Self-supporting nicdmo ternary composite metal oxide catalyst and use thereof

Abstract

The application relates to a self-supporting NiCdMo ternary composite metal oxide catalyst and application thereof, and a preparation method of the catalyst is as follows: foam nickel is cleaned under ultrasonic conditions to obtain a foam nickel substrate; nickel metal salt, molybdenum metal salt and cadmium metal salt are dissolved in an ethylene glycol aqueous solution, the mixture is stirred uniformly at room temperature, and then is transferred to a polytetrafluoroethylene-lined high-pressure kettle, the foam nickel substrate is added, the high-pressure kettle is sealed, and a solvothermal reaction is carried out; after being naturally cooled to room temperature, the obtained precursor is washed and vacuum dried to obtain A; A is calcined in an inert atmosphere, and is naturally cooled to room temperature to obtain B; B is calcined in a 5 vol.% NH3 / N2 atmosphere, and is naturally cooled to room temperature to obtain the self-supporting NiCdMo ternary composite metal oxide catalyst. The self-supporting NiCdMo ternary composite metal oxide catalyst exhibits high catalytic activity and long-term stability in urea oxidation reaction and hydrogen evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst technology, specifically to a self-supporting NiCdMo ternary composite metal oxide catalyst and its application. Background Technology

[0002] The global energy system is facing a severe crisis due to the imbalance between supply and demand of fossil fuels, urgently requiring renewable energy to replace the traditional energy system. Water electrolysis for hydrogen production, with its clean and flexible characteristics, has become one of the core pathways to solving the energy crisis and building a new energy system. However, its large-scale industrial application still faces many obstacles due to factors such as high production costs, significant electrolysis energy consumption, and bottlenecks in core technologies.

[0003] Urea oxidation reaction (UOR), as an ideal alternative anode reaction to oxygen evolution reaction (OER), offers a solution to the technical and cost challenges of hydrogen production via water electrolysis. Compared to OER, UOR has a theoretical potential of only 0.37 V (vs. RHE), far lower than OER's 1.23 V (vs. RHE), significantly reducing anode overpotential and overall cell voltage. This results in a 20%–30% reduction in hydrogen production energy consumption compared to traditional water electrolysis. Furthermore, UOR does not require precious metal catalysts; non-precious metal-based materials such as iron, cobalt, and nickel can achieve high catalytic activity, significantly reducing catalyst costs. In addition, UOR has superior reaction kinetics compared to OER, adapting to high current densities and improving Faraday efficiency. It can also utilize industrial and domestic urea wastewater as an electrolyte, eliminating the need for high-purity deionized water. Simultaneously, it achieves urea degradation and mineralization, combining energy production with environmental remediation. This effectively alleviates the water resource constraints and cost pressures of traditional water electrolysis hydrogen production technology, making it an important development direction for upgrading electrolysis hydrogen production technology.

[0004] Single-metal catalysts exhibit excellent catalytic activity and structural stability for urea reductase (UOR) in alkaline media, with their intrinsic electronic structure showing good compatibility with alkaline systems. However, single-metal catalysts suffer from sluggish intrinsic kinetics of active sites, making them prone to surface reconstruction during long-term electrolysis, ultimately leading to catalytic activity decay or even deactivation. To address this, researchers often introduce heterometallic elements such as cobalt, iron, and molybdenum for precise doping, significantly improving overall catalytic performance through electronic structure modulation and multi-element synergistic coordination effects. However, bimetallic doped systems are prone to problems such as metal ion dissolution, active component aggregation, and inactive impurity phase formation in alkaline media, directly resulting in a sharp reduction in the number of effective active sites. Furthermore, these doped catalysts have weak resistance to various impurities in actual urea wastewater, making them unsuitable for the stringent requirements of continuous industrial operation. Therefore, overcoming the technical bottlenecks of traditional metal doping and constructing a new generation of metal catalytic systems that can maintain high catalytic activity and structural stability over long periods in complex electrolyte environments has become a core challenge in propelling UOR technology from laboratory research to practical industrial applications. Summary of the Invention

