A method for preparing a nitrogen-doped carbon-supported ruthenium catalyst for electrolytic hydrogen evolution

Abstract

The present application relates to a kind of for electrolytic hydrogen production with the preparation method and its application of nitrogen-doped carbon material as carrier load ruthenium catalyst, wherein with the preparation method of nitrogen-doped carbon material as carrier load ruthenium catalyst, it includes the following steps: (1) the preparation of nitrogen-doped carbon carrier;Melamine, lignin or the uniform mixing of primary biomass containing lignin obtains the precursor of nitrogen-doped carbon material;The precursor is calcined under high-temperature argon atmosphere to obtain nitrogen-doped carbon material.(2) load ruthenium on nitrogen-doped carbon carrier;After the uniform mixing of precursor ruthenium salt and nitrogen-doped carbon material is dried, it is calcined under high-temperature hydrogen atmosphere to obtain with the preparation method of nitrogen-doped carbon material as carrier load ruthenium catalyst.The operation is simple, and part of carbon comes from natural biomass, and the cost is low, and the catalyst obtained in catalytic hydrogen evolution process has higher catalytic activity.

Description

Technical Field

[0001] This invention relates to a method for preparing a ruthenium catalyst supported on a nitrogen-doped carbon material and its application in hydrogen production via water electrolysis, belonging to the field of catalyst preparation technology. Background Technology

[0002] Energy is a crucial material foundation for economic development and social progress. Severe energy pressures and environmental pollution threaten ecological balance and constrain sustainable socio-economic development. Therefore, developing new energy industries characterized by low energy consumption and low emissions is imperative. Hydrogen energy, as an ideal green energy source, possesses unparalleled potential development value. Compared to fossil fuels, hydrogen has advantages such as high calorific value, concentrated heat energy, low heat loss, good combustion performance, and its combustion product being environmentally friendly and pollution-free water. Electrolysis of water is an ideal method for producing high-purity hydrogen; however, the high overpotential of the cathode reaction in water electrolysis significantly limits its commercial application. Therefore, developing a catalyst with a low onset potential, a small overpotential, and an extremely high reaction rate is crucial for hydrogen production via water electrolysis.

[0003] Carbon materials are widely used in energy conversion due to their unique physicochemical properties, controllable molecular structure and chemical composition, excellent electrical conductivity, resistance to acid and alkali corrosion, and environmental friendliness. Research has found that by utilizing the differences in electronegativity and atomic size between nitrogen and carbon atoms, introducing nitrogen atoms into the carbon framework can modify the physicochemical properties of carbon materials, activate carbon atoms near nitrogen atoms to obtain more reaction sites, and thus greatly improve the cathode reaction activity of water electrolysis. The preparation method of nitrogen-doped carbon materials typically involves uniformly mixing nitrogen-containing molecules with a carbon source followed by heat treatment. This invention uses lignin as the carbon source. Lignin is a bioactive natural polymer with many advantages over other carbon sources, including resource renewability and wide availability. With a carbon content as high as 50%, lignin is an ideal raw material for preparing nitrogen-doped carbon materials.

[0004] Precious metal phosphorus (Pt) is generally considered the most efficient catalyst for the cathode reaction of water electrolysis to produce hydrogen, exhibiting good catalytic activity. However, its high price greatly limits its industrial application. To reduce costs, some naturally abundant precious metals, such as Ru, Ir, and Pd, have also been used as cathode electrocatalysts in recent years. Studies have shown that the Gibbs free energy and MH bond energy (where M represents the metal) of the metal determine its activity in water electrolysis to produce hydrogen. Based on Ru's exchange current density, which is second only to Pt in the volcano reaction diagram, and its moderate Ru-H bond energy, Ru-based catalysts can be considered the best alternative to Pt-based catalysts. Summary of the Invention

[0005] In view of the above background, the problem to be solved by the present invention is to provide a method for preparing a ruthenium catalyst supported on a nitrogen-doped carbon material and its application in hydrogen production by electrolysis. The method for preparing the cathode catalyst for hydrogen production by water electrolysis provided by the present invention is simple, low in cost, and has excellent activity in hydrogen production by water electrolysis under both acidic and alkaline conditions.

