A carbon-based three-dimensional gas diffusion electrode for electrogeneration of hydrogen peroxide and a preparation method thereof
By constructing confined single-atom nanotubes and a hydrophobic-aerophilic layer on a carbon-based gas diffusion electrode, the problem of high production cost of traditional hydrogen peroxide is solved, and efficient electrochemical oxygen reduction to prepare hydrogen peroxide is achieved, which is suitable for chemical industry and environmental remediation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2021-12-16
- Publication Date
- 2026-06-05
Smart Images
Figure HDA0003414749940000011
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing an electrode, particularly a carbon-based three-dimensional gas diffusion electrode for an electrogenerated hydrogen peroxide process, belonging to the field of electrode preparation technology. Background Technology
[0002] Hydrogen peroxide (commonly known as hydrogen peroxide solution) is a powerful oxidizing agent with significant applications in energy, chemical, environmental, and medical fields. In the chemical and medical industries, it is frequently used as a bleaching agent and disinfectant; in the semiconductor industry, it plays a crucial role as a wafer cleaning agent; as an epoxidizing agent, it can be used in the production of propylene oxide; and it is also a vital pollutant oxidizing agent in advanced oxidation water treatment processes. Due to its widespread applications, global hydrogen peroxide production reached 5.5 million tons in 2015 and continues to grow rapidly.
[0003] Currently, global hydrogen peroxide production mainly relies on the energy-intensive anthraquinone process. This process involves a combination of multiple steps, including the continuous hydrogenation and oxidation of anthraquinone, to produce hydrogen peroxide. The hydrogenation step utilizes an expensive palladium catalyst, and the product undergoes complex purification and separation processes to finally obtain hydrogen peroxide. Traditional anthraquinone processes often involve high investment and construction costs, and centralized production and transportation also pose significant risks. In addition, hydrogen peroxide can also be synthesized directly from hydrogen and oxygen; photocatalytic synthesis of hydrogen peroxide is also an environmentally friendly route. Electrochemical oxygen reduction is currently a very promising method for hydrogen peroxide production.
[0004] The electrochemical oxygen reduction method mainly uses 2e - The transfer process involves the partial reduction of O2 to prepare hydrogen peroxide (O2 + 2H2O). + +2e - →H2O2), which can produce H2O2 solution in situ in the aqueous phase, has the advantages of being clean, efficient, low-energy, and capable of decentralized production. Among them, a highly efficient and stable electrode is the key to realizing this process. Summary of the Invention
[0005] Gas diffusion electrodes are currently one of the most widely used and efficient types of electrodes in this field. They primarily involve modifying the electrode interface with a gas-philic layer to create channels for gas diffusion, promoting gas mass transfer at the interface and thus improving the electrochemical reaction efficiency. Due to the significantly reduced gas mass transfer at the interface limiting the electrochemical reaction, these electrodes generally exhibit high current density and high current efficiency.
[0006] This invention provides a carbon-based gas diffusion electrode and its preparation method. The carbon-based material is selected from carbon felt, which has a relatively abundant porous structure, providing ample diffusion channels for gas diffusion. This invention constructs confined single-atom nanotube materials with high catalytic activity and selectivity on the surface of the carbon felt material, providing abundant and efficient reaction sites for the electrochemical reduction of oxygen. Simultaneously, the electrode is modified with hydrophobic and oxy-particle materials to provide good diffusion channels for the gas. Therefore, the gas diffusion electrode involved in this invention has higher current efficiency and H2O2 yield compared to traditional diffusion electrodes.
[0007] According to one aspect of the present invention, a gas diffusion electrode is provided, comprising a gas diffusion electrode body, and a catalyst layer and a hydrophobic-hydrophilic layer sequentially laminated on the gas diffusion electrode body; wherein the catalyst layer is grown in situ on the gas diffusion electrode body.
[0008] The catalyst in the catalyst layer is a longitudinally grown confined single-atom carbon-nitrogen nanotube material, wherein the single atom is selected from at least one of iron atoms, cobalt atoms, and nickel atoms.
[0009] Optionally, the catalyst layer is obtained from a transition metal in situ at high temperature, wherein the atomic ratio of the surface single-atom transition metal is 0.1-2.0%.
