Ohmic contact-based heterostructure catalyst and preparation method and application thereof

Abstract

The invention discloses an ohmic contact base heterostructure catalyst as well as a preparation method and application thereof, relates to a heterostructure catalyst as well as a preparation method and application thereof, and aims to solve the technical problems of low catalytic activity and poor stability of an existing water electrolysis catalyst in high current density. The catalyst is an ohmic contact base heterostructure catalyst composed of self-supported metal nickel nanoparticles and nickel molybdate nanowires, and is marked as Ni / Ni2Mo3O8 / CC. The preparation method comprises the following steps: placing electrically treated carbon cloth in an ammonium molybdate and N, N-dimethylformamide solution for solvothermal reaction to obtain a self-supporting molybdenum-molybdenum nanowire precursor; the precursor is placed in a nickel acetate solution for a weak base etching reaction, and NiMoO4-coated Ni (OH) 2 is obtained; and then carrying out carbonization treatment on the Ohmic contact base heterostructure catalyst and dicyandiamide to obtain the Ohmic contact base heterostructure catalyst. The catalyst can be used as a cathode and / or an anode in electrolytic water hydrogen production under high current density in an alkaline electrolyte.

Description

Technical Field

[0001] The present invention relates to a heterostructure catalyst and its preparation method and application, belonging to the technical field of hydrogen production. Background Art

[0002] With the global energy structure transformation towards cleaner energy, hydrogen energy has become an ideal energy carrier due to its high energy density, zero carbon emissions, and storability. As a key approach for green hydrogen production, water electrolysis technology has received extensive attention globally in recent years. However, water electrolysis technology still faces many challenges, such as high energy consumption during the electrolysis process, especially the slow kinetics of the oxygen evolution reaction (OER), resulting in a working voltage generally in the range of 1.8 - 2.2 V, which significantly increases the operating cost. To break through these bottlenecks, recent research has focused on developing non-precious metal catalysts and improving the catalytic activity and stability of catalysts through various optimization strategies.

[0003] In recent years, binary transition metal oxides (such as NiCo2O4, CoMn2O4, and NiMoO4) have been widely studied in the field of water splitting due to their advantages of high natural abundance, low cost, and environmental friendliness. However, the catalytic performance of pristine binary transition metal oxides for the hydrogen evolution reaction (HER) is generally poor, which is mainly attributed to the poor regulation of the Gibbs free energy (ΔG) of reaction intermediates and their low intrinsic conductivity. To improve the performance of such electrocatalysts, researchers generally adopt strategies such as defect construction, morphology design, and heterostructure engineering. Among them, coupling two components with different catalytic activities for HER and OER is a common method to improve the overall water splitting performance. Based on this advantage, composite catalysts with excellent electrochemical performance, such as CoO@CoP nanowire arrays and (Ni-Fe)S x / NiFe(OH)2 hollow microtube / sphere thin films, have been successfully prepared. However, if the two components are simply combined without interfacial electron interaction, the improvement of their activity is often limited. Therefore, in recent years, researchers have developed a heterostructure engineering strategy to regulate the surface electronic structure by constructing a well-defined heterointerface. So far, a variety of heterointerfacial electrocatalysts have been designed, including NiPS3 / Ni2P heterojunctions, MoO3 / Ni-NiO nanohybrids, NiO / Co3O4 heterointerfaces, and Co / CoP Janus nanoparticles. These catalysts exhibit excellent bifunctional catalytic performance for water splitting due to the strong electron interaction induced by charge transfer between components. However, most current heterojunction catalysts still exist in powder form and need to be loaded on a conductive substrate with the help of binders such as Nafion during the electrode preparation process. The use of binders not only covers the active sites but also increases the interfacial resistance, thus reducing the catalytic efficiency, especially with low catalytic activity and poor stability at high current densities. Background Art

[0005] The present invention aims to solve the technical problems of low catalytic activity and poor stability of existing electrolyzed water catalysts at high current densities, and provides an ohmic contact-based heterostructure catalyst, a preparation method thereof, and an application thereof.

