A three-dimensional gas diffusion structure electrode, its preparation method, and its application in electrocatalytic synthesis.

Abstract

This invention discloses a three-dimensional gas diffusion structure electrode, its preparation method, and its electrocatalytic synthesis application, belonging to the field of electrocatalysis technology. The three-dimensional gas diffusion structure electrode uses a monolithic carbon material as a carrier and a metal as the active component. The monolithic carbon material can be columnar, plate-like, tubular, or formed into a honeycomb structure. The monolithic porous carbon is prepared using phenolic resin as the carbon source, achieving primary pore formation through a microemulsion method, combined with a physical activation method, introducing metal active species to obtain a metal-doped / coated three-dimensional gas diffusion structure electrode. Taking the application of this three-dimensional gas diffusion structure electrode in the electrocatalytic carbon dioxide reduction reaction as an example, the gaseous reactants are directly introduced into the interior of the three-dimensional gas diffusion structure electrode and diffuse outwards, enhancing the interaction between the reactants and the catalyst, exhibiting good electrocatalytic performance. This invention is easy to operate, highly feasible, and has the potential for industrial-scale application.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis technology, and relates to a three-dimensional gas diffusion structure electrode, its preparation method, and its electrocatalytic synthesis application. Background Technology

[0002] Under the call for the development and utilization of renewable green energy, electrocatalytic small molecule conversion technology for clean energy production is booming. Among these technologies, carbon dioxide, one of the major greenhouse gases, can be converted into high-value-added chemicals and fuels via electrocatalysis, driven by electricity. This process not only helps mitigate the adverse environmental impacts of continuously increasing atmospheric carbon dioxide levels but also reduces dependence on fossil fuels to some extent. The core of efficient electrocatalytic carbon dioxide conversion lies in the design of highly efficient electrocatalysts. Currently, common catalysts can be divided into carbon-based catalysts and metal-based catalysts. By controlling the electron transfer number, carbon dioxide can be converted into carbon monoxide, formic acid, methanol, ethylene, and other C2+ products. Carbon-based catalysts, especially those co-doped with transition metals and nitrogen, have received widespread attention in recent years due to their wide availability, tunable pore structure, and easy surface chemical modification. However, since carbon-based catalysts are often in powder form, the electrode preparation process requires a series of steps such as slurry preparation and coating, which not only reduces the electrode's conductivity and stability but also makes the process cumbersome.

[0003] Monolithic electrode structures can effectively solve the problems associated with powder electrodes and offer numerous advantages in applications. For example, the monolithic structure directly avoids the use of film-forming binders in electrode sheet fabrication, reducing inactive components and their adverse effects on conductivity. Furthermore, monolithic electrodes can effectively enrich the number of active centers, making it possible to stably obtain industrial-grade current densities. Currently, research on metal-based monolithic tubular electrodes is in full swing. The research team of Wei Wei and Chen Wei at the Shanghai Advanced Research Institute designed a porous metal hollow fiber gas permeation electrode, which was applied to electrocatalytic CO2RR in an aqueous electrolyte, enabling highly selective preparation of C1 or C2. 2+This product provides a paradigm for advancing the industrialization of CO2RR (EnergyEnviron.Sci.,2022,15,5391-5404; Angew.Chem.Int.Ed.2022,61,e202210432). Carbon-based materials possess excellent conductivity, wide availability, and tunable surface wettability. However, the development and application of carbon-based monolithic electrodes currently face research gaps. On the one hand, the preparation of carbon-based monolithic electrodes places higher demands on material synthesis, requiring not only a well-developed porous structure to enhance mass transfer but also sufficient strength to withstand the impact of gas flow during the reaction. On the other hand, controlling the three-phase interface environment of the monolithic electrode to ensure a sufficient number of accessible active sites is also a challenge for the application of carbon-based monolithic electrodes. Therefore, developing efficient carbon-based monolithic electrodes for CO2RR still faces significant challenges. Summary of the Invention