[0010] Optionally, the gas diffusion electrode body has a porous structure, preferably at least one of graphite carbon felt and carbon paper; the thickness of the gas diffusion electrode body is 1 mm to 5 mm.
[0011] The material of the hydrophobic and hydrophilic layer is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, and stearic acid.
[0012] According to one aspect of the present invention, a method for preparing the above-mentioned gas diffusion electrode is provided, comprising the following steps:
[0013] (1) Under a closed, non-active atmosphere, the gas diffusion electrode body is immersed in an alkaline solution for heat treatment, washed and dried to obtain an alkaline-treated gas diffusion electrode body.
[0014] (2) Immerse the alkali-treated gas diffusion electrode body in an alcohol solution of metal salt, dry it, and repeat the immersion 3 to 5 times;
[0015] (3) After mixing the gas diffusion electrode body processed in step (2) with a carbon-nitrogen source, it is calcined in an inactive atmosphere to obtain a two-dimensional electrode.
[0016] (4) Immerse the two-dimensional electrode described in step (3) in an acidic solution, wash and dry it;
[0017] (5) The two-dimensional electrode after acid treatment in step (4) is immersed in a solution containing hydrophobic and anaerobic materials, dried, heated in an inactive atmosphere, and cooled to obtain the gas diffusion electrode.
[0018] Optionally, in step (1), the alkaline solution is selected from at least one of KOH solution and NaOH solution, and the concentration of the alkaline solution is 1-10 mol / L, preferably 2 mol / L; the amount of alkaline solution used is based on immersing the gas diffusion electrode body; the heat treatment time is 48-96 h, the temperature is 120-180 °C, and the pressure is 1-3 MPa, preferably 1 MPa;
[0019] In step (4), the acidic solution is selected from at least one of hydrochloric acid solution and sulfuric acid solution, and the concentration of the acidic solution is 1-5 mol / L, preferably 1 mol / L; the soaking time in the acidic solution is 6-10 h, and the temperature is 70-90℃.
[0020] Optionally, in step (2), the immersion time in the alcohol solution of the metal salt is 0.1 to 2 min, preferably 1 min; the concentration of the transition metal salt solution is 0.1 to 2 mol / L; and the volume ratio of the diffusion electrode to the alcohol solution is 1:50 to 1:1000.
[0021] The metal salt is selected from at least one of the chloride, nitrate, and sulfate of a metal, and the metal is selected from at least one of iron, cobalt, and nickel;
[0022] The alcohol solution is selected from at least one of ethanol and methanol.
[0023] Optionally, in step (3), the carbon-nitrogen source is selected from at least one of dicyandiamide, melamine, and XX; the molar ratio of the carbon-nitrogen source to the metal salt is 2 to 10.
[0024] In step (3), the carbon-nitrogen source is selected from at least one of dicyandiamide, melamine, and urea; the molar ratio of the carbon-nitrogen source to the metal salt is 2 to 10 or the carbon-nitrogen source is in excess.
[0025] The roasting process involves heating the temperature to 700-1000°C at a rate of 3-10°C / min, followed by cooling to room temperature.
[0026] The roasting process involves heating the temperature to 800°C at a rate of 3°C / min and then cooling it to room temperature.
[0027] Optionally, in step (5), the immersion time in the solution containing the hydrophobic and oxy-hydrophobic material is 5 to 20 seconds; the concentration of the solution containing the hydrophobic and oxy-hydrophobic material is 0.5 wt% to 2.0 wt%; the ratio of the acid-treated two-dimensional electrode to the solution containing the hydrophobic and oxy-hydrophobic material is 1:50 to 1:1000; and the heating is carried out at a heating rate of 3 to 10 °C / min to 270 to 360 °C.
[0028] According to one aspect of the present invention, the above-described gas diffusion electrode and the application of the gas diffusion electrode prepared by the above-described method in the electrochemical reduction of oxygen are provided.
[0029] Optionally, in the application of the gas diffusion electrode in the electrochemical reduction of oxygen to prepare hydrogen peroxide, the gas diffusion electrode is the negative electrode.
[0030] The gas diffusion electrode prepared by this invention can be installed in an electrolytic cell in two main ways: immersion and semi-immersion.
