Multilayer gas diffusion electrode and preparation method and application thereof

Abstract

The invention relates to the field of gas diffusion electrodes, and discloses a multilayer gas diffusion electrode and a preparation method and application thereof, the electrode comprises a gas diffusion layer, a hydrophobic layer, a conductive layer, a catalyst layer and a porous protective layer, a catalyst in the catalyst layer comprises nitrogen-doped bismuth nanoparticles and a structural unit which is used for carrying out graft modification on the nitrogen-doped bismuth nanoparticles and is shown in a formula (1), R1 and R2 are hydrogen or alkyl respectively, and the sum of carbon numbers of R1 and R2 is smaller than 4. The gas diffusion electrode disclosed by the invention is excellent in performance and outstanding in stability in carbon dioxide electrolysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas diffusion electrodes, in particular to a multilayer gas diffusion electrode and its preparation method and application. BACKGROUND

[0002] Carbon dioxide electrolysis technology, i.e. electrochemical carbon dioxide reduction technology, is one of the most concerned carbon dioxide conversion and utilization technologies at present. This process not only converts carbon dioxide into useful chemicals in a mild and efficient manner, helping to achieve the carbon peak and carbon neutralization targets of China, but also converts renewable electrical energy into chemical energy in the products, realizing long-term storage and utilization of intermittent energy. Among the many carbon dioxide electrolysis products, formic acid / formate is one of the most economically valuable products. Formate has a wide range of industrial applications, such as additives in animal feed, drilling fluids for oil exploration, etc., and is also an important chemical production raw material. However, the industrial application of this conversion process is severely limited by the low operating life of the gas diffusion electrode. In most current studies, the life is less than 20 hours, which is far lower than the actual industrial production requirement (more than 10,000 hours). Therefore, developing a gas diffusion electrode with high stability has become a key challenge for current carbon dioxide electrolysis to formic acid technology. SUMMARY

[0003] The gas diffusion electrode has a catalyst on the front surface and is in contact with the liquid electrolyte, while the back surface of the gas diffusion electrode is in contact with gaseous carbon dioxide. The carbon dioxide diffuses through the internal pores of the multilayer gas diffusion electrode to reach the catalyst layer and the electrolyte side to react. Therefore, a high-performance gas diffusion electrode needs to have high porosity and air permeability to ensure efficient mass transfer of carbon dioxide gas. It also needs to have high hydrophobicity to prevent electrolyte from penetrating and clogging the internal pores of the electrode. In addition, it also needs to have low resistance, high activity, and structural stability.

[0004] However, the inventors of the present application have found that the existing gas diffusion electrode has the following defects and deficiencies:

[0005] 1. The product selectivity and life of the catalyst used are low.

[0006] 2. The electrode has low hydrophobicity. The hydrophobicity of the currently commercialized gas diffusion electrode, such as carbon paper, is mainly provided by doping polytetrafluoroethylene in the microporous carbon powder layer. The mass fraction of polytetrafluoroethylene is generally between 5% and 30%. The hydrophobicity provided by this amount of polytetrafluoroethylene cannot meet the needs of carbon dioxide electrolysis and is not sufficient to resist the penetration of electrolyte, thereby failing to ensure long-term stability of performance. If the amount of polytetrafluoroethylene is increased, the conductivity of the electrode will decrease, the voltage required for the reaction will increase, and the overall energy efficiency will decrease.

[0007] 3. The electrode catalyst layer is prone to detachment. In existing gas diffusion electrode structures, the catalyst is mostly uniformly mixed with a binder and then co-loaded onto a carbon substrate. However, as the reaction time increases, firstly, the catalyst is easily detached due to continuous scouring by the flowing electrolyte; secondly, the binder is also easily dissolved by the organic products of carbon dioxide electrolysis, leading to a decrease in its ability to fix the catalyst particles, which also causes catalyst detachment. Detachment of the electrode catalyst layer leads to a decrease in catalyst loading, ultimately resulting in a decrease in the activity of the gas diffusion electrode and an inability to maintain stable operation.

[0008] The purpose of this invention is to overcome the problems of low product selectivity and short electrode life in existing gas diffusion electrodes, and to provide a gas diffusion electrode with high product selectivity, long electrode life, high hydrophobicity, and strong catalyst binding ability.

[0009] To achieve the above objectives, the present invention provides a multilayer gas diffusion electrode, which includes a gas diffusion layer, a hydrophobic layer, a conductive layer, a catalyst layer, and a porous protective layer. The catalyst layer comprises nitrogen-doped bismuth nanoparticles and structural units of formula (1) grafted onto the nitrogen-doped bismuth nanoparticles.

[0010]

[0011] In this case, R1 and R2 are each hydrogen or alkyl, and the sum of the carbon numbers of R1 and R2 is less than 4.

[0012] A second aspect of the present invention provides a method for preparing the gas diffusion electrode described herein.

[0013] A third aspect of the present invention provides the application of the gas diffusion electrode described herein in carbon dioxide electrolysis.

[0014] The gas diffusion electrode of this invention features three key improvements. First, it employs a higher-performance catalyst to form the catalyst layer, resulting in superior catalyst product selectivity and lifetime compared to existing technologies. Second, a strongly hydrophobic layer is constructed on top of the traditional gas diffusion layer, supplemented by a conductive polymer layer. This maximizes the electrode's hydrophobicity without sacrificing conductivity, effectively suppressing electrolyte penetration. Third, a porous protective layer is constructed on the surface pores of the catalyst layer, ultimately significantly improving the electrode's lifetime. The gas diffusion electrode designed in this invention exhibits excellent performance and outstanding stability in carbon dioxide electrolysis. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the morphology of nitrogen-doped bismuth nanoparticles prepared in Example 1 of this invention.

[0016] Figure 2This is a schematic diagram of the gas diffusion electrode in Embodiment 1 of the present invention;

[0017] Figure 3 To obtain the voltage-time curves of the carbon dioxide electrolyzer using the gas diffusion electrode in Example 1 of this invention and the conventional gas diffusion electrode, as well as the scatter plot of the Faraday efficiency of formic acid over time, an applied current density of 200 mA / cm² was used. -2 ;

[0018] Figure 4 To obtain the voltage-time curve of the carbon dioxide electrolyzer using the gas diffusion electrode in Comparative Example 4 of this invention, and the scatter plot of the Faraday efficiency of formic acid over time, an applied current density of 200 mA cm⁻¹ was used. -2 . Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] This invention provides a multilayer gas diffusion electrode, comprising a gas diffusion layer, a hydrophobic layer, a conductive layer, a catalyst layer, and a porous protective layer. The catalyst layer comprises nitrogen-doped bismuth nanoparticles and structural units of formula (1) grafted onto the nitrogen-doped bismuth nanoparticles.

[0021]

[0022] In this case, R1 and R2 are each hydrogen or alkyl, and the sum of the carbon numbers of R1 and R2 is less than 4.

[0023] The multilayer gas diffusion electrode structure of the present invention contains grafting units as shown in Formula 1 in the catalyst layer, and the catalyst in the electrode has high product selectivity and long catalyst lifetime.

[0024] According to a preferred embodiment of the present invention, R1 and R2 are each hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, or 3-butyl, and the sum of the carbon numbers of R1 and R2 is less than 4.

[0025] According to a preferred embodiment of the present invention, R1 is hydrogen, and R2 is hydrogen, methyl or ethyl, for example, R1 is hydrogen and R2 is hydrogen, R1 is hydrogen and R2 is methyl, or R1 is hydrogen and R2 is ethyl.

[0026] Using the aforementioned grafting unit can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0027] According to a preferred embodiment of the present invention, the structural unit shown in formula (1) is covalently connected to nitrogen-doped bismuth nanoparticles.

[0028] In this invention, a wide range of nitrogen-doped bismuth nanoparticles can be selected. Commonly used nitrogen-doped bismuth nanoparticles can all achieve the purpose of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the nitrogen content in the nitrogen-doped bismuth nanoparticles is 1% to 10% by atomic percentage. Using the aforementioned preferred nitrogen-doped bismuth nanoparticles can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0029] In this invention, the particle size of the nitrogen-doped bismuth nanoparticles can be selected over a wide range. Commonly used nitrogen-doped bismuth nanoparticle sizes can achieve the objectives of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the particle size of the nitrogen-doped bismuth nanoparticles is 5 nm to 200 nm. Using the aforementioned preferred nitrogen-doped bismuth nanoparticles can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0030] According to a preferred embodiment of the present invention, the nitrogen-doped bismuth nanoparticles have a particle size of 30 nm to 200 nm. Using the aforementioned preferred nitrogen-doped bismuth nanoparticles can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0031] In this invention, the coverage of the structural unit shown in formula (1) can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the coverage of the structural unit shown in formula (1) in the catalyst is 5% to 50%.

