrer for 30 minutes to dissolve them, and obtain a mixed solution;

[0044] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 min each time, repeated 3 times, and finally placed in a culture dish and dried in an electric blast drying oven at 50 ° C for 6 h for use;

[0045] The stirred solution was transferred to a 50 mL polytetrafluoroethylene-lined autoclave, and a piece of treated C / C composite material was placed to ensure that it was immersed in the solution. The autoclave was sealed tightly and the volume filling ratio was controlled at 50%. Finally, the autoclave was placed in an electric blast drying oven with the temperature parameters set to 140 ° C and the holding time set to 16 h. After the invention was completed and cooled to room temperature, the V-Ni3S2-C / C was removed and rinsed with ultrapure water and ethanol alternately for 5 times, and then sealed and air-dried at room temperature.

[0046] Step 3. Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source, i.e., 1513.4 mg of melamine, at the other end, ensuring that the molar ratio of the V source to the nitrogen source is 1:6. Place the nitrogen source at the air inlet end and calcine in a tubular furnace under an argon atmosphere for 2 h at a calcination temperature of 800 °C and a heating rate of 10 °C / min to obtain a Ni / Ni3S2 / VN-C / C sample.

[0047] Example 4:

[0048] Step 1: Weigh 290.79 mg of nickel nitrate, weigh 174.13 mg of vanadium acetylacetonate, ensure that the molar ratio of nickel to vanadium source is 2:1, weigh 112.5 mg of thioacetamide, ensure that the molar ratio of nickel to S source is 2:3; mix and grind the above raw materials evenly, add them to 25 mL of ethanol, stir on a magnetic stirrer for 30 minutes to dissolve them, and obtain a mixed solution;

[0049] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 min each time, repeated 3 times, and finally placed in a culture dish and dried in an electric blast drying oven at 50 ° C for 6 h for use;

[0050] The stirred solution was transferred to a 50 mL polytetrafluoroethylene-lined autoclave, and a piece of treated C / C composite material was placed to ensure that it was immersed in the solution. The autoclave was sealed and the volume filling ratio was controlled at 50%. Finally, the autoclave was placed in an electric blast drying oven with the temperature parameters set to 100 ° C and the holding time set to 15 h. After the invention was completed and cooled to room temperature, the V-Ni3S2-C / C was removed and rinsed with ultrapure water and ethanol alternately for 5 times, and then sealed and dried at room temperature;

[0051] Step 3: Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source, i.e., 120.1 mg of urea, at the other end, to ensure that the molar ratio of the V source to the nitrogen source is 1:4. Place the nitrogen source at the air inlet end and calcine in a tubular furnace under an argon atmosphere for 4 h at a calcination temperature of 700 °C and a heating rate of 10 °C / min to obtain a Ni / Ni3S2 / VN-C / C sample.

[0052] Example 5:

[0053] Step 1: Weigh 256.91 mg of nickel acetylacetonate (Ni(CH3COCHCOCH3)2), weigh 91 mg of vanadium sulfate (VSO4·7H2O), ensure that the molar ratio of nickel to vanadium source is 3:1, weigh 112.5 mg of thioacetamide, ensure that the molar ratio of nickel to sulfur source is 2:3; mix and grind the above raw materials, add them to 25 mL of ethanol, stir on a magnetic stirrer for 30 minutes to dissolve them, and obtain a mixed solution;

[0054] Step 2: Ultrapure water and ethanol were used to perform ultrasonic cleaning on the carbon / carbon substrate alternately for 10 min each time, repeated 3 times, and finally placed in a culture dish and dried in an electric blast drying oven at 50 ° C for 6 h for use;

[0055] The stirred solution was transferred to a 50 mL polytetrafluoroethylene-lined autoclave, and a piece of treated C / C composite material was placed to ensure that it was immersed in the solution. The autoclave was sealed tightly and the volume filling ratio was controlled at 50%. Finally, the autoclave was placed in an electric blast drying oven with the temperature parameters set to 170 ° C and the holding time set to 12 h. After the invention was completed and cooled to room temperature, the V-Ni3S2-C / C was removed and rinsed with ultrapure water and ethanol alternately for 5 times, and then sealed and dried at room temperature.

[0056] Step 3. Place the V-Ni3S2-C / C obtained in step 2 in a porcelain boat, place the small porcelain boat at one end of the large porcelain boat, and place a nitrogen source, i.e., 252.24 mg of melamine, at the other end, ensuring that the molar ratio of the V source to the nitrogen source is 1:6. Place the nitrogen source at the air inlet end and calcine in a tubular furnace under an argon atmosphere for 1 h at a calcination temperature of 1200 °C and a heating rate of 10 °C / min to obtain a Ni / Ni3S2 / VN-C / C sample.

[0057] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material, characterized in that: The following steps are involved: Step 1: Take a nickel source and a vanadium source at a molar ratio of 0.5 to 3:1, and take thioacetamide at a molar ratio of 1:(1 to 2) to a sulfur source. Mix and grind the above raw materials until uniform, then add them to ethanol and stir on a magnetic stirrer to dissolve them to obtain a mixed solution. Step 2: The mixed solution prepared in step 1 is transferred to the polytetrafluoroethylene liner of the autoclave, and the pretreated C / C composite material is placed to ensure that it is immersed in the mixed solution and sealed. Finally, the autoclave is placed in an electric blast drying oven, the temperature parameters are set to 100-170 ° C, and the holding time is 10-16 h for solvent thermal reaction. After the invention is completed, it is cooled to room temperature, taken out, washed, sealed and dried at room temperature to obtain V-Ni3S2-C / C; Step 3: Place the V-Ni3S2-C / C obtained in step 2 in a small porcelain boat, place the small porcelain boat at one end of a large porcelain boat, and place a nitrogen source at the other end to ensure that the molar ratio of the vanadium source to the nitrogen source is 1:(4-6). Place the nitrogen source at the air inlet end, and use a tubular furnace to heat from room temperature to 700-1200 ° C under an argon atmosphere and calcine for 1-4 h to obtain Ni / Ni3S2 / VN-C / C; The nitrogen source in step three includes any one of urea, dicyandiamide and melamine.

2. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The nickel source described in step 1 includes any one of nickel dichloride, nickel acetylacetonate and nickel nitrate.

3. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The vanadium source in step 1 includes any one of vanadium trichloride, vanadium acetylacetonate and vanadium sulfate.

4. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The pretreatment method of the C / C composite material described in step 2 includes: ultrasonic cleaning the carbon / carbon matrix with ultrapure water and ethanol alternately for 10 minutes each time, repeated 3 times, and finally placing it in a culture dish and drying it in an electric blast drying oven at 50 ° C for 6 hours.

5. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The filling ratio of the polytetrafluoroethylene liner described in step 2 is 50%.

6. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The washing described in step 2 is to rinse alternately with ultrapure water and ethanol 3 to 5 times.

7. The method for preparing the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material according to claim 1, wherein: The heating rate of the tubular furnace during the calcination process described in step 3 is 10°C / min.

8. A Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material prepared by the method according to any one of claims 1 to 7.

9. Use of the Ni / Ni3S2 / VN-C / C bifunctional electrocatalytic material as claimed in claim 8 as an electrocatalyst for hydrogen production, oxygen production or complete water splitting in a strong alkaline environment.

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