Membrane electrode and preparation method and application thereof

Abstract

The invention discloses a membrane electrode as well as a preparation method and application thereof. The membrane electrode comprises an ion exchange membrane layer, a conductive composite layer and a gas diffusion electrode layer which are sequentially stacked, the conductive composite layer is of a hollow structure, the edge size of the conductive composite layer is larger than that of the gas diffusion electrode layer, the gas diffusion electrode layer comprises a catalyst layer and a gas diffusion layer, and the catalyst layer and the gas diffusion layer are sequentially stacked. The gas diffusion electrode layer is sequentially composed of a catalyst layer and a gas diffusion layer which are arranged in a stacked mode, the conductive composite layer comprises a polymer film layer and a conductive layer, the conductive composite layer is sequentially composed of a polymer film layer and a conductive layer which are arranged in a stacked mode, and the gas diffusion layer is preferably a PTFE layer. According to the membrane electrode comprising the arrangement, the current problem of a gas diffusion electrode is effectively inhibited, so that the electrochemical performance of the membrane electrode is more excellent and more durable.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy conversion technology, specifically to a membrane electrode, its preparation method, and its application. Background Technology

[0002] The use of gas diffusion electrodes (GDEs) in electrolyzers effectively overcomes the mass transfer limitations in the electrochemical reduction of CO2. In continuous electrolyzers, GDEs ensure that CO2 gas diffuses through a porous gas diffusion layer (GDL) and then through the liquid film to the active sites in the catalyst layer (CL). This improved carbon dioxide mass transfer enables electrolyzers with GDEs to achieve a current-rate of 100 mA / cm². 2 The aforementioned current density makes the electrochemical conversion of carbon dioxide economically feasible on an industrial scale. A typical commercial GDL consists of a carbon fiber support layer (CFS) and a microporous layer (MPL), with the catalyst coated on the microporous layer. The microporous layer is typically composed of a mixture of carbon black and hydrophobic polytetrafluoroethylene (PTFE), which can mitigate flooding in GDE. Once liquid electrolyte permeates or floods into the MPL and CFS layers, it significantly affects CO2 transport to the active catalyst sites, weakening the CO2 mass transfer enhancement effect of GDE and thus impacting the overall performance of the electrochemical carbon dioxide reduction reaction (CO2RR).

[0003] In a carbon dioxide electroreduction electrolyzer, the hydrophobicity of the cathode gas diffusion layer (GDL) has a significant effect on suppressing the cross-linking of water and alkaline cations. The hydrophobicity of the cathode gas diffusion layer (GDL) can not only prevent flooding caused by the adsorption of electrolyte solution and / or organic liquid products, but also suppress the increase of hydrogen evolution reaction (HER). Common strategies to improve the hydrophobicity of the cathode gas diffusion layer (GDL) include (1) using microporous layers (MPLs) of carbon paper treated with polytetrafluoroethylene (PTFE), (2) adding PTFE particles to the catalyst layer, and (3) using expanded polytetrafluoroethylene (e-PTFE) membranes as permeable support materials.

[0004] Carbon fiber supported cathodes (GDEs) exhibit superior conductivity; however, even with PTFE-treated porous layers, flooding can still occur after a certain period of operation due to potential fissures within the porous layer, leading to a decline in electrochemical performance. In contrast, cathodes based on e-PTFE films in the GDL demonstrate better sustainability and durability in suppressing flooding during CO2RR. However, because e-PTFE is electronically insulating, tabs need to be added between the catalyst layer and the current collector. Limited by the size of these tabs, this typically results in uneven electron transport, localized heating, increased internal resistance, and voltage rise. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the following defects in the prior art:

[0006] (1) Membrane electrodes prepared based on PTFE fiber gas diffusion layers cannot conduct electricity uniformly and will have flooding phenomenon, which leads to a decrease in electrochemical performance;

[0007] (2) Due to the insulation of the PTFE fiber gas diffusion layer itself, it is impossible to connect individual cells in series;

[0008] (3) PTFE electronic insulation cannot be directly electrochemically deposited;

[0009] (4) Metal electrodes prepared by electrostatic sputtering alone are too dense, have low electrochemical active area, block the pores of PTFE-GDL, and are not conducive to gas diffusion.

[0010] Therefore, this invention provides a membrane electrode, its preparation method, and its application. The conductive composite layer (a structure composed of a conductive layer and a polymer layer) included in the membrane electrode of this invention enables more uniform electron conduction from the membrane electrode to the current collector, allowing the membrane electrode based on the PTFE fiber gas diffusion layer to be engineered for practical applications. This effectively suppresses flooding problems in gas diffusion electrodes, resulting in superior and more durable electrochemical performance of the membrane electrode. Furthermore, this application presents a design method for integrating a membrane electrode including e-PTFE into a zero-gap electrolyzer. Through simple, highly conductive, and durable front-side conductive contacts, it achieves a full-cell voltage in a zero-gap electrolyzer that is similar to that of a carbon fiber supported cathode GDE. The conductive composite layer in this application also solves the insulation problem inherent in the PTFE-based gas diffusion layer, thereby enabling series connection of individual cells.