[0032] According to a preferred embodiment of the present invention, the coverage of the structural unit shown in formula (1) in the catalyst is 10% to 45%. The coverage of the structural unit shown in the aforementioned preferred formula (1) can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0033] In this invention, coverage refers to the condition where, during the grafting process, the sample surface is considered fully covered if the compound described in formula (2), such as 2-hydroxymethylimidazolium, 1-(1H-imidazol-2-yl)ethanol, or 1-(1H-imidazol-2-yl)propanol, is sufficiently present. Based on this, the required coverage is obtained by calculating the ratio between the XPS signal peak intensity (C1s characteristic peak) of the existing sample and the fully covered sample.

[0034] Catalysts having the aforementioned structure of this invention can achieve the objectives of this invention. There are no special requirements for the preparation method of the catalyst. According to a preferred embodiment of this invention, a method for preparing the catalyst is provided, comprising the following steps:

[0035] 1) Synthesis of nitrogen-doped bismuth nanoparticles;

[0036] 2) The compound described in formula (2) reacts with nitrogen-doped bismuth nanoparticles to achieve covalent grafting;

[0037]

[0038] In this case, R1 and R2 are each hydrogen or alkyl, and the sum of the carbon numbers of R1 and R2 is less than 4;

[0039] Preferably,

[0040] R1 and R2 are each hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, or 3-butyl, and the sum of the carbon numbers of R1 and R2 is less than 4.

[0041] More preferably, the compound of formula (2) is one or more of 2-hydroxymethylimidazolium, 1-(1H-imidazol-2-yl)ethanol, and 1-(1H-imidazol-2-yl)propanol.

[0042] Step 1) of the preferred synthesis of nitrogen-doped bismuth nanoparticles according to the present invention includes: mixing bismuth nanoparticles with a nitrogen source solution and performing hydrothermal treatment under ammonia protection. In the nitrogen doping step, the present invention employs high-pressure ammonia treatment, which facilitates the diffusion of nitrogen atoms into the interior of the bismuth nanoparticles, achieving uniform doping. Furthermore, the amount of nitrogen doping can be precisely adjusted by controlling the pressure, enabling controllable preparation of the product. High-pressure ammonia also has a certain reducing property, which is beneficial for removing bismuth oxides and allowing nitrogen to replace oxygen in the bismuth nitride lattice. This method is applicable to bismuth nanomaterials of various morphologies and offers high operational flexibility.

[0043] In this invention, there are no special requirements for the volume concentration of ammonia. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the volume concentration of ammonia is 30% or more. Pure ammonia can be used, or pure ammonia can be diluted with an inert gas, such as a mixture of 30% ammonia and 70% argon. Unless otherwise specified, pure ammonia is used in this invention.

[0044] In this invention, the range of selectable hydrothermal treatment conditions is relatively wide, and commonly used hydrothermal treatment conditions can all be applied to this invention.

[0045] According to a preferred embodiment of the present invention, the hydrothermal treatment conditions preferably include a molar ratio of bismuth to nitrogen in the nitrogen source solution of 1:1 to 1:50, more preferably 1:2 to 1:20. Nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0046] According to a preferred embodiment of the present invention, the hydrothermal treatment conditions preferably include a temperature of 180°C to 270°C. The nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0047] According to a preferred embodiment of the present invention, the hydrothermal treatment conditions preferably include a pressure of 8 MPa to 12 MPa. The nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0048] According to a preferred embodiment of the present invention, the hydrothermal treatment conditions preferably include a time of 1 to 3 hours. After hydrothermal treatment, the mixture is naturally cooled to room temperature, the gas is released, and the nitrogen-doped bismuth nanoparticles are collected.

[0049] The nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0050] In this invention, the range of nitrogen sources is relatively wide, for example, ammonia water and / or urea solution. Nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0051] According to a preferred embodiment of the present invention, preferably, the concentration of the urea solution is 0.10 mol / L to 0.50 mol / L, and the concentration of the ammonia solution is 0.50 mol / L to 2.00 mol / L. The nitrogen-doped bismuth nanoparticles synthesized using the aforementioned preferred method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0052] In this invention, there are no special requirements for the method of covalent grafting of the compound described in formula (2) with nitrogen-doped bismuth nanoparticles in step 2). Any method that can achieve grafting can achieve the purpose of this invention. According to a preferred embodiment of this invention, step 2) is carried out by microwave-assisted synthesis.

[0053] According to a preferred embodiment of the present invention, the microwave-assisted synthesis method preferably includes mixing nitrogen-doped bismuth nanoparticles with the compound of formula (2), adding a solvent, and then feeding the mixture into a microwave reactor for microwave reaction.

[0054] In this invention, the range of solvents that can be selected is relatively wide, and various commonly used solvents can be used in this invention. According to a preferred embodiment of this invention, preferably, the solvent is selected from one or more of ethanol, diethyl ether, chloroform, methanol, and ethylene glycol.

[0055] In this invention, the conditions for microwave reaction can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of this invention.

[0056] According to a preferred embodiment of the present invention, preferably, the conditions for microwave reaction include a temperature of 60°C to 100°C.

[0057] According to a preferred embodiment of the present invention, preferably, the microwave reaction conditions include a power of 80W to 120W.

[0058] According to a preferred embodiment of the present invention, preferably, the microwave reaction conditions include a time of 5 to 15 minutes.

[0059] According to a preferred embodiment of the present invention, preferably, the conditions for microwave reaction include: the molar concentration of the compound of formula (2) is 0.04 mol / L to 0.20 mol / L.

[0060] In this invention, there are no special requirements for the amount of nitrogen-doped bismuth nanoparticles. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the ratio of the compound of formula (2) to nitrogen-doped bismuth nanoparticles is (0.001 mol to 0.1 mol) / g, more preferably (0.005 mol to 0.05 mol) / g. For example, the ratio of the compound of formula (2) to nitrogen-doped bismuth nanoparticles is 0.01 mol / g, 0.02 mol / g, 0.03 mol / g, and 0.04 mol / g.

[0061] After the microwave reaction, the catalyst is washed and purified. Conventional washing procedures can be used in this invention and are existing technologies, so they will not be described in detail here.

[0062] In this invention, there are no special requirements for the purification method. One embodiment is illustrated, but this does not limit the scope of the invention. For example, centrifugal precipitation is used for purification. Specifically, the catalyst is dissolved in water, and centrifuged to remove the precipitate. The precipitate mainly consists of oversized bismuth nanoparticles and unreacted imidazole substances. The centrifugation speed is generally between 3000 rpm and 6000 rpm. Higher speeds result in better centrifugation, but excessive speed can damage the product structure. The supernatant is then mixed with an organic solvent such as ethanol, allowed to settle, impurities are removed, the precipitate is collected, and dried at 50°C to 120°C to obtain the final catalyst product.

[0063] In the step of covalently grafting imidazole groups, the present invention preferably employs a microwave-assisted synthesis method. Microwave heating can directly act on the reactant molecules, which helps the imidazole groups to uniformly cover the surface of nanoparticles. In addition, microwave heating has the advantages of being fast and efficient, which can shorten the reaction time and increase the yield. Traditional heating methods rely on conduction and convection, resulting in uneven heating, long reaction times, and insufficient uniform coverage of the covalently grafted groups. Therefore, microwave-assisted synthesis can efficiently complete the covalent grafting reaction of imidazole groups in a shorter time.

[0064] The catalyst synthesized using the aforementioned preferred microwave reaction conditions in this invention can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0065] In this invention, there are no special requirements for the method of synthesizing bismuth nanoparticles; bismuth nanoparticles synthesized by various methods are all applicable to this invention. For example, monodisperse bismuth nanoparticles can be synthesized by thermal decomposition or hydrothermal methods. Alternatively, an ultra-fast injection of a reducing agent for precipitation can be considered to control the nucleation rate and obtain monodisperse particles. Furthermore, electrochemical synthesis and ultrasonic synthesis are also optional preparation methods.

[0066] For the present invention, hydrothermal synthesis of bismuth nanoparticles is preferred. Preferably, the synthesis steps of the bismuth nanoparticles include: reflux heating to form a bismuth-ethylene glycol complex; high-temperature heating to synthesize bismuth nanoparticles; and cooling and collecting the product, for example, by allowing it to stand to collect the precipitate. The catalyst synthesized under the aforementioned preferred conditions of the bismuth nanoparticle synthesis method can further improve the product selectivity and catalyst lifetime of the catalyst in the electrode.

[0067] In this invention, various reflux heating conditions are applicable. Preferably, the reflux heating conditions include: reflux at 100℃~150℃ for 1 hour to 3 hours, and bismuth source concentration of 0.05mol / L~0.20mol / L.

[0068] In this invention, various high-temperature heating conditions are applicable. Preferably, the high-temperature heating conditions include: holding at 280℃~320℃ for 20 minutes to 60 minutes.