[0031] The gas diffusion electrode of this invention can use pure oxygen or air to provide oxygen for the electrochemical reaction during the electrochemical generation of hydrogen peroxide.
[0032] The gas diffusion electrode of this invention needs to be operated in an electrolyte aqueous solution, and the electrolytes that can be used include Na2SO4, KOH, perchloric acid, etc.
[0033] As one embodiment of the present invention, a method for preparing a gas diffusion electrode includes the following steps:
[0034] (1) Immerse a two-dimensional graphite carbon felt material of a certain size in a 2 mol / L KOH solution, and treat it in a sealed pressure-resistant container at 120-180℃ and 1.0 MPa nitrogen for 48-96 hours. After treatment, wash it with deionized water 3-5 times until the surface is clean, and dry it for later use.
[0035] (2) Immerse the carbon felt material treated with alkali in step (1) in b mL amol / L Co(NO3)2 alcohol solution for 1 min, then remove and air dry naturally. Repeat this process 3 to 5 times, where the volume of b is 50 to 1000 times the volume of the carbon felt.
[0036] (3) The carbon felt material impregnated with Co salt and dried in step (2) is placed in a ceramic boat containing 2a to 10a mol of dicyandiamide powder and calcined under N2 conditions. The calcination heating rate is 3℃ / min. After heating to 800℃, it is naturally cooled to room temperature.
[0037] (4) Place the two-dimensional electrode prepared in step (3) in a 1 mol / L hydrochloric acid solution and treat it at 70-90℃ for 6-10 h. After treatment, rinse it with deionized water 5-10 times and then dry it.
[0038] (5) The two-dimensional electrode prepared in step (4) is placed in a polytetrafluoroethylene (PTFE) aqueous solution for 10 seconds and then removed. It is dried under a baking lamp and heated to 350°C at a heating rate of 10°C / min under N2 atmosphere and then cooled naturally to obtain a three-dimensional electrode with good gas diffusion performance.
[0039] The substrate material of the electrode involved in this invention is usually a carbon felt material with high porosity. The thickness of the carbon felt material is generally no more than 5 mm, and the carbon felt material can be appropriately cut according to the reactor.
[0040] This invention involves longitudinally modifying a nanostructure on a two-dimensional graphite carbon felt substrate, and in situ growing a nanotube catalytic layer with confined single atoms on the substrate material, thereby improving the gas transfer efficiency at the electrode interface. The nanostructure of the electrode in this invention is prepared in situ using a cobalt salt precursor (such as CoCl2, Co(NO3)2, CoSO4, etc.), and the Co-Nx catalytic active sites on it have high oxygen reduction activity and selectivity. The resulting novel gas diffusion electrode can significantly improve oxygen utilization and current efficiency.
[0041] The growth of nanotube catalyst layers with confined single atoms is based on the high-temperature catalytic cracking and assembly of carbon and nitrogen sources by transition metals (cobalt salts). Dicyandiamide is used as the nitrogen and carbon source during the calcination process. Alternatively, melamine can be used as the carbon source and the carbon source can be partially or completely replaced by dicyandiamide for electrode preparation in this step.
[0042] To construct a good gas diffusion channel, this invention relates to modifying the surface of the previously prepared electrode with hydrophobic and anaerobic materials such as polytetrafluoroethylene.
[0043] The beneficial effects of this invention include:
[0044] Studies have shown that Co-N xCatalytic active centers possess electrocatalytic activity that can replace noble metals, exhibiting excellent performance in the electroreduction of oxygen to produce hydrogen peroxide. However, effectively immobilizing catalytic nanomaterials containing such catalytic centers is one of the key issues for their further practical application. The in-situ growth strategy employed in this invention not only achieves effective immobilization of Co-Nx unit nanotube structures, but also effectively reduces the impedance between the nanotube structure and the substrate carbon felt, thereby improving current efficiency. While modifying this preparation with PTFE material may cause some shielding of catalytic active sites, it significantly reduces the limitation of oxygen mass transfer and improves the current efficiency of the electrode.
[0045] The electrode prepared by this invention can generate hydrogen peroxide by in-situ electroreduction of oxygen in an aqueous phase, with higher current efficiency and H2O2 yield. It can be used in the dispersion preparation of hydrogen peroxide, and the generated hydrogen peroxide can be further applied in the fields of chemical engineering and environmental remediation. Attached Figure Description
[0046] Figure 1 Schematic diagrams of immersion and semi-immersion electrolytic cells. Detailed Implementation
[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.