[0006] The present invention provides a method for preparing a ruthenium catalyst supported on a nitrogen-doped carbon material, comprising the following steps: (1) Preparation of nitrogen-doped carbon support; nitrogen-doped carbon material is obtained by calcining the precursor nitrogen source and carbon source under high temperature argon atmosphere; (2) Ruthenium is loaded on nitrogen-doped carbon support; ruthenium precursor salt and nitrogen-doped carbon material are calcined under high temperature hydrogen atmosphere to obtain ruthenium catalyst supported on nitrogen-doped carbon material.

[0007] The preparation methods of the precursor nitrogen source and carbon source in step (1) are as follows: Melamine and lignin are uniformly mixed in a mass ratio of 1-20:1 to obtain a precursor for nitrogen-doped carbon materials.

[0008] The calcination procedure in step (1) is as follows: the heating rate is 2℃ / min, the temperature is raised to 600℃, and the calcination time is 2h; then the temperature is raised to the final temperature at a heating rate of 2℃ / min, and the calcination time is 1h. The final temperature is 800-1200℃, preferably 900-1100℃.

[0009] In step (2), the ruthenium salt is selected from ruthenium trichloride.

[0010] In step (2), the ruthenium trichloride is mixed with nitrogen-doped carbon at a mass ratio of 1:4 to 99 and then dried.

[0011] In step (2), the calcination temperature is 400℃, the calcination time is 3h, and the heating rate is 5℃ / min.

[0012] The application of ruthenium catalyst supported on nitrogen-doped carbon material in water electrolysis for hydrogen production.

[0013] The loading amount of the ruthenium catalyst supported on nitrogen-doped carbon material is 0.5-1.0 mg / cm³. 2 .

[0014] The hydrogen production reaction by water electrolysis is carried out in an acidic 0.5 mol / L H2SO4 electrolyte and an alkaline 1.0 mol / L KOH electrolyte, with the H2SO4 electrolyte having a pH of 0 and the KOH electrolyte having a pH of 14.

[0015] The beneficial effects of this invention are: The results show that the ruthenium catalyst supported on nitrogen-doped carbon material exhibits excellent catalytic activity in both acidic 0.5 mol / L H₂SO₄ electrolyte and alkaline 1.0 mol / L KOH electrolyte. The catalyst achieves a current density of 10 mA / cm² in 0.5 mol / L H₂SO₄. 2 The corresponding hydrogen evolution overpotential is -0.047V, and the current density of this catalyst in 1.0 mol / L KOH is 10 mA / cm². 2 The corresponding hydrogen evolution overpotential is -0.013V, far lower than that of commercial platinum-carbon catalysts. This demonstrates that ruthenium supported on nitrogen-doped carbon can serve as a highly efficient hydrogen evolution catalyst. The introduction of ruthenium sites facilitates water adsorption and dissociation, and also promotes the Tafel reaction. This method of preparing ruthenium catalysts supported on nitrogen-doped carbon is simple, inexpensive, and exhibits high catalytic activity, showing promise as a replacement for noble metal Pt-based materials. Attached Figure Description

[0016] Figure 1 This is a distribution diagram of carbon, nitrogen, oxygen and ruthenium in the target product obtained in Example 1.

[0017] Figure 2 This is a distribution diagram of carbon, nitrogen, oxygen, and ruthenium in the target product obtained in Comparative Example 1.

[0018] Figure 3 This is a distribution diagram of carbon, oxygen, and ruthenium in the target product obtained in Comparative Example 2. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described in detail below with reference to examples.