[0069] Specifically, for example, a method for synthesizing bismuth nanoparticles involves adding a bismuth source and ethylene glycol to a three-necked flask, connecting a reflux condenser, and heating under nitrogen protection to reflux, generating a bismuth ethylene glycol reducer. The temperature is then rapidly increased to the desired level, held, and the ethylene glycol is evaporated by air oxidation. After cooling to room temperature, the precipitate is collected by allowing it to stand.

[0070] In this invention, the gas diffusion layer is used to provide gas permeability to the electrode. The range of gas diffusion layers is wide, and commonly used gas diffusion layers can be applied to this invention. One embodiment is illustrated, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the gas diffusion layer is selected from one or more of carbon paper, carbon felt, carbon cloth, and carbon fiber layers, preferably carbon paper.

[0071] In this invention, a hydrophobic layer is used to provide hydrophobicity and prevent electrolyte penetration and blockage of gas diffusion channels. Commonly used hydrophobic layers are applicable to this invention. The hydrophobic layer contains a hydrophobic agent, and the range of hydrophobic agents is relatively wide. This invention exemplifies one embodiment but does not limit the scope of the invention. According to a preferred embodiment of the invention, the hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene copolymer, preferably polytetrafluoroethylene. Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity of the gas diffusion electrode, and strong catalyst binding capacity.

[0072] In this invention, there are no special requirements for the number-average molecular weight of the hydrophobic agent. Taking polytetrafluoroethylene as an example, its number-average molecular weight can range from 5,000 to several million to achieve the purpose of this invention.

[0073] In this invention, the conductive layer is used to improve the conductivity of the electrode and avoid interference with the reaction activity. Commonly used conductive layers are applicable to this invention. The conductive layer contains a conductive polymer, and the range of conductive polymers that can be selected is quite wide. One embodiment is illustrated, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the conductive polymer is selected from one or more of polypyrrole, polyaniline, poly(p-phenylene), and poly-3,4-ethylenedioxythiophene, preferably poly-3,4-ethylenedioxythiophene. Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0074] In this invention, there are no special requirements for the number-average molecular weight of the conductive polymer; the number-average molecular weight of the conductive polymer can range from 10,000 to 500,000 to achieve the purpose of this invention.

[0075] In this invention, a porous protective layer is used to protect the catalyst layer, preventing changes in the catalyst's structure and morphology, as well as catalyst detachment. The material of the porous protective layer has a wide range of options; commonly used porous protective layers are applicable to this invention. This invention exemplifies one embodiment but does not limit the scope of the invention. According to a preferred embodiment of the invention, the material of the porous protective layer is selected from one or more of cobalt oxide, zinc oxide, manganese oxide, alumina, silicate glass, porous carbon materials, magnesium fluoride, and niobium oxide, preferably alumina. Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity of the gas diffusion electrode, and strong catalyst binding capacity.

[0076] In this invention, any gas diffusion electrode having the aforementioned composition and structure can achieve the purpose of this invention. There are no special requirements regarding the loading amount of the hydrophobic layer, calculated as a hydrophobic agent. One embodiment is illustrated illustratively, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the loading amount of the hydrophobic layer, calculated as a hydrophobic agent, is 0.5 mg / cm³ relative to the gas diffusion layer. 2 ~10mg / cm 2 Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0077] In this invention, any gas diffusion electrode having the aforementioned composition and structure can achieve the purpose of this invention. There are no special requirements for the loading amount of the conductive layer, based on the conductive polymer. One embodiment is illustrated exemplarily, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the loading amount of the conductive layer, based on the conductive polymer, is 0.1 mg / cm² relative to the gas diffusion layer. 2 ~10mg / cm 2Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0078] In this invention, any gas diffusion electrode having the aforementioned composition and structure can achieve the purpose of this invention. There are no special requirements for the catalyst layer loading, based on the amount of catalyst. One embodiment is illustrated illustratively, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the catalyst layer loading, based on the amount of catalyst, is 0.1 mg / cm³ relative to the gas diffusion layer. 2 ~5mg / cm 2 Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0079] In this invention, any gas diffusion electrode having the aforementioned composition and structure can achieve the objectives of this invention. There are no special requirements regarding the thickness of the porous protective layer. One embodiment is illustrated, but this does not limit the scope of the invention. According to a preferred embodiment of this invention, the thickness of the porous protective layer is 80 nm to 300 nm, for example, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, or 280 nm. Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0080] In this invention, any gas diffusion electrode having the aforementioned composition and structure can achieve the purpose of this invention. There are no special requirements for the porosity of the porous protective layer. One embodiment is illustrated, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the porosity of the porous protective layer is 30% to 70%, for example, 35%, 40%, 45%, 50%, 55%, 60%, and 65%. Using the aforementioned technical solution, the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0081] In this invention, any gas diffusion electrode with the aforementioned technical features can achieve the purpose of this invention. There are no special requirements for the preparation method of the gas diffusion electrode. An embodiment is illustrated, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the preparation method of the gas diffusion electrode includes sequentially constructing a hydrophobic layer, a conductive layer, a catalyst layer and a porous protective layer on the gas diffusion layer.

[0082] This invention provides a method for preparing the gas diffusion electrode described herein. According to a preferred embodiment of the invention, the method for preparing the gas diffusion electrode includes: (1) coating a hydrophobic agent slurry onto a gas diffusion layer and drying it to form electrode I; (2) electrodepositing a conductive layer onto electrode I to form electrode II; (3) coating a catalyst slurry onto electrode II and drying it to form electrode III; and (4) forming a porous protective layer on electrode III by solution-gel method, plasma-assisted deposition, electrochemical polymerization, self-assembly, electroplating, or nanoplastic processing. By employing the aforementioned technical solutions, each function can be separated into a multilayer structure and prepared independently, avoiding mutual constraints. Furthermore, the advantages of various processes can be maximized, and the controllability is strong.

[0083] According to a preferred embodiment of the present invention, the gas diffusion layer is pretreated before coating with a hydrophobic agent to increase the defect density on the surface of the gas diffusion layer, which facilitates the loading of the subsequent hydrophobic layer.

[0084] As long as the purpose of this invention can be achieved, there are no special requirements for the method of pretreating the gas diffusion layer. One embodiment is illustrated, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, plasma is used to pretreat the gas diffusion layer.

[0085] Specifically, for example, the gas diffusion layer is cut to the required specifications, cleaned with deionized water and ethanol, and then treated with air plasma to increase the defect density on the surface of the gas diffusion layer, which facilitates the loading of the subsequent hydrophobic layer.

[0086] In this invention, the mass concentration of the hydrophobic agent in the hydrophobic agent slurry in step (1) can be selected from a wide range. This is an example of one embodiment, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the mass concentration of the hydrophobic agent in the hydrophobic agent slurry is 1wt% to 10wt%, for example, the mass concentration of the hydrophobic agent is 2wt%, 4wt%, 6wt%, or 8wt%.

[0087] Specifically, in step (1), polytetrafluoroethylene emulsion (60% mass fraction, Sigma Aldrich) is used, and deionized water is added to dilute it to the required mass concentration. The mixture is then mixed evenly to obtain the hydrophobic agent slurry.

[0088] In this invention, commonly used coating methods can all be used in step (1). One embodiment is illustrated, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the coating in step (1) is done by spraying. When spraying with a sprayer, the electrode is laid flat on the platform, and the hydrophobic agent is only loaded on the upward-facing side. The change in electrode mass is determined by weighing, and the increase in mass per unit area is the load. When the load reaches the target, spraying is stopped.

[0089] In this invention, there are no special requirements for drying in step (1). The drying conditions can be selected according to the prior art. This invention illustrates one implementation method, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the drying conditions in step (1) include: a temperature of 40°C to 120°C, for example, a temperature of 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C.

[0090] In this invention, there are no special requirements for drying in step (1). The drying conditions can be selected according to the prior art. This invention illustrates one implementation method, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the drying conditions in step (1) include: a time of 0.5h to 10h, for example, a time of 1h, 2h, 4h, 6h, or 8h.

[0091] The electrode structure of this invention has a pure hydrophobic layer, which is obviously more hydrophobic than the traditional carbon paper electrode, which only contains a certain amount of hydrophobic agent (5-30%).

[0092] In this invention, as long as the purpose of this invention can be achieved, there are no special requirements for the electrodeposition method in step (2). An exemplary embodiment is given, but this does not limit the scope of this invention. According to a preferred embodiment of this invention, the electrodeposition method in step (2) includes: immersing electrode I, which serves as the cathode, and anode in an electrolyte containing conductive polymer monomer, redox agent, and solvent, and conducting an electrostatic reaction to form a conductive layer on the hydrophobic side of electrode I to obtain electrode II.

[0093] In this invention, the range of anodes that can be selected is relatively wide. This invention illustrates one embodiment, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the anode is selected from one or more of graphite rods, platinum wires, platinum sheets, and metallic nickel, preferably graphite rods.

