Catalyst for urea oxidation assisted electro-catalysis hydrogen production
The preparation of Ni-Co-based self-supporting catalysts through the co-calcination strategy solved the activity and stability of urea oxidation catalysts, and achieved low-cost and efficient urea electrolysis hydrogen production, with wide application prospects.
Patent Information
- Application Number
- CN202510485078.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-18
AI Technical Summary
The existing urea oxidation catalysts have insufficient activity and poor stability, and the need for adhesives leads to an increase in interface resistance, which limits the application performance of urea electrolytic hydrogen production technology.
The catalyst was prepared by co-calcining strategy, and through the combination of physical deposition and electrochemical deposition, a Ni-Co-based self-supporting heterostructure was formed, the active site and electronic structure were optimized, and the use of adhesives was avoided.
It significantly reduces the overpotential of the urea oxidation reaction, improves energy conversion efficiency, achieves long-term stability and low-cost hydrogen production performance, and is suitable for sustainable energy and environmental governance.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the fields of novel polymer functional materials and electrocatalysis, and particularly relates to a catalyst for urea oxidation-assisted electrocatalytic hydrogen production. Background Art
[0002] With the increasing energy demand and the exacerbation of environmental problems, there is an urgent need for environmentally friendly renewable energy to reduce the consumption of fossil fuels. Hydrogen (H2) is often proposed as an important energy carrier due to its good gravimetric energy density, zero pollution, and special recyclability. However, several strategies for producing H2, such as coal gasification and steam methane reforming, have the disadvantages of low H2 purity, high energy consumption, and unsatisfactory efficiency. Therefore, promising hydrogen production methods such as electrocatalytic water splitting and photoelectrochemical water splitting have been proposed.
[0003] In the field of hydrogen energy production, traditional electrolytic water hydrogen production technology is limited by the high theoretical potential (1.23 V vs. RHE) and slow kinetics of the anodic oxygen evolution reaction (OER), resulting in excessively high overall energy consumption. In addition, the mixing of oxygen and hydrogen during the OER process poses an explosion risk, further increasing the system complexity. In recent years, the strategy of replacing OER with low-potential organic molecule oxidation reactions has received attention. Among them, the urea oxidation reaction (UOR) has become a research hotspot due to its ultra-low theoretical potential (0.37 V vs. RHE) and the synergistic effect of wastewater treatment. However, existing UOR catalysts generally face problems such as insufficient activity and poor stability. For example, traditional nickel-based or cobalt-based sulfide catalysts have limited active sites, low charge transfer efficiency, and slow surface reconstruction kinetics, resulting in limited practical application performance. In addition, powder catalysts need to rely on adhesives (such as Nafion), which not only block active sites but also increase the interfacial resistance, further reducing the catalytic efficiency. Therefore, designing a self-supporting heterostructure catalyst with both high activity and high stability and without adhesives has become the key to promoting the development of urea electrolysis hydrogen production technology. Summary of the Invention
[0004] The purpose of the present invention is to provide a catalyst for urea oxidation-assisted electrocatalytic hydrogen production, which adopts a co-calcination strategy to prepare a catalyst with excellent urea oxidation performance and excellent stability and other multi-functional integration, and solves the problems of high energy consumption, high cost, and complex process of current urea oxidation catalysts. At the same time, compared with the equivalent commercial nickel foam electrode, this catalyst has excellent performance advantages, can significantly reduce the required energy consumption, and highlights greater commercial value potential.
[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a catalyst for urea oxidation-assisted electrocatalytic hydrogen production, comprising the following steps: (1) The carbon paper was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, then placed in an aqueous solution of 2-methylimidazole for physical deposition reaction, and then immersed in a mixed aqueous solution of 2-methylimidazole and cobalt nitrate for heating deposition reaction. After the reaction ended, the sample was taken out, washed with ultrapure water, and dried under vacuum to obtain sample A; (2) Sample A was placed in a tube furnace for calcination and naturally cooled to room temperature to obtain sample B; (3) Sample B was subjected to electrochemical deposition treatment with an aqueous solution of nickel nitrate as the electrochemical deposition solution, and then the sample was rinsed with ultrapure water and dried under vacuum to obtain sample C; (4) Sample C was placed in a tube furnace, sulfur powder was added for calcination, and it was naturally cooled to room temperature to obtain the catalyst.