[0006] The ohmic contact-based heterostructure catalyst of the present invention is an ohmic contact-based heterostructure catalyst composed of self-supporting nickel nanoparticles and nickel molybdate nanowires, denoted as Ni / Ni2Mo3O8 / CC.

[0007] The preparation method of the above-mentioned ohmic contact-based heterostructure catalyst is carried out according to the following steps:

[0008] First, the carbon cloth is electro-treated; then ammonium molybdate is dissolved in N,N-dimethylformamide to obtain an ammonium molybdate solution; the ammonium molybdate solution is transferred to a reaction kettle, and the electro-treated carbon cloth is also placed in the reaction kettle. The reaction kettle is heated to 180-200 °C and maintained for 14-18 h for a solvothermal reaction to obtain a self-supporting molybdenum nanowire precursor.

[0009] Second, the self-supporting molybdenum nanowire precursor is placed in a nickel acetate solution, and the temperature is raised to 80-100 °C and maintained for 3-9 h for a weak base etching reaction to obtain NiMoO4@Ni(OH)2.

[0010] Third, NiMoO4@Ni(OH)2 and dicyandiamide are respectively placed in a magnetic boat, and the magnetic boat is placed in a tube furnace. An inert gas is introduced into the tube furnace. Dicyandiamide is placed at the inlet position, and NiMoO4@Ni(OH)2 is placed at the outlet position. The tube furnace is heated to 650-950 °C at a heating rate of 10 °C / min, and carbonization treatment is carried out in an inert gas atmosphere for 2-4 h. After cooling to room temperature, an ohmic contact-based heterostructure catalyst is obtained.

[0011] Preferably, in the first step, the method for electro-treating the carbon cloth is: using the carbon cloth as the working electrode, the saturated calomel electrode as the reference electrode, and graphite as the counter electrode, and performing cyclic voltammetry scanning for 20-25 cycles in the voltage range of 1.5-2.0 V.

[0012] Preferably, in the second step, the nickel acetate solution is prepared with a mixed solution of deionized water and ethanol with a volume ratio of 1:1 as the solvent and nickel acetate as the solute; wherein the concentration of nickel acetate is 30-100 mmol / L.

[0013] Preferably, in the third step, the inert gas is argon or nitrogen.

[0014] The application of the ohmic contact-based heterostructure catalyst prepared by the above method is to use the ohmic contact-based heterostructure catalyst in the electrolyzed water hydrogen production reaction at high current density in an alkaline electrolyte as the cathode and / or anode.

[0015] Preferably, the high current density is 100 A cm -2 .

[0016] The beneficial effects of the present invention are mainly reflected in the following aspects: First, in terms of catalytic activity, the electrolytic water hydrogen production system constructed with the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared by the present invention as the anode and cathode exhibits excellent catalytic performance under alkaline conditions, and its catalytic activity is superior to that of traditional noble metal-based catalyst systems, which is mainly attributed to the optimized electronic structure and reduced reaction energy barrier; Second, in terms of stability, the Ni / Ni2Mo3O8 / CC catalyst system of the present invention maintains a stable voltage output under long-term high current density working conditions, showing excellent durability and structural integrity, which benefits from the intrinsic chemical stability of the material and the optimized interfacial charge transport characteristics; In terms of cost control, the present invention uses transition metal elements with relatively high crustal abundances as active components, significantly reducing the material cost and providing feasibility for large-scale production; In terms of the preparation process, the present invention uses a simple and rapid solvothermal method, weak base etching and high-temperature calcination method to prepare the catalyst. By adjusting parameters such as solvothermal and weak base etching time, calcination temperature and calcination time, precise control of the material morphology and crystal structure is achieved. This method has the characteristics of simple process and good repeatability; In terms of structural characteristics, the unique nano-composite structure of the present invention forms a rich crystal heterointerface. This structure not only provides a large number of active sites, but also promotes mass transfer and electron transfer during the reaction process, thus significantly improving the catalytic efficiency. This structural advantage has been fully verified by systematic material characterization. When the ohmic contact-based heterostructure catalyst of the present invention is used for the electrolytic water hydrogen production reaction, when the current density is 100 mA cm -2 , the required working potential is 1.61 - 1.65 V. The catalyst of the present invention can efficiently and stably electrolyze water to produce hydrogen and is used in the field of electrolytic water hydrogen production. Description of the Drawings