[0094] In this invention, the hydrophobic layer side of electrode I is the front side. In order to prevent conductive polymer from depositing on the back side of electrode I, the back side of electrode I is shielded, for example, by attaching a Kapton film to the back side of electrode I.

[0095] In this invention, the range of conductive polymer monomers that can be selected in step (2) is relatively wide. This invention illustrates one embodiment, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the conductive polymer monomer is selected from one or more of pyrrole, aniline, biphenyl, and 3,4-ethylenedioxythiophene, preferably 3,4-ethylenedioxythiophene.

[0096] According to a preferred embodiment of the present invention, in step (2), the molar concentration of the conductive polymer monomer is 0.01 mol / L to 0.1 mol / L, for example, the molar concentration of the conductive polymer monomer is 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, or 0.08 mol / L. The aforementioned technical solution has advantages such as uniform loading and controllable loading.

[0097] In this invention, the range of redox agents that can be selected in step (2) is relatively wide. This is an example of one embodiment, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the redox agent is selected from one or more of FeCl3, sodium persulfate, potassium persulfate, potassium permanganate, and ferric perchlorate, preferably FeCl3.

[0098] According to a preferred embodiment of the present invention, in step (2), the molar concentration of the oxidizing and reducing agent is 0.01 to 0.1 mol / L, for example, the molar concentration of the oxidizing and reducing agent is 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, or 0.08 mol / L. The aforementioned technical solution has the advantages of simple operation and high repeatability.

[0099] In this invention, the range of solvents that can be selected is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, in step (2), the solvent is selected from one or more of acetone, water, acetonitrile, acetone, and tetrahydrofuran.

[0100] According to a preferred embodiment of the present invention, the solvent is a mixed solution of acetone and water, with a volume ratio of acetone to water of 1:4 to 4:1. Using the aforementioned technical solution, the catalyst in the gas diffusion electrode exhibits high product selectivity, long catalyst lifetime, high hydrophobicity, and strong catalyst binding capacity.

[0101] Specifically, the electrodeposition method in step (2) includes: dissolving the conductive polymer monomer in a solvent, adding a redox agent, and using the prepared solution as the electrolyte. Electrode I is used as the cathode, with the hydrophobic side of the electrode as the front and a Kapton film attached to the back to prevent the deposition of the conductive polymer. A graphite rod is used as the anode and immersed in the electrolyte. The reaction is carried out at 1.0V for 30 minutes to obtain a uniform conductive polymer layer. The loading is controlled by controlling the reaction time: after a certain reaction time, the electrode is thoroughly rinsed and dried, and the loading is determined by the mass change before and after the reaction. In this invention, it has been tested that a loading of approximately 2 mg / cm³ corresponds to a voltage of 1.0V for 30 minutes. 2 .

[0102] The gas diffusion electrode of the present invention constructs a strongly hydrophobic layer on the basis of a traditional gas diffusion layer, and supplements it with a conductive polymer layer, thereby maximizing the hydrophobicity of the electrode without sacrificing conductivity and effectively inhibiting electrolyte penetration.

[0103] In this invention, the mass concentration of the catalyst in the catalyst slurry in step (3) can be selected from a wide range. This is an example of one embodiment, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the mass concentration of the catalyst in the catalyst slurry is 0.5wt% to 5wt%, for example, the mass concentration of the catalyst is 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, or 4.5wt%.

[0104] In this invention, in step (3), the catalyst slurry contains additives, which act as binders for the catalyst particles and optimize electron transfer on the catalyst surface. A wide range of additives can be selected; one embodiment is illustrated, but this does not limit the scope of the invention. For example, the additive may be selected from a Nafion solution (5% by mass).

[0105] In this invention, the range of optional amounts of additives is relatively wide. One embodiment is illustrated by example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, in step (3), the amount of additive is 2% to 20% of the mass of the catalyst.

[0106] According to a preferred embodiment of the present invention, in step (3), the solvent in the catalyst slurry can be selected from a wide range. This is an example of an embodiment, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the solvent is selected from one or more of isopropanol, ethanol, methanol, and acetone, preferably isopropanol.

[0107] Specifically, the preparation of the catalyst slurry includes: dispersing the catalyst in a solvent, adding additives, and ultrasonically dispersing for 10 to 60 minutes.

[0108] In this invention, commonly used coating methods can all be used in step (3). One embodiment is illustrated, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the coating in step (3) is done by spraying. When spraying with a sprayer, the electrode is laid flat on the platform, and the catalyst slurry is only loaded on the upward-facing side. The change in electrode mass is determined by weighing, and the increase in mass per unit area is the load. When the load reaches the target, spraying is stopped.

[0109] In this invention, there are no special requirements for drying in step (3). The drying conditions can be selected according to the prior art. This invention illustrates one implementation method, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the drying conditions in step (3) include: a temperature of 40 to 100°C, for example, a temperature of 50°C, 60°C, 70°C, 80°C, or 90°C.

[0110] In this invention, there are no special requirements for drying in step (3). The drying conditions can be selected according to the prior art. This invention illustrates one implementation method, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the drying conditions in step (3) include: a time of 0.2 to 6 hours, for example, a time of 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours.

[0111] According to a preferred embodiment of the present invention, in step (4), a porous protective layer is formed on electrode III by plasma-assisted deposition. The aforementioned technical solution has advantages such as simple operation, high repeatability, and adjustable protective layer structure.

[0112] Specifically, the method for forming a porous protective layer on electrode III by plasma-assisted deposition in step (4) includes: placing electrode III into the cavity of a plasma magnetron sputtering instrument, using a suitable target source, and forming an Ar-O2 mixed plasma through magnetron discharge. Setting the plasma power, ion energy, gas flow rate, and sputtering time to form a porous protective layer with the required thickness and porosity.

[0113] In this invention, the range of selectable conditions for plasma-assisted deposition is relatively wide. One embodiment is illustrated by example, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the target source is selected from one or more of aluminum targets, cobalt targets, carbon targets, zinc targets, silicon dioxide targets, magnesium fluoride targets, niobium oxide targets and aluminum oxide targets, preferably aluminum targets.

[0114] In this invention, the range of selectable conditions for plasma-assisted deposition is relatively wide. One embodiment is illustrated, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the plasma power supply power is 20W to 500W, for example, the plasma power supply power is 50W, 100W, 150W, 200W, 250W, 300W, 350W, 400W or 450W.

[0115] In this invention, the range of selectable conditions for plasma-assisted deposition is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the ion energy is 50 eV to 100 eV.

[0116] In this invention, the range of selectable conditions for plasma-assisted deposition is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. Gas flow rate: argon 10 sccm to 30 sccm and / or oxygen 5 sccm to 15 sccm.

[0117] In this invention, the range of selectable conditions for plasma-assisted deposition is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. The sputtering time is 10 minutes to 120 minutes, for example, sputtering times of 20 minutes, 40 minutes, 60 minutes, 80 minutes, and 100 minutes.

[0118] The gas diffusion electrode of the present invention has the following characteristics: First, it employs a catalyst with better performance to form the catalyst layer, which has higher catalyst product selectivity and lifetime than the prior art; second, it constructs a strongly hydrophobic layer on the basis of the traditional gas diffusion layer and supplements it with a conductive polymer layer, thereby maximizing the hydrophobicity of the electrode without sacrificing conductivity and effectively inhibiting electrolyte penetration; third, it constructs a porous protective layer on the surface pores of the catalyst layer, thereby effectively preventing catalyst layer deactivation and shedding.

[0119] This invention provides the application of the gas diffusion electrode described herein in carbon dioxide electrolysis.

[0120] According to a preferred embodiment of the present invention, the gas diffusion electrode of the present invention is particularly suitable for use in the electrolysis of carbon dioxide to produce formic acid.

[0121] The gas diffusion electrode of the present invention is directly applied as a cathode electrode in carbon dioxide electrolysis, exhibiting excellent performance and outstanding stability in carbon dioxide electrolysis.

[0122] The electrolysis conditions of this invention are not particularly required. The following is an illustrative description, but it does not limit the scope of the invention.

[0123] According to a preferred embodiment of the present invention, preferred electrolysis conditions include: the electrolyte comprising one or more inorganic salt solutions selected from potassium hydroxide, potassium bicarbonate, and potassium chloride.

[0124] According to a preferred embodiment of the present invention, preferred electrolysis conditions include: the cations in the electrolyte include one or more of potassium, sodium, and cesium.

[0125] According to a preferred embodiment of the present invention, the preferred electrolysis conditions include: the cation concentration in the electrolyte is 0.01 mol / L to 3.00 mol / L.

[0126] According to a preferred embodiment of the present invention, the preferred electrolysis conditions include: a test current density of 20 mA / cm². 2 ~500mA / cm2 .

[0127] The present invention will be described in detail below through embodiments.

