Gas-phase diffusion electrode for electrocatalytic reduction of co 2 to produce formic acid, as well as manufacturing method therefor and use thereof

Abstract

The present application provides a manufacturing method for a gas-phase diffusion electrode for electrocatalytic reduction of CO2 to produce formic acid, and the use thereof. The method comprises: acquiring a first mixed solution; acquiring a second mixed solution; and uniformly mixing the first mixed solution and the second mixed solution, then coating same on the surface of a substrate, and placing same at the temperature of -30℃-100℃ for 1-48 hours so as to obtain a gas-phase diffusion electrode. The manufacturing method involves coating the surface of the substrate with a conductive polymer monomer and bismuth- or tin-based metal components, so as to form the integrated conductive polymer-catalyst / hydrophobic substrate composite gas-phase diffusion electrode, which not only can enhance the stability between metal active components and a substrate material, but also has the characteristics such as more excellent conductivity, higher specific surface area and rich surface chemical reaction sites, thus facilitating rapid adsorption and activation of CO2 molecules during reaction, and exhibiting excellent formic acid catalytic activity and stability in electrolytic cells for electrocatalytic reduction of CO2.

Description

A gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid, preparation method and application thereof Technical Field

[0001] The present application relates to the technical field of electrocatalytic CO2 reduction, and in particular to a preparation method and application of a gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid. Background Art

[0002] In the CO2 molecule, the C=O bond length is Bond energy up to 750KJmol -1 , resulting in high thermodynamic stability and difficulty in activation. Therefore, sufficient energy is required to overcome the reaction energy barrier during CO2 conversion. Based on the energy supply, CO2 reduction can be categorized into three pathways: thermochemical, photochemical, and electrochemical. Thermochemical conversion, exemplified by CO2 hydrogenation, was the first to receive research and attention. For example, in the 1970s, Imperial Chemical Industries in the United Kingdom developed a commercial Cu / ZnO / Al2O3 catalyst for methanol production at 200-300°C and 50-100 atm. Furthermore, thermochemical conversion can also produce methane, formic acid, and high-carbon products such as olefins and gasoline. However, the thermochemical conversion of CO2 requires demanding reaction conditions, typically requiring high temperatures and high pressures. Compared to thermochemical conversion, the photochemical conversion of CO2 operates under much milder conditions. In photochemical conversion, photogenerated electrons generated by a semiconductor catalyst under sunlight can reduce CO2. However, current CO2 photochemical conversion suffers from poor product selectivity and low production rates, making it difficult to commercialize.

[0003] Compared to thermochemical and photochemical conversions, electrochemical conversion of CO2 offers the following advantages: mild reaction conditions, allowing it to proceed at room temperature and pressure; a controllable reaction process, enabling the selectivity and rate of product formation to be regulated by varying the potential, catalyst, and electrolyte; powered by electricity from renewable energy sources (wind and solar energy), enabling a carbon-neutral cycle; and modular reaction systems, making industrial production easier. Therefore, electrochemical conversion of CO2 holds great promise for reducing atmospheric CO2 concentrations.

[0004] Formic acid (HCOOH) product as 2e -The reduction product, HCOOH, has been extensively studied in CO2 electroreduction reactions. Catalysts with HCOOH selectivity primarily include p-block main-group metal elements such as In, Sn, Sb, Tl, Pb, and Bi, as well as transition metals such as Co, Cu, Pd, Cd, and Hg. With the development of increasingly efficient catalysts, the selectivity and activity of HCOOH products have steadily improved. Due to their weak adsorption of *H, Bi-based catalysts can, to a certain extent, suppress the competing reaction (HER) in CO2 electroreduction reactions, resulting in better selectivity for the HCOOH product. However, traditional powdered Bi-based catalysts have poor conductivity, low current density, and are prone to shedding during electrolysis, resulting in low long-term stability and efficiency, which limits their practical industrial applications.

[0005] Summary of the Invention

[0006] In view of this, it is necessary to provide a preparation method and application of a gas-phase diffusion electrode with low cost, high selectivity, good conductivity and excellent stability to address the defects of traditional electrodes in the electrocatalytic reduction of CO2 to formic acid, such as low selectivity, poor stability and poor conductivity.