[0011] Furthermore, the membrane electrode preparation method provided by the present invention uses electrostatic sputtering-assisted pulsed electrochemical deposition to coat a silver catalyst layer onto the surface of the e-PTFE gas diffusion layer, making the e-PTFE gas diffusion layer conductive, which can then be used to prepare a working electrode for electrochemical deposition; and the pulsed electrochemical deposition method used, under a large current density, makes it easy for the working electrode to generate a hydrogen evolution reaction while depositing metal, resulting in a three-dimensional porous structure of deposited metal, thus having a larger electrochemical surface area, which is beneficial for gas diffusion.

[0012] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0013] The present invention provides a membrane electrode comprising an ion exchange membrane layer, a conductive composite layer, and a gas diffusion electrode layer stacked sequentially, wherein the conductive composite layer has a hollow structure and the edge dimension of the conductive composite layer is larger than the edge dimension of the gas diffusion electrode layer.

[0014] The gas diffusion electrode layer preferably includes a catalyst layer and a gas diffusion layer, and more preferably, the gas diffusion electrode layer is composed of a catalyst layer and a gas diffusion layer stacked in sequence.

[0015] The conductive composite layer preferably includes a polymer film layer and a conductive layer; more preferably, the conductive composite layer is composed of a polymer film layer and a conductive layer stacked in sequence.

[0016] The gas diffusion layer is preferably a PTFE layer.

[0017] In this invention, the ion exchange membrane in the ion exchange membrane layer can be a conventional ion exchange membrane in the art, such as anion exchange membrane, cation exchange membrane, amphoteric exchange membrane, or bipolar membrane, preferably an anion exchange membrane, more preferably a basic anion exchange membrane, such as a sulfated anion exchange membrane. ® X37-50 (manufactured by Dioxide Materials).

[0018] In this invention, the inner edge dimension of the conductive composite layer is preferably (1-3) * (1-3) cm. 2 For example, 2*2 cm 2 .

[0019] In this invention, the outer edge dimension of the conductive composite layer is preferably (5-7) * (5-7) cm. 2 For example, 6*6 cm 2 .

[0020] Furthermore, the edge size of the conductive layer is preferably (5-7) * (5-7) cm. 2 For example, 5*5 cm 2 .

[0021] Furthermore, the conductive layer is preferably located on the side closest to the gas diffusion electrode layer.

[0022] Furthermore, the conductive material in the conductive layer can be a conventional conductive material in the art, preferably copper, gold, silver or platinum, for example, copper.

[0023] The copper is preferably in the form of copper powder or copper foil, for example, copper foil.

[0024] The thickness of the conductive layer is preferably 2μm-20μm, for example 12μm.

[0025] Furthermore, the edge size of the polymer film layer is preferably (5-7) * (5-7) cm. 2 For example, 6*6 cm 2 .

[0026] Furthermore, the polymer membrane in the polymer film layer can be a conventional polymer membrane in the art, preferably a fluorinated polymer membrane or a non-fluorinated polymer membrane, such as a polytetrafluoroethylene (PTFE) membrane, more preferably an expanded polytetrafluoroethylene (e-PTFE) membrane.

[0027] The thickness of the polymer film is preferably 20μm-100μm, for example 30μm-40μm.

[0028] In this invention, the conductive composite layer is preferably prepared by any one of the following two methods:

[0029] Method 1: After hot-pressing the conductive layer and the polymer film layer to obtain the initial composite layer, the center part of the initial composite layer is cut off to obtain a conductive composite layer with a hollow structure.

[0030] Method 2: The conductive layer is electrostatically sputtered onto the polymer film to obtain an electrostatic sputtered composite layer. The center part of the electrostatic sputtered composite layer is then cut off to obtain a conductive composite layer with a hollow structure.

[0031] In Method 1, the preferred temperature for hot pressing is 40-120℃, for example, 80℃.

[0032] In Method 2, the electrostatic sputtering time is preferably 360-420s, for example 380s.

[0033] In Method 2, the current of the electrostatic sputtering is preferably 0.01-0.02A, for example, 0.016A.

[0034] In Method 2, the specific mass of the electrostatic sputtering is preferably 0.1-0.2 mg / cm³. -2 For example, 0.13 mg cm -2 Here, specific mass refers to the mass of the conductive layer electrostatically sputtered per unit area of ​​the polymer film.

[0035] In Method 2, the electrostatic sputtering apparatus can be a conventional electrostatic sputtering apparatus in the art, preferably a Balzers Union SCD 004.

[0036] In this invention, the edge size of the gas diffusion electrode layer is preferably (3-4) * (3-4) cm. 2 For example, 4*4cm 2 .

[0037] The catalyst layer is preferably located on the side closest to the conductive composite layer.

[0038] In this invention, the gas diffusion electrode layer is preferably prepared by coating a catalyst layer onto a gas diffusion layer.

[0039] The catalyst layer is prepared from catalyst ink. The catalyst ink may contain conventional catalysts in the art, preferably Ag catalysts, Au catalysts, or Au-Ag alloy catalysts, and more preferably Ag catalysts.

[0040] The Ag catalyst is preferably present in the form of Ag powder, Ag nanoparticles, or Ag flakes, for example, Ag nanoparticles.