[0128] In the following preparation examples, nitrogen content was determined using an elemental analyzer (Vario EL III) with helium as the carrier gas, and a thermal conductivity detector was used to detect the nitrogen component content. The particle size of the bismuth nanoparticles was measured using TEM (Hitachi H-7650B) with an accelerating voltage of 80 kV, and characterization was performed within the magnification range of 20–25 kV. Morphology was characterized using a high-performance field emission SEM (Zeiss Merlin) with an accelerating voltage of 5 kV. XPS spectra were characterized using a Shimadzu AXIS Supra instrument, with Kα rays (1486.7 eV) from an aluminum target as the incident X-ray source, and a spot size of 1 × 0.8 mm. All obtained XPS spectra were corrected according to the C1s peak position (284.6 eV).

[0129] Product testing:

[0130] The concentrations of hydrogen and carbon monoxide in the gaseous products were detected using a gas chromatograph (Agilent 7890B), and the Faraday efficiency was calculated using the following formula:

[0131]

[0132] Where Q is the volumetric flow rate of the gas at the electrolytic cell outlet, and c i The concentration of gaseous products (including hydrogen and carbon monoxide) in the outlet gas is given by F, where F is the Faraday constant with a value of 96485 C·mol⁻¹. -1 I represents the magnitude of the reaction current.

[0133] The concentration of formic acid (salt) in the liquid phase of the electrolyte after the reaction was quantitatively detected using nuclear magnetic resonance spectroscopy, and the Faradaic efficiency of the formic acid product, i.e., the formic acid selectivity, was calculated according to the following formula:

[0134]

[0135] Where V is the total volume of the cathode electrolyte after the reaction, and t is the test duration.

[0136] The electrode performance evaluation, including the test method for the energy efficiency of the gas diffusion electrode, involves directly applying the prepared gas diffusion electrode as the cathode electrode in carbon dioxide electrolysis. A 1 mol / L potassium bicarbonate solution is used as the electrolyte for both the anode and cathode. DuPont's Nafion XL is used as the cation exchange membrane, and carbon paper supported on an iridium oxide catalyst is used as the anode electrode. The current density is 200 mA / cm².-2 Electrolysis tests were conducted under the specified conditions, and product detection and Faraday efficiency calculations were performed according to the methods described above. The electrolytic cell voltage was recorded as E(V), and the energy efficiency can be calculated using the following formula:

[0137] Energy efficiency (%) = 1.35 / E × 100%

[0138] Where 1.35 represents the thermodynamic equilibrium voltage of the electrolytic cell, which is the difference between the reduction of carbon dioxide to formic acid at the cathode (-0.12V) and the oxygen evolution reaction at the anode (+1.23V).

[0139] The test methods for the thickness and porosity of the porous protective layer in the gas diffusion electrode are as follows: The thickness of the porous protective layer is measured using a scanning electron microscope (Zeiss, model Merlin) with an accelerating voltage of 5kV. The electrode side is vertically attached to the sample stage surface, and the thickness of the porous protective layer is measured within the range of magnification of 50 to 100k. The porosity is measured using a mercury intrusion porosimeter: Following the same loading process parameters as step (4), a porous protective layer is loaded on the surface of the silicon wafer. After loading the porous protective layer on the surface of the silicon wafer, the silicon wafer sample is placed in the sample chamber of the mercury intrusion porosimeter, vacuumed, and then mercury is injected. After the test is completed, the porosity of the sample (minus the volume of the silicon wafer) is obtained in the MicroActive software, which is the porosity of the porous protective layer of the silicon wafer and electrode corresponding to the sputtering process parameters and time.

[0140] The raw materials used in the following examples are: bismuth nitrate (manufacturer: Maclean, 99.9% metal basis), ethylene glycol (manufacturer: Alfa Aesar, 99% purity), ammonia (manufacturer: Acros, 28-30% aqueous solution, diluted to the required concentration), 2-hydroxymethylimidazole (reagent supplier: Alfa Aesar, catalog number Y25677, 97% purity), carbon paper (Sigracet 28BC), and other raw materials are chemically pure reagents.

[0141] Preparation Example 1

[0142] I. Synthesis of Monodisperse Bismuth Nanoparticles

[0143] 1 mmol of bismuth nitrate (manufacturer: Maclean, 99.9% metal basis) and 20 ml of ethylene glycol (manufacturer: Alfa Aesar, 99% purity) were added to a three-necked flask. A reflux condenser was connected, and the mixture was heated to 120°C and refluxed for 2 hours under nitrogen protection to generate a bismuth glycol reducer. The temperature was then rapidly increased to 300°C and held for 30 minutes to evaporate the ethylene glycol by air oxidation. After cooling to room temperature, the precipitate was collected to obtain monodisperse bismuth nanoparticles.

[0144] II. High-pressure ammonia nitriding

[0145] 100 mg of the bismuth nanoparticle sample synthesized in the previous step was mixed with 5 ml of 1 mol / L ammonia solution (manufacturer: Acros, 28-30% aqueous solution, diluted to the desired concentration) and transferred to a stainless steel high-pressure reactor. After sealing, the reactor was heated to 250 °C under 10 MPa ammonia pressure and maintained for 2 hours. Then, it was allowed to cool naturally to room temperature, the gas was released, and the nitrogen-doped bismuth nanoparticles were collected. Elemental analysis using a Vario EL III instrument showed a nitrogen content of 8.6% (atomic percentage). The morphology of the nitrogen-doped bismuth nanoparticles is as follows. Figure 1 As shown, by Figure 1 It can be seen that the synthesized bismuth nanoparticles exhibit a regular spherical nanoparticle morphology with a particle size of approximately 50 nanometers to 200 nanometers.

[0146] III. Microwave-assisted 2-hydroxymethylimidazolium grafting reaction

[0147] Mix 50 mg of nitrogen-doped bismuth nanoparticles with 0.5 mmol of 2-hydroxymethylimidazole (reagent supplier: Alfa Aesar, catalog number Y25677, purity 97%), add 5 ml of ethanol, heat to 80 °C in a microwave reactor, and react for 10 minutes at a microwave power of 100 W. Repeat the washing process three times to obtain the product.

[0148] IV. Centrifugal precipitation purification

[0149] The product was dissolved in water and centrifuged at 4000 rpm to remove the precipitate, which mainly consisted of oversized bismuth nanoparticles and unreacted imidazole substances. The supernatant was then mixed with ethanol, allowed to settle, impurities were removed, the precipitate was collected, and dried at 60°C to obtain the final catalyst product.

[0150] In the XPS spectrum of the grafted catalyst, a C1s characteristic peak of 2-hydroxymethylimidazolium appeared at positions 284–288 eV, and the O1s characteristic peak at 532 eV showed a red shift and increased intensity, proving that a covalent bond was formed between the hydroxyl group and the bismuth nanoparticles, thus demonstrating the successful grafting of the 2-hydroxymethylimidazolium group. By comparison with a fully covered sample, the coverage of the 2-hydroxymethylimidazolium group was measured to be 30%.

[0151] Preparation Example 2

[0152] I. Synthesis of Monodisperse Bismuth Nanoparticles

[0153] 1 mmol of bismuth nitrate and 10 ml of ethylene glycol were added to a three-necked flask, which was then connected to a reflux condenser. Under nitrogen protection, the mixture was heated to 100 °C and refluxed for 3 hours to generate a bismuth glycol reducer. The temperature was then rapidly increased to 280 °C and held for 60 minutes to evaporate the ethylene glycol by air oxidation. After cooling to room temperature, the precipitate was collected to obtain monodisperse bismuth nanoparticles.

[0154] II. High-pressure ammonia nitriding

[0155] 100 mg of the bismuth nanoparticle sample synthesized in the previous step was mixed with 8 ml of 0.5 mol / L ammonia solution and transferred to a stainless steel high-pressure reactor. After sealing, the reactor was heated to 180 °C under an ammonia pressure of 8 MPa and maintained for 3 hours. It was then allowed to cool naturally to room temperature, the gas was released, and the nitrogen-doped bismuth nanoparticles were collected. Elemental analysis using a Vario EL III instrument showed a nitrogen content of 3.2% (atomic percentage). The nitrogen-doped bismuth nanoparticles had a particle size of approximately 30 nm to 80 nm.

[0156] III. Microwave-assisted grafting reaction

[0157] 50 mg of nitrogen-doped bismuth nanoparticles and 0.5 mmol of 1-(1H-imidazol-2-yl)ethanol (reagent supplier: Adamas, catalog number 3425210, purity 95%) were mixed, and 5 ml of methanol was added. The mixture was heated to 60 °C in a microwave reactor and reacted for 15 minutes at a microwave power of 120 W. The reaction was repeated three times to obtain the product.