[0007] To solve the above problems, this application adopts the following technical solutions:

[0008] One of the purposes of this application is to provide a method for preparing and applying a gas-phase diffusion electrode for electrocatalytic reduction of CO2 to produce formic acid, comprising the following steps:

[0009] Obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer;

[0010] obtaining a second mixed solution, the second mixed solution comprising a component containing bismuth or tin and a solvent mixed solution;

[0011] The first mixed solution and the second mixed solution are uniformly mixed and then coated on the surface of the substrate, and then placed at a temperature of -30°C to 100°C for 1 to 48 hours to obtain the vapor diffusion electrode.

[0012] In some embodiments, in the step of obtaining a first mixed solution comprising an acidic solution, a solvent, a dispersant, and a mixed solution of a conductive polymer monomer, a molar ratio of the conductive polymer monomer to the acidic solution is 1:1-20.

[0013] In some embodiments, in the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer, the acidic solution includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, and camphorsulfonic acid.

[0014] In some embodiments, in the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer, the solvent is one or more of water, methanol, ethanol, isopropanol, acetonitrile, ethyl acetate, chloroform, dichloromethane, acetone, N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0015] In some embodiments, in the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer, the conductive polymer monomer is one or more of aniline, pyrrole, thiophene, indole, pyridine, carbazole, dopamine and para-phenylene vinyl monomers.

[0016] In some embodiments, in the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer, the dispersant is one or more of isopropyl alcohol, methanol, ethanol, ethyl acetate, acetonitrile, N-methylpyrrolidone, and dimethylformamide.

[0017] In some embodiments, in the step of obtaining a second mixed solution, wherein the second mixed solution includes a bismuth- or tin-containing component and a solvent mixed solution, the bismuth- or tin-containing component includes one or more of bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxycarbonate, bismuth chloride, bismuth bromide, bismuth iodide, bismuth salicylate, bismuth powder, bismuth oxide powder, bismuth sulfide powder, stannous chloride, tin tetrachloride, tin oxide powder, and tin sulfide powder.

[0018] In some embodiments, the molar concentration of the bismuth- or tin-containing component is controlled at 0.01-5 mol / L.

[0019] In some embodiments, after uniformly mixing the first mixed solution and the second mixed solution, the mixed solution is coated on the surface of the substrate, and then placed at a temperature of -30°C to 100°C for 1-48 hours to obtain the vapor diffusion electrode, the coating includes one of drip coating, spray coating, scraping coating, and spin coating.

[0020] In some embodiments, the substrate includes polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, non-woven fabric, fiber resin film and modified substrate materials thereof.

[0021] In some embodiments, before the step of uniformly mixing the first mixed solution and the second mixed solution and coating the mixed solution on the surface of the substrate, the step further includes washing the substrate several times with water and / or an organic solvent and drying the substrate.

[0022] The second purpose of this application is to provide a gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid, which is prepared by any of the preparation methods described.

[0023] The third purpose of this application is to provide an application of a gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid.

[0024] This application adopts the above technical solution, and its beneficial effects are as follows:

[0025] The present application provides a preparation method and application of a gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid, obtaining a first mixed solution, the first mixed solution comprising a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer; obtaining a second mixed solution, the second mixed solution comprising a bismuth- or tin-containing component and a solvent mixed solution; uniformly mixing the first mixed solution and the second mixed solution and applying the mixed solution to the surface of a substrate, and then placing the mixed solution at a temperature of -30°C to 100°C for 1-48 hours to obtain the gas-phase diffusion electrode. The preparation method of the gas-phase diffusion electrode of the present application comprises applying a conductive polymer monomer, a bismuth- or tin-based metal component to the surface of a substrate to form an integrated conductive polymer-catalyst / hydrophobic substrate composite gas-phase diffusion electrode, which not only enhances the stability between the metal active components (metal salts, metal particles and metal ligand complexes, etc.) and the substrate material, but also has better conductivity, higher specific surface area and abundant surface chemical reaction sites, etc., which contribute to the rapid adsorption and activation of CO2 molecules during the reaction process, thereby exhibiting excellent catalytic activity and stability in the electrocatalytic CO2 reduction electrolytic cell.

[0026] In addition, the present application provides a gas-phase diffusion electrode for electrocatalytic reduction of CO2 to produce formic acid, which is environmentally friendly, low-cost, efficient and stable, and can efficiently realize the electrocatalytic reduction of carbon dioxide to produce formic acid, and has prospects for large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] FIG1 is a flow chart showing the steps of a method for preparing a gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid, provided in an embodiment.