[0041] The catalyst ink is preferably prepared using the following steps:

[0042] Catalyst ink is obtained by mixing Ag nanoparticles, carbon black, perfluorinated resin solution and isopropanol.

[0043] The preferred size distribution range of the Ag nanoparticles is 5-100 nm, for example, 20-40 nm.

[0044] The purity of the Ag nanoparticles is preferably 99-99.99%, for example, 99.9%.

[0045] Preferably, the Ag nanoparticles are Ag nanoparticles purchased from Thermo Fisher Scientific.

[0046] The purity of the carbon black is preferably 98-99.9%, for example, 99%.

[0047] The carbon black is preferably carbon black purchased from Thermo Fisher Scientific.

[0048] The perfluororesin solution is obtained by mixing perfluorosulfonic acid resin and a solvent, wherein the solvent is preferably water, ethanol, isopropanol or acetone, for example, water.

[0049] The mass concentration of the perfluorinated resin solution is preferably 1-10%, for example, 5%.

[0050] The perfluorinated resin solution is preferably a 5% Nafion resin solution purchased from DuPont.

[0051] The purity of the isopropanol is preferably 99-99.9%, for example, 99.7%.

[0052] The isopropanol is preferably isopropanol purchased from Sigma Aldrich.

[0053] In the catalyst ink, the preferred mass ratio of Ag nanoparticles, carbon black, perfluorinated resin solution and isopropanol is about 1:1:10:55.

[0054] Furthermore, the mixing step preferably includes an ultrasonic treatment step to make the Ag nanoparticles, carbon black, perfluororesin solution and isopropanol more uniformly dispersed.

[0055] The ultrasonic treatment time is preferably 20-40 minutes, for example, 30 minutes.

[0056] The specific surface area of ​​the catalyst layer is preferably 0.7-0.9 m². 2 g -1 For example, 0.85 m 2 g -1 .

[0057] The average pore size of the catalyst layer is preferably 0.14-0.17 μm, for example, 0.1581 μm.

[0058] The pore volume of the catalyst layer is preferably 35-40 μm, for example, 37.57 cm³. 3 g -1 .

[0059] The thickness of the catalyst layer is preferably 180-220 μm, for example, 200 μm.

[0060] The catalyst layer preferably weighs 0.02-0.03g, for example, 0.0268g.

[0061] The gas diffusion layer is preferably an e-PTFE layer, for example, an e-PTFE layer or an e-PTFE porous fiber membrane layer.

[0062] Furthermore, the e-PTFE porous fiber membrane is preferably a commercially available e-PTFE porous fiber membrane, and more preferably a hydrophobic polyamide e-PTFE porous fiber membrane, such as the Sterlitech Aspire composite ePTFE membrane QP952.

[0063] The specific surface area of ​​the gas diffusion layer is preferably 0.5-0.8 m². 2 g -1 For example, 0.69 m 2 g -1 .

[0064] The average pore size of the gas diffusion layer is preferably 0.13-0.16 μm, for example, 0.1492 μm.

[0065] The pore volume of the gas diffusion layer is preferably 33-35 μm, for example, 34.49 cm. 3 g -1 .

[0066] The thickness of the gas diffusion layer is preferably 127-229 μm, for example, 189 μm.

[0067] The weight of the gas diffusion layer is preferably 0.02-0.03g, for example, 0.0268g.

[0068] Furthermore, the coating method preferably includes one or more of spraying, electrostatic sputtering, and electrochemical deposition, such as electrostatic sputtering and electrochemical deposition.

[0069] Furthermore, the coating preparation steps are preferably as follows:

[0070] (a) The catalyst layer is coated onto the gas diffusion layer by electrostatic sputtering to obtain the primary gas diffusion electrode layer;

[0071] (b) The initial gas diffusion electrode layer and the reference electrode are placed in an aqueous electrolyte solution to obtain an electrodeposition solution;

[0072] (c) The electrodeposition solution is connected to an electrochemical deposition apparatus and electrodeposited to obtain a gas diffusion electrode layer including a porous catalyst layer.

[0073] (d) Immediately after deposition, the gas diffusion electrode layer was removed from the electrolytic cell, rinsed in 0.1 M KHCO3 to neutralize the residual sulfuric acid, then rinsed with ultrapure water and dried in air.

[0074] In step (a), the electrostatic sputtering time is preferably 360-420s, for example 380s.

[0075] In step (a), the current of the electrostatic sputtering is preferably 0.01-0.02A, for example, 0.016A.

[0076] In step (a), the specific mass of the electrostatic sputtering is preferably 0.1-0.2 mg cm⁻¹. -2 For example, 0.13 mg cm -2 Here, the specific mass refers to the mass of the catalyst layer electrostatically sputtered per unit area of ​​the gas diffusion layer.

[0077] In step (a), the thickness of the primary gas diffusion electrode layer is preferably about 100 nm to 150 nm, for example, about 120 nm.

[0078] In step (a), the electrostatic sputtering apparatus can be a conventional electrostatic sputtering apparatus in the art, preferably a Balzers Union SCD 004.

[0079] In step (b), the primary gas diffusion electrode layer and the reference electrode are placed before the aqueous electrolyte solution, preferably the primary gas diffusion electrode layer is fixed with an insulating electrode clamp.