[0048] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0049] Example 1
[0050] A piece of graphite carbon felt material measuring 20mm*25mm*2mm was cut and placed in a 200ml autoclave containing a 2mol / L KOH solution. After introducing 1MPa of N2, the temperature was raised to 150℃ and treated for 72 hours. Following treatment, the material was removed and ultrasonically cleaned three times with deionized water. After cleaning, it was dried in an oven at 80℃. The resulting carbon felt was named CF. -OH ;
[0051] Prepare 500 mL of 1 mol / L Co(NO3)2 alcohol solution, and add carbon felt CF -OH After immersing in a 1 mol / L Co(NO3)2 alcohol solution for 1 min, the material was removed and air-dried naturally. This process was repeated three times to obtain a carbon felt substrate material with uniformly dispersed Co elements.
[0052] The carbon felt was then placed on a ceramic boat containing 0.25 mol of dicyandiamide. The temperature was increased to 800°C at a rate of 3°C / min under a nitrogen flow rate of 100 ml / min, and then naturally cooled to room temperature. After removal, the carbon felt electrode was immersed in a 1 mol / L hydrochloric acid solution and treated at 70°C for 8 hours. After removal, it was vacuum dried at 60°C.
[0053] The carbon felt electrode was then immersed in 500 mL of 1 wt% PTFE aqueous solution for 10 seconds, removed, and dried under a heat lamp. This process was repeated twice. The electrode was then heated to 350 °C at a heating rate of 10 °C / min under a N2 atmosphere and then allowed to cool naturally to room temperature, thus forming the gas diffusion electrode p-Co-NCNT / CF.
[0054] Evaluation results: This electrode performs well in semi-immersion electrolytic reactors (such as...) Figure 1 In the figure shown, the positive electrode is a platinum electrode, the electrolyte is a 0.1M Na₂SO₄ solution, and the negative current density is 200 mA / cm². 2 Under the specified conditions, the hydrogen peroxide yield reached 90 mg / (h·cm³). 2 ).
[0055] Example 2
[0056] Under the same conditions as in Example 1, except that the concentration of the Co(NO3)2 solution was adjusted to 2 mol / L, the prepared electrode was applied to a semi-immersion electrode tank reactor with a cathode current density of 200 mA / cm². 2 Under the specified conditions, the hydrogen peroxide yield reached 120 mg / (h·cm³). 2 ).
[0057] Example 3
[0058] Under the same conditions as in Example 1, except that the concentration of the Co(NO3)2 solution was adjusted to 0.5 mol / L, the prepared electrode was applied to a semi-immersion electrode tank reactor with a cathode current density of 200 mA / cm². 2 Under the specified conditions, the hydrogen peroxide yield reached 50 mg / (h·cm³). 2 ).
[0059] Example 4
[0060] Under the same conditions as in Example 1, except that the calcination temperature of the carbon felt and dicyandiamide mixture was adjusted to 700°C, the prepared electrode was applied to a semi-immersion electrode tank reactor with a negative current density of 200 mA / cm². 2 Under the specified conditions, the hydrogen peroxide yield reached 110 mg / (h·cm³). 2 ).
[0061] Example 5
[0062] Under the same conditions as in Example 1, except that the calcination temperature of the carbon felt and dicyandiamide mixture was adjusted to 900°C, the prepared electrode was applied to a semi-immersion electrode tank reactor with a cathode current density of 200 mA / cm². 2 Under the specified conditions, the hydrogen peroxide yield reached 80 mg / (h·cm³). 2 ).