[0029] FIG2 is a SEM schematic diagram of the conductive polymer-bismuth-based catalyst composite material in Example 1.

[0030] FIG3 is a bar graph of the Faraday efficiency of the catalyst electrodes for catalytic reduction of CO2 to produce formic acid and hydrogen at different current densities in Example 1 (a, b, c) and Comparative Example 1 (d, e, f).

[0031] FIG4 is a formic acid signal peak under the NMR (400 HMz) test conditions of Example 1. DETAILED DESCRIPTION

[0032] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0033] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0035] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Please refer to FIG1 , which is a flowchart of the method for preparing a vapor diffusion electrode provided in this embodiment, including the following steps S110 to S130 . The implementation of each step is described in detail below.

[0037] Step S110: obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer.

[0038] In this embodiment, in the step of obtaining a first mixed solution comprising an acidic solution, a solvent, a dispersant and a mixed solution of a conductive polymer monomer, a molar ratio of the conductive polymer monomer to the acidic solution is 1:1-20.

[0039] In this embodiment, the acidic solution includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, and camphorsulfonic acid.

[0040] In this embodiment, the solvent is one or more of water, methanol, ethanol, isopropanol, acetonitrile, ethyl acetate, chloroform, dichloromethane, acetone, N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.

[0041] In this embodiment, the conductive polymer monomer is one or more of aniline, pyrrole, thiophene, indole, pyridine, carbazole, dopamine, and p-phenylene vinyl monomers.

[0042] It is understood that the conductive polymer monomers provided herein possess long-range conjugated structures. Typical conductive polymers include polyacetylene, polypyrrole, polythiophene, polyaniline, and their derivatives. The excellent electrochemical properties of conductive polymers can be utilized to improve the properties of modified electrode surfaces, such as increasing the electrode's specific surface area, enhancing conductivity, increasing electron transfer capacity, and providing binding sites for the modification of other materials. More importantly, by improving the electrochemical properties of modified electrodes, their practical value can be enhanced.

[0043] In this embodiment, the dispersant is one or more of isopropyl alcohol, methanol, ethanol, ethyl acetate, acetonitrile, N-methylpyrrolidone, and dimethylformamide.

[0044] Step S120: obtaining a second mixed solution, wherein the second mixed solution includes a component containing bismuth or tin and a solvent mixed solution.

[0045] In this embodiment, the bismuth or tin-containing component includes one or more of bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxycarbonate, bismuth chloride, bismuth bromide, bismuth iodide, bismuth salicylate, bismuth powder, bismuth oxide powder, bismuth sulfide powder, stannous chloride, tin tetrachloride, tin oxide powder, and tin sulfide powder.

[0046] In this embodiment, the molar concentration of the bismuth- or tin-containing component is controlled to be 0.01-5 mol / L.

[0047] Step S130: uniformly mixing the first mixed solution and the second mixed solution, coating the mixed solution on the surface of the substrate, and then placing the mixed solution at a temperature of -30°C to 100°C for 1 to 48 hours to obtain the vapor diffusion electrode.

[0048] Specifically, the first mixed solution and the second mixed solution are uniformly mixed and then coated on the substrate surface by dripping, spraying, scraping or spin coating to form a continuous and stable coating on the substrate surface, and then placed at a temperature of -30°C to 100°C for 1-48 hours to obtain the vapor diffusion electrode.

[0049] In this embodiment, the substrate includes polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, non-woven fabric, fiber resin film and modified substrate materials thereof.

[0050] In this embodiment, before the step of uniformly mixing the first mixed solution and the second mixed solution and then coating the mixed solution on the surface of the substrate, the step further includes washing the substrate several times with water and / or an organic solvent and drying the substrate.