[0080] In step (b), the reference electrode may be a platinum electrode.

[0081] In step (b), the aqueous electrolyte solution can be a conventional aqueous electrolyte solution in the art, and the aqueous electrolyte solution is preferably composed of Ag2SO4 and H2SO4.

[0082] The Ag2SO4 concentration is preferably 0.01~0.03M, for example 0.02M;

[0083] The concentration of H2SO4 is preferably 1~3M, for example 1.5M.

[0084] In step (c), the charge density of the electrodeposition is preferably 20, 30, 40 or 50 A s cm⁻¹. -2 For example, 50 As cm -2 .

[0085] The pulse ratio in the electrodeposition is preferably 2:0, 2:1, 1:1, 1:2 or 1:4, for example, 1:4.

[0086] The pause time after electrodeposition is 5-25ms, preferably 10ms.

[0087] In step (c), the specific surface area of ​​the porous catalyst layer is preferably 0.7-1 m². 2 g -1 For example, 0.88m 2 g -1 .

[0088] The average pore size of the porous catalyst layer is preferably 0.1-0.3 μm, for example, 0.2426 μm.

[0089] The pore volume of the gas diffusion layer is preferably 35-40 μm, for example, 37.72 cm³. 3 g -1 .

[0090] The thickness of the porous catalyst layer is preferably 260-300 μm, for example, 280 μm.

[0091] The porous catalyst layer preferably weighs 0.03-0.06g, for example, 0.04647g.

[0092] Furthermore, the coating preparation steps are preferably as follows:

[0093] The catalyst layer is coated onto the gas diffusion layer using a spraying device and then dried to obtain the gas diffusion electrode layer.

[0094] Specifically, a hydrophobic layer is preferably coated on the gas diffusion layer before the catalyst layer is coated onto the gas diffusion layer using a spraying device.

[0095] Furthermore, the hydrophobic layer is preferably a fluorinated compound or a silane coupling agent, such as a perfluorosulfonic acid resin.

[0096] The drying temperature is preferably 80~120℃, for example, 100℃.

[0097] The catalyst loading in the gas diffusion electrode layer is preferably 0.1~4 mg / cm³. 2 For example, 1.0 ± 0.1 mg / cm 2 .

[0098] The spraying device can be a conventional spraying device in the art, preferably a manual spray gun, such as the RS PRO Air Brush Kit with a needle tip of 0.3 mm.

[0099] The present invention provides a method for preparing the membrane electrode as described above, the method comprising the following steps: (i) coating a catalyst layer onto a gas diffusion layer to obtain a gas diffusion electrode layer; (ii) sequentially bonding an ion exchange membrane layer, a conductive composite layer and the gas diffusion electrode layer to obtain a membrane electrode.

[0100] The present invention provides an electrolytic cell cathode structure, which includes a membrane electrode and a flow field plate as described above.

[0101] In this invention, the flow field plate is preferably attached to the gas diffusion layer in the membrane electrode.

[0102] In this invention, the flow field plate is preferably attached to the edge of the conductive composite layer in the membrane electrode.

[0103] In this invention, the flow field plate is preferably a conventional flow field plate in the art, and more preferably a titanium flow field plate.

[0104] The present invention provides an electrolytic cell, which includes the electrolytic cell cathode structure as described above.

[0105] The present invention provides a battery comprising a membrane electrode, an anode, an anode flow field plate, and an electrolyte as described above.

[0106] In this invention, the anode can be a conventional anode in the art, such as a titanium mesh plated with IrO2.

[0107] In this invention, the anode flow field plate can be a conventional anode flow field plate in the art, such as a titanium flow field plate.

[0108] In this invention, the electrolyte can be a conventional electrolyte in the art, such as a 2 mol / L KHCO3 solution, wherein the KHCO3 (analytical grade GR, Tianjin Guangfu) is dissolved in ultrapure water to prepare the 2M electrolyte.

[0109] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0110] The reagents and raw materials used in this invention are all commercially available.

[0111] Furthermore, unless otherwise specified, all numerical values ​​modified by the term "about" in relation to the mass of components and other related terms used herein are subject to an error range of ±5%, for example:

[0112] The positive and progressive effects of this invention are as follows: This invention provides a membrane electrode that can more uniformly conduct electrons from the membrane electrode to the current collector, enabling the engineering application of membrane electrodes based on PTFE fiber gas diffusion layers. It effectively suppresses flooding problems in gas diffusion electrodes, resulting in superior and more durable electrochemical performance of the membrane electrode. The membrane electrode preparation method provided by this invention employs electrostatic sputtering-assisted pulsed electrochemical deposition of a porous silver catalyst on the surface of the e-PTFE gas diffusion layer, making the e-PTFE gas diffusion layer conductive. This allows it to be further prepared as a working electrode for electrochemical deposition. Furthermore, the pulsed electrochemical deposition method, at a higher current density, facilitates hydrogen evolution reaction during metal deposition, resulting in a three-dimensional porous structure of deposited metal with a larger electrochemical surface area, which is beneficial for gas diffusion. Attached Figure Description

[0113] Figure 1 This is a flowchart of the fabrication steps of the membrane electrode of this application.

