Preparation method of catalytic electrode and application of catalytic electrode in photoelectrocatalytic reduction of nitrogen
By spraying catalyst slurry onto the electrode of the photoelectrocatalytic reduction of nitrogen and setting up continuous flow of nitrogen and electrolyte, the problem of low mass transfer efficiency was solved, and the efficient reduction of nitrogen to ammonia was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN AERONAUTICAL UNIV
- Filing Date
- 2026-03-03
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, the mass transfer efficiency of nitrogen gas in the photoelectrocatalytic nitrogen reduction process is low, resulting in low current density and poor selectivity.
The method for preparing catalytic electrodes includes spraying a catalyst slurry onto a gas diffusion layer to form anode and cathode gas diffusion electrodes, and setting up continuously flowing nitrogen gas and electrolyte in an electrolytic cell. A stable three-phase interface is formed through the gas diffusion layer to improve the mass transfer efficiency of nitrogen gas.
This improved the mass transfer efficiency of nitrogen, enhanced the current density and selectivity, and enabled a highly efficient process for reducing nitrogen to ammonia.
Smart Images
Figure CN122013219A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photoelectrocatalytic reduction of nitrogen technology, and relates to a method for preparing a catalytic electrode and its application in photoelectrocatalytic reduction of nitrogen. Background Technology
[0002] Ammonia (NH3) is one of the world's most important chemical products. It can not only be used to synthesize artificial fertilizers, providing sufficient food for human society, but also, due to its high energy density (one-third that of diesel) and ease of transportation, serve as an important energy carrier and storage intermediate, making it a highly efficient renewable fuel. Nitrogen (N2) constitutes approximately 78% of the air. If the ubiquitous N2 in the air could be reduced to the more economically viable NH3, it would undoubtedly solve fertilizer and industrial development problems. Currently, industrial NH3 production mainly employs the Haber-Bosch process, which converts ammonia (NH3) under high temperature (400-500℃), high pressure (200-300 atm), and the presence of a catalyst (Fe or Ru-based). However, this reaction is kineticly slow and requires high temperatures to accelerate. The energy consumed in NH3 production each year accounts for more than 1% of the world's total annual energy consumption, accompanied by 400 Mt of carbon dioxide emissions annually. Therefore, there is an urgent need to develop a milder, greener, more efficient, and sustainable ammonia synthesis technology to replace the traditional Haber-Bosch process.
[0003] Catalysis and photoelectrocatalysis are considered energy-saving and environmentally friendly NH3 production processes. They can directly produce ammonia from air and water using solar energy under environmental conditions. However, the efficiency of photocatalytic nitrogen reduction is not as high as that of photoelectrocatalytic nitrogen reduction. This is because photocatalysis, since the redox reaction occurs on the particle surface, easily causes the recombination of photogenerated electrons and holes. Not all photons can be used in the photocatalytic process, which reduces the efficiency. Photoelectrocatalysis can effectively enhance the carrier migration rate of photoelectrocatalysts and improve the electron-hole separation efficiency and photoelectrocatalytic nitrogen reduction performance under the application of bias voltage. Therefore, photoelectrocatalytic nitrogen reduction (NRR) is a highly effective way to achieve clean, energy-saving and sustainable development of N2 and H2O to NH3. Specifically, photoelectrocatalytic nitrogen reduction (NRR) is mainly divided into the following three steps: (1) adsorption of nitrogen gas, the catalyst surface has enough nitrogen adsorption sites to fix nitrogen gas; (2) excitation of photons, the catalyst absorbs light energy and generates photoexcited electrons (e-). Photogenerated electrons are excited and migrate to the conduction band (CB), leaving holes in the valence band (VB); (3) there is some recombination of photogenerated electrons and holes, and at the same time some electrons and holes migrate to the surface of the catalyst and participate in the redox reaction.
[0004] Currently, among existing technologies, Chinese patent CN108842163A discloses the application of a bipolar membrane with a copper-metal-organic framework material as the intermediate interface layer in photoelectrocatalytic nitrogen fixation. This application uses a bipolar membrane containing a copper-metal-organic framework material as the separator between the cathode and anode chambers, prepares an ionic liquid electrolyte solution, uses metals and their oxides as the anode, and semiconductor materials and transition metal oxides as the cathode. Under photoelectrocatalysis, nitrogen gas is fixed and reduced to ammonia. Furthermore, Chinese patent CN109082682A discloses the application of a bipolar membrane with a zinc-metal-organic framework material as the intermediate interface layer in photoelectrocatalytic nitrogen fixation. This application uses a bipolar membrane containing a zinc-metal-organic framework material as the separator between the cathode and anode chambers, prepares an ionic liquid electrolyte solution, uses metals and their oxides as the anode, and semiconductor materials and transition metal oxides as the cathode. Under photoelectrocatalysis, nitrogen gas is fixed and reduced to ammonia.