[0051] It is understood that conductive polymers not only have the ability to transport charge themselves, but also provide conductive carriers (electrons, ions, or holes) within the polymer structure. Carriers are free electrons or holes in the polymer. During the conductive process, the carriers can move in a directed manner within the polymer under the action of an electric field to form an electric current. The conductivity of the structured conductive polymer after doping can be significantly increased, and the conductivity value can even be increased to the conductivity range of metals. The main chain of the conductive polymer usually has a conjugated structure, and its polymerization process is mostly oxidative coupling of monocyclic precursors. When the organic compound has a co-wheel structure, the π electron system increases, the delocalization of the electrons is enhanced, and the range of mobility is increased. When the conjugated structure reaches a sufficiently large size, the compound can provide free electrons and have a conductive function. Therefore, the conductive polymer is mixed in situ with the active metal component, and the polymer and the metal active component are uniformly polymerized and connected to the substrate surface through in situ polymerization to form an integrated conductive polymer-metal oxide electrode material, which can not only enhance the adhesion of the metal active component to the substrate surface, but also enhance the conductivity of the substrate material.

[0052] The metal-conductive polymer composite gas-phase diffusion electrode provided by the present invention can be applied to a reaction system for producing CO by electrocatalytic reduction of CO2.

[0053] The preparation method of the gas-phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid prepared in the above embodiment of the present application comprises obtaining a first mixed solution, wherein the first mixed solution comprises a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer; obtaining a second mixed solution, wherein the second mixed solution comprises a mixed solution of a bismuth- or tin-containing component and a solvent; uniformly mixing the first mixed solution and the second mixed solution and applying the resultant to the surface of a substrate, and then placing the resultant at a temperature of -30°C to 100°C for 1-48 hours to obtain the gas-phase diffusion electrode. Since the main chain of the conductive polymer usually has a conjugated structure, its polymerization process is mostly oxidative coupling of a monocyclic precursor. Therefore, an oxidizing metal salt can be used instead of an initiator to initiate the polymerization in situ, and the catalytic selectivity and stability are improved by designing the metal-conductive polymer composite electrode. In addition, the gas-phase diffusion electrode prepared in the present application can promote the diffusion of CO2 molecules to the electrode surface, promote the coupling of CO2 molecules with electrons or protons, quickly open the C=O double bond, form a reaction intermediate, and ultimately generate a formic acid product with a high Faraday efficiency, thereby realizing the circular economic utilization and conversion of carbon dioxide.

[0054] The following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0055] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0056] Example 1

[0057] A method for preparing a conductive polymer-bismuth-based catalyst composite electrode material for electrocatalytic CO2 reduction to produce formic acid comprises the following steps:

[0058] (1) Prepare polyaniline monomer solution (Solution A): Take 0.8 mmol of acetic acid solution, add 0.4 mmol of aniline, and then add 200 μL of isopropanol, stir and mix well, and pre-cool for 2 hours;

[0059] (2) Preparation of bismuth nitrate solution (Solution B): Take 0.1 mmol of bismuth nitrate solution, add 100 μL of isopropanol, and pre-cool for 2 h;

[0060] (3) Prepare Nafion solution: Disperse 10 μL of Nafion in 1000 μL of isopropanol and add it dropwise to a 4×4 cm 2 On PTFE substrate;

[0061] (4) Solution A and solution B in Example 1 were uniformly mixed and rapidly added dropwise to the surface of the PTFE carbon membrane to initiate an in situ polymerization reaction at a reaction temperature of 0°C and a reaction time of 12 h to prepare a polyaniline-bismuth-based catalyst composite electrode material, which was labeled as Bi-PANI / PTFE composite electrode material.

[0062] Table 1 shows the electrocatalytic performance of the catalyst samples prepared in Example 1 at different voltages.

[0063] Example 2

[0064] A method for preparing a conductive polymer-bismuth-based catalyst composite electrode material for electrocatalytic CO2 reduction to produce formic acid comprises the following steps:

[0065] (1) Prepare polypyrrole monomer solution (Solution A): Take 0.8 mmol of acetic acid solution, add 0.4 mmol of pyrrole, and then add 200 μL of isopropanol, stir and mix evenly, and pre-cool for 2 hours;

[0066] (2) Prepare bismuth nitrate solution (Solution B): Take 0.1 mmol of bismuth nitrate solution, add 100 μL of isopropanol, and pre-cool for 2 h;

[0067] (3) Prepare Nafion solution: Disperse 10 μL of Nafion in 1000 μL of isopropanol and add it dropwise to a 4×4 cm 2 On PTFE carbon film substrate;

[0068] (4) Solution A and solution B were uniformly mixed and rapidly added dropwise to the surface of the PTFE substrate to initiate an in situ polymerization reaction at a reaction temperature of 0°C and a reaction time of 12 h to prepare a polypyrrole-bismuth-based catalyst composite electrode material, which was labeled as Bi-PPy / PTFE composite electrode material.