[0017] Figure 1 Electron micrograph of the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1; a and b are scanning electron microscope images of the Ni / Ni2Mo3O8 / CC heterostructure catalyst, and c is a transmission electron microscope image of the Ni / Ni2Mo3O8 / CC heterostructure catalyst;

[0018] Figure 2 X-ray diffraction patterns of the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1, the Ni / CC catalyst prepared in Comparative Example 1, and the Ni2Mo3O8 / CC catalyst prepared in Comparative Example 2;

[0019] Figure 3X-ray photoelectron spectroscopy (XPS) pattern of the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1; where a and b are the XPS spectra of Mo 3d and Ni 2p of the Ni / Ni2Mo3O8 / CC heterostructure, respectively.

[0020] Figure 4 Linear sweep voltammetry (LSV) curve of the hydrogen production reaction device by electrolyzing water in an alkaline electrolyte with the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1 as the cathode and anode, respectively.

[0021] Figure 5 Chronopotentiometry curve of the hydrogen production reaction device by electrolyzing water in an alkaline electrolyte with the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1 as the cathode and anode, respectively. Detailed implementation manners

[0022] The present invention will be further described in detail below in conjunction with specific examples and drawings.

[0023] Example 1: The preparation method of the ohmic contact-based heterostructure catalyst in this example is carried out according to the following steps:

[0024] First, using carbon cloth as the working electrode, saturated calomel electrode as the reference electrode, and graphite as the counter electrode, cyclic voltammetry scanning is carried out in the voltage range of 1.5 - 2.0V for 25 cycles to obtain the electro-treated carbon cloth; then, 0.14 mmol of ammonium molybdate is dissolved in 13 mL of N,N-dimethylformamide to obtain an ammonium molybdate solution; the ammonium molybdate solution is transferred to a reaction kettle, and the electro-treated carbon cloth is also placed in the reaction kettle. The reaction kettle is heated to 200°C and maintained for 15 h for a solvothermal reaction to obtain a self-supporting molybdenum nanowire precursor.

[0025] Second, 7.5 mL of deionized water and 7.5 mL of absolute ethanol are mixed evenly, and 0.31 g of nickel acetate tetrahydrate is added and stirred until clear to obtain a nickel acetate solution; the self-supporting molybdenum nanowire precursor is placed in the nickel acetate solution, and the temperature is raised to 90°C and maintained for 5 h for a weak base etching reaction to obtain NiMoO4@Ni(OH)2.

[0026] Third, NiMoO4@Ni(OH)2 and 0.8 g of dicyandiamide are respectively placed in a porcelain boat, and the porcelain boat is placed in a tube furnace. An inert gas is introduced into the tube furnace. Dicyandiamide is placed at the inlet position, and NiMoO4@Ni(OH)2 is placed at the outlet position; the tube furnace is heated to 750°C at a heating rate of 10°C / min, and carbonization treatment is carried out for 2 h in an inert gas atmosphere. After cooling to room temperature, an ohmic contact-based heterostructure catalyst is obtained, denoted as Ni / Ni2Mo3O8 / CC.