[0063] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A gas diffusion electrode, characterized in that, It includes a gas diffusion electrode carbon felt body, and a catalyst layer and a hydrophobic-hydrophilic layer sequentially composited on the gas diffusion electrode carbon felt body; the catalyst layer is grown in situ on the gas diffusion electrode body; The catalyst in the catalyst layer is a longitudinally grown confined single-atom carbon-nitrogen nanotube material, wherein the single atom is selected from at least one of iron atoms, cobalt atoms, and nickel atoms; the material of the hydrophobic and anaerobic layer is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, and stearic acid. The gas diffusion electrode is used for the electrochemical reduction of oxygen to prepare hydrogen peroxide, and the gas diffusion electrode is the negative electrode; The gas diffusion electrode is prepared by the following steps: (1) Under a closed, non-active atmosphere, the gas diffusion electrode body is immersed in an alkaline solution for heat treatment, washed and dried to obtain an alkaline-treated gas diffusion electrode body. (2) Immerse the alkali-treated gas diffusion electrode body in an alcohol solution of metal salt, dry it, and repeat the immersion 3 to 5 times; (3) After mixing the gas diffusion electrode body treated in step (2) with a carbon and nitrogen source, it is calcined in an inactive atmosphere to obtain a two-dimensional electrode; (4) Immerse the two-dimensional electrode described in step (3) in an acidic solution, wash and dry it; (5) The two-dimensional electrode after acid treatment in step (4) is immersed in a solution containing hydrophobic and anaerobic materials, dried, heated in an inactive atmosphere, and cooled to obtain the gas diffusion electrode. The carbon and nitrogen source is selected from at least one of dicyandiamide, melamine, and urea.
2. The gas diffusion electrode according to claim 1, characterized in that, The atomic ratio of surface single-atom transition metals in the catalyst layer is 0.1-2.0%.
3. The gas diffusion electrode according to claim 1, characterized in that, The gas diffusion electrode carbon felt body has a porous structure, and the thickness of the gas diffusion electrode carbon felt body is 1mm~5mm.
4. The gas diffusion electrode according to claim 3, characterized in that, The gas diffusion electrode carbon felt body is a graphite carbon felt.
5. The gas diffusion electrode according to claim 1, characterized in that, In step (1), the alkaline solution is selected from at least one of KOH solution and NaOH solution, and the concentration of the alkaline solution is 1~10 mol / L; the heat treatment time is 48~96h, the temperature is 120~180℃, and the pressure is 1~3MPa; In step (4), the acidic solution is selected from at least one of hydrochloric acid solution and sulfuric acid solution, and the concentration of the acidic solution is 1~5 mol / L; the soaking time in the acidic solution is 6~10h, and the temperature is 70~90℃.
6. The gas diffusion electrode according to claim 5, characterized in that, In step (1), the concentration of the alkaline solution is 2 mol / L.
7. The gas diffusion electrode according to claim 5, characterized in that, In step (1), the pressure of the heat treatment is 1 MPa.
8. The gas diffusion electrode according to claim 5, characterized in that, In step (4), the concentration of the acidic solution is 1 mol / L.
9. The gas diffusion electrode according to claim 1, characterized in that, In step (2), the immersion time in the alcohol solution of the metal salt is 0.1~2 min; The concentration of the transition metal salt solution was 0.1–2 mol / L; the volume ratio of the diffusion electrode to the alcohol solution was 1:50–1:1000. The metal salt is selected from at least one of the following: metal chloride, nitrate, and sulfate.
10. The gas diffusion electrode according to claim 9, characterized in that, In step (2), the immersion time in the alcohol solution of the metal salt is 1 minute.
11. The gas diffusion electrode according to claim 1, characterized in that, In step (3), the molar ratio of the carbon-nitrogen source to the metal salt is 2 to 10 or the carbon-nitrogen source is in excess; The roasting process involves heating the temperature to 700-1000℃ at a rate of 3-10℃ / min and then cooling it to room temperature.
12. The gas diffusion electrode according to claim 1, characterized in that, In step (5), the immersion time in the solution containing the hydrophobic and oxyphilic material is 5 to 20 seconds; the concentration of the solution containing the hydrophobic and oxyphilic material is 0.5 wt% to 2.0 wt%; the ratio of the acid-treated two-dimensional electrode to the solution containing the hydrophobic and oxyphilic material is 1:50 to 1:1000; and the heating is carried out at a heating rate of 3 to 10 °C / min to 270 to 360 °C.
13. The application of the gas diffusion electrode according to any one of claims 1 to 12 in the electrochemical reduction of oxygen, wherein the gas diffusion electrode is used to prepare hydrogen peroxide by the electrochemical reduction of oxygen, and the gas diffusion electrode is a negative electrode.