[0020] Example 1: The nitrogen source is melamine, and the carbon source is alkali lignin, with a mass ratio of 20:1; (1) Melamine and alkali lignin were mixed evenly in a mortar at a mass ratio of 20:1 to obtain the precursor; (2) The precursor was placed in a high-temperature tube furnace and heated to 600°C at a heating rate of 2°C / min under an argon atmosphere. After calcination for 2 hours, the temperature was further increased to 1000°C at a heating rate of 2°C / min and calcined for 1 hour to obtain the desired nitrogen-doped carbon material, denoted as NC-AL; (3) Prepare a ruthenium trichloride solution with a ruthenium mass percentage of 2%. Take 0.5 g of the prepared ruthenium trichloride solution and place it in a beaker. Add 0.5 g of NC-AL to the beaker, sonicate for 30 min, and then dry to obtain the catalyst precursor; (4) The catalyst precursor was placed in a reduction furnace and heated to 400°C at a heating rate of 5°C / min under a hydrogen atmosphere. After calcination for 3 hours, the target catalyst was obtained, which was denoted as 2%Ru / NC-AL.

[0021] Example 2: The only difference from Example 1 is that the carbon source is organic lignin. The resulting target catalyst is denoted as 2%Ru / NC-OL.

[0022] Example 3: Preparation of the 2%Ru / NC-EL catalyst. The only difference from Example 1 is that the carbon source is enzymatic hydrolysis of lignin. The resulting target catalyst is denoted as 2%Ru / NC-EL.

[0023] Example 4: The only difference from Example 1 is that the carbon source is birch. The resulting target catalyst is denoted as 2%Ru / NC-B.

[0024] Comparative Example 1: (1) Take 6g of melamine as a precursor; (2) The precursor was placed in a high-temperature tube furnace and heated to 600°C at a heating rate of 2°C / min under an argon atmosphere. After calcination for 2 hours, a graphitic carbon nitride material was obtained, denoted as g-C3N4.

[0025] Comparative Example 2: (1) Prepare a ruthenium trichloride solution with a ruthenium mass percentage of 2%. Take 0.5 g of the prepared ruthenium trichloride solution and place it in a beaker. Add 0.5 g of g-C3N4 to the beaker, sonicate for 30 min, and then dry to obtain the catalyst precursor; (2) The catalyst precursor was placed in a reduction furnace and heated to 400°C at a heating rate of 5°C / min under a hydrogen atmosphere. After calcination for 3 hours, the target catalyst was obtained, which was denoted as 2%Ru / g-C3N4.

[0026] Comparative Example 3: (1) Take 3g of alkali lignin as a precursor; (2) The precursor was placed in a high-temperature tube furnace and heated to 600°C at a heating rate of 2°C / min under an argon atmosphere. After calcination for 2 hours, the temperature was increased to 1000°C at a heating rate of 2°C / min and calcined for 1 hour to obtain carbon material, denoted as C.

[0027] Comparative Example 4: (1) Prepare a ruthenium trichloride solution with a ruthenium mass percentage of 2%. Take 0.5 g of the prepared ruthenium trichloride solution and place it in a beaker. Add 0.5 g of C to the beaker, sonicate for 30 min, and then dry to obtain the catalyst precursor; (2) The catalyst precursor was placed in a reduction furnace and heated to 400°C at a heating rate of 5°C / min under a hydrogen atmosphere. After calcination for 3 hours, the target catalyst was obtained, which was denoted as 2%Ru / C.

[0028] Comparative Example 5: The 20% Pt / C catalyst was purchased from Suzhou Shengernuo Technology Co., Ltd.

[0029] Electrolysis of water to produce hydrogen performance test steps Experiments were conducted on the catalyst samples obtained in Examples 1-4 and Comparative Examples 1-5 respectively; 5 mg of sample was dispersed in 500 μL of ethanol and 25 μL of Nafion solution, and ultrasonically dispersed for 30 min to obtain homogeneous catalyst ink, which was used as a dispersion for later use. 50-100 μL of the dispersion was dropped onto both sides of carbon paper in two portions to prepare a working electrode. After air drying, it was used for the hydrogen evolution reaction. The catalyst loading in the samples ranged from 0.5 to 1.0 mg / cm³. 2 (The content of catalyst loaded on the electrode surface per unit area), the test voltage range for the hydrogen evolution reaction is 0.1-0.2V (vs RHE); the hydrogen evolution reaction is carried out in H2-saturated 0.5mol / L H2SO4 electrolyte and 1.0mol / L KOH electrolyte, the pH of H2SO4 electrolyte is 0, and the pH of KOH electrolyte is 14.