[0069] Table 2 shows the electrocatalytic performance of the catalyst samples prepared in Example 2 at different voltages.

[0070] Example 3

[0071] A method for preparing a conductive polymer-bismuth-based catalyst composite electrode material for electrocatalytic CO2 reduction to produce formic acid comprises the following steps:

[0072] (1) Prepare polythiophene monomer solution (Solution A): Take 1.6 mmol of acetic acid solution, add 0.8 mmol of thiophene, and then add 200 μL of isopropanol, stir and mix evenly, and pre-cool for 2 hours;

[0073] (2) Prepare bismuth nitrate solution (Solution B): Take 0.1 mmol of bismuth nitrate solution, add 100 μL of isopropanol, and pre-cool for 2 h;

[0074] (3) Prepare Nafion solution: Disperse 10 μL of Nafion in 1000 μL of isopropanol and add it dropwise to a 4×4 cm 2 On PTFE carbon film substrate;

[0075] (4) Solution A and solution B were evenly mixed and rapidly added dropwise to the surface of the PTFE carbon membrane to initiate an in situ polymerization reaction at a reaction temperature of 0°C and a reaction time of 12 h to prepare a polyaniline-bismuth-based catalyst composite electrode material, which was labeled as Bi-PTH / PTFE composite electrode material.

[0076] Table 3 shows the electrocatalytic performance of the catalyst samples prepared in Example 3 at different voltages.

[0077] Example 4

[0078] A method for preparing a conductive polymer-bismuth-based catalyst composite electrode material for electrocatalytic CO2 reduction to produce formic acid comprises the following steps:

[0079] (1) Prepare polyacetylene monomer solution (Solution A): Take 0.8 mmol of acetic acid solution, add 0.4 mmol of aniline, and then add 200 μL of isopropanol, stir and mix well, and pre-cool for 2 hours;

[0080] (2) Prepare bismuth nitrate solution (Solution B): Take 0.1 mmol of bismuth nitrate solution, add 100 μL of isopropanol, and pre-cool for 2 h;

[0081] (3) Prepare Nafion solution: Disperse 10 μL of Nafion in 1000 μL of isopropanol and add it dropwise to a 4×4 cm 2 On PTFE substrate;

[0082] (4) Solution A and solution B were evenly mixed and rapidly added dropwise to the surface of the PTFE carbon membrane to initiate an in situ polymerization reaction at a reaction temperature of 0°C and a reaction time of 12 h to prepare a polyaniline-bismuth-based catalyst composite electrode material, which was labeled as Bi-PA / PTFE composite electrode material.

[0083] Table 4 Electrocatalytic performance of the catalyst samples prepared in Example 4 at different voltages.

[0084] Example 5

[0085] A method for preparing a conductive polymer-bismuth-based catalyst composite electrode material for electrocatalytic CO2 reduction to produce formic acid comprises the following steps:

[0086] (1) Prepare polyaniline monomer solution (Solution A): Take 1.6 mmol of acetic acid solution, add 0.8 mmol of aniline, and then add 400 μL of isopropanol, stir and mix well, and pre-cool for 2 hours;

[0087] (2) Prepare bismuth nitrate-tin nitrate solution (Solution B): Take 0.4 mmol bismuth nitrate solution and 0.1 mmol silver nitrate solution, add 800 μL isopropanol, and pre-cool for 2 h;

[0088] (3) Prepare Nafion solution: Disperse 80 μL of Nafion in 2000 μL of isopropanol and add it dropwise to a 8×8 cm 2 On PTFE carbon film substrate;

[0089] (4) Solution A and solution B were evenly mixed and rapidly added dropwise to the surface of the PTFE carbon membrane to initiate an in situ polymerization reaction at a reaction temperature of 0°C and a reaction time of 12 h to prepare a polyaniline-bismuth-based catalyst composite electrode material, which was labeled as BiSn-PANI / PTFE composite electrode material.