[0114] Figure 2 This is a schematic diagram of the membrane electrode structure of this application (the left image is a front view, and the right image is a side cross-section view). Detailed Implementation

[0115] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0116] Example 1

[0117] Step 1, Preparation of the catalyst layer: 100 mg of Ag nanoparticles (AgNPs, 99.9% purity, 20-40 nm particle size, purchased from Thermo Fisher Scientific), 100 mg of carbon black (CB, 99% purity, purchased from Thermo Fisher Scientific), and 1 mL of perfluorinated resin solution (5% Nafion resin, DuPont) were mixed in 7 mL of isopropanol (IPA, ≥99.7% purity, purchased from Sigma Aldrich) to obtain the catalyst ink. The catalyst ink was then coated onto the surface of the e-PTFE layer (gas diffusion layer) to form a catalyst layer. The catalyst ink was ultrasonically treated for 30 minutes before coating to fully disperse the solid material.

[0118] Step 2, Preparation of the gas diffusion electrode layer: The gas diffusion electrode layer is formed by drying the catalyst layer and gas diffusion layer formed on the surface of the e-PTFE layer. The specific steps are as follows: First, a layer of perfluorosulfonic acid resin (5% Nafion resin, DuPont) is sprayed onto the surface of the e-PTFE layer using a manual spray gun with a fixed airflow (RSPRO Air Brush Kit, 0.3 mm tip). Then, the catalyst ink is sprayed onto the surface of the e-PTFE layer using the same manual spray gun, forming a catalyst layer on the e-PTFE layer surface. The catalyst layer and the e-PTFE layer together constitute the initial gas diffusion electrode layer. Then, drying is performed at 100°C to evaporate isopropanol and water to obtain the gas diffusion electrode layer. The loading of the catalyst layer formed on the surface of the e-PTFE layer by coating with a mixture of AgNPs, CB, and perfluororesin solution is 1.0 ± 0.1 mg / cm². 2 The prepared gas diffusion electrode layer has an area of ​​4*4 cm. 2 .

[0119] Step 3, Preparation of the conductive composite layer: A 5*5 cm... 2 The copper foil layer (conductive layer, 12μm thick) and 6*6 cm 2 The e-PTFE membrane layer (polymer membrane layer, Sterlitech Aspire composite ePTFE membrane QP952, thickness 30μm-40μm) was hot-pressed at 80℃, with the center 2*2 cm 2 The portion is cut away to obtain a conductive composite layer, wherein the inner edge dimension of the conductive composite layer is 2*2 cm. 2 The outer edge dimensions are 6*6cm. 2 .

[0120] Step 4, Fabrication of the membrane electrode: Sustaining ®The X37-50 membrane layer (ion exchange membrane layer) (manufactured by Dioxide Materials), the above-mentioned conductive composite layer, and the gas diffusion electrode layer are sequentially bonded together to obtain a membrane electrode. The copper foil layer in the conductive composite layer is in contact with the catalyst layer in the gas diffusion electrode layer, and the PTFE membrane layer in the conductive composite layer is in contact with the Sustaining... ® X37-50 film layer contact; then Sustaining ® The X37-50 ion exchange membrane layer is placed on top of the conductive composite layer to form a membrane electrode.

[0121] Step 5, Battery Formation: The membrane electrode prepared above is placed on the upper layer of a titanium flow field plate with matching dimensions, so that the e-PTFE layer in the gas diffusion electrode layer of the membrane electrode is attached to the flow field plate. The edge dimension of the titanium flow field plate is larger than the size of the gas diffusion electrode layer, and the outer edge dimension of the conductive composite layer is also larger than the size of the gas diffusion electrode layer, thereby forming a conductive connection between the conductive composite layer, the gas diffusion electrode layer and the flow field plate in the membrane electrode. Then, IrO2-plated titanium mesh anode, titanium flow field plate and 2M KHCO3 solution (KHCO3 (superior grade GR, purchased from Tianjin Guangfu, 2M prepared by dissolving in ultrapure water) are added and assembled using conventional methods to form a battery.

[0122] Example 2

[0123] Step 1, Preparation of the primary gas diffusion electrode layer: First, an e-PTFE porous fiber membrane (gas diffusion layer, QP952, manufactured by Sterlitech Aspire) is used as the substrate. A thin conductive silver layer (catalyst layer) is formed by electrostatic sputtering (Balzers Union SCD 004). The optimal electrostatic sputtering parameters are: time 380s, current 0.016A, and specific mass 0.13mg / cm³. -2 It has a thickness of approximately 120nm.

[0124] Step 2, Preparation of the gas diffusion electrode layer: After fixing the primary gas diffusion electrode layer with a tetrafluoroethylene electrode clamp, a working electrode of the primary gas diffusion electrode layer is formed. A platinum sheet electrode is used as a reference electrode. The two electrodes are placed in an aqueous electrolyte solution (0.02 M Ag2SO4 + 1.5 M H2SO4) to obtain an electrodeposition solution. The electrodeposition solution is connected to an electrochemical workstation (Autolab, PGSTAT30), and deposition is performed using pulsed current (PC) to obtain the gas diffusion electrode layer. The optimal parameters for pulsed electrochemical deposition with different charge densities are 50 A s cm⁻¹. -2 The pulse ratio is 1:4, and the pause time remains unchanged at 10ms.