[0005] One objective of this invention is to provide a self-supporting NiCdMo ternary composite metal oxide catalyst, which addresses the problem of poor catalytic activity and structural stability of existing catalysts in urea oxidation reactions under electrolyte conditions. Another objective of this invention is to provide applications of the self-supporting NiCdMo ternary composite metal oxide catalyst.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: This self-supporting NiCdMo ternary composite metal oxide catalyst is prepared by the following method: S1. Clean the nickel foam under ultrasonic conditions to obtain a nickel foam substrate; S2. Dissolve nickel, molybdenum, and cadmium metal salts in an aqueous ethylene glycol solution. The molar ratio of nickel, cadmium, and molybdenum metal salts is (1~8): (1~8): (1~10). After stirring evenly at room temperature, transfer the solution to a polytetrafluoroethylene-lined autoclave, add a nickel foam substrate, seal the autoclave, and carry out a solvothermal reaction. After naturally cooling to room temperature, wash the obtained precursors with deionized water and ethanol, respectively, and dry them under vacuum to obtain A. S3. Calcine A in an inert atmosphere and cool it naturally to room temperature to obtain B; S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere and cool naturally to room temperature to obtain a self-supporting NiCdMo ternary composite metal oxide catalyst, denoted as NiCdMoON / NF.

[0007] In the above scheme, S1 specifically involves cleaning the nickel foam sequentially with 3 mol / L hydrochloric acid solution, deionized water, and ethanol under ultrasonic conditions to obtain a nickel foam substrate. The nickel foam has a length of 3 cm and a width of 2 cm, and the ultrasonic cleaning time for each cycle is 10~60 min.

[0008] In the above scheme S2, the nickel metal salt is one of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel sulfate hexahydrate, nickel citrate, nickel lactate, nickel oxalate dihydrate, and nickel acetylacetonate dihydrate; the cadmium metal salt is one of cadmium nitrate tetrahydrate, cadmium acetate dihydrate, cadmium chloride, cadmium sulfate, cadmium acetylacetonate, cadmium carbonate, anhydrous cadmium acetate, cadmium oxalate, and cadmium formate; and the molybdenum metal salt is one of ammonium molybdate tetrahydrate, potassium molybdate, sodium molybdate dihydrate, molybdenum trioxide, molybdenum molybdate ammonium tetramolybdate, tetramethylammonium molybdate, molybdenum acid, and molybdenum acetylacetonate.

[0009] In the above scheme, the volume ratio of ethylene glycol to water in the aqueous ethylene glycol solution is 1:1 to 1:10; the temperature of the solvothermal reaction is 100 to 220 ºC, and the time is 5 to 48 h.

[0010] In the above scheme S3, the inert gas used in the inert atmosphere is Ar or N2, the calcination temperature is 300~1200 ºC, the calcination time is 1~12 h, and the heating rate during calcination is 1~30 ºC min. −1 .

[0011] In the above scheme S4, the calcination temperature is 300~1100 ºC, the calcination time is 1~10 h, and the heating rate during calcination is 1~30 ºC min. −1 .

[0012] The aforementioned self-supporting NiCdMo ternary composite metal oxide catalyst is used in the urea oxidation coupled hydrogen production reaction. Beneficial effects

[0013] 1. This invention discloses a method for preparing a self-supporting NiCdMo ternary composite metal oxide catalyst. Based on a simple solvothermal method combined with inert gas calcination, three metal elements, Ni, Cd and Mo, are introduced simultaneously to construct a multi-component metal oxide material with abundant oxygen vacancies. Then, N is doped into the NiCdMo metal oxide lattice using 5 vol.% NH3 / N2 as a nitrogen source, and finally a self-supporting NiCdMo ternary composite metal oxide catalyst with high active site density, fast charge transport capability and excellent structural stability is obtained.

[0014] 2. The self-supporting NiCdMo ternary composite metal oxide catalyst disclosed in this invention utilizes Mo to construct the structural framework and active building blocks, employs Ni as a catalytic promoter and charge balance center, utilizes Cd to regulate the crystal structure and electronic environment, and introduces N to strengthen the catalyst framework structure, thereby enhancing structural stability through coordination. Based on the strong coupling effect of these four elements, this catalyst can effectively reduce the reaction energy barrier, accelerate mass transfer and charge transfer processes, and exhibit high catalytic activity and long-term stability in urea oxidation and hydrogen evolution reactions. Attached Figure Description

[0015] Figure 1 This is a transmission electron microscope image of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1. Figure 2 Fourier transform infrared spectra of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1 and the comparative examples. Figure 3 The X-ray photoelectron spectroscopy (XPS) spectrum of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1 is shown below. Figure 4 The self-supported NiCdMo ternary composite metal oxide catalyst obtained in Example 1 and each comparative example were mixed in 1 mol L −1 HER linear sweep voltammetry curve in KOH solution; Figure 5 The self-supported NiCdMo ternary composite metal oxide catalyst obtained in Example 1 and each comparative example were mixed in 1 mol L −1 KOH + 0.5 mol L −1 UOR linear sweep voltammetric curve in urea solution. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings: Example 1

[0017] This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 15 min each to obtain a nickel foam substrate.