[0027] The surface morphology and microstructure of the Ni / Ni2Mo3O8 / CC heterostructure catalyst obtained in Example 1 were analyzed. Figure 1 Figure 1 is the electron microscope image of the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1, where a and b are the scanning electron microscope images of the Ni / Ni2Mo3O8 / CC heterostructure catalyst, and c is the transmission electron microscope image of the Ni / Ni2Mo3O8 / CC heterostructure catalyst. From Figure 1 a and b of Figure 1, it can be observed that the nanowires in Ni / Ni2Mo3O8 / CC grow uniformly on the surface of the carbon cloth. In addition, the nanowires are interconnected with each other, forming a three-dimensional network array structure with open pores. This unique array structure not only provides sufficient void space for the rapid diffusion of the electrolyte and the rapid release of the generated gas, but also provides the necessary conditions for the good structural stability of the self-supporting electrode during the OER and HER catalytic processes. The high-magnification SEM image shows that some discrete nanoparticles are uniformly distributed on the surface of the nanowires, indicating that there may be an interface formed between the nanowires and the nanoparticles. Figure 1 c of Figure 1 is the HR-TEM image of the Ni / Ni2Mo3O8 / CC catalyst in Example 1, Figure 1 c of Figure 1 further reveals the nanosheet structure of the Ni / Ni2Mo3O8 / CC catalyst, and a clear interface can be seen, as shown by the green dotted line. Lattice fringes in different directions are observed on both sides of the green dotted line. The lattice fringes of 0.202 and 0.248 nm match the (111) plane of metallic Ni and the (112) plane of Ni2Mo3O8 respectively. The metallic Ni and Ni2Mo3O8 have a tightly bound heterojunction interface, which is beneficial to promoting electron transfer.

[0028] Comparative Example 1: The comparative example is to prepare a Ni / CC electrocatalyst for hydrogen production by electrolysis of water. The specific preparation method is carried out according to the following steps:

[0029] I. Take 12 mM nickel nitrate monohydrate as the nickel deposition solution and add it to the electrolytic cell. Using the carbon cloth as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum mesh as the counter electrode, deposit at a constant potential of -1V for 1000 s. After the sample after constant potential deposition is washed clean with deionized water and absolute ethanol respectively, and dried with nitrogen, a Ni(OH)2 / CC nanosheet precursor is obtained;

[0030] II. The obtained Ni(OH)2 / CC nanosheet precursor and 0.8 g of dicyandiamide are respectively placed in a magnetic boat, and the magnetic boat is put into a tubular furnace. Nitrogen is introduced into the tubular furnace. The Ni(OH)2 / CC nanosheet precursor is placed at the air inlet position, and dicyandiamide is placed at the air outlet position. The tubular furnace is heated to 750 °C at a heating rate of 10 °C / min, and carbonization treatment is carried out for 2 h in a nitrogen atmosphere. After cooling to room temperature, a self-supporting Ni / CC catalyst is obtained.

[0031] Comparative Example 2: In this comparative example, a Ni2Mo3O8 / CC electrolytic water hydrogen production catalyst is prepared. The specific preparation method is carried out according to the following steps:

[0032] I. First, using carbon cloth as the working electrode, saturated calomel electrode as the reference electrode, and graphite as the counter electrode, cyclic voltammetry scanning is carried out for 25 cycles in the voltage range of 1.5 - 2.0 V to obtain the electro-treated carbon cloth. Take 0.14 mmol of ammonium molybdate tetrahydrate and put it into 13 mL of N,N-dimethylformamide solution. Then place the electro-treated carbon cloth in the solution and heat it at 200 °C for 15 h. The obtained samples are washed clean with deionized water and absolute ethanol respectively, and after drying with nitrogen, a molybdenum nanowire precursor is obtained.

[0033] II. After mixing 7.5 mL of deionized water and 7.5 mL of absolute ethanol evenly, add 0.31 g of nickel acetate tetrahydrate and stir until it is clear to obtain a nickel acetate solution. Place the self-supporting molybdenum nanowire precursor in the nickel acetate solution, heat it to 90 °C and keep it for 5 h for a weak base etching reaction. The obtained samples are washed clean with deionized water and absolute ethanol respectively, and after drying with nitrogen, a NiMoO4@Ni(OH)2 precursor is obtained.