[0090] Table 5 shows the electrocatalytic performance of the catalyst samples prepared in Example 5 at different voltages

[0091] Comparative Example 1

[0092] 10 mL of deionized water was added to 0.296 g of Bi(NO₃)₃·5H₂O. Subsequently, 1.0 M KOH was added to the solution and stirred for 2 h. The resulting Bi₂O₃ precipitate was washed three times with deionized water by ultrasonication and centrifugation, then dried at 80°C overnight. 30 mg of the Bi₂O₃ catalyst was added to 180 μL of a 5% Nafion solution and 3 mL of 2-propanol, sonicated for 30 min, and then dripped dropwise onto the surface of a PTFE membrane and dried. The resulting Bi₂O₃ catalyst electrode material was then evaluated for performance in the same electrolytic cell under the same operating conditions.

[0093] Table 6 shows the electrocatalytic performance of the catalyst samples prepared in Comparative Example 1 at different voltages

[0094] Comparative Example 2

[0095] Bismuth nanoparticles (20 nm) were used as primary nanoparticles and calcined at 400°C for 2 hours in an argon-hydrogen atmosphere containing 10% hydrogen. The resulting elemental bismuth catalyst electrode material was evaluated in the same electrolytic cell under the same operating conditions.

[0096] Table 7 shows the electrocatalytic performance of the catalyst samples prepared in Comparative Example 2 at different voltages

[0097] Comparative Example 3

[0098] 250mg Bi(NO3)3·5H2O was dissolved in 20mL ethylene glycol and stirred, which was recorded as solution (1). 15mL oleylamine and 15mL ethanol were added to the above solution (1) and stirred continuously. Stirring was continued at room temperature for 12h to form a suspension. It was washed with ethanol and deionized water several times, centrifuged, dried, and heat-treated at 300℃ for 2h to remove BiO x -OAm surface residual oleylamine, the product is named BiO x -300. 1 mg of prepared BiO x -300 powder was mixed with 250 μL of ethanol and 6 μL of 5% Nafion and ultrasonicated for 30 min to obtain a uniform ink. The ink was dropped on a PTFE (2.0×2.0 cm 2 ) and dried to serve as cathode electrode material.

[0099] Table 8 Electrocatalytic performance of the catalyst samples prepared in Comparative Example 3 at different voltages.

[0100] Effect verification

[0101] The performance of the Bi-based catalyst electrodes of Examples 1-5 and Comparative Examples 1-2 of the present invention was evaluated using a membrane electrode (MEA) electrolytic cell as a CO2 catalytic reduction reaction device. The specific measurement conditions were:

[0102] Gaseous products were directly detected by online gas chromatography (GC2014, Shimadzu, Japan) with a sampling interval of 20 minutes. Liquid products were detected by liquid nuclear magnetic resonance (NMR) (400 μM): 50 μL of liquid product, 500 μL of deuterated water (D₂O), and 100 μL of 6 mM DSS were collected and mixed in an NMR tube. 0.1 mL of deuterated water (D₂O) and 0.1 mL of 6 mM DSS were added to an NMR tube and mixed. A standard curve was generated using HCOONa·2H₂O and the internal standard DSS. The formic acid concentration at each potential was determined by comparing the HCOOH to DSS peak area ratio with the standard curve.

[0103] Membrane electrode (MEA) electrolytic cell CO2 electroreduction performance test: anode electrode is InO x / TiO2 mesh, the anode is passed through 1MKOH circulating liquid; the cathode is set with an electrolysis window with an area of ​​1.2x 1.2, and the cathode is passed through CO2 humidified gas. In the MEA electrolytic cell, the gas and liquid products after electroreduction can directly enter the cathode chamber through the gas diffusion electrode (GDE), the gas products enter the chromatograph, and the liquid products are washed with water and stored in the liquid solution bottle.

[0104] Calculation of Faradaic efficiency (FE): The Faradaic efficiency of formic acid at a given potential is calculated using the following formula: FEHCOOH = CHCOOH × V × N × F / Q

[0105] Wherein, CHCOOH is the concentration of formic acid in the electrolyte;

[0106] V, cathode chamber electrolyte volume;

[0107] N is the number of electrons transferred to form the product. For HCOOH, N is equal to 2:

[0108] F, Faraday constant, 96485 coulombs per mole (Cmol);

[0109] Q is the charge obtained by integrating the current-time curve.

[0110] Calculation of formic acid yield: The formic acid yield at a given potential is calculated using the following formula:

[0111] VHCOOH=(CHCOOH×V) / (S×t)

[0112] Wherein, vHCOOH, formic acid yield;

[0113] CHCOOH, formic acid concentration in the electrolyte;

[0114] V, cathode chamber electrolyte volume;

[0115] S, geometric area of ​​the working electrode;

[0116] t, electroreduction time.