[0005] However, in the aforementioned existing technologies, the traditional single-compartment or double-compartment H-type photoelectrochemical reactors have limited dissolution and diffusion of nitrogen in the electrolyte, which restricts the mass transfer efficiency of nitrogen molecules. Therefore, photoelectrocatalytic nitrogen reduction still suffers from low current density and poor selectivity. Thus, in order to solve the above technical problems, it is urgent to design a method for preparing a catalytic electrode to prepare a high-efficiency electrode and apply it in photoelectrocatalytic nitrogen reduction. Summary of the Invention
[0006] This invention proposes a method for preparing a catalytic electrode and its application in photoelectrocatalytic reduction of nitrogen, which effectively solves the problems in the prior art.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a catalytic electrode, comprising the following steps:
[0008] S1. Weigh out the anode catalyst powder and cathode catalyst powder, disperse them separately in a solvent, add Nafion solution to each, and then ultrasonically disperse them evenly to obtain the anode catalyst slurry and cathode catalyst slurry.
[0009] S2. Place the gas diffusion layer on the heating platform and heat it to 50-100℃;
[0010] S3. Weigh the anode catalyst slurry or cathode catalyst slurry, spray it evenly onto the gas diffusion layer, and dry it under an inert atmosphere to obtain the anode gas diffusion electrode and the cathode gas diffusion electrode.
[0011] Furthermore, the anode catalyst powder comprises one of Fe, Co, Ni, Ir, Ru metal or metal oxide catalysts or nickel foam.
[0012] Furthermore, the cathode catalyst powder includes one of the following: boron-doped diamond catalyst, bismuth oxyhalide catalyst, titanium dioxide-based catalyst, layered double hydroxide catalyst, and graphite carbonitride catalyst.
[0013] Further, the bismuth oxyhalide catalyst includes one or more of BiOBr, BiOCl, Bi5O7I, and Bi5O7Br; the graphite carbonitride catalyst includes one or more of Vg-C3N4, g-C3N4 / rGO, S-doped g-C3N4, g-C3N4 / ZnMoCdS, Fe-doped g-C3N4, Ga2O3-DBD / g-C3N4, TiO2@C / g-C3N4, and g-C3N4 / MgAlFeO NRs.
[0014] Further, the solvent includes anhydrous ethanol, isopropanol, or a mixture of isopropanol and deionized water in equal volumes; the concentration of the catalytic electrode powder dissolved in the solvent is 0.5–10 g / L, the mass fraction of the Nafion solution is 5 wt%–20 wt%, and the volume ratio of the Nafion solution to the solvent is 1:20–1:5.
[0015] Furthermore, the gas diffusion layer material includes carbon fiber paper, carbon fiber woven fabric, non-woven fabric, or carbon black paper.
[0016] Further, in step S3, the loading of the anode catalyst slurry and cathode catalyst slurry after spraying is 0.005–10 mg / cm³. －2 .
[0017] The present invention also proposes an application in which the anode gas diffusion electrode and the cathode gas diffusion electrode prepared by the above method are used as the anode and cathode of the photoelectrocatalytic reduction of nitrogen in an electrolytic cell, respectively.
[0018] Furthermore, the anode gas diffusion electrode is inserted into the anode chamber of the electrolytic cell, and the cathode gas diffusion electrode is inserted into the cathode chamber of the electrolytic cell; the anode chamber and the cathode chamber are respectively filled with anolyte and catholyte; an anion exchange membrane is provided between the anode chamber and the cathode chamber; and a light-illuminating window is provided on the electrolytic cell.
[0019] A gas chamber is provided on one side of the electrolytic cell, and the gas in the gas chamber can come into contact with the cathode gas diffusion electrode.
[0020] A continuously flowing anolyte and a continuously flowing catholyte are supplied to the anode chamber and the cathode chamber, respectively, while a continuously flowing nitrogen gas is supplied to the gas chamber.