[0006] In the above step (1), the carbon paper was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water and then reserved; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain an aqueous solution of 2-methylimidazole; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain an aqueous solution of cobalt nitrate; the washed carbon paper was immersed in 20 mL of the aqueous solution of 2-methylimidazole, and a physical deposition reaction was carried out at room temperature. Then, the carbon paper was taken out from the aqueous solution of 2-methylimidazole, the aqueous solution of 2-methylimidazole after the physical deposition reaction and 20 mL of the aqueous solution of cobalt nitrate were quickly stirred and mixed to obtain a mixed aqueous solution. Then, the carbon paper taken out from the aqueous solution of 2-methylimidazole was immersed in the mixed aqueous solution, and a heating deposition reaction was carried out at 30 °C. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried under vacuum at 50 °C to obtain sample A; Among them, the time of the physical deposition reaction was 10 min, and the time of the heating deposition reaction was 7 - 15 h.
[0007] In the above step (2), the conditions for calcination were: in an argon atmosphere, the temperature was raised to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h.
[0008] In the above step (3), the concentration of the aqueous solution of nickel nitrate was 0.2 M.
[0009] In the above step (3), the current density for the electrochemical deposition treatment was -10 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 900 - 2400 s.
[0010] In the above step (4), the conditions for calcination were: in an argon atmosphere, the temperature was raised to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h.
[0011] A catalyst obtained by the above preparation method.
[0012] The application of the above-mentioned catalyst in the catalysis of urea oxidation reaction.
[0013] The application of the above-mentioned catalyst in the field of hydrogen production assisted by electrolysis of urea.
[0014] The advantages of the present invention are as follows: (1) The prepared catalyst exhibits excellent catalytic activity in the urea oxidation reaction, significantly reducing the overpotential compared with the traditional oxygen evolution reaction and remarkably improving the energy conversion efficiency.
[0015] (2) The synthesis method of the prepared catalyst is simple. By utilizing the electron coupling effect between transition metals, the electronic structure of the active sites is optimized, the surface dynamic reconstruction is accelerated, and fast reaction kinetics is achieved, showing the prospect of industrial application.
[0016] (3) The prepared catalyst has both the functions of urea degradation in wastewater and energy-saving hydrogen production. It maintains long-term stability under 0.33 M urea conditions, and without noble metals, it has low cost, providing an integrated solution for sustainable energy and environmental governance, and having great potential for application in the field of energy chemistry. Description of the Drawings
[0017] Figure 1 : Voltage-current diagrams of the catalysts in Examples 1 to 5 in the LSV test (a) and comparison diagram of the urea oxidation reaction performance and oxygen evolution reaction performance of the catalyst electrode material in Example 1 (b).
[0018] Figure 2 : Impedance diagrams (a) and Bode diagrams (b) of Examples 3, Comparative Example 1, and Comparative Example in EIS.
[0019] Figure 3 : XPS spectra of the catalysts in Examples 3, Comparative Example 1, and Comparative Example 2.
[0020] Figure 4 : Contact angle performance exhibition diagrams of the catalysts in Examples 3, Comparative Example 1, and Comparative Example 2 with the solution.
[0021] Figure 5 : Tafel diagrams (a) and effective active area calculation diagrams (b) of the catalysts in Examples 3, Comparative Example 1, and Comparative Example 2.
[0022] Figure 6 : Stability test diagram of the catalyst in Example 3.
[0023] Figure 7 : Hydrogen production performance diagrams of the catalysts in Examples 3, Comparative Example 1, and Comparative Example 2.
[0024] Figure 8 : TEM diagram of the morphological characterization of the catalyst in Example 3. Detailed Embodiments
[0025] To make the content of the present invention more understandable, the technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, the present invention is not limited thereto.
[0026] Example 1: S1: Prepare Sample A The commercial carbon paper (size: 2 cm × 3 cm × 0.1 mm, weight: 0.35 g) was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, and then reserved; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain Solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain Solution B. The washed carbon paper was immersed in 20 mL of Solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then, the carbon paper was taken out from Solution A. The physically deposited Solution A and 20 mL of Solution B were quickly stirred and mixed to obtain a mixed solution. Then, the carbon paper taken out from Solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 7 h. After the reaction, the carbon paper was taken out, washed with ultrapure water, and dried in vacuum at 50 °C to obtain Sample A.
[0027] S2: Prepare Sample B The Sample A of S1 was placed in a tubular furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain Sample B.
