Membrane electrode assembly for co2 electroreduction and method of making and using same

Abstract

The application relates to the field of electrochemical energy conversion, in particular to a membrane electrode assembly for CO2 electro-reduction and a preparation method and application thereof. The membrane electrode assembly for CO2 electro-reduction comprises: a substrate membrane, which is a perfluorosulfonic acid proton exchange membrane; a modified coating layer located on at least one surface of the substrate membrane, which comprises an amphoteric dopant and a bonding component; the surface of the amphoteric dopant has acid sites and alkaline sites at the same time, which are used for catalyzing water molecule dissociation, buffering local pH and enhancing anion conduction; and a cathode catalytic layer and an anode catalytic layer arranged on opposite sides of the substrate membrane respectively. By introducing the amphoteric doping coating layer on the surface of the perfluorosulfonic acid proton exchange membrane, the synergistic effect of water dissociation catalysis, acid-base buffering and anion conduction enhancement is utilized, so that the hydrogen evolution reaction of the cathode side under high current conditions is effectively inhibited, the CO2 electro-reduction efficiency is improved, and the CO2 electro-reduction performance is improved. + The pH in the membrane fluctuates sharply and the hydrogen evolution reaction increases sharply.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy conversion, and in particular to membrane electrode assemblies for CO2 electroreduction, their preparation methods and applications. Background Technology

[0002] The CO2 electroreduction reaction converts renewable electrical energy into high-value-added fuels and chemical raw materials. The reaction process typically takes place in an electrolytic cell, where CO2 gains electrons at the cathode and undergoes a reduction reaction, while water, usually at the anode, loses electrons to produce oxygen. Among these reactions, the conversion of CO2 to CO is one of the most industrially promising in the field of CO2 electroreduction due to its mature technology and high economic feasibility.

[0003] In the industrialization of CO2 electroreduction technology, membrane electrode oscillators (MEAs) have become the preferred device for industrial applications due to their core advantages of high current density, low energy consumption, compact structure, and easy product separation. Membrane materials, as the core components of MEAs, undertake crucial functions such as ion conduction, anode-cathode separation, and inhibition of product cross-linking. Their performance directly determines the feasibility of industrialization. Currently, the mainstream core types in industrial applications include proton exchange membranes, anion exchange membranes, and bipolar membranes.

[0004] Although the three core membrane materials have established a foundation for application in MEA systems, they still face common key bottlenecks in large-scale continuous industrial operation scenarios: insufficient ion transport interface efficiency, leading to increased ion migration resistance; under long-term high current density operation, the membrane is prone to stability problems such as deformation, functional group degradation, or interlayer delamination; and some membrane types have high cell voltage and high energy consumption, which restricts the economic efficiency of industrialization.

[0005] Current research focuses on optimizing the core MEA structure. For example, Chinese patent CN120550646A adds an intermediate layer between the cathode and anolyte exchange membranes, adjusting the swelling characteristics of the three polymer layers to maintain a tight and affinity-based state during long-term testing, thus stabilizing the catalytic layer and extending the reaction lifetime. Chinese patent CN120967385A, by introducing a single-atom catalyst intermediate layer, significantly reduces the water dissociation voltage, improves catalytic efficiency and stability, and is suitable for electrochemical water splitting, energy conversion, and other fields.

[0006] However, these solutions, when applied to industrial applications with even higher currents, still fail to solve the fundamental problem. A large amount of H... + Hydrogen flows into the cathode, causing a large amount of hydrogen evolution reaction. This not only reduces performance but also significantly damages the membrane electrode structure. The originally well-constructed interface cannot operate continuously, resulting in a synergistic problem of "internal acid-base balance of the membrane and stability of the membrane electrode interface," which limits the industrial-scale promotion of CO2 electroreduction equipment. Summary of the Invention

[0007] In order to achieve long-term stable operation under high current conditions and solve the technical problems of performance degradation, selectivity drop and energy consumption increase of membrane electrodes under high current in the prior art, this application provides a membrane electrode assembly for CO2 electroreduction, its preparation method and application.