[0004] To address the challenges in the development and application of current carbon-based monolithic electrodes, this invention discloses a three-dimensional gas diffusion structure electrode, its preparation method, and its application in electrocatalytic synthesis. This is a universal method for preparing highly efficient carbon-based monolithic electrodes for electrocatalytic reactions. Taking the electrocatalytic CO2 reduction reaction as an example, this three-dimensional gas diffusion structure electrode exhibits high CO2 single-pass conversion and high stability at high current densities. The three-dimensional gas diffusion structure electrode can shorten the CO2 diffusion path and increase the CO2 concentration near the active center, thereby significantly improving the product formation rate. Furthermore, the three-dimensional gas diffusion structure electrode possesses a balanced porous structure and graphitization degree, enabling the construction of a favorable three-phase interface environment. The monolithic carbon material carrier required for this method is derived from phenolic resin. Firstly, a foaming agent—imidazolium-based microemulsions—is introduced into the phenolic resin polymerization process to optimize the structural properties, resulting in a monolithic porous carbon material with a simple preparation method and excellent structural properties. The polymer exhibits good elasticity and high system homogeneity, making it easy to mold. Therefore, by controlling the polymerization mold, columnar, tubular, or plate-shaped polymers and monolithic derived carbon can be obtained in one step. In addition, by adding a small amount of binder and carrying out kneading and extrusion molding steps, honeycomb polymers and monolithic derived carbon can also be obtained, which greatly expands the application scenarios of this monolithic carbon.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A three-dimensional gas diffusion structure electrode includes an integral carbon material carrier and a metal active component, wherein the metal active component is iron, cobalt, manganese, nickel, bismuth, or copper, and is uniformly dispersed on the carrier as metal single atoms and metal nanoparticles; the specific surface area of ​​the carbon electrode is 1559–2530 m². 2 / g, pore volume is 0.69~1.49cm³ 3 / g, with a strength of 0.3-0.8MP; the integral carbon material carrier is columnar, tubular, plate-shaped, or formed into a honeycomb structure.

[0007] The density of the three-dimensional gas diffusion structure electrode is 0.2–0.4 g / cm³. 3 .

[0008] The structure of the carbon electrode can effectively promote the diffusion of reactant gases, increase the exposure of active sites, resist gas impacts during the reaction, and improve stability. Taking the CO2 electroreduction reaction as an example, by loading different electrocatalytic CO2 reduction product metal active sites, the product can be controlled from the gas phase to the liquid phase, or even to multi-carbon products.

[0009] The present invention also provides a method for preparing the three-dimensional gas diffusion structure electrode, comprising the following steps:

[0010] S1 At room temperature, an imidazole compound and a foaming agent are dissolved in a solvent and stirred until the solution is clear and transparent to obtain a foaming agent-imidazole compound solution; the foaming agent is one or more of oleic acid and sodium oleate;

[0011] S2 adds phenol and aldehyde to a solvent and stirs to form a uniform, colorless, and transparent phenol-aldehyde solution; then adds the phenol-aldehyde solution to a foaming agent-imidazolium compound solution and continues stirring until a pale yellow, transparent sol solution is formed.

[0012] S3 pours the sol solution into a sealed container, places it in an oven for polymerization and aging, then removes the polymer and cools it to room temperature, and dries it to obtain a monolithic polymer; or the monolithic polymer is pulverized into powder, mixed with solvent and binder, and then kneaded, shaped and dried to obtain a molded polymer;

[0013] S4 first places the monolithic polymer or molded polymer under an inert gas protection condition for high-temperature carbonization at a carbonization temperature of 800-1000℃; then it is activated under an activating gas atmosphere to obtain a porous monolithic carbon carrier through physical activation and pore formation at an activation temperature of 600-900℃.

[0014] S5 uses an impregnation method to load the metal active components onto a monolithic carbon support, followed by high-temperature carbonization, acid washing, and drying in an inert atmosphere to obtain a three-dimensional gas diffusion structure electrode.

[0015] The shape of the monolithic polymer is determined according to the shape of the sealed container, such as columnar, tubular, or plate-shaped. The molded polymer is honeycomb-shaped.

[0016] The imidazole compound is one or more selected from imidazole, 1-methylimidazolium, 2-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-butylimidazolium, 2-ethylimidazolium, and 2-propylimidazolium, and the concentration of the imidazole compound in the sol solution is 0.001–0.5 mol / L. -1 The molar ratio of the imidazole compound to the foaming agent is 1:1 to 1:5.

[0017] The solvents mentioned in steps S1 and S2 are water, methanol, ethanol, isopropanol, or N,N-dimethylformamide.