[0117] As shown in Figure 3, Example 1 and Comparative Example 1 show that the conductive polymer-bismuth-based catalyst provided by the present invention, when used in a CO2 electroreduction process to produce formic acid, maintains high formic acid selectivity (above 96%) while also improving long-term stability, enabling the MEA electrolytic cell to operate stably and continuously for a long time while maintaining a stable and high formic acid current efficiency. When other catalytically active components besides bismuth are introduced, they can synergize with the bismuth element, further improving the stable operation time of the MEA electrolytic cell.

[0118] It can be understood that the various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above are merely preferred embodiments of the present application and only specifically describe the technical principles of the present application. These descriptions are intended only to explain the principles of the present application and should not be construed in any way as limiting the scope of protection of the present application. Based on the explanations herein, any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application, as well as other specific implementations of the present application that can be conceived by those skilled in the art without inventive effort, shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid, characterized in that: The steps include: Obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant, and a conductive polymer monomer; Obtaining a second mixed solution, wherein the second mixed solution includes a component containing bismuth or tin and a solvent mixed solution; The first mixed solution and the second mixed solution are uniformly mixed and then coated on the surface of the substrate, and then placed at a temperature of -30°C to 100°C for 1 to 48 hours to obtain the vapor diffusion electrode.

2. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1, characterized in that: In the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer, the molar ratio of the conductive polymer monomer to the acidic solution is 1:1-20.

3. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1, characterized in that: In the step of obtaining a first mixed solution, wherein the first mixed solution includes an acidic solution, a solvent, a dispersant and a mixed solution of a conductive polymer monomer, the acidic solution includes one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid and camphorsulfonic acid.

4. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1 or 2, characterized in that: In the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer, the solvent is one or more of water, methanol, ethanol, isopropanol, acetonitrile, ethyl acetate, chloroform, dichloromethane, acetone, N-methylpyrrolidone, dimethylformamide and dimethyl sulfoxide.

5. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1 or 2, characterized in that: In the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer, the conductive polymer monomer is one or more of aniline, pyrrole, thiophene, indole, pyridine, carbazole, dopamine and p-phenylene vinylene monomers.

6. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1 or 2, characterized in that: In the step of obtaining a first mixed solution, wherein the first mixed solution includes a mixed solution of an acidic solution, a solvent, a dispersant and a conductive polymer monomer, the dispersant is one or more of isopropanol, methanol, ethanol, ethyl acetate, acetonitrile, N-methylpyrrolidone and dimethylformamide.

7. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1, characterized in that: In the step of obtaining a second mixed solution, wherein the second mixed solution includes a bismuth- or tin-containing component and a solvent mixed solution, the bismuth- or tin-containing component includes one or more of bismuth nitrate, bismuth sulfate, bismuth acetate, bismuth oxycarbonate, bismuth chloride, bismuth bromide, bismuth iodide, bismuth salicylate, bismuth powder, bismuth oxide powder, bismuth sulfide powder, stannous chloride, tin tetrachloride, tin oxide powder, and tin sulfide powder.

8. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 7, characterized in that: The molar concentration of the bismuth or tin-containing component is controlled at 0.01-5 mol / L.

9. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1, characterized in that: In the step of uniformly mixing the first mixed solution and the second mixed solution and coating them on the surface of the substrate, and then placing them at a temperature of -30°C-100°C for 1-48 hours to obtain the vapor diffusion electrode, the coating includes one of drip coating, spray coating, scraping coating, and spin coating.

10. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 1 or 9, characterized in that: The substrate includes polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, non-woven fabric, fiber resin film and modified substrate materials thereof.

11. The method for preparing a gas phase diffusion electrode for electrocatalytic CO2 reduction to produce formic acid according to claim 10, characterized in that: Before the step of uniformly mixing the first mixed solution and the second mixed solution and coating the mixed solution on the surface of the substrate, the method further includes washing the substrate several times with water and / or an organic solvent and drying the substrate.

12. A gas phase diffusion electrode, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 11.

13. Use of the gas phase diffusion electrode as claimed in claim 12 in CO2 electrocatalytic reduction reaction.

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