[0158] IV. Centrifugal precipitation purification

[0159] The product was dissolved in water, and the precipitate was removed by centrifugation at 6000 rpm. The precipitate mainly consisted of oversized bismuth nanoparticles and unreacted imidazole substances. The supernatant was then mixed with ethanol, allowed to settle, impurities were removed, the precipitate was collected, and dried at 60°C to obtain the final catalyst product. By comparison with a fully covered sample, the coverage of the 1-(1H-imidazol-2-yl)ethanol group was measured to be 41%.

[0160] Preparation Example 3

[0161] I. Synthesis of Monodisperse Bismuth Nanoparticles

[0162] 10 mmol of bismuth acetate (manufacturer: Sigma Aldrich, purity ≥99.99 trace metal basis) and 50 mL of ethylene glycol were added to a three-necked flask. A reflux condenser was connected, and the mixture was heated to 150 °C and refluxed for 1 hour under nitrogen protection to generate a bismuth glycol reducer. The temperature was then rapidly increased to 320 °C and held for 20 minutes to evaporate the ethylene glycol by air oxidation. After cooling to room temperature, the precipitate was collected to obtain monodisperse bismuth nanoparticles.

[0163] II. High-pressure ammonia nitriding

[0164] 1g of the synthesized bismuth nanoparticle sample from the previous step was mixed with 40ml of 2mol / L ammonia solution and transferred to a stainless steel high-pressure reactor. After sealing, the reactor was heated to 270℃ under 12MPa ammonia pressure and maintained for 1 hour. It was then allowed to cool naturally to room temperature, the gas was released, and the nitrogen-doped bismuth nanoparticles were collected. Elemental analysis using a Vario EL III instrument showed a nitrogen content of 9.2% (atomic percentage). The nitrogen-doped bismuth nanoparticles had a particle size of approximately 40 nm to 120 nm.

[0165] III. Microwave-assisted grafting reaction

[0166] Mix 50 mg of nitrogen-doped bismuth nanoparticles with 0.5 mmol of 1-(1H-imidazol-2-yl)propanol, add 5 ml of ethylene glycol, heat to 100 °C in a microwave reactor, and react for 5 minutes while maintaining a microwave power of 80 W. Repeat the washing process three times to obtain the product.

[0167] IV. Centrifugal precipitation purification

[0168] The product was dissolved in water, and the precipitate was removed by centrifugation at 4000 rpm. The precipitate mainly consisted of oversized bismuth nanoparticles and unreacted imidazole substances. The supernatant was then mixed with ethanol, allowed to settle, impurities were removed, the precipitate was collected, and dried at 60°C to obtain the final catalyst product. By comparison with a fully covered sample, the coverage of the 1-(1H-imidazol-2-yl)propanol group was measured to be 10%.

[0169] Preparation Example 4

[0170] I. Synthesis of Monodisperse Bismuth Nanoparticles

[0171] 1 mmol of bismuth nitrate and 20 mL of ethylene glycol were added to a three-necked flask, which was then connected to a reflux condenser. Under nitrogen protection, the mixture was heated to 100 °C and refluxed for 1 hour to generate a bismuth glycol reducer. The temperature was then rapidly increased to 280 °C and held for 30 minutes to evaporate the ethylene glycol by air oxidation. After cooling to room temperature, the precipitate was collected to obtain monodisperse bismuth nanoparticles.

[0172] II. High-pressure ammonia nitriding

[0173] 100 mg of the bismuth nanoparticle sample synthesized in the previous step was mixed with 8 ml of 0.5 mol / L ammonia solution and transferred to a stainless steel high-pressure reactor. After sealing, the reactor was heated to 180 °C under an ammonia pressure of 8 MPa and maintained for 1.5 hours. It was then allowed to cool naturally to room temperature, the gas was released, and the nitrogen-doped bismuth nanoparticles were collected. Elemental analysis using a Vario EL III instrument showed a nitrogen content of 2.5% (atomic percentage). The particle size of the nitrogen-doped bismuth nanoparticles was approximately 60 nm to 160 nm.

[0174] III. Microwave-assisted grafting reaction

[0175] Mix 50 mg of nitrogen-doped bismuth nanoparticles with 0.5 mmol of 2-hydroxymethylimidazole, add 5 ml of ethanol, heat to 60 °C in a microwave reactor, and react for 5 minutes at a microwave power of 80 W. Repeat the washing process three times to obtain the product.

[0176] IV. Centrifugal precipitation purification

[0177] The product was dissolved in water and centrifuged at 4000 rpm to remove the precipitate, which mainly consisted of oversized bismuth nanoparticles and unreacted imidazole substances. The supernatant was then mixed with ethanol, allowed to settle, impurities were removed, the precipitate was collected, and dried at 60°C to obtain the final catalyst product. By comparison with a fully covered sample, the 2-hydroxymethylimidazolium group coverage was measured to be 41%.

[0178] Preparation Example 5

[0179] The method was followed as in Example 1, except that in the high-pressure ammonia nitriding step, 0.3 mol / L urea solution was used instead of ammonia water, with a volume of 5 mL; all other conditions remained the same. The nitrogen content was determined to be 6.5% (atomic percentage). The particle size of the nitrogen-doped bismuth nanoparticles was approximately 70 nm to 130 nm.

[0180] Preparation Example 6

[0181] The method was followed in Example 1, except that the reaction time in the high-pressure ammonia nitriding step was 5 hours. The nitrogen content after synthesis was measured to be 16.2%.

[0182] Preparation Example 7

[0183] The method of Example 1 is different except that in the monodisperse bismuth nanoparticle synthesis step, the high temperature is 400°C, resulting in the synthesized nitrogen-doped bismuth nanoparticles having a particle size of 260 nm to 320 nm.

[0184] Preparation Example 8

[0185] The method of Example 1 was followed, except that the reaction time in the microwave-assisted grafting reaction step was 1 hour, and after centrifugation and purification, the coverage of the 2-hydroxymethylimidazolium group was measured to be 64%.

[0186] Preparation Example 9

[0187] The method was followed in Example 1, except that in the microwave-assisted grafting reaction step, the volume of ethanol used was 3 mL, resulting in a concentration of 0.167 mol / L for 2-hydroxymethylimidazole and a measured coverage of 52% for the 2-hydroxymethylimidazole group.

[0188] Preparation Example 10

[0189] The method was followed in Example 1, except that in the microwave-assisted grafting reaction step, the volume of ethanol used was 2 mL, resulting in a concentration of 0.25 mol / L for 2-hydroxymethylimidazole and a measured coverage of 63% for the 2-hydroxymethylimidazole group.

[0190] Preparation Example 11

[0191] The method is the same as in Example 1, except that the reaction atmosphere in the nitrogen doping step is nitrogen gas instead of ammonia gas.

[0192] Preparation of Comparative Example 1

[0193] Unlike Example 1, Comparative Example 1 did not undergo a covalent grafting step during catalyst preparation. The specific preparation process is as follows:

[0194] 1. Synthesis of monodisperse bismuth nanoparticles

[0195] 1 mmol of bismuth nitrate and 20 mL of ethylene glycol were added to a three-necked flask, which was then connected to a reflux condenser. Under nitrogen protection, the mixture was heated to 120 °C and refluxed for 2 hours to generate a bismuth glycol reducer. The temperature was then rapidly increased to 300 °C and held for 30 minutes to allow air oxidation and evaporation of the ethylene glycol and nitrate. After cooling to room temperature, the precipitate was collected to obtain monodisperse bismuth nanoparticles.

[0196] 2. High-pressure ammonia nitriding

[0197] The synthesized bismuth nanoparticle sample from the previous step was mixed with 5 ml of ammonia water and transferred to a stainless steel high-pressure reactor. After sealing, the reactor was heated to 250 °C under ammonia pressure of 10 MPa and maintained for 2 hours. Then, it was allowed to cool naturally to room temperature, the gas was released, and the nitrogen-doped bismuth nanoparticles were collected.

[0198] 3. Centrifugal precipitation purification

[0199] The product was dissolved in water and centrifuged at 4000 rpm to remove the precipitate, which mainly consisted of excessively large nitrogen-doped bismuth nanoparticles. The supernatant was then mixed with ethanol, allowed to settle, impurities were removed, the precipitate was collected, and dried at 60°C to obtain the final catalyst product.

[0200] Preparation of Comparative Example 2

[0201] The method is the same as in Example 1, except that the compound covalently grafted with the nitrogen-doped bismuth nanoparticles is replaced with (2-imidazolium-1-phenyl)methanol (structural formula: The dosage remains 0.5 mmol.

[0202] Preparation of Comparative Example 3

[0203] The method is the same as in Example 1, except that the high-pressure ammonia nitriding step is omitted in the catalyst synthesis process, and the monodisperse bismuth nanoparticles are directly subjected to microwave-assisted grafting reaction.

[0204] Example 1

[0205] 1) Pretreatment of the gas diffusion layer

[0206] Cut a gas diffusion layer to a size of 2×2cm (using SGL 29BC carbon paper). After cleaning with deionized water and ethanol, treat with air plasma for 5 minutes to increase the defect density on the surface of the gas diffusion layer, which will facilitate the loading of the subsequent hydrophobic layer.