[0028] S3: Prepare Sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain Solution C. Using Solution C as the electrochemically deposited solution, the Sample B of S2 was subjected to electrochemically deposited treatment by a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode). The current density of the electrochemically deposited was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1200 s. The sample was rinsed with ultrapure water and dried in vacuum at 50 °C to obtain Sample C.
[0029] S4: Prepare Sample D The Sample C of S3 was placed in a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain Sample D, which is the catalyst.
[0030] Example 2: S1: Prepare Sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was ultrasonically washed with absolute ethanol and then rinsed with ultrapure water, and set aside; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then, the carbon paper was taken out from solution A. The physically deposited solution A and 20 mL of solution B were quickly stirred and mixed to obtain a mixed solution. Then, the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 9 h. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried in vacuo at 50 °C to obtain sample A.
[0031] S2: Preparation of sample B The sample A of S1 was placed in a tubular furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the furnace temperature was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0032] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemically deposited solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemically deposited treatment on the sample B of S2. The current density of the electrochemically deposited was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1200 s. The sample was rinsed with ultrapure water and dried in vacuo at 50 °C to obtain sample C.
[0033] S4: Preparation of sample D The sample C of S3 was placed in a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the furnace temperature was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which was the catalyst.
[0034] Example 3: S1: Preparation of sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, and then reserved; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then, the carbon paper was taken out from solution A. The physically deposited solution A and 20 mL of solution B were quickly stirred and mixed to obtain a mixed solution. Then, the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 11 h. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried in vacuum at 50 °C to obtain sample A.
[0035] S2: Preparation of sample B The sample A of S1 was placed in a tubular furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0036] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemical deposition solution, the sample B of S2 was subjected to electrochemical deposition treatment by a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode). The current density of the electrochemical deposition was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1200 s. The sample was rinsed with ultrapure water and dried in vacuum at 50 °C to obtain sample C.
[0037] S4: Preparation of sample D The sample C of S3 was placed in a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which was the catalyst.
[0038] Example 4: S1: Preparation of sample A The commercial carbon paper (sized 2 cm × 3 cm × 0.1 mm and weighing 0.35 g) was ultrasonically washed with anhydrous ethanol and then rinsed with ultrapure water, and set aside; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then the carbon paper was taken out from solution A, and the physically deposited solution A and 20 mL of solution B were quickly stirred and mixed to obtain a mixed solution. Then the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 13 h. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried in vacuum at 50 °C to obtain sample A.
[0039] S2: Preparation of sample B The sample A of S1 was put into a tubular furnace, and in an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0040] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemically deposited solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemically deposited treatment on the sample B of S2. The current density of the electrochemically deposited was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1200 s. The sample was rinsed with ultrapure water and dried in vacuum at 50 °C to obtain sample C.
[0041] S4: Preparation of sample D The sample C of S3 was put into a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which was the catalyst.
[0042] Example 5: S1: Preparation of sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, and then reserved; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then, the carbon paper was taken out from solution A. The physically deposited solution A and 20 mL of solution B were rapidly stirred and mixed to obtain a mixed solution. Then, the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 15 h. After the reaction, the carbon paper was taken out, washed with ultrapure water, and dried in vacuum at 50 °C to obtain sample A.
[0043] S2: Preparation of sample B The sample A of S1 was placed in a tubular furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0044] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemically deposited solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemically deposited treatment on the sample B of S2. The current density of the electrochemically deposited was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1200 s. The sample was rinsed with ultrapure water and dried in vacuum at 50 °C to obtain sample C.
[0045] S4: Preparation of sample D The sample C of S3 was placed in a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which was the catalyst.
[0046] Example 6: S1: Preparation of sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was ultrasonically washed with absolute ethanol and then rinsed with ultrapure water, and then set aside; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then the carbon paper was taken out from solution A. The physically deposited solution A and 20 mL of solution B were rapidly stirred and mixed to obtain a mixed solution. Then the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 11 h. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried in vacuo at 50 °C to obtain sample A.
[0047] S2: Preparation of sample B The sample A of S1 was placed in a tube furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the furnace temperature was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0048] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemically deposited solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemically deposited treatment on the sample B of S2. The current density of the electrochemical deposition was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 900 s. The sample was rinsed with ultrapure water and dried in vacuo at 50 °C to obtain sample C.
[0049] S4: Preparation of sample D The sample C of S3 was placed in a tube furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the furnace temperature was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which is the catalyst.