[0021] Furthermore, the flow rate of nitrogen is 5–100 sccm; the flow rates of the cathode electrolyte and the anode electrolyte are 1–100 sccm; the anode gas diffusion electrode and the cathode gas diffusion electrode are powered by a DC regulated power supply with a voltage of 0.2–2.0V; the illumination window uses one or more of the following as a light source: one sunlight, two sunlights, ultraviolet light, infrared light, and visible light.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] In this invention, the cathode gas diffusion electrode is used in the photoelectrocatalytic nitrogen reduction reaction. It can separate the gas and liquid, and with the continuous flow of nitrogen, anolyte and cathode electrolyte, nitrogen does not need to be dissolved in the liquid first. Nitrogen passes through the gas diffusion layer, cathode catalyst and cathode electrolyte to form a stable three-phase interface, which effectively improves the mass transfer efficiency of nitrogen, thereby increasing the current density and improving selectivity. Attached Figure Description
[0024] Figure 1 This is a perspective view of the electrolytic cell in this invention;
[0025] Figure 2 This is an exploded view of the electrolytic cell in this invention.
[0026] In the diagram: 1. Anode chamber; 2. Cathode chamber; 3. Gas chamber; 4. Anion exchange membrane; 5. Illumination window; 6. Anode; 7. Cathode; 8. Anode electrolyte inlet; 9. Anode electrolyte outlet; 10. Cathode electrolyte inlet; 11. Cathode electrolyte outlet; 12. Gas outlet; 13. Gas inlet. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Example 1
[0029] This invention proposes a method for preparing a catalytic electrode, comprising the following steps:
[0030] S1. Weigh 5-15 mg of anode catalyst powder and cathode catalyst powder respectively, disperse them in 10-30 mL of solvent, add 17-50 μL of Nafion solution (5%) to each, and then ultrasonically disperse them evenly to obtain anode catalyst slurry and cathode catalyst slurry;
[0031] S2. Place the gas diffusion layer on the heating platform and heat it to 50-100℃;
[0032] S3. Weigh 50-500 μL of anode catalyst slurry or cathode catalyst slurry, spray it evenly onto the gas diffusion layer, and dry it under an inert atmosphere to obtain the anode gas diffusion electrode and the cathode gas diffusion electrode.
[0033] In this embodiment, in step S1, the ultrasonic dispersion time is 10 to 120 minutes, preferably 30 to 60 minutes;
[0034] In this embodiment, in step S2, the temperature is preferably heated to 70-90°C;
[0035] In this embodiment, in step S1, the solvent includes anhydrous ethanol, isopropanol, or a mixture of isopropanol and deionized water in equal volumes; the concentration of the catalytic electrode powder dissolved in the solvent is 0.5–10 g / L, the mass fraction of the Nafion solution is 5 wt%–20 wt%, and the volume ratio of the Nafion solution to the solvent is 1:20–1:5.
[0036] In this embodiment, in step S2, the gas diffusion layer material includes carbon fiber paper, carbon fiber woven fabric, non-woven fabric, or carbon black paper.
[0037] In this embodiment, in step S3, the loading of the anode catalyst slurry and cathode catalyst slurry after spraying is 0.005–10 mg / cm³. －2 ;
[0038] In this embodiment, the anode catalyst powder includes one of Fe, Co, Ni, Ir, Ru metal or metal oxide catalysts or nickel foam;
[0039] In this embodiment, the cathode catalyst powder includes one of the following: boron-doped diamond catalyst, bismuth oxyhalide catalyst, titanium dioxide-based catalyst, layered double hydroxide catalyst, and graphite carbonitride catalyst.
[0040] Preferably, the bismuth oxyhalide catalyst includes one or more of BiOBr, BiOCl, Bi5O7I, and Bi5O7Br; the graphite carbonitride catalyst includes one or more of Vg-C3N4, g-C3N4 / rGO, S-doped g-C3N4, g-C3N4 / ZnMoCdS, Fe-doped g-C3N4, Ga2O3-DBD / g-C3N4, TiO2@C / g-C3N4, and g-C3N4 / MgAlFeO NRs; and the layered double hydroxide includes one or more of nickel-iron double hydroxide, nickel-cobalt double hydroxide, and nickel-chromium double hydroxide.