[0018] The phenol mentioned in step S2 is phenol, resorcinol, hydroquinone, catechol, cresol, or bisphenol A.

[0019] The aldehyde mentioned in step S2 is formaldehyde, acetaldehyde, or furfural.

[0020] The molar mass ratio of phenol to aldehyde is 1:2 to 1:6.

[0021] The molar ratio of imidazole to phenol is 3–15.

[0022] The polymerization aging temperature in step S3 is 50–120°C, and the aging time is 2–12 h.

[0023] In step S3, the drying process is either atmospheric pressure drying or freeze drying.

[0024] The solvent mentioned in step S3 is water, ethanol, or isopropanol.

[0025] The binder mentioned in step S3 is guar gum powder, hydroxypropyl methylcellulose, methylcellulose, polyvinylpyrrolidone, or polyvinyl alcohol.

[0026] The mass ratio of polymer powder:solvent:binder in step S3 is 60:120:1 to 6:12:1.

[0027] The activation time in step S4 is 1 to 3 hours, and the activation gas during the activation process is water vapor, carbon dioxide, or hydrogen.

[0028] It should be noted that the activation conditions in step S4 significantly affect the porous structure and structural strength of the porous monolithic carbon support, and are also key influencing factors in the subsequent preparation of the three-dimensional gas diffusion structure electrode and its electrocatalytic performance research.

[0029] In step S5, the carbonization temperature is 700–1000℃, the carbonization time is 1–3 hours, and the inert atmosphere is argon or nitrogen.

[0030] The acid used for pickling is one or more of hydrochloric acid and sulfuric acid, with a concentration of 3-5 mol / L. -1 The pickling time is 24-36 hours.

[0031] The present invention also provides the application of the three-dimensional gas diffusion structure electrode in electrocatalytic synthesis, wherein the reaction gas is transported from one end of the three-dimensional gas diffusion structure electrode, flows into the interior of the integral electrode first and then diffuses outward.

[0032] Further applications in electrocatalytic CO2 reduction:

[0033] The electrocatalytic CO2 reduction test was conducted using CO2-saturated 0.5M KHCO3 as the electrolyte in an H-type electrolytic cell under a three-electrode system. A Nafion 117 proton exchange membrane separated the cathode and anode. A three-dimensional gas diffusion structure electrode served as the working electrode, a saturated Ag / AgCl electrode as the reference electrode, and a platinum sheet electrode as the counter electrode. Electrocatalytic performance was tested and analyzed using a potentiostatic electrolysis method.

[0034] The beneficial effects of this invention are:

[0035] 1. This invention proposes a three-dimensional gas diffusion structure electrode, its preparation method, and its application in electrocatalytic synthesis. The monolithic carbon support of the three-dimensional gas diffusion structure electrode uses phenolic resin as the carbon source, introduces microemulsions of imidazole compounds as templates for primary pore formation, and then performs secondary pore formation through a physical activation method to improve the specific surface area and pore volume. After secondary activation, the material exhibits a well-developed pore structure with a specific surface area of ​​1559–2530 m². 2 / g, pore volume is 0.69~1.49cm³ 3 / g, which is beneficial for the exposure of active centers in electrocatalytic reactions and mass transfer diffusion. The synthesis steps of the monolithic carbon material are simple and the conditions are mild, which expands the application scenarios of the derived monolithic carbon.

[0036] 2. Using the prepared monolithic carbon material as a carrier, loaded metals are applied as active centers for electrocatalytic synthesis. For example, the prepared three-dimensional gas diffusion structure electrode is applied to the electrocatalytic reduction of CO2, exhibiting excellent electrocatalytic performance. The three-dimensional gas diffusion structure electrode prepared in this invention is a novel attempt in gas diffusion electrode configuration. By optimizing the supply method of reactants, i.e., forcing the interaction between gaseous reactants and the electrode in a direct supply manner, the monolithic electrode has abundant gas flow channels, which can break the barrier of low solubility of CO2 in aqueous electrolytes (only 34 mM at room temperature and pressure), significantly increasing the local concentration of reactant gas and enhancing the supply of reactants. On the other hand, the three-dimensional gas diffusion structure electrode has a high specific surface area, which is conducive to increasing the number of accessible active sites. The aggregated carbon particles facilitate continuous electron transfer, and the highly efficient local microenvironment constructed by the well-developed porous structure provides an effective guarantee for CO2 mass transfer and diffusion and the suppression of excessive proton supply. Benefiting from the above advantages, the three-dimensional gas diffusion structure electrode can achieve a CO selectivity of over 90%, with a CO generation rate 11.6 times higher than that of coated electrode sheets, and exhibits good stability at high current densities. Furthermore, formic acid can be prepared by loading bismuth onto the three-dimensional gas diffusion structure electrode; formic acid, acetic acid, and ethanol can be prepared by loading copper onto the three-dimensional gas diffusion structure electrode. The distribution of CO2 reduction products can be controlled by changing the type of metal. Attached Figure Description