[0008] In a first aspect, this application provides a membrane electrode assembly for CO2 electroreduction, employing the following technical solution: A membrane electrode assembly for CO2 electroreduction includes: Basement membrane: perfluorosulfonic acid proton exchange membrane; A modified coating layer located on at least one surface of the base film includes an amphoteric dopant and a binder component; the surface of the amphoteric dopant simultaneously has acidic and basic sites, which are used to catalyze the dissociation of water molecules, buffer local pH, and enhance anion conduction. The cathode catalyst layer and the anode catalyst layer are respectively disposed on opposite sides of the substrate membrane.

[0009] By adopting the above technical solution, the amphoteric dopant is an aqueous amphoteric material with both protonable basic sites and deprotonable acidic sites on its surface. By introducing an amphoteric doping coating layer onto the surface of the perfluorosulfonic acid proton exchange membrane, the membrane electrode can synergistically achieve a triple function under high current conditions: the acidic sites (-OH2) of the amphoteric material... + ) and basic sites (-O) - Water molecules at the catalytic membrane-catalyst interface dissociate into H+. + and OH - It supplements ion transport carriers and reduces ion migration resistance; amphoteric substances can neutralize the large amount of H on the cathode side. + The influx of protons causes localized acidification, stabilizing the membrane microenvironment and thus inhibiting the competitive hydrogen evolution reaction, maintaining a high CO Faraday efficiency over a long period. The charged groups on the surface of amphoteric substances can enhance the reaction of anions (such as HCO3-). - OH - This improves the conductivity of the membrane, further reducing the internal resistance. Therefore, this component breaks through the limitations of traditional membrane electrodes at 1 A / cm². 2 Overcoming the bottleneck of performance degradation under high current, achieving long-term stable operation.

[0010] Furthermore, the perfluorosulfonic acid proton exchange membrane is one of Nafion 115, Nafion 117, Nafion 212, Nafion 112 or Dow perfluorosulfonic acid membrane.

[0011] By adopting the above technical solutions, the aforementioned perfluorosulfonic acid proton exchange membranes are all industrially mature products with excellent chemical stability, proton conductivity, and mechanical strength. Using these membranes as substrates provides a robust adhesion base for the amphoteric doping coating and ensures that the membrane electrode does not swell, creep, or degrade under long-term high current density operation. Furthermore, these membranes have broad process compatibility in the field of CO2 electroreduction, facilitating the direct integration of the membrane electrode assembly of this invention into existing MEA electrolyzer production lines, thus lowering the threshold for industrialization.

[0012] Furthermore, the amphoteric dopant is at least one of carbon powder, zirconium oxide, aluminum oxide, titanium dioxide, hydroxyapatite, zinc oxide, or heteroatom-doped carbon spheres.

[0013] By employing the above technical solutions, the aforementioned materials all possess amphoteric surface characteristics, meaning they can simultaneously protonate and deprotonate in an aqueous environment to form both acidic and basic sites. Specifically, the abundant hydroxyl groups on the surface of metal oxides (ZrO2, Al2O3, TiO2, ZnO) can undergo amphoteric dissociation; carbon-based materials (carbon powder, heteroatom-doped carbon spheres) can also acquire amphoteric properties through surface functional groups or heteroatom doping. These materials can be uniformly composited with binders in a slurry, forming a stable porous network structure after spraying. Zirconia and alumina not only possess strong buffering capacity but also good thermal stability and mechanical strength, preventing the coating from detaching under high-current erosion. The selectivity of multiple materials allows for flexible industrial formulation adjustments to adapt to different operating conditions.

[0014] Furthermore, based on the total weight of the solid components in the modified coating layer, the weight percentage of the amphoteric dopant is 10-50%, and the weight percentage of the binder component is 50-90%.

[0015] By adopting the above technical solution, a 10-50% proportion of amphoteric dopant is a key balance design. If the proportion is too low (<10%), the water dissociation catalysis and acid-base buffering effect are insufficient, failing to suppress the hydrogen evolution reaction under high current; if the proportion is too high (>50%), the binder component is relatively reduced, the mechanical strength and adhesion of the coating layer decrease, and it is prone to peeling or cracking. A binder component proportion of 50-90% ensures that the amphoteric particles are fully encapsulated and firmly anchored to the substrate membrane surface, while maintaining the ion conductivity of the coating layer. This proportion range has been experimentally verified to allow the membrane electrode to operate at 1 A / cm. 2 The interfacial adhesion retention rate under current is ≥85