[0041] Example 2
[0042] This invention proposes a method for preparing a catalytic electrode, comprising the following steps:
[0043] S1. Weigh 15 mg of anode catalyst powder and cathode catalyst powder respectively, disperse them in 30 mL of solvent, add 50 μL of Nafion solution (5%) to each, and then ultrasonically disperse for 60 minutes to obtain anode catalyst slurry and cathode catalyst slurry;
[0044] S2. Place the gas diffusion layer on the heating platform and heat it to 70°C;
[0045] S3. Weigh 500 μL of anode catalyst slurry or cathode catalyst slurry, spray it evenly onto the gas diffusion layer, and dry it under an inert atmosphere to obtain an anode gas diffusion electrode and a cathode gas diffusion electrode.
[0046] In this embodiment, the cathode catalyst powder is a boron-doped diamond catalyst; the anode catalyst powder is an iridium oxide catalyst.
[0047] Example 3
[0048] The difference compared to Example 2 is that the cathode catalyst powder used is GNP / BSi / Cr, which is a boron-doped diamond catalyst.
[0049] Example 4
[0050] The difference compared to Example 2 is that the cathode catalyst powder used is TiO2 / Au / a-TiO2, which is a titanium dioxide-based catalyst.
[0051] Example 5
[0052] The difference compared to Example 2 is that the cathode catalyst powder used is BiOBr;
[0053] Example 6
[0054] The present invention also proposes an application in which the anode gas diffusion electrode and the cathode gas diffusion electrode prepared by the method in the above embodiments are used as the anode 6 and cathode 7 of the photoelectrocatalytic reduction of nitrogen in an electrolytic cell, respectively.
[0055] In this embodiment, as Figures 1 to 2As shown, the anode gas diffusion electrode is inserted into the anode chamber 1 of the electrolytic cell, and the cathode gas diffusion electrode is inserted into the cathode chamber 2 of the electrolytic cell; the anode chamber 1 and the cathode chamber 2 are respectively filled with anolyte and catholyte; an anion exchange membrane 4 is provided between the anode chamber 1 and the cathode chamber 2; a light-illuminating window 5 is provided on the electrolytic cell, the distance between the light-illuminating window 5 and the cathode gas diffusion electrode is less than 6 mm, and a transparent cover is provided on the light-illuminating window 5; the anode chamber 1 is provided with an anolyte outlet 9 and an anolyte inlet 8; the cathode chamber 2 is provided with a cathode electrolyte outlet 11 and a cathode electrolyte inlet 10;
[0056] A gas chamber 3 is provided on one side of the electrolytic cell. The gas in the gas chamber 3 can contact the cathode gas diffusion electrode. The gas chamber 3 is provided with a gas inlet 13 and a gas outlet 12. Continuously flowing anolyte and catholyte are provided to the anode chamber 1 and cathode chamber 2, respectively, while continuously flowing nitrogen is provided to the gas chamber 3. The nitrogen in the gas chamber 3 is transferred through the cathode gas diffusion electrode and reacts. The generated products and unreacted gases are discharged from the gas outlet 12.
[0057] In this embodiment, both the cathode electrolyte and the cathode electrolyte are deionized water or Na2SO3 solution;
[0058] In this embodiment, the flow rate of nitrogen is 5-100 sccm; the flow rates of the cathode electrolyte and the anode electrolyte are 1-100 sccm; the anode gas diffusion electrode and the cathode gas diffusion electrode are powered by a DC regulated power supply with a voltage of 0.2-2.0V; the illumination window 5 uses one or more of the following as light sources: one sunlight, two sunlights, ultraviolet light, infrared light, and visible light. In this embodiment, a 350W xenon lamp (Beijing PLS-SXW300D) is used as the light source.
[0059] In this embodiment, nitrogen is fixed and reduced to ammonia under photoelectrocatalysis; the ammonia yield can then be detected by quantitative methods, including gas chromatography, indophenol blue method, ammonia / ammonium ISE method, phenol salt method, salicylate method, Nessler's reagent method, OPA fluorescence method combined with flow injection method, etc.
[0060] By adjusting the light power and operating voltage, the catalytic activity and selectivity of the catalyst for the reduction of nitrogen to ammonia under different photoelectric conditions were tested.
[0061] Example 7
[0062] Compared with Example 6, the differences are: the flow rate of nitrogen is 50 sccm; the flow rates of the cathode electrolyte and the anolyte are 50 sccm; and the illumination intensity of the light source uses two sunlights.