[0050] Example VII: S1: Preparation of sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, and then reserved; 10 mmol of 2-methylimidazole was weighed and dissolved in 20 mL of ultrapure water to obtain solution A; 0.625 mmol of cobalt nitrate hexahydrate was weighed and dissolved in 20 mL of ultrapure water to obtain solution B. The washed carbon paper was immersed in 20 mL of solution A, and a physical deposition reaction was carried out at room temperature for 10 min. Then, the carbon paper was taken out from solution A. The physically deposited solution A and 20 mL of solution B were rapidly stirred and mixed to obtain a mixed solution. Then, the carbon paper taken out from solution A was immersed in the mixed solution, and a heating deposition reaction was carried out at 30 °C for 11 h. After the reaction ended, the carbon paper was taken out, washed with ultrapure water, and dried in vacuum at 50 °C to obtain sample A.
[0051] S2: Preparation of sample B The sample A of S1 was placed in a tubular furnace. In an argon atmosphere of 50 sccm, it was heated to 800 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 800 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample B.
[0052] S3: Preparation of sample C 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution C. Using solution C as the electrochemical deposition solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemical deposition treatment on the sample B of S2. The current density of the electrochemical deposition was -5 mA / cm 2 , the voltage was -0.1 V, the temperature was 20 °C, and the time was 1500 s. The sample was rinsed with ultrapure water and dried in vacuum at 50 °C to obtain sample C.
[0053] S4: Preparation of sample D The sample C of S3 was placed in a tubular furnace, 0.3 g of sulfur powder was added, and in an argon atmosphere of 50 sccm, it was heated to 300 °C at a heating rate of 10 °C / min, and the temperature in the furnace was maintained at 300 °C for calcination for 2 h, and then naturally cooled to room temperature to obtain sample D, which is the catalyst.
[0054] Comparative example 1 (without introducing cobalt element): S1: Preparation of sample A The commercial carbon paper (with dimensions of 2 cm × 3 cm × 0.1 mm and a weight of 0.35 g) was successively ultrasonically washed with absolute ethanol and rinsed with ultrapure water, and then reserved; 1 mmol of nickel nitrate was dissolved in 50 ml of ultrapure water to obtain solution A. Using solution A as the electrochemical deposition solution, a three-electrode electrolysis system (Hg / HgO as the reference electrode and a carbon rod as the counter electrode) was used to carry out electrochemical deposition treatment on the washed carbon paper. The current density of the electrochemical deposition was -5 mA / cm 2, with a voltage of -0.1 V, a temperature of 20 °C, and a time of 1200 s, rinse the sample with ultrapure water and dry it in vacuum at 50 °C to obtain sample A.
[0055] S2: Prepare sample B Put sample A from S1 into a tubular furnace, add 0.3 g of sulfur powder, and in an argon atmosphere of 50 sccm, heat it at a heating rate of 10 °C / min to 300 °C, keep the furnace temperature at 300 °C and calcine for 2 h, then naturally cool to room temperature to obtain sample B, which is the catalyst.
[0056] Comparative example 2 (without introducing nickel element): S1: Prepare sample A Ultrasonically wash the commercial carbon paper (size: 2 cm × 3 cm × 0.1 mm, weight: 0.35 g) with absolute ethanol and then rinse it with ultrapure water for later use; weigh 10 mmol of 2-methylimidazole and dissolve it in 20 mL of ultrapure water to obtain solution A; weigh 0.625 mmol of cobalt nitrate hexahydrate and dissolve it in 20 mL of ultrapure water to obtain solution B. Immerse the washed carbon paper into 20 mL of solution A, carry out a physical deposition reaction at room temperature for 10 min, then take out the carbon paper from solution A, quickly stir and mix the physical deposition reaction solution A and 20 mL of solution B to obtain a mixed solution, and then immerse the carbon paper taken out from solution A into the mixed solution, carry out a heating deposition reaction at 30 °C for 11 h. After the reaction, take out the carbon paper, wash it with ultrapure water, and dry it in vacuum at 50 °C to obtain sample A.
[0057] S2: Prepare sample B Put sample A from S1 into a tubular furnace, and in an argon atmosphere of 50 sccm, heat it at a heating rate of 10 °C / min to 800 °C, keep the furnace temperature at 800 °C and calcine for 2 h, then naturally cool to room temperature to obtain sample B.