[0018] S2. Dissolve 0.25 mmol nickel nitrate hexahydrate, 0.25 mmol cadmium nitrate hexahydrate, and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水In a mixture of 1:4 (coal, water, and oxygen), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, the autoclave was sealed, and a solvothermal reaction was carried out at 120 ºC for 6 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0019] S3. Calcine A in a N2 atmosphere at 5 ºC for 1 minute. −1 The heating rate was set at 400 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0020] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 5 ºC min. −1 The catalyst NiCdMoON / NF was obtained by heating at 350 ºC for 1 h and then naturally cooling to room temperature.

[0021] The morphology and structure of the self-supporting NiCdMo ternary composite metal oxide catalyst prepared in Example 1 were characterized.

[0022] like Figure 1 The image shown is a transmission electron microscope image of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1. The image shows that the catalyst exhibits the morphological characteristics of nanorods.

[0023] like Figure 2 The image shows the Fourier transform infrared spectrum of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1. The image shows the spectrum at ~605 cm⁻¹. −1 ~778 cm −1 and ~958 cm −1 The absorption peak at ~1626 cm⁻¹ is attributed to the stretching vibration of the metal-oxygen bond. −1 The absorption peak at ~3421 cm⁻¹ is attributed to the stretching vibration of C=C(N). −1 The absorption peak at that point is related to the stretching vibration of −OH.

[0024] like Figure 3 The image shows the full X-ray photoelectron spectroscopy spectrum of the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1, proving the presence of carbon, nitrogen, oxygen, nickel, cadmium and molybdenum elements in the catalyst.

[0025] This self-supporting NiCdMo ternary composite metal oxide catalyst was used for urea oxidation coupled hydrogen production reaction, and its performance was tested.

[0026] All electrochemical performance tests of this invention were conducted using a Shanghai Chenhua CHI 760E electrochemical workstation. A classic three-electrode system was used, with the working electrode being the 1 cm × 1 cm catalyst obtained in Example 1, the reference electrode being an Ag / AgCl electrode, and the counter electrode being a platinum sheet electrode. Different electrolytes were prepared for the urea oxidation reaction and the hydrogen evolution reaction, with the UOR test electrolyte being a 1 mol·L⁻¹ solution. −1 KOH + 0.5 mol·L −1 Urea, HER test electrolyte is 1 mol·L −1 KOH. Furthermore, each comparative example was used as the working electrode, and parallel control tests were conducted under the same test system and conditions as described above. Example 2

[0027] This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 10 min each to obtain a nickel foam substrate.

[0028] S2. Dissolve 0.25 mmol nickel acetate tetrahydrate, 0.25 mmol cadmium nitrate hexahydrate, and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水 In a mixture of 1:4 (coal, water, and oxygen), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, the autoclave was sealed, and a solvothermal reaction was carried out at 120 ºC for 6 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0029] S3. Calcine A in a N2 atmosphere at 8 ºC min. −1 The heating rate was set at 450 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0030] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 8 ºC min. −1 The heating rate was set at 350 ºC for 1 h, and the catalyst was naturally cooled to room temperature to obtain a self-supporting NiCdMo ternary composite metal oxide catalyst. Example 3

[0031] This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 20 min each to obtain a nickel foam substrate.

[0032] S2. Dissolve 0.25 mmol nickel nitrate hexahydrate, 0.25 mmol cadmium nitrate hexahydrate, and 2.5 mmol sodium molybdate dihydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水 In a mixture of 1:4 (coal, water, and oxygen), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, and the autoclave was sealed. A solvothermal reaction was carried out at 160 ºC for 6 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0033] S3. Calcine A in a N2 atmosphere at 10 °C for 1 minute. −1 The heating rate was set at 400 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0034] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 10 °C for min. −1 The heating rate was set at 400 ºC for 2 h, and the catalyst was naturally cooled to room temperature to obtain a self-supporting NiCdMo ternary composite metal oxide catalyst. Example 4

[0035] This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 15 min each to obtain a nickel foam substrate.