[0063] The catalytic activity of the cathode gas diffusion electrodes prepared in Examples 2-5 was characterized by potentiostatic method, and the specific evaluation results are shown in Table 1 below.
[0064] Table 1: Catalytic activity of different cathode gas diffusion electrodes
[0065]
[0066] As can be seen from the table above, under the same reaction conditions, Example 4 has a higher ammonia yield and ammonia faradaic efficiency; and increasing the light irradiation or increasing the voltage will improve the ammonia yield and ammonia faradaic efficiency.
[0067] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a catalytic electrode, characterized in that, Includes the following steps: S1. Weigh the anode catalyst powder and the cathode catalyst powder, disperse them separately in a solvent, add Nafion solution to both and then ultrasonically disperse them evenly to obtain the anode catalyst slurry and the cathode catalyst slurry; S2. Place the gas diffusion layer on the heating platform and heat it to 50-100℃; S3. Weigh the anode catalyst slurry or cathode catalyst slurry, spray it evenly onto the gas diffusion layer, and dry it under an inert atmosphere to obtain the anode gas diffusion electrode and the cathode gas diffusion electrode.
2. The method for preparing the catalytic electrode according to claim 1, characterized in that: The anode catalyst powder includes one of Fe, Co, Ni, Ir, Ru metal or metal oxide catalysts or nickel foam.
3. The method for preparing the catalytic electrode according to claim 1, characterized in that: The cathode catalyst powder includes one of the following: boron-doped diamond catalyst, bismuth oxyhalide catalyst, titanium dioxide-based catalyst, layered double hydroxide catalyst, and graphite carbonitride catalyst.
4. The method for preparing the catalytic electrode according to claim 3, characterized in that: The bismuth oxyhalide catalyst includes one or more of BiOBr, BiOCl, Bi5O7I, and Bi5O7Br; the graphite carbonitride catalyst includes one or more of Vg-C3N4, g-C3N4 / rGO, S-doped g-C3N4, g-C3N4 / ZnMoCdS, Fe-doped g-C3N4, Ga2O3-DBD / g-C3N4, TiO2@C / g-C3N4, and g-C3N4 / MgAlFeO NRs.
5. The method for preparing the catalytic electrode according to claim 1, characterized in that: The solvent includes anhydrous ethanol, isopropanol, or a mixture of isopropanol and deionized water in equal volumes; the concentration of the catalytic electrode powder dissolved in the solvent is 0.5–10 g / L, the mass fraction of the Nafion solution is 5 wt%–20 wt%, and the volume ratio of the Nafion solution to the solvent is 1:20–1:
5.
6. The method for preparing the catalytic electrode according to claim 1, characterized in that: The gas diffusion layer material includes carbon fiber paper, carbon fiber woven fabric, non-woven fabric, or carbon black paper.
7. The method for preparing the catalytic electrode according to claim 1, characterized in that: In step S3, the loading of the anode catalyst slurry and cathode catalyst slurry after spraying is 0.005–10 mg / cm³. －2 .
8. An application characterized in that, The anode gas diffusion electrode and the cathode gas diffusion electrode prepared by the method of any one of claims 1-7 are used as the anode and cathode of the photoelectrochemical reduction of nitrogen in an electrolytic cell, respectively.
9. The application according to claim 8, characterized in that: The anode gas diffusion electrode is inserted into the anode chamber of the electrolytic cell, and the cathode gas diffusion electrode is inserted into the cathode chamber of the electrolytic cell; the anode chamber and the cathode chamber are respectively filled with anolyte and catholyte; an anion exchange membrane is provided between the anode chamber and the cathode chamber; and a light-illuminating window is provided on the electrolytic cell. A gas chamber is provided on one side of the electrolytic cell, and the gas in the gas chamber can come into contact with the cathode gas diffusion electrode. A continuously flowing anolyte and a continuously flowing catholyte are supplied to the anode chamber and the cathode chamber, respectively, while a continuously flowing nitrogen gas is supplied to the gas chamber.
10. The application according to claim 9, characterized in that: The flow rate of nitrogen is 5–100 sccm; the flow rates of the cathode electrolyte and the anode electrolyte are 1–100 sccm; the anode gas diffusion electrode and the cathode gas diffusion electrode are powered by a DC regulated power supply with a voltage of 0.2–2.0V; the illumination window uses one or more of the following as a light source: one sunlight, two sunlights, ultraviolet light, infrared light, and visible light.