[0034] III. The NiMoO4@Ni(OH)2 precursor and 0.8 g of dicyandiamide are respectively placed in a magnetic boat, and the magnetic boat is put into a tubular furnace. Inert gas is introduced into the tubular furnace. Dicyandiamide is placed at the air inlet position, and the NiMoO4@Ni(OH)2 precursor is placed at the air outlet position. The tubular furnace is heated to 750 °C at a heating rate of 10 °C / min, and carbonization treatment is carried out for 2 h in an inert gas atmosphere. After cooling to room temperature, a self-supporting Ni / Ni2Mo3O8 / CC heterostructure nanoparticle / nanowire catalyst is obtained. The obtained Ni / Ni2Mo3O8 / CC heterostructure is placed in 1.0 M HCl solution and left standing for 3 h to obtain a Ni2Mo3O8 / CC catalyst.

[0035] Figure 2 X-ray diffraction patterns of the Ni / Ni2Mo3O8 / CC heterostructure catalyst prepared in Example 1, the self-supporting Ni / CC catalyst prepared in Comparative Example 1, and the Ni2Mo3O8 / CC catalyst prepared in Comparative Example 2. From Figure 2It can be seen that the diffraction peaks at 32.6°, 36.1°, 49.1° and 64.8° correspond to the (103), (112), (211) and (220) crystal planes of Ni2Mo3O8 (JCPDS, No. 37-0855), respectively. The diffraction peaks at 44.4°, 51.9° and 76.2° correspond to the (111), (200) and (220) planes of nickel metal (JCPDS, No. 87-0712). In addition, a relatively broad diffraction peak was observed at around 26.1°, which comes from the carbon cloth substrate and the outermost NC layer of the nanowires. Therefore, the main catalytically active components in the Ni / Ni2Mo3O8 / CC self-supporting electrode are Ni2Mo3O8 and Ni.

[0036] Subsequently, XPS was further used to analyze the chemical structure and electronic state of the Ni / Ni2Mo3O8 / CC heterostructure catalyst obtained in Example 1, the Ni / CC obtained in Comparative Example 1, and the Ni2Mo3O8 / CC catalyst in Comparative Example 2. Figure 3 is the X-ray photoelectron spectroscopy diagram of the Ni / Ni2Mo3O8 / CC heterostructure, where Figure 3 a and b are the XPS spectra of Mo 3d and Ni 2p of the Ni / Ni2Mo3O8 / CC heterostructure, respectively. As Figure 3 shown in a of 0 , the peaks located at 852.9 and 870.9 eV correspond to Ni 2+ , while the peaks at 855.4 and 872.7 eV correspond to Ni 0 , and 861.6 and 880.4 eV are the satellite peaks of Ni2Mo3O8. It is worth noting that the peak of Ni 2+ in Ni / Ni2Mo3O8 / CC shows a positive shift relative to Ni / CC, while the peak of Ni Figure 3 in Ni / Ni2Mo3O8 / CC shows a negative shift relative to Ni2Mo3O8 / CC, indicating that electrons transfer from metallic Ni to Ni2Mo3O8. The XPS spectrum of Mo3d ( 3+ b of 4+ ) shows that the Mo element in Ni / Ni2Mo3O8 / CC and Ni2Mo3O8 / CC has three valence states (+3, +4, +6). On the one hand, the peak of the Mo element in Ni / Ni2Mo3O8 / CC migrates to a lower binding energy relative to Ni2Mo3O8 / CC; on the other hand, relative to the content of the corresponding Mo species in Ni2Mo3O8 / CC, the contents of Mo 6+The content of the species decreases. The transfer of the binding energy and the increase in the low-valence Mo species further confirm the electron transfer from metallic Ni to Ni2Mo3O8 in Ni / Ni2Mo3O8 / CC. The XPS analysis results indicate that there may be an Ni / Ni2Mo3O8 heterojunction interface in Ni / Ni2Mo3O8 / CC, so there is an electronic interaction between the Ni and Mo elements of the Ni / Ni2Mo3O8 / CC catalyst. The above characterization results all confirm the successful preparation of the Ni / Ni2Mo3O8 / CC heterostructured nanosheet catalyst.