[0037] Figure 1 Optical photographs of the cylindrical, tubular, and honeycomb three-dimensional gas diffusion structure electrodes.

[0038] Figure 2 This is the nitrogen adsorption isotherm diagram of the three-dimensional gas diffusion structure electrode in Example 1.

[0039] Figure 3 The image shows the Ni 2p peak results of the XPS of the three-dimensional gas diffusion structure electrode in Example 1.

[0040] Figure 4 The figure shows the stability results of the three-dimensional gas diffusion structure electrode C in 0.5M KHCO3 electrolyte in Example 1.

[0041] Figure 5 The figure shows the CO selectivity results of the three-dimensional gas diffusion structure electrode C and electrode sheet in 0.5M KHCO3 electrolyte in Example 1.

[0042] Figure 6 The graph shows the CO generation rate of the three-dimensional gas diffusion structure electrode C and electrode sheet in 0.5M KHCO3 electrolyte in Example 1. Detailed Implementation

[0043] The present invention will be described in detail below through some representative examples. It should be understood that the following examples are merely illustrative and should not be construed as limiting the protection of this invention. Any technical solutions implemented based on the content described in this invention should be covered within the protection scope of this invention.

[0044] Example 1

[0045] 1. Preparation of a three-dimensional gas diffusion structure electrode carrier: 1-methylimidazole and 500 μL of oleic acid were added to 4 mL of water and stirred to dissolve, yielding an oleic acid-1-methylimidazole aqueous solution with a molar ratio of 1:1 for 1-methylimidazole and oleic acid. 4 mL of a 0.1 mol / L resorcinol aqueous solution was prepared, and 0.1 g of a 37 wt.% formaldehyde aqueous solution was added to obtain a phenolic solution. The prepared phenolic solution was then added to the oleic acid-1-methylimidazole aqueous solution. The mixture was placed in a quartz tube and a quartz tube container with a central cylinder, respectively, and polymerized in a 70℃ oven for 2 h. After removing the monolithic polymer, it was cooled at room temperature and then dried in a 50℃ oven under normal pressure (without volume shrinkage) to obtain columnar and tubular polymers. The polymer was pulverized and mixed with pyrrolidone, with ethanol added as a solvent, wherein the mass ratio of polymer powder:ethanol:pyrrolidone was 20:40:1. After thorough mixing, the polymer is shaped into a honeycomb structure and dried at 50°C to obtain a honeycomb-shaped polymer. Under an argon-protected atmosphere, the columnar, tubular, and honeycomb polymers are carbonized to 800°C and held for 2 hours, then cooled to room temperature. They are then placed in a pyrolysis furnace and activated to 850°C under a moisture atmosphere, held for 1 hour, and allowed to cool naturally to obtain columnar, tubular, and honeycomb porous monolithic carbon supports that do not collapse during pyrolysis.

[0046] 2. Preparation of three-dimensional gas diffusion structure electrodes: A nickel nitrate and ethylenediamine coordination solution was prepared with a nickel-to-carbon support mass ratio of 7.5 wt.%. The columnar, tubular, and honeycomb porous monolithic carbon supports prepared in step 1 were respectively immersed in the nickel-to-ethylenediamine coordination solution. An equal volume of active nickel component was then impregnated onto the columnar, tubular, and honeycomb monolithic carbon supports. Under a nitrogen atmosphere, the carbonization was carried out at 800℃ for 1 h, followed by cooling to room temperature. The resulting materials were then immersed in 4M hydrochloric acid for 24 h, washed with water until neutral, and dried to obtain columnar, tubular, and honeycomb three-dimensional gas diffusion structure electrodes, named three-dimensional gas diffusion structure electrodes A, B, and C, respectively.