[0036] S2. Dissolve 0.25 mmol nickel nitrate hexahydrate, 0.25 mmol cadmium acetate dihydrate, and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水 In a mixture of 1:5 (coal, water, and fuel), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, and the autoclave was sealed. A solvothermal reaction was carried out at 120 ºC for 10 h. After naturally cooling to room temperature, the resulting precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0037] S3. Calcine A in a N2 atmosphere at 10 °C for 1 minute.−1 The heating rate was set at 500 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0038] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 10 °C for min. −1 The self-supported NiCdMo ternary composite metal oxide catalyst was obtained by heating at 450 ºC for 1 h and then naturally cooling to room temperature. Example 5

[0039] This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 20 min each to obtain a nickel foam substrate.

[0040] S2. Dissolve 0.25 mmol nickel nitrate hexahydrate, 0.25 mmol cadmium nitrate hexahydrate, and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水 In a mixture of 1:3 (coefficient of molecular weight), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL polytetrafluoroethylene-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, the autoclave was sealed, and a solvothermal reaction was carried out at 160 ºC for 10 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, respectively, and then dried under vacuum to obtain A.

[0041] S3. Calcine A in a N2 atmosphere at 10 °C for 1 minute. −1 The heating rate was set at 550 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0042] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 10 °C for min. −1 The self-supported NiCdMo ternary composite metal oxide catalyst was obtained by heating at 400 ºC for 1 h and then naturally cooling to room temperature.

[0043] Comparative Example 1: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 15 min each to obtain a nickel foam substrate.

[0044] S2. Dissolve 0.25 mmol nickel nitrate hexahydrate and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇: v 水 In a mixture of 1:4 (coal, water, and oxygen), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, the autoclave was sealed, and a solvothermal reaction was carried out at 120 ºC for 6 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0045] S3. Calcine A in a N2 atmosphere at 5 ºC for 1 minute. −1 The heating rate was set at 400 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0046] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 5 ºC min. −1 The catalyst NiMoON / NF was obtained by heating at 350 ºC for 1 h and then naturally cooling to room temperature.

[0047] Comparative Example 2: S1. Take a piece of nickel foam with a size of 2 cm × 3 cm and clean it sequentially with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 15 min each to obtain a nickel foam substrate.

[0048] S2. Dissolve 0.25 mmol cadmium nitrate hexahydrate and 0.36 mmol ammonium molybdate tetrahydrate in 25 mL of ethylene glycol aqueous solution (v 乙二醇 : v 水 In a mixture of 1:4 (coal, water, and oxygen), the mixture was stirred thoroughly at room temperature and then transferred to a 50 mL PTFE-lined autoclave. A 2 cm × 3 cm nickel foam substrate was added, the autoclave was sealed, and a solvothermal reaction was carried out at 120 ºC for 6 h. After naturally cooling to room temperature, the obtained precursor was washed with deionized water and ethanol, and then vacuum dried to obtain A.

[0049] S3. Calcine A in a N2 atmosphere at 5 ºC for 1 minute. −1 The heating rate was set at 400 ºC for 2 h, and then naturally cooled to room temperature to obtain B.

[0050] S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere at 5 ºC min. −1 The catalyst CdMoON / NF was obtained by heating at 350 ºC for 1 h and then naturally cooling to room temperature.

[0051] Comparative Example 3: A piece of nickel foam with dimensions of 2 cm × 3 cm was sequentially cleaned with 3 mol / L hydrochloric acid solution, deionized water and ethanol under ultrasonic conditions for 15 min each to obtain pretreated nickel foam, denoted as NF.

[0052] The performance of the self-supported NiCdMo ternary composite metal oxide catalyst of this invention and the urea oxidation coupled hydrogen production reaction of the comparative example were compared by test.

[0053] All electrochemical performance tests of this invention were conducted using a Shanghai Chenhua CHI 760E electrochemical workstation. A classic three-electrode system was used, with the working electrode being the 1 cm × 1 cm catalyst obtained in Example 1, the reference electrode being an Ag / AgCl electrode, and the counter electrode being a platinum sheet electrode. Different electrolytes were prepared for the urea oxidation reaction and the hydrogen evolution reaction, with the UOR test electrolyte being a 1 mol·L⁻¹ solution. −1 KOH + 0.5 mol·L −1 Urea, HER test electrolyte is 1 mol·L −1 KOH. Furthermore, each comparative example was used as the working electrode, and parallel control tests were conducted under the same test system and conditions as described above.

[0054] like Figure 4 The figure shows the HER linear sweep voltammetry curves for Example 1 and each comparative example. It can be seen from the figure that the self-supported NiCdMo ternary composite metal oxide catalyst obtained in Example 1 exhibits the best HER activity at 10 mA cm⁻¹. −2 100 mA cm −2 and 200 mA cm −2 The overpotentials at the current densities were only 138 mV, 245 mV and 269 mV, which were superior to NiMoON / NF in Comparative Example 1 (227 mV, 397 mV and 499 mV), CdMoON / NF in Comparative Example 2 (199 mV, 373 mV and 478 mV) and NF in Comparative Example 3 (247 mV, 438 mV and 535 mV).