[0125] Steps 3-5 are the same as in Example 1.

[0126] Example 3

[0127] Steps 1-2 are the same as in Example 2.

[0128] Step 3, Preparation of conductive composite layer: Cut the PTFE film to the required size, and then electrostatically sputter layer A (copper foil layer) on the surface of the PTFE film. The electrostatic sputtering working parameters are the same as in step 1 of Example 2. Finally, cut it to the required size to obtain conductive composite layer.

[0129] Steps 4-5 are the same as in Example 1.

[0130] Comparative Example 1

[0131] Except for replacing the gas diffusion layer in Example 1 with a commercially available ordinary carbon fiber gas diffusion layer, the composition and preparation steps of all other layers are exactly the same as in Example 1.

[0132] Comparative Example 2

[0133] Except that the e-PTFE layer in Example 1 was replaced with a commercially available gas diffusion layer (GDL) with hydrophobic properties (Sigracet-38 BC, purchased from SGL carbon), which is made of macroporous carbon paper and a dense microporous carbon black layer (MPL) and treated with polytetrafluoroethylene (PTFE); the composition and preparation steps of all other layers are exactly the same as in Example 1.

[0134] Comparative Example 3

[0135] Except for placing the conductive composite layer of Example 1 between the catalyst layer and the e-PTFE layer (gas diffusion layer), the composition and preparation steps of all other layers are exactly the same as in Example 1.

[0136] Example 1: Testing of the physical properties of electrostatic sputtering-pulse deposition film electrodes

[0137] Table 1: Physical properties of the electrostatic sputtering-pulse deposition film electrode in Example 2

[0138]

[0139] Example 2: Testing of steady-state electrolysis time of the battery

[0140] The batteries of Examples 1-3 and Comparative Examples 1-3 were connected to a potentiostat, and a 150 mA cm⁻¹ was applied. -2 Electrolysis is performed using an electric current, and the steady-state electrolysis time is recorded. Here, steady-state electrolysis refers to the time during which the battery maintains stable and normal operation.

[0141] Example 3: Coulomb efficiency test

[0142] CO2 (99.995%, AirLiquid) was continuously supplied to the gas chambers of the batteries in Examples 1-3 and Comparative Examples 1-3 at a flow rate of 20 N / mL / min. -1 Meanwhile, the pressure controller (Bronkhorst, purchased from the Netherlands) maintained a pressure of 30 mbar. A peristaltic pump (DOSAFlex, dosatonic GmbH, purchased from Germany) was used to deliver the electrolyte at a flow rate controlled at 3 L / h. -1 The battery was connected to an Autolab (PGSTAT30) electrochemical workstation, with the current density set to 200 mA / cm². 2 A gas chromatograph (Agilent 8860GC System) was used to detect and quantify the gaseous products of CO2RR. The gaseous products H2, CO, and CO2 were analyzed every 5 minutes of electrolysis to calculate the coulombic efficiency.

[0143] The results of electrochemical performance tests (steady-state electrolysis time and coulombic efficiency) performed on the batteries in all the above embodiments and comparative examples are listed in Table 2 below.

[0144] Table 2 Electrochemical performance test data of Examples 1-3 and Comparative Examples 1-3

[0145]

[0146] As shown in Table 2 above, compared to the battery membrane electrode prepared by electrostatic sputtering assisted pulse electrochemical deposition (i.e., Example 1), the coulombic efficiency of the battery membrane electrode prepared by electrostatic sputtering assisted pulse electrochemical deposition in Examples 2-3 is higher, reaching 95%-96%. Compared to batteries using other commercially available components as the gas diffusion layer in the membrane electrode (i.e., Comparative Examples 1-2), the batteries using an e-PTFE layer as the gas diffusion layer in the membrane electrode in this application (i.e., Examples 1-3) exhibit superior electrochemical performance, with a coulombic efficiency of over 92% and a steady-state electrolysis time of over 80 hours. Furthermore, compared to the conductive composite layer placed between the catalyst layer and the e-PTFE layer in Comparative Example 3 (or other cases not before the catalyst layer), the electrochemical performance of placing the conductive composite layer before the catalyst layer in this application (i.e., Examples 1-3) is superior.

Claims

1. A membrane electrode, characterized in that, It includes an ion exchange membrane layer, a conductive composite layer, and a gas diffusion electrode layer stacked sequentially, wherein the conductive composite layer has a hollow structure and the edge size of the conductive composite layer is larger than the edge size of the gas diffusion electrode layer; The gas diffusion electrode layer includes a catalyst layer and a gas diffusion layer, which are sequentially composed of a catalyst layer and a gas diffusion layer stacked together; the conductive composite layer includes a polymer film layer and a conductive layer, which are sequentially composed of a polymer film layer and a conductive layer stacked together. The gas diffusion layer is a PTFE layer.