[0047] 3. The three-dimensional gas diffusion structure electrode AC is applied to the electrocatalytic CO2 reduction reaction, including the following steps:

[0048] (1) Electrocatalytic CO2 performance test: An H-type electrolytic cell and a three-electrode system were used. The cathode chamber contained a working electrode and a reference electrode (saturated Ag / AgCl electrode), and the anode chamber was a platinum sheet counter electrode. The two chambers were separated by a Nafion 117 proton exchange membrane. KHCO3 was used as the electrolyte, and the test potential window was -0.6 to -0.8 V (relative to the reversible hydrogen electrode). The reactant CO2 gas was supplied by directly delivering high-purity CO2 to one end of the carbon electrode AC, and then diffusing outward from the inside of the monolithic electrode.

[0049] (2) Product detection: The electrocatalytic CO2 reduction products were detected and analyzed online using Agilent 7890B gas chromatography and nuclear magnetic resonance hydrogen spectroscopy. The three-dimensional gas diffusion structure electrode AC prepared in this invention produces CO2 electrocatalytic CO2 reduction products, with no liquid phase products.

[0050] 4. The three-dimensional gas diffusion structure electrode AC prepared in Example 1 was characterized and its performance was tested and analyzed:

[0051] Depend on Figure 1 It is known that the structure of the three-dimensional gas diffusion structure electrode can be fabricated into columnar, tubular, and honeycomb structures according to the application scenario to meet the actual testing needs of different reactions. Figure 2 It is known that, after activation by water vapor, the carbon support of the three-dimensional gas diffusion structure electrode AC has a well-developed porous structure with a specific surface area of ​​2177 m². 2 / g, pore volume 1.29cm 3 The density of the three-dimensional gas diffusion structure electrode is 0.25 g / cm³, which is beneficial for enriching active sites and increasing the exposure and mass transfer diffusion of active sites in electrocatalytic reactions. 3 This results in a relatively loose electrode structure, which promotes electrolyte wetting and gas diffusion. The three-dimensional gas diffusion structure electrode can achieve a strength of 0.5 MPa, resisting the impact of gas flow generated during electrolysis and maintaining high stability. Figure 3 It is known that the metal species on the carbon electrode coexist in single-atom and particle forms. The electrocatalytic CO2 reduction to CO performance is shown in Table 1. This invention conducts stability tests on the monolithic electrode C for electrocatalytic CO2 reduction to CO production, as shown in... Figure 4 It is known that under a high current of 100mA, the selectivity of the monolithic electrode C shows almost no decay within 2.5 hours and remains above 90%, demonstrating its high stability.

[0052] Table 1. Activity results of the three-dimensional gas diffusion structure electrode AC at -0.8V (relative to the reversible hydrogen electrode).

[0053]

[0054] Example 2

[0055] In Implementation Example 1, the activation temperature of the monolithic carbon material in step 1 is changed to 800℃, and the specific surface area is 1559m². 2 g -1 The pore volume is 0.69 cm. 3 / g, the remaining steps, including the synthesis of polymer materials and the application of the prepared three-dimensional gas diffusion structure electrode to electrocatalytic CO2 reduction, are the same as in Example 1.

[0056] Example 3

[0057] In Implementation Example 1, the activation temperature of the monolithic carbon material in step 1 was changed to 900℃, increasing the specific surface area to 2530m². 2 g -1 The pore volume is 1.49 cm. 3 / g, the remaining steps, including the synthesis of polymer materials and the application of the prepared three-dimensional gas diffusion structure electrode to electrocatalytic CO2 reduction, are the same as in Example 1.

[0058] Example 4

[0059] In Example 1, the metallic nickel in step 2 was replaced with metallic bismuth. The remaining steps, including the synthesis and molding of the polymer material and the application of the prepared three-dimensional gas diffusion structure electrode to the electrocatalytic CO2 reduction using a honeycomb-shaped monolithic carbon support, were identical to those in Example 1. This example was named Example D, and its product was formic acid.

[0060] Example 5

[0061] In Example 1, the metallic nickel in step 2 is replaced with metallic copper. The remaining steps, including the synthesis and molding of the polymer material, the application of the prepared three-dimensional gas diffusion structure electrode to the electrocatalytic CO2 reduction using a honeycomb-shaped monolithic carbon support, are identical to those in Example 1. This example is named Example E, and its products include carbon monoxide, ethylene, formic acid, acetic acid, and ethanol.