[0055] like Figure 5 The figure shows the UOR linear sweep voltammetry curves for Example 1 and each comparative example. It can be seen from the figure that the self-supporting NiCdMo ternary composite metal oxide catalyst obtained in Example 1 exhibits the best HER activity at 10 mA cm⁻¹. −2 100 mA cm −2 and 200 mA cm −2The potentials at the current densities were only 1.35 V, 1.36 V and 1.37 V, which were better than NiMoON / NF in Comparative Example 1 (1.41 V, 1.48 V and 1.53 V), CdMoON / NF in Comparative Example 2 (1.37 V, 1.42 V and 1.48 V) and NF in Comparative Example 3 (1.44 V, 1.55 V and 2.05 V).

[0056] In summary, this application combines solvothermal and gas calcination methods to prepare a self-supported NiCdMo ternary composite metal oxide catalyst, which exhibits excellent catalytic activity for urea oxidation and hydrogen evolution reactions.

Claims

1. A self-supporting NiCdMo ternary composite metal oxide catalyst, characterized in that: This self-supporting NiCdMo ternary composite metal oxide catalyst was prepared by the following method: S1. Clean the nickel foam under ultrasonic conditions to obtain a nickel foam substrate; S2. Dissolve nickel, molybdenum, and cadmium metal salts in an aqueous ethylene glycol solution. The molar ratio of nickel, cadmium, and molybdenum metal salts is (1~8): (1~8): (1~10). After stirring evenly at room temperature, transfer the solution to a polytetrafluoroethylene-lined autoclave, add a nickel foam substrate, seal the autoclave, and carry out a solvothermal reaction. After naturally cooling to room temperature, wash the obtained precursors with deionized water and ethanol, respectively, and dry them under vacuum to obtain A. S3. Calcine A in an inert atmosphere and cool it naturally to room temperature to obtain B; S4. Calcine B in a 5 vol.% NH3 / N2 atmosphere and allow it to cool naturally to room temperature to obtain a self-supporting NiCdMo ternary composite metal oxide catalyst, denoted as NiCdMoON / NF.

2. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 1, characterized in that: S1 specifically involves cleaning the nickel foam sequentially with 3 mol / L hydrochloric acid solution, deionized water, and ethanol under ultrasonic conditions to obtain a nickel foam substrate. The nickel foam has a length of 3 cm and a width of 2 cm, and the ultrasonic cleaning time for each cycle is 10-60 min.

3. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 2, characterized in that: The nickel metal salt in S2 is one of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel acetate tetrahydrate, nickel sulfate hexahydrate, nickel citrate, nickel lactate, nickel oxalate dihydrate, and nickel acetylacetone dihydrate.

4. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 3, characterized in that: The cadmium metal salt in S2 is one of cadmium nitrate tetrahydrate, cadmium acetate dihydrate, cadmium chloride, cadmium sulfate, cadmium acetylacetone, cadmium carbonate, anhydrous cadmium acetate, cadmium oxalate, and cadmium formate.

5. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 4, characterized in that: The molybdenum metal salt in S2 is one of ammonium molybdate tetrahydrate, potassium molybdate, sodium molybdate dihydrate, molybdenum trioxide, molybdenum molybdate ammonium citrate, ammonium tetramolybdate, tetramethylammonium acetate, molybdic acid, and molybdenum acetylacetonate.

6. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 5, characterized in that: The volume ratio of ethylene glycol to water in the ethylene glycol aqueous solution is 1:1 to 1:10; the temperature of the solvothermal reaction is 100 to 220ºC, and the time is 5 to 48 h.

7. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 6, characterized in that: The inert gas used in the inert atmosphere of S3 is Ar or N2, the calcination temperature is 300~1200ºC, the calcination time is 1~12 h, and the heating rate during calcination is 1~30ºCmin. -1 .

8. The self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 7, characterized in that: The calcination temperature in S4 is 300~1100 ºC, the calcination time is 1~10 h, and the heating rate during calcination is 1~30 ºC min. -1 .

9. A self-supporting NiCdMo ternary composite metal oxide catalyst according to claim 8, characterized in that: The self-supporting NiCdMo ternary composite metal oxide catalyst is used in the urea oxidation coupled hydrogen production reaction.

Images