[0037] The Ni / Ni2Mo3O8 / CC heterostructured catalyst prepared in Example 1 was taken to test its performance for hydrogen production by electrolyzing water. The Ni / Ni2Mo3O8 / CC heterostructured nanosheet catalyst obtained in Example 1 was used as the anode and cathode (Ni / Ni2Mo3O8 / CC||Ni / Ni2Mo3O8 / CC) respectively, and an alkaline solution was used as the electrolyte. With the help of the Shanghai Chenhua CHI-660E electrochemical workstation, the performance of hydrogen production by electrolyzing water was tested. At the same time, a commercial IrO2 catalyst was used as the anode and a commercial Pt / C catalyst was used as the cathode (Pt / C / CC||IrO2 / CC) to test the performance of urea-assisted hydrogen production by electrolyzing water under the same conditions. In addition, the Ni / Ni2Mo3O8 / CC heterostructured catalyst obtained in Example 1 was used as the anode and cathode (Ni / Ni2Mo3O8 / CC||Ni / Ni2Mo3O8 / CC) respectively to conduct the stability test of hydrogen production by electrolyzing water. Figure 4 is the linear sweep voltammetry curve of the hydrogen production by electrolyzing water reaction device in the alkaline electrolyte constructed with Ni / Ni2Mo3O8 / CC heterostructures as the cathode and anode respectively, where Figure 4 a is the comparison diagram of the LSV curves of the hydrogen production by electrolyzing water device constructed with Ni / Ni2Mo3O8 / CC heterostructured catalysts as the cathode and anode respectively and RuO2 and Pt / C as the anode and cathode respectively in the alkaline electrolyte; Figure 5 is the chronoamperometry curve of the hydrogen production by electrolyzing water device constructed with Ni / Ni2Mo3O8 / CC heterostructures as the cathode and anode respectively in the alkaline electrolyte. From Figure 4 it can be seen that for the hydrogen production by electrolyzing water reaction, Ni / Ni2Mo3O8 / CC only needs to apply voltages of 1.51 and 1.63 V respectively to obtain current densities of 10 and 100 mA cm -2 while Pt / C / CC||IrO2 / CC needs 1.58 and 1.72 V respectively to obtain current densities of 10 and 50 mAcm -2 indicating that the Ni / Ni2Mo3O8 / CC prepared in Example 1 has excellent performance for hydrogen production by electrolyzing water.

[0038] The Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained in Example 1 were used as the anode and cathode (Ni / Ni2Mo3O8 / CC||Ni / Ni2Mo3O8 / CC) respectively to conduct the stability test for hydrogen production by electrolyzing water. From Figure 5 It can be seen that in the alkaline electrolyte, the Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained in Example 1 can stably operate at a current density of 50 mA cm -2 for at least 25 h, indicating that the catalysts have excellent stability in the process of hydrogen production by electrolyzing water.

[0039] Example 2: The difference between this example and Example 1 is that the solvothermal temperature in Step 1 is 180 °C, and other steps and parameters are the same as those in Example 1.

[0040] Example 3: The difference between this example and Example 1 is that the solvothermal temperature in Step 1 is 190 °C, and other steps and parameters are the same as those in Example 1.

[0041] The catalysts obtained in Examples 1, 2 and 3 under different solvothermal temperature conditions were compared. The results showed that the catalysts obtained in Examples 2 and 3 could not form the Ni / Ni2Mo3O8 / CC heterostructure.

[0042] Example 4: The difference between this example and Example 1 is that the solvothermal reaction time in Step 1 is 14 h, and other steps and parameters are the same as those in Example 1.

[0043] Example 5: The difference between this example and Example 1 is that the solvothermal reaction time in Step 1 is 16 h, and other steps and parameters are the same as those in Example 1.