[0062] Comparative Example 1

[0063] The monolithic carbon electrode C sample prepared in Example 1 was ground and then dispersed in a solution of water, ethanol, and Nafion (volume ratio 16:3:1). The catalyst concentration was 5 mg / mL. The mixture was ultrasonically modulated to form a homogeneous slurry. This slurry was then coated onto carbon paper to obtain an electrode sheet containing the catalyst. The electrocatalytic CO2RR performance was then tested. The CO Faraday efficiency was 90%, and the CO formation rate was 123 μmol / cm³. -2 h -1 .

[0064] Comparative Example 2

[0065] In Example 1, the 1-methylimidazole raw material was replaced with hexadecyltrimethylammonium bromide. The rest of the process, including the monolithic carbon synthesis, remained the same as in Example 1. The prepared polymer was inelastic, brittle, and unable to form a tubular structure. It showed significant shrinkage before and after drying, and the derived carbon material had a high density of 0.9 g cm⁻¹. -3 Furthermore, the polymer, after being pulverized, cannot be molded into a honeycomb structure using the molding method of Example 1.

[0066] Conclusion: The fabrication of a three-dimensional gas diffusion structure electrode and its application in electrosynthesis reactions represent a new breakthrough in the development of structured electrodes. This patent describes a three-dimensional gas diffusion structure electrode fabricated from a monolithic carbon material with high strength and well-developed porosity, and its application in electrocatalytic reactions. Taking the electrocatalytic CO2 reduction reaction as an example, the monolithic electrode exhibits high reactant conversion rate, product formation rate, and selectivity. The monolithic electrode also demonstrates good stability, which is crucial for industrial applications. Figure 5 Compared to Comparative Example A, the CO selectivity of the three-dimensional gas diffusion structure electrode C is higher than that of the electrode sheet at different potentials. For example, at -0.6V (relative to the reversible hydrogen electrode), the CO Faradaic efficiency is increased by 1.5 times, and at -0.8V (relative to the reversible hydrogen electrode), the CO Faradaic efficiency is 93%. Furthermore, the monolithic electrode avoids the use of polymer binders, which can disrupt the continuity of carbon particles and reduce the electrode's conductivity. Therefore, the monolithic electrode is more conducive to maintaining high conductivity. These properties synergistically construct a favorable microenvironment for the electrocatalytic reaction, which is beneficial for the gas-consuming electrocatalytic CO2 reduction reaction. The three-dimensional gas diffusion structure electrode AC exhibits a high CO generation rate in the electrocatalytic CO2 reduction reaction, especially the three-dimensional gas diffusion structure electrode C. Figure 6 For example, at a potential of -0.8V (relative to the reversible hydrogen electrode), the activity increased by 11.6 times. Since the three-dimensional gas diffusion structure electrode is a permeable electrode structure, meaning that the reactant CO2 gas is directly transported from one end of the electrode and then rapidly penetrates forward and through the sidewalls via the flow channels in the honeycomb structure, it solves the problem of low CO2 solubility in the electrolyte and directly increases the supply of reactants near the local active centers. Using monolithic carbon materials as a substrate and loading different electrocatalytic CO2 reduction product active sites, it is also possible to control the product transition from the gas phase to the liquid phase, and even to multi-carbon products. Therefore, the synthesis method of the three-dimensional gas diffusion structure electrode proposed in this invention has good versatility and will provide a new approach for the design of electrosynthesized structural electrodes.