[0058] S3: Prepare sample C Put sample B from S2 into a tubular furnace, add 0.3 g of sulfur powder, and in an argon atmosphere of 50 sccm, heat it at a heating rate of 10 °C / min to 300 °C, keep the furnace temperature at 300 °C and calcine for 2 h, then naturally cool to room temperature to obtain sample C, which is the catalyst.
[0059] Figure 1 a is the voltage-current diagram of the catalysts in Examples 1 to 5 during the LSV test; the test is carried out using a three-electrode system, the catalyst is the working electrode, Hg / HgO is the reference electrode, the carbon rod is the counter electrode, the scanning rate is 20 mV / s, the scanning range is 0 - 1 V, and the electrolyte is an aqueous solution containing 1 M KOH and 0.33 M urea. Figure 1Figure b shows the comparison of the urea oxidation reaction performance and oxygen evolution reaction performance of the catalyst in Example 1. The test was carried out using a three-electrode system. The catalyst was the working electrode, Hg / HgO was the reference electrode, and the carbon rod was the counter electrode. The scanning rate was 20 mV / s, and the scanning range was 0 - 1 V. The test solution for the oxygen evolution reaction performance test was 1 M KOH aqueous solution, and the test solution for the urea oxidation reaction performance test was an aqueous solution containing 1 M KOH and 0.33 M urea. The results showed that the urea oxidation catalytic activity of the catalyst was significantly improved compared with the oxygen evolution reaction performance.
[0060] Figure 2 Figure a shows the EIS impedance performance test diagram of the catalysts in Example 3, Comparative Example 1, and Comparative Example 2. The test was carried out using a three-electrode system. The catalyst was the working electrode, Hg / HgO was the reference electrode, and the carbon rod was the counter electrode. The scanning rate was 20 mV / s, and the scanning range was 0 - 1 V. The electrolyte was an aqueous solution containing 1 M KOH and 0.33 M urea. Through electrochemical tests, it was found that the impedance magnitudes of the three catalysts at 1.4 V were Comparative Example 1 > Comparative Example 2 > Example 3, indicating that the electron transfer rate of the catalyst in Example 3 was significantly improved. At the same time, through electrochemical tests, the starting potential range of the catalyst in Example 3 was confirmed Figure 2 Figure b. It can be found through the potential range screening of the Bode diagram that the urea oxidation reaction starts at 1.2 - 1.3 V.
[0061] Figure 3 Figure shows the XPS diagrams of the catalysts in Example 3, Comparative Example 1, and Comparative Example 2. The XPS analysis results showed that Ni and Co elements were successfully introduced into the catalyst in Example 3, indicating that the catalyst was successfully synthesized.
[0062] Figure 4 Figure shows the solution contact angle diagrams of the catalysts in Example 3, Comparative Example 1, and Comparative Example 2. As can be seen from the figure, due to the interaction between Ni and Co elements, the solution contact angle of the catalyst decreased from 137.7° to 55.3° and then to 0°. It shows that the introduction of Co element into Ni material can significantly reduce the contact angle between the material and the solution, enabling it to better contact the solution and release gas faster, thereby improving the catalytic performance.
[0063] Figure 5Tafel slope comparison chart (a) and ECSA active surface area comparison chart (b) of the catalysts of Example 3, Comparative Example 1, and Comparative Example 2; the test was carried out using a three-electrode system, the catalyst was the working electrode, Hg / HgO was the reference electrode, the carbon rod was the counter electrode, the scanning rate was 20 mV / s, the scanning range was 0 - 1 V, and the electrolyte was an aqueous solution containing 1 M KOH and 0.33 M urea. The Tafel slopes of the three catalysts were measured by electrochemical tests, and it was obtained that the tafel value of the catalyst in Example 3 (114.7 mV / dec) was much smaller than that of Comparative Example 1 (163.1 mV / dec) and Comparative Example 2 (182.7 mV / dec), indicating that the catalyst in Example 3 had a better current response and the best performance. The Cdl value of the catalyst in Example 3 (6.71 mF / cm 2 ) was much larger than that of Comparative Example 1 (1.55 mF / cm 2 ) and Comparative Example 2 (4.68 mF / cm 2 ), indicating that the number of active sites exposed by the catalyst in Example 3 was more and the catalytic efficiency was higher.