[0207] 2) Construct a hydrophobic layer

[0208] Take 1 mL of polytetrafluoroethylene emulsion (60% by mass, Sigma Aldrich), dilute with deionized water to 10 mL, and mix thoroughly. Use an ultrasonic sprayer to evenly apply the mixture to the surface of the gas diffusion layer, controlling the loading rate to approximately 5 mg / cm². 2 Dry in an oven at 60°C for 2 hours.

[0209] 3) Constructing a conductive polymer layer

[0210] Electrolyte preparation: Dissolve 3,4-ethylenedioxythiophene (EDOT, manufacturer Alfa) in 100 mL of a mixed solvent of acetone and water (acetone to water volume ratio of 1:1), and then add FeCl3 as a redox agent; the molar concentration of 3,4-ethylenedioxythiophene in the electrolyte is 0.05 mol / L, and the molar concentration of FeCl3 is 0.02 mol / L.

[0211] Using the gas diffusion electrode from step 2) as the cathode, with the hydrophobic side of the gas diffusion layer as the front and a Kapton film attached to the back to prevent the deposition of conductive polymer, a graphite rod was used as the anode and immersed in the electrolyte. The reaction was carried out at 1.0V for 30 minutes to obtain a uniform poly-3,4-ethylenedioxythiophene (PEDOT) conductive polymer layer, with the loading controlled at approximately 2 mg / cm³. 2 .

[0212] 4) Constructing the catalyst layer

[0213] 30 mg of the catalyst prepared in Example 1 was dispersed in 6 mL of isopropanol solvent, and 60 μL of Nafion solution (DuPont, D521, 5% by mass) was added. The mixture was then ultrasonically dispersed for 30 minutes. After uniform dispersion, the dispersion solution was uniformly loaded onto the surface of the conductive polymer layer of the gas diffusion electrode in step 3) using an ultrasonic sprayer, with the loading amount controlled to be approximately 1 mg / cm³. 2 Dry in an oven at 60°C for 2 hours.

[0214] 4) Construct a porous protective layer

[0215] The gas diffusion electrode prepared in step 3) was placed in the chamber of a plasma magnetron sputtering instrument. An aluminum target was used, and Ar-O2 mixed plasma was formed by magnetron discharge. The plasma power was 100W, the ion energy was 50eV-100eV, the gas flow rate was 20 sccm for argon and 5 sccm for oxygen, and the sputtering time was 40 minutes, resulting in an alumina protective layer with a thickness of approximately 80 nm and a porosity of 50%.

[0216] At this point, the gas diffusion electrode fabrication is complete.

[0217] Figure 2 This is a schematic diagram of the gas diffusion electrode in Embodiment 1 of the present invention.

[0218] Figure 3 To illustrate the voltage-time curves of the carbon dioxide electrolyzer using the gas diffusion electrode of Example 1 of this invention and a conventional gas diffusion electrode, as well as the scatter plot of the Faraday efficiency of formic acid over time, an applied current density of 200 mA cm⁻¹ was used. -2 .Depend on Figure 3 As can be seen, the gas diffusion electrode of this invention achieves an energy efficiency of approximately 43%. During an electrolysis period exceeding 300 hours, the electrode's performance did not degrade, and the Faradaic efficiency of the formic acid product, i.e., the formic acid selectivity, remained consistently above 80%, demonstrating excellent stability. In contrast, the stabilization time of a conventional gas diffusion electrode (Sigracet 28BC) is less than 4 hours.

[0219] Examples 2-11

[0220] Same as Example 1, but with a different catalyst. The catalyst was derived from Preparation Examples 2-11.

[0221] Example 12

[0222] Same as Example 1, but with a hydrophobic layer loading of 1 mg / cm³. 2 The conductive layer loading is 0.2 mg / cm². 2 The catalyst loading was 4 mg / cm³. 2 .

[0223] Example 13

[0224] Same as Example 1, but with a hydrophobic layer loading of 8 mg / cm³. 2 The conductive layer loading is 8 mg / cm². 2 The catalyst loading was 0.3 mg / cm³. 2 .

[0225] Comparative Examples 1-3

[0226] Same as Example 1, but the catalyst used was the same as that used in Comparative Examples 1-3.

[0227] Comparative Example 4

[0228] Unlike Example 1, Comparative Example 4 did not use the catalyst synthesized in this invention, but instead used bismuth nanoparticles directly as the catalyst. The remaining steps were the same as in Example 1.

[0229] Comparative Example 5

[0230] Same as Example 1, but omitting the step of loading a conductive polymer layer.

[0231] Evaluation of gas diffusion electrodes

[0232] The gas diffusion electrode prepared above was directly applied as the cathode electrode in carbon dioxide electrolysis. A 1.5 mol / L potassium bicarbonate solution was used as the electrolyte for both the anode and cathode, DuPont's Nafion XL was used as the cation exchange membrane, and a porous titanium felt supported on an iridium oxide catalyst was used as the anode electrode. The electrolyte flow rate was controlled at 8 mL / min using a peristaltic pump. The carbon dioxide gas flow rate was 20 mL / min. A constant reaction current was applied to the electrolytic cell using an electrochemical workstation (Gamry Interface 1000), and a constant current test was performed at a current density of 200 mA / cm². -2 Electrolysis was performed under specific conditions, and the test duration was 1 hour.

[0233] The energy efficiency of the gas diffusion electrode and the Faraday efficiency of the product formic acid of the present invention are shown in Table 1.

[0234] Figure 3 The voltage-time curves of a carbon dioxide electrolyzer using the gas diffusion electrode of Embodiment 1 of the present invention and a conventional gas diffusion electrode are shown, as well as a scatter plot of the Faraday efficiency of formic acid versus time, with an applied current density of 200 mA cm⁻¹. -2 .Depend on Figure 3 As can be seen, the gas diffusion electrode of this invention achieves an energy efficiency of approximately 43%. During an electrolysis period exceeding 300 hours, the electrode's performance did not degrade, and the Faradaic efficiency of the formic acid product, i.e., the formic acid selectivity, remained consistently above 80%, demonstrating excellent stability. In contrast, the stabilization time of a conventional gas diffusion electrode (Sigracet 28BC) is less than 4 hours.

[0235] Under the same test conditions as in Example 1, the electrode prepared in Comparative Example 4 exhibits the following performance: Figure 4 As shown, the Faradaic efficiency of the product formic acid, i.e., the selectivity of formic acid, decreased to about 50% after about 20 hours. The electrode lifetime and product Faradaic efficiency were significantly lower than those in Example 1. In addition, the electrolysis voltage required for Comparative Example 1 was increased to over 4V, which was significantly higher than that of Example 1 (~3.1V), resulting in lower energy efficiency.

[0236] Table 1

[0237] Example number Energy efficiency (%) Faradaic efficiency of product formic acid (%) Example 1 43 83 Example 2 43 82 Example 3 44 83.5 Example 4 45 80 Example 5 42 81 Example 6 41 71 Example 7 41 73 Example 8 45 65 Example 9 44 73 Example 10 42 72 Example 11 43 70 Example 12 44 83 Example 13 46 84 Comparative example 1 35 50 Comparative example 2 30 41 Comparative example 3 32 64 Comparative example 4 33 65 Comparative example 5 25 37

[0238] Through Table 1 and Figure 3 The results show that the gas diffusion electrode of the present invention achieves an energy efficiency of approximately 43%. During an electrolysis period exceeding 300 hours, the electrode performance did not degrade, and the Faradaic efficiency of the formic acid product, i.e., the formic acid selectivity, remained consistently above 80%, demonstrating excellent stability. In contrast, the stabilization time of the conventional gas diffusion electrode (Sigracet 28BC) is less than 4 hours.

[0239] Under the same test conditions as in Example 1, the electrode prepared in Comparative Example 1 exhibits the following performance: Figure 4 As shown, the Faradaic efficiency of the product formic acid, i.e., the selectivity of formic acid, decreased to about 50% after about 20 hours. The electrode lifetime and product Faradaic efficiency were significantly lower than those in Example 1. Figure 4 Furthermore, the electrolysis voltage required for Comparative Example 1 was increased to over 4V, significantly higher than that for Example 1 (~3.1V), resulting in lower energy efficiency.

[0240] Therefore, this technical solution is significantly superior to the comparative example in terms of electrode life, product selectivity, and energy efficiency, proving that this technical solution has a significant improvement effect in terms of technical performance.

[0241] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A multilayer gas diffusion electrode, comprising a gas diffusion layer, a hydrophobic layer, a conductive layer, a catalyst layer, and a porous protective layer, characterized in that, The catalyst layer comprises nitrogen-doped bismuth nanoparticles and structural units of formula (1) grafted onto the nitrogen-doped bismuth nanoparticles: In this case, R1 and R2 are each hydrogen or alkyl, and the sum of the carbon numbers of R1 and R2 is less than 4.