2. The membrane electrode according to claim 1, characterized in that, It meets one or more of the following conditions: (1) The ion exchange membrane in the ion exchange membrane layer is an anion exchange membrane, a cation exchange membrane, an amphoteric exchange membrane or a bipolar membrane, preferably an anion exchange membrane, more preferably a basic anion exchange membrane, such as Sustainion® X37-50; (2) The inner edge dimension of the conductive composite layer is (1-3)*(1-3)cm 2 For example, 2*2 cm 2 ; (3) The outer edge dimension of the conductive composite layer is (5-7)*(5-7)cm 2 For example, 6*6 cm 2 ; (4) The edge dimension of the gas diffusion electrode layer is (3-4) * (3-4) cm. 2 For example, 4*4 cm 2 ; (5) The edge dimension of the conductive layer is (5-7) * (5-7) cm 2 For example, 5*5 cm 2 ; (6) The conductive layer is located on the side closest to the gas diffusion electrode layer; (7) The conductive material in the conductive layer is copper, gold, silver, platinum, for example, copper; wherein the copper exists in the form of copper powder, copper foil, for example, copper foil; (8) The thickness of the conductive layer is 2μm-20μm, for example 12μm; (9) The edge dimension of the polymer film layer is (5-7)*(5-7)cm 2 For example, 6*6 cm 2 ; (10) The polymer membrane in the polymer membrane layer is a fluorinated polymer membrane or a non-fluorinated polymer membrane, preferably a polytetrafluoroethylene (PTFE) membrane, and more preferably an expanded polytetrafluoroethylene (e-PTFE) membrane; (11) The thickness of the polymer film is 20 μm - 100 μm, for example 30 μm - 40 μm; (12) The catalyst layer is located on the side closest to the conductive composite layer; (13) The gas diffusion electrode layer is prepared by coating the catalyst layer onto the gas diffusion layer; (14) The catalyst layer is prepared from catalyst ink; (15) The specific surface area of ​​the catalyst layer is 0.7-0.9 m². 2 g -1 For example, 0.85 m 2 g -1 ; (16) The average pore size of the catalyst layer is 0.14-0.17 μm, for example, 0.1581 μm; (17) The pore volume of the catalyst layer is 35-40 μm, for example, 37.57 cm. 3 g -1 ; (18) The thickness of the catalyst layer is 180-220 μm, for example, 200 μm; (19) The catalyst layer weighs 0.02-0.03g, for example, 0.0268g; (20) The gas diffusion layer is an e-PTFE layer, for example, an e-PTFE layer or an e-PTFE porous fiber membrane layer; (21) The specific surface area of ​​the gas diffusion layer is 0.5-0.8 m². 2 g -1 For example, 0.69 m 2 g -1 ; (22) The average pore size of the gas diffusion layer is 0.13-0.16 μm, for example, 0.1492 μm; (23) The pore volume of the gas diffusion layer is 33-35 μm, for example, 34.49 cm. 3 g -1 ; (24) The thickness of the gas diffusion layer is 127-229 μm, for example, 189 μm; (25) The weight of the gas diffusion layer is 0.02-0.03g, for example, 0.0268g.

3. The membrane electrode according to claim 1, characterized in that, The conductive composite layer is prepared by either of the following two methods: Method 1: After hot-pressing the conductive layer and the polymer film layer to obtain the initial composite layer, the center part of the initial composite layer is cut off to obtain the conductive composite layer with a hollow structure. Method 2: The conductive layer is electrostatically sputtered onto the polymer film to obtain an electrostatic sputtered composite layer. The center part of the electrostatic sputtered composite layer is then cut off to obtain a conductive composite layer with a hollow structure.

4. The membrane electrode according to claim 3, characterized in that, It meets one or more of the following conditions: (1) In Method 1, the temperature of the hot pressing is 40-120℃, for example 80℃; (2) In Method 2, the electrostatic sputtering time is 360-420s, for example 380s; (3) In method two, the current of electrostatic sputtering is 0.01-0.02A, for example, 0.016A; (4) In Method 2, the specific mass of the electrostatic sputtering is 0.1-0.2 mg cm⁻¹. -2 For example, 0.13 mg cm -2 Here, specific mass refers to the mass of the conductive layer electrostatically sputtered per unit area of ​​the polymer film. (5) In Method 2, the coating method includes one or more of the following: spraying, electrostatic sputtering and electrochemical deposition, such as electrostatic sputtering and electrochemical deposition. (6) In Method 2, the preparation steps of the coating are as follows: (a) the catalyst layer is coated onto the gas diffusion layer by electrostatic sputtering to obtain a primary gas diffusion electrode layer; (b) the initial gas diffusion electrode layer and the reference electrode are placed in an aqueous electrolyte solution to obtain an electrodeposition solution; (c) the electrodeposition solution is connected to an electrochemical deposition device and electrodeposited to obtain a gas diffusion electrode layer including a porous catalyst layer; (d) immediately after deposition, the gas diffusion electrode layer is taken out from the electrolytic cell, rinsed in 0.1 MKHCO3 to neutralize the residual sulfuric acid, then rinsed with ultrapure water and dried in air; (7) In Method 2, the preparation steps of the coating are as follows: the catalyst layer is coated onto the gas diffusion layer by a spraying device and then dried to obtain the gas diffusion electrode layer.