[0064] Figure 6 The following is the stability test result of the catalyst in Example 3. Its stability was investigated by chronoamperometry. After the material underwent a 36-h urea oxidation catalytic reaction, it could still maintain good catalytic performance for the urea oxidation reaction, and the change in the current was within 5%, which fully confirmed that the catalyst had good stability.
[0065] Figure 7 The following is the hydrogen production performance comparison chart of the catalysts of Example 3, Comparative Example 1, and Comparative Example 2. The cathodic curves of the three catalysts were measured by electrochemical tests, and the test solution was an aqueous solution containing 1 M KOH and 0.33 M urea. It was obtained that the catalytic activity of the hydrogen production performance of the catalyst in Example 3 could be greatly improved.
[0066] Figure 8 The following is the morphological characterization diagram of the catalyst in Example 3. From Figure 8 a and 8b, it can be seen that the catalyst presented a hierarchical lamellar structure. From Figure 8 c, the crystal structure could be observed more obviously. From Figure 8 d - 8g, it can be seen that the elements in the material were dispersed on the surface of the material, indicating that the prepared catalyst grew evenly.
Claims
1. A preparation method of a catalyst for urea oxidation-assisted electrocatalytic hydrogen production, characterized in that: It includes the following steps: (1) Ultrasonically wash the carbon paper with absolute ethanol and then rinse it with ultrapure water successively. Then place it in an aqueous 2-methylimidazole solution for physical deposition reaction, and then immerse it in a mixed aqueous solution of 2-methylimidazole and cobalt nitrate for heat deposition reaction. After the reaction ends, take out the sample, wash it with ultrapure water, and dry it under vacuum to obtain sample A; (2) Place sample A in a tubular furnace for calcination and cool it naturally to room temperature to obtain sample B; (3) Perform electrochemical deposition treatment on sample B using an aqueous nickel nitrate solution as the electrochemical deposition solution, then rinse the sample with ultrapure water and dry it under vacuum to obtain sample C; (4) Place sample C in a tubular furnace, add sulfur powder for calcination, and cool it naturally to room temperature to obtain the catalyst.
2. The preparation method according to claim 1, characterized in that: In step (1), the carbon paper is ultrasonically washed with absolute ethanol and then rinsed with ultrapure water successively for standby; weigh 10 mmol of 2-methylimidazole and dissolve it in 20 mL of ultrapure water to obtain an aqueous 2-methylimidazole solution; weigh 0.625 mmol of cobalt nitrate hexahydrate and dissolve it in 20 mL of ultrapure water to obtain an aqueous cobalt nitrate solution; immerse the washed carbon paper in 20 mL of the aqueous 2-methylimidazole solution and carry out a physical deposition reaction at room temperature. Then take out the carbon paper from the aqueous 2-methylimidazole solution, quickly stir and mix the aqueous 2-methylimidazole solution after the physical deposition reaction and 20 mL of the aqueous cobalt nitrate solution to obtain a mixed aqueous solution. Then immerse the carbon paper taken out from the aqueous 2-methylimidazole solution in the mixed aqueous solution and carry out a heat deposition reaction at 30 °C. After the reaction ends, take out the carbon paper, wash it with ultrapure water, and dry it under vacuum at 50 °C to obtain sample A.
3. The preparation method according to claim 2, characterized in that: The time of the physical deposition reaction is 10 min, and the time of the heat deposition reaction is 7 - 15 h.
4. The preparation method according to claim 1, characterized in that: In step (2), the conditions for calcination are: in an argon atmosphere, heat up to 800 °C at a heating rate of 10 °C / min, and keep the furnace temperature at 800 °C for calcination for 2 h.
5. The preparation method according to claim 1, characterized in that: In step (3), the concentration of the aqueous nickel nitrate solution is 0.2 M.
6. The preparation method according to claim 1, wherein: In step (3), the current density of the electrochemical deposition treatment is -10 mA / cm 2 , the voltage is -0.1 V, the temperature is 20 °C, and the time is 900 - 2400 s.
7. The preparation method according to claim 1, wherein: In step (4), the conditions for calcination are: in an argon atmosphere, heat up to 300 °C at a heating rate of 10 °C / min, and keep the furnace temperature at 300 °C for calcination for 2 h.
8. A catalyst obtained by the preparation method according to any one of claims 1 - 7.
9. Use of the catalyst according to claim 8, characterized in that: Applied to the catalysis of urea oxidation reaction.
10. The use of the catalyst according to claim 8, characterized in that: Applied to the field of hydrogen production assisted by electrolysis of urea.