2. The gas diffusion electrode according to claim 1, wherein, In the catalyst layer, the catalyst contains: In the structural unit shown in formula (1), R1 and R2 are each hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, or 3-butyl, and the sum of the carbon numbers of R1 and R2 is less than 4. Preferably, R1 is hydrogen, and R2 is hydrogen, methyl, or ethyl; and / or The structural unit shown in equation (1) is covalently connected to nitrogen-doped bismuth nanoparticles; and / or In nitrogen-doped bismuth nanoparticles, the nitrogen content, by atomic percentage, is 1%–10%; and / or The nitrogen-doped bismuth nanoparticles have a particle size of 5 nm to 200 nm, preferably 30 nm to 200 nm; and / or The coverage of the structural unit shown in formula (1) is 5% to 50%, more preferably 10% to 45%.

3. The gas diffusion electrode according to claim 1 or 2, wherein, The method for preparing the catalyst in the catalyst layer includes the following steps: 1) Synthesis of nitrogen-doped bismuth nanoparticles; 2) The compound described in formula (2) reacts with nitrogen-doped bismuth nanoparticles to achieve covalent grafting; In this case, R1 and R2 are each hydrogen or alkyl, and the sum of the carbon numbers of R1 and R2 is less than 4; Preferably, R1 and R2 are each hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, or 3-butyl, and the sum of the carbon numbers of R1 and R2 is less than 4; More preferably, the compound of formula (2) is one or more of 2-hydroxymethylimidazolium, 1-(1H-imidazol-2-yl)ethanol, and 1-(1H-imidazol-2-yl)propanol.

4. The gas diffusion electrode according to claim 3, wherein, Step 1) includes: Bismuth nanoparticles were mixed with a nitrogen source solution and subjected to hydrothermal treatment under ammonia protection. Preferably, the conditions for hydrothermal treatment include: The molar ratio of bismuth to nitrogen in the nitrogen source solution is 1:1 to 1:50, preferably 1:2 to 1:20; and / or Temperature is 180℃~270℃, and / or Pressure of 8MPa to 12MPa, and / or The time is 1 to 3 hours; and / or The nitrogen source is ammonia water and / or urea solution; Preferably, the concentration of the urea solution is 0.10 mol / L to 0.50 mol / L, and the concentration of the ammonia solution is 0.50 mol / L to 2.00 mol / L; and / or Step 2) Microwave-assisted synthesis: Preferably, the process involves mixing nitrogen-doped bismuth nanoparticles with the compound of formula (2), adding a solvent, and then feeding the mixture into a microwave reactor for microwave reaction. Preferably, the solvent is selected from one or more of ethanol, diethyl ether, chloroform, methanol, and ethylene glycol; The conditions for microwave reaction include: Temperatures of 60℃ to 100℃; and / or Power of 80W to 120W; and / or The time is 5 to 15 minutes; and / or The molar concentration of the compound described in formula (2) is 0.04 mol / L to 0.20 mol / L; The ratio of the compound described in formula (2) to nitrogen-doped bismuth nanoparticles is (0.001 mol to 0.1 mol) / g, preferably (0.005 mol to 0.05 mol) / g; and / or Bismuth nanoparticles are synthesized using hydrothermal methods. Preferably, the synthesis steps of the bismuth nanoparticles include: reflux heating to form a bismuth-ethylene glycol complex; high-temperature heating to synthesize bismuth nanoparticles; and cooling and collecting the product. Preferably, The reflux heating conditions include: reflux at 100℃~150℃ for 1 hour to 3 hours, and bismuth source concentration of 0.05mol / L~0.20mol / L; High-temperature heating conditions include: holding at 280℃~320℃ for 20 minutes~60 minutes.

5. The gas diffusion electrode according to any one of claims 1-4, wherein, The gas diffusion layer is selected from one or more of carbon paper, carbon felt, carbon cloth, and carbon fiber layers, preferably carbon paper; and / or The hydrophobic layer contains a hydrophobic agent selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene copolymer, preferably polytetrafluoroethylene; and / or The conductive layer contains a conductive polymer selected from one or more of polypyrrole, polyaniline, poly(p-phenylene), and poly-3,4-ethylenedioxythiophene, preferably poly-3,4-ethylenedioxythiophene; and / or The porous protective layer is made of one or more of the following materials: cobalt oxide, zinc oxide, manganese oxide, aluminum oxide, silicate glass, porous carbon materials, magnesium fluoride, and niobium oxide, with aluminum oxide being preferred.

6. The gas diffusion electrode according to any one of claims 1-5, wherein, Compared to the gas diffusion layer, The hydrophobic loading of the hydrophobic layer is 0.5 mg / cm³, calculated based on the hydrophobic agent. 2 ~10mg / cm 2 ; and / or The conductive layer has a loading of 0.1 mg / cm² based on the conductive polymer. 2 ~10mg / cm 2 ; and / or The catalyst loading of the catalyst layer is 0.1 mg / cm³. 2 ~5mg / cm 2 ; and / or The thickness of the porous protective layer is 80 nm to 300 nm; and / or The porosity of the porous protective layer is 30% to 70%.

7. The method for preparing the gas diffusion electrode according to any one of claims 1-6, characterized in that, include: A hydrophobic layer, a conductive layer, a catalyst layer, and a porous protective layer are sequentially constructed on the gas diffusion layer.

8. The method according to claim 7, wherein, The method includes: (1) Coating a hydrophobic slurry onto the gas diffusion layer and drying it to form electrode I; (2) Electrodeposit a conductive layer on electrode I to form electrode II; (3) Coat electrode II with catalyst slurry and dry it to form electrode III; (4) A porous protective layer is formed on electrode III by solution-gel method, plasma-assisted deposition, electrochemical polymerization, self-assembly, electroplating or nanoplastic processing; Preferably, Before coating with a hydrophobic agent, the gas diffusion layer is pretreated; more preferably, plasma pretreatment is used.

9. The method according to claim 7 or 8, wherein, In step (1): In the hydrophobic agent slurry, the mass concentration of the hydrophobic agent is 1wt% to 10wt%; and / or The coating is applied by spraying; and / or The drying conditions include a temperature of 40℃ to 120℃ and / or a time of 0.5h to 10h; and / or The electrodeposition method in step (2) includes: Electrode I, which serves as the cathode, and the anode are immersed in an electrolyte containing conductive polymer monomers, oxidizing and reducing agents, and solvents. An electric current is applied to react and a conductive layer is formed on the hydrophobic side of electrode I to obtain electrode II. Preferably, The anode is selected from one or more of graphite rods, platinum wires, platinum sheets, and metallic nickel, preferably graphite rods; and / or Electrode I has its hydrophobic layer side as the front side and a Kapton membrane attached to its back side; and / or The conductive polymer monomer is selected from one or more of pyrrole, aniline, biphenyl, and 3,4-ethylenedioxythiophene, preferably 3,4-ethylenedioxythiophene; preferably, the molar concentration of the conductive polymer monomer in the electrolyte is 0.01 mol / L to 0.1 mol / L; and / or The redox agent is selected from one or more of FeCl3, sodium persulfate, potassium persulfate, potassium permanganate, and ferric perchlorate, preferably FeCl3; the molar concentration of the redox agent is 0.01 mol / L to 0.1 mol / L; and / or The solvent is selected from one or more of acetone, water, acetonitrile, acetone, and tetrahydrofuran. Preferably, the solvent is a mixed solution of acetone and water, with a volume ratio of acetone to water of 1:4 to 4:

1. and / or In step (3): In the catalyst slurry, the mass concentration of the catalyst is 0.5 wt% to 5 wt%; and / or In the catalyst slurry, the solvent is selected from one or more of isopropanol, ethanol, methanol, and acetone, preferably isopropanol; and / or The coating is applied by spraying; and / or Drying conditions include: a temperature of 40℃ to 100℃, and / or a time of 0.2h to 6h; In step (4): A porous protective layer was formed on electrode III by plasma-assisted deposition; Preferably, The conditions for plasma-assisted deposition include: The target source is selected from one or more of aluminum targets, cobalt targets, carbon targets, zinc targets, silicon dioxide targets, magnesium fluoride targets, niobium oxide targets, and aluminum oxide targets, preferably aluminum targets; and / or Plasma power supply: 20W~500W; and / or Ion energy: 50 eV to 100 eV; and / or Gas flow rate: Argon 10 sccm~30 sccm and / or Oxygen 5 sccm~15 sccm; and / or Splashing time: 10 to 120 minutes.

10. The application of the gas diffusion electrode according to any one of claims 1-6 in carbon dioxide electrolysis, particularly suitable for the production of formic acid by carbon dioxide electrolysis.

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