5. The membrane electrode according to claim 2 or 4, characterized in that, It meets one or more of the following conditions: (1) The catalyst ink is an Ag catalyst, an Au catalyst or an Au-Ag alloy catalyst, preferably an Ag catalyst; wherein the Ag catalyst exists in the form of Ag powder, Ag nanoparticles or Ag flakes, for example, Ag nanoparticles; (2) The catalyst ink is prepared by the following steps: Ag nanoparticles, carbon black, perfluorinated resin solution and isopropanol are mixed to obtain the catalyst ink; (3) The e-PTFE porous fiber membrane is a hydrophobic polyamide e-PTFE porous fiber membrane, such as the sterlitech Aspire composite ePTFE membrane QP952; (4) In step (a), the electrostatic sputtering time is 360-420s, for example 380s; (5) In step (a), the current of the electrostatic sputtering is 0.01-0.02A, for example, 0.016A; (6) In step (a), the specific mass of the electrostatic sputtering is 0.1-0.2 mg cm⁻¹. -2 For example, 0.13 mg cm -2 Here, the specific mass refers to the mass of the catalyst layer electrostatically sputtered per unit area of ​​the gas diffusion layer; (7) In step (a), the thickness of the primary gas diffusion electrode layer is 100nm-150nm, for example, 120nm; (8) In step (b), the primary gas diffusion electrode layer and the reference electrode are placed before the aqueous electrolyte solution, and the primary gas diffusion electrode layer is fixed with an insulating electrode clamp. (9) In step (b), the reference electrode is a platinum electrode; (10) In step (b), the aqueous electrolyte solution is composed of Ag2SO4 and H2SO4; (11) In step (c), the charge density of the electrodeposited charge is 20, 30, 40 or 50 A s cm⁻¹. -2 For example, 50 A scm -2 ; (12) In step (c), the pulse ratio in the electrodeposition is 2:0, 2:1, 1:1, 1:2 or 1:4, for example, 1:4; (13) In step (c), the pause time after the electrodeposition is 5-25ms, for example 10ms; (14) In step (c), the specific surface area of ​​the porous catalyst layer is 0.7-1 m². 2 g -1 For example, 0.88 m 2 g -1 ; (15) In step (c), the average pore size of the porous catalyst layer is 0.1-0.3 μm, for example, 0.2426 μm; (16) In step (c), the pore volume of the gas diffusion layer is 35-40 μm, for example, 37.72 cm. 3 g -1 ; (17) In step (c), the thickness of the porous catalyst layer is 260-300 μm, for example, 280 μm; (18) In step (c), the weight of the porous catalyst layer is 0.03-0.06 g, for example, 0.04647 g; (19) Before applying the catalyst layer to the gas diffusion layer using a spraying device, a hydrophobic layer is applied to the gas diffusion layer; (20) The drying temperature is 80~120℃, for example, 100℃; (21) The catalyst loading in the gas diffusion electrode layer is 0.1~4 mg / cm³. 2 For example, 1.0 ± 0.1 mg / cm 2 .

6. The membrane electrode according to claim 5, characterized in that, It meets one or more of the following conditions: (1) The size distribution range of the Ag nanoparticles is 5-100 nm, for example 20-40 nm; (2) The purity of the Ag nanoparticles is 99-99.99%, for example, 99.9%; (3) The purity of the carbon black is 98-99.9%, for example, 99%; (4) The perfluorinated resin solution is obtained by mixing perfluorosulfonic acid resin and a solvent; wherein, the solvent is preferably water, ethanol, isopropanol or acetone, for example, water; the mass concentration of the perfluorinated resin solution is preferably 1-10%, for example 5%; (5) The purity of the isopropanol is 99-99.9%, for example, 99.7%; (6) In the catalyst ink, the mass ratio of Ag nanoparticles, carbon black, perfluorinated resin solution and isopropanol is 1:1:10:

55. (7) The mixing step includes an ultrasonic treatment step; wherein the ultrasonic treatment time is preferably 20-40 min, for example, 30 min; (8) The concentration of Ag2SO4 is 0.01~0.03M, for example 0.02M; (9) The concentration of H2SO4 is 1~3M, for example 1.5M; (10) The hydrophobic layer is a fluorinated compound or a silane coupling agent, for example, perfluorosulfonic acid resin.

7. A method for preparing a membrane electrode as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: (i) coating a catalyst layer onto a gas diffusion layer to obtain a gas diffusion electrode layer; (ii) then sequentially bonding an ion exchange membrane layer, a conductive composite layer, and a gas diffusion electrode layer to obtain a membrane electrode.

8. A cathode structure for an electrolytic cell, characterized in that, It includes the membrane electrode and flow field plate as described in any one of claims 1-6; The flow field plate is preferably bonded to the gas diffusion layer in the membrane electrode; The flow field plate is preferably attached to the edge of the conductive composite layer in the membrane electrode; The flow field plate is preferably a titanium flow field plate.

9. An electrolytic cell, characterized in that, It includes the electrolytic cell cathode structure as described in claim 6.

10. A battery, characterized in that, It includes a membrane electrode, an anode, an anode flow field plate, and an electrolyte as described in any one of claims 1-6; The battery preferably includes a membrane electrode, an anode, an anode flow field plate, and an electrolyte as described in any one of claims 1-6; The anode is preferably a titanium mesh plated with IrO2; The anode flow field plate is preferably a titanium flow field plate; The electrolyte is preferably a 2 mol / L KHCO3 solution.

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