[0044] Example 6: The difference between this example and Example 1 is that the solvothermal reaction time in Step 1 is 17 h, and other steps and parameters are the same as those in Example 1.

[0045] Example 7: The difference between this example and Example 1 is that the solvothermal reaction time in Step 1 is 18 h, and other steps and parameters are the same as those in Example 1.

[0046] The hydrogen production performance of the self-supported Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained in Examples 1, 4, 5, 6 and 7 under different solvothermal reaction time conditions was compared. The results were as follows: when the solvothermal reaction time in Step 1 was 14, 15, 16, 17 and 18 h, the overall water splitting voltages required to reach a current density of 100 mA cm -2 were 1.82, 1.63, 1.68, 1.74 and 1.78 V respectively. By comparison, it can be seen that when the solvothermal reaction time is 15 h, its electrocatalytic overall water splitting performance is better.

[0047] Example 8: The difference between this example and Example 1 is that the temperature of the weak base etching reaction in Step 2 is 80 °C, and other steps and parameters are the same as those in Example 1.

[0048] Example 9: The difference between this example and Example 1 is that the temperature of the weak base etching reaction in Step 2 is 100 °C, and other steps and parameters are the same as those in Example 1.

[0049] The electrocatalytic water splitting performance of the self-supported Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained in Examples 1, 8, and 9 at different weak base etching reaction temperatures was compared. The results showed that when the weak base etching reaction temperatures were 80, 90, and 100 °C, the overall water splitting voltages required to reach a current density of 100 mA cm -2 were 1.67, 1.63, and 1.75 V, respectively. By comparison, when the weak base etching reaction temperature was 90 °C, its electrocatalytic overall water splitting performance was better.

[0050] Example 10: The difference between this example and Example 1 is that the weak base etching reaction time in Step 2 is 3 h, and other steps and parameters are the same as those in Example 1.

[0051] Example 11: The difference between this example and Example 1 is that the weak base etching reaction time in Step 2 is 7 h, and other steps and parameters are the same as those in Example 1.

[0052] Example 12: The difference between this example and Example 1 is that the weak base etching reaction time in Step 2 is 9 h, and other steps and parameters are the same as those in Example 1.

[0053] The electrocatalytic water splitting performance of the self-supported Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained in Examples 1, 10, 11, and 12 at different weak base etching reaction times was compared. The results showed that when the weak base etching reaction times were 3, 5, 7, and 9 h, the overall water splitting voltages required to reach a current density of 100 mA cm -2 were 1.83, 1.63, 1.66, and 1.75 V, respectively. By comparison, when the weak base etching reaction time was 5 h, its electrocatalytic overall water splitting performance was better.

[0054] Example 13: The difference between this example and Example 1 is that the temperature of the tubular furnace in Step 3 is 650 °C, and other steps and parameters are the same as those in Example 1.

[0055] Example 14: The difference between this example and Example 1 is that the temperature of the tubular furnace in Step 3 is 850 °C, and other steps and parameters are the same as those in Example 1.

[0056] Example 15: The difference between this example and Example 1 is that the temperature of the tubular furnace in Step 3 is 950 °C, and other steps and parameters are the same as those in Example 1.

[0057] The hydrogen production performance of self-supported Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained at different calcination temperatures in Examples 1, 13, 14, and 15 for water electrolysis was compared. The results were as follows: When the calcination temperatures were 650, 750, 850, and 950 °C, the overall water splitting voltages required to reach a current density of 100 mA cm -2 were 1.74, 1.63, 1.68, and 1.71 V, respectively. By comparison, when the calcination temperature was 750 °C, its electrocatalytic overall water splitting performance was better.

[0058] Example 16: The difference between this example and Example 1 is that the calcination time in the tubular furnace in Step 3 was 3 h, and the other steps and parameters were the same as those in Example 1.

[0059] Example 17: The difference between this example and Example 1 is that the calcination time in the tubular furnace in Step 3 was 4 h, and the other steps and parameters were the same as those in Example 1.