[0030] The electrocatalytic hydrogen evolution performance of the target products obtained in Examples 1-4 and Comparative Examples 1-5 above is shown in Table 1.

[0031] Table 1. Hydrogen evolution activity data for different catalysts in water electrolysis.

[0032] Table 1 shows that when the current density reaches 10 mA / cm² 2 At that time, the 2% Ru / NC-AL catalyst sample had the highest hydrogen evolution activity in water electrolysis, with overpotentials of 47 mV and 13 mV in H2-saturated 0.5 mol / L H2SO4 electrolyte and 1.0 mol / L KOH electrolyte, respectively, making it the optimal catalyst.

Claims

1. A method for preparing a ruthenium catalyst supported on a nitrogen-doped carbon material, characterized in that, Includes the following steps: (1) Preparation of nitrogen-doped carbon support: Nitrogen-doped carbon is obtained by calcining the precursor nitrogen source and carbon source under a high temperature argon atmosphere; (2) Ruthenium supported on nitrogen-doped carbon: The precursor ruthenium salt and the nitrogen-doped carbon were calcined in a high-temperature hydrogen atmosphere to obtain a catalyst with ruthenium supported on nitrogen-doped carbon. In step (1), the precursor nitrogen source is melamine, and the carbon source is lignin. In step (1), the nitrogen-doped carbon precursor is prepared as follows: melamine and lignin source are uniformly mixed to obtain the nitrogen-doped carbon precursor; In step (1), the calcination is as follows: the heating rate is 2℃ / min, the temperature is raised to 600℃, and the calcination time is 2h; then the temperature is raised to the final temperature at a heating rate of 2℃ / min, and the calcination time is 1h, to obtain nitrogen-doped carbon; wherein the final temperature is 800-1200℃. The lignin source includes isolated lignin and lignin-containing protozoa; wherein the isolated lignin is alkali lignin, organic lignin, or enzymatically hydrolyzed lignin; and the lignin-containing protozoa is hardwood or softwood.

2. The preparation method according to claim 1, characterized in that: The mass ratio of melamine to lignin source is 1-20:

1.

3. The preparation method according to claim 1, characterized in that, The method for loading ruthenium on a nitrogen-doped carbon support in step (2) is as follows: Ruthenium salt was uniformly mixed with nitrogen-doped carbon and dried, then calcined in a hydrogen atmosphere to obtain a catalyst with ruthenium supported on nitrogen-doped carbon.

4. The preparation method according to claim 3, characterized in that, In step (2), the ruthenium salt is selected from ruthenium trichloride.

5. The preparation method according to claim 4, characterized in that, In step (2), the mass ratio of ruthenium to nitrogen-doped carbon in ruthenium trichloride is 1:4-99.

6. The preparation method according to claim 3, characterized in that, In step (2), the calcination temperature is 400℃, the calcination time is 3h, and the heating rate is 5℃ / min.

7. The application of a ruthenium catalyst supported on a nitrogen-doped carbon material, prepared by the method according to any one of claims 1-6, in hydrogen production by water electrolysis.

8. The application according to claim 7, characterized in that, Five mg of ruthenium catalyst sample supported on nitrogen-doped carbon material was dispersed in 500 μL of ethanol and 25 μL of Nafion solution. After ultrasonic dispersion for 30 min, a homogeneous catalyst ink was obtained and used as a dispersion for later use. 50-100 μL of the dispersion was dropped onto both sides of carbon paper in two batches to prepare a working electrode. After natural drying, it was used for hydrogen evolution reaction.

9. The application according to claim 8, characterized in that, The loading amount of the ruthenium catalyst supported on nitrogen-doped carbon material is 0.5-1.0 mg / cm³. 2 .

10. The application according to claim 9, characterized in that, The hydrogen evolution reaction is carried out in an acidic 0.5 mol / L H2SO4 electrolyte saturated with H2 and an alkaline 1.0 mol / L KOH electrolyte, with the H2SO4 electrolyte having a pH of 0 and the KOH electrolyte having a pH of 14.

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