Claims

1. A three-dimensional gas diffusion structure electrode, characterized in that: The electrode comprises an integral carbon material carrier and a metal active component, wherein the metal active component is iron, cobalt, manganese, nickel, bismuth, or copper, and is uniformly dispersed on the carrier as metal single atoms and metal nanoparticles; the electrode has a specific surface area of ​​1559~2530 m². 2 / g, pore volume 0.69~1.49 cm³ 3 / g, with a strength of 0.3-0.8 MPa; the integral carbon material carrier is columnar, tubular, plate-shaped, or formed into a honeycomb structure; the density of the three-dimensional gas diffusion structure electrode is 0.2~0.4 g / cm³. 3 The method for preparing the three-dimensional gas diffusion structure electrode includes the following steps: S1. At room temperature, an imidazole compound and a foaming agent are dissolved in a solvent and stirred until the solution is clear and transparent to obtain a foaming agent-imidazole compound solution; the foaming agent is one or more of oleic acid and sodium oleate. S2 Add phenol and aldehyde to a solvent and stir to form a uniform, colorless, and transparent phenol-aldehyde solution; then add the phenol-aldehyde solution to a foaming agent-imidazolium compound solution and continue stirring until a pale yellow transparent sol solution is formed. S3 Pour the sol solution into a sealed container, place it in an oven for polymerization and aging, then remove the polymer and cool it to room temperature, and dry it to obtain a monolithic polymer; or crush the monolithic polymer into powder, mix it with solvent and binder, and obtain a molded polymer through kneading, molding and drying. S4 involves first subjecting the monolithic or molded polymer to high-temperature carbonization under an inert gas atmosphere, at a carbonization temperature of 800~1000°C. o C; Further activation treatment is carried out under an activating gas atmosphere to obtain a porous monolithic carbon carrier through physical activation and pore formation. The activation temperature is 600~900℃. o C.

2. A method for preparing the three-dimensional gas diffusion structure electrode according to claim 1, characterized in that: Includes the following steps: S1. At room temperature, an imidazole compound and a foaming agent are dissolved in a solvent and stirred until the solution is clear and transparent to obtain a foaming agent-imidazole compound solution; the foaming agent is one or more of oleic acid and sodium oleate. S2 Add phenol and aldehyde to a solvent and stir to form a uniform, colorless, and transparent phenol-aldehyde solution; then add the phenol-aldehyde solution to a foaming agent-imidazolium compound solution and continue stirring until a pale yellow transparent sol solution is formed. S3 Pour the sol solution into a sealed container, place it in an oven for polymerization and aging, then remove the polymer and cool it to room temperature, and dry it to obtain a monolithic polymer; or crush the monolithic polymer into powder, mix it with solvent and binder, and obtain a molded polymer through kneading, molding and drying. S4 The monolithic polymer or molded polymer is first placed under an inert gas protection condition for high-temperature carbonization at a carbonization temperature of 800~1000 ℃; then it is activated under an activating gas atmosphere to obtain a porous monolithic carbon carrier through physical activation and pore formation at an activation temperature of 600~900 ℃. S5 The metal active components are loaded onto an integral carbon support by impregnation, and then subjected to high-temperature carbonization, acid washing and drying in an inert atmosphere to obtain the three-dimensional gas diffusion structure electrode.

3. The method for preparing the three-dimensional gas diffusion structure electrode as described in claim 2, characterized in that: The imidazole compound is one or more selected from imidazole, 1-methylimidazolium, 2-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-butylimidazolium, 2-ethylimidazolium, and 2-propylimidazolium, and the concentration of the imidazole compound in the sol solution is 0.001~0.5 mol / L. -1 The molar ratio of the imidazole compound to the foaming agent is 1:1 to 1:

5.

4. The method for preparing the three-dimensional gas diffusion structure electrode as described in claim 2, characterized in that: The molar ratio of phenol to aldehyde is 1:2 to 1:6; the molar ratio of imidazole to phenol is 3 to 15.

5. The method for preparing the three-dimensional gas diffusion structure electrode as described in claim 2, characterized in that: The mass ratio of polymer powder, solvent, and binder in step S3 is 60:120:1 to 6:12:

1.

6. The method for preparing the three-dimensional gas diffusion structure electrode as described in claim 2, characterized in that: The activation time in step S4 is 1 to 3 hours, and the activation gas during the activation process is water vapor, carbon dioxide or hydrogen.

7. The method for preparing the three-dimensional gas diffusion structure electrode as described in claim 2, characterized in that: In step S5, the carbonization temperature is 700~1000 ℃, the carbonization time is 1~3 h, and the inert atmosphere is argon or nitrogen.

8. The application of the three-dimensional gas diffusion structure electrode as described in claim 1 in electrocatalytic synthesis, characterized in that: The reactive gas is delivered from one end of the three-dimensional gas diffusion structure electrode, first flowing into the interior of the integral structure electrode and then diffusing outward.

9. The application of the three-dimensional gas diffusion structure electrode as described in claim 8 in electrocatalytic synthesis, characterized in that: It is used for electrocatalytic CO2 reduction.

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