[0060] The hydrogen production performance of self-supported Ni / Ni2Mo3O8 / CC heterostructure catalysts obtained at different calcination times in Examples 1, 16, and 17 for water electrolysis was compared. The results were as follows: When the calcination times were 2, 3, and 4 h, the overall water splitting voltages required to reach a current density of 100 mA cm -2 were 1.63, 1.69, and 1.78 V, respectively. By comparison, when the calcination time was 2 h, its electrocatalytic overall water splitting performance was better.

[0061] Of course, the above-mentioned preferred embodiments only represent several implementation manners of the present invention, and do not limit the scope of the invention patent of the present invention. Any several deformations, substitutions, and improvements made without departing from the essence of the inventive concept of the present invention are also included in the protection scope of the present invention. Therefore, the protection scope of the invention patent of the present invention shall be subject to the appended claims.

Claims

1. An ohmic contact-based heterostructure catalyst, characterized in that The catalyst is an ohmic contact-based heterostructure catalyst composed of self-supporting nickel metal nanoparticles and nickel molybdate nanowires, denoted as Ni / Ni2Mo3O8 / CC.

2. A method for preparing an ohmic contact-based heterostructure catalyst according to claim 1, characterized in that The method is carried out according to the following steps: I. Electrically treat the carbon cloth; then dissolve ammonium molybdate in N,N-dimethylformamide to obtain an ammonium molybdate solution; transfer the ammonium molybdate solution to a reaction kettle, and also put the electrically treated carbon cloth into the reaction kettle. Heat the reaction kettle to 180-200 °C and keep it for 14-18 h for solvothermal reaction to obtain a self-supporting molybdenum nanowire precursor. II. Place the self-supporting molybdenum nanowire precursor in a nickel acetate solution, heat it to 80-100 °C and keep it for 3-9 h for weak base etching reaction to obtain NiMoO4@Ni(OH)2. III. Place NiMoO4@Ni(OH)2 and dicyandiamide in a magnetic boat respectively, and put the magnetic boat into a tubular furnace. Pass an inert gas into the tubular furnace. Place dicyandiamide at the inlet position and NiMoO4@Ni(OH)2 at the outlet position; heat the tubular furnace to 650-950 °C at a heating rate of 10 °C / min and carry out carbonization treatment for 2-4 h in an inert gas atmosphere. After cooling to room temperature, obtain the ohmic contact-based heterostructure catalyst.

3. The preparation method of an ohmic contact-based heterostructure catalyst according to claim 2, wherein, The method for electrically treating the carbon cloth described in step I: Use the carbon cloth as the working electrode, the saturated calomel electrode as the reference electrode, and graphite as the counter electrode, and perform cyclic voltammetry scanning for 20-25 cycles in the voltage range of 1.5-2.0 V.

4. The preparation method of an ohmic contact-based heterostructure catalyst according to claim 2 or 3, wherein The nickel acetate solution described in step II is prepared with a mixed solution of deionized water and ethanol with a volume ratio of 1:1 as the solvent and nickel acetate as the solute; the concentration of nickel acetate is 30 mmol / L.

5. The preparation method of an ohmic contact-based heterostructure catalyst according to claim 2 or 3, characterized in that, The inert gas described in step III is argon or nitrogen.

6. Use of a catalyst of an ohmic contact-based heterostructure according to claim 1, characterized in that, This application is to use the ohmic contact-based heterostructure catalyst as the cathode and / or anode in the electrolytic water hydrogen production reaction at a high current density in an alkaline electrolyte.

7. Use of a catalyst of an ohmic contact-based heterostructure according to claim 6, characterized in that, The large current density is 100 A / cm -2 .

8. The application of an ohmic contact-based heterostructure catalyst according to claim 6, characterized in that, In the electrolytic water hydrogen production reaction, when the current density is 100 mA cm -2 , the required working potential is 1.61 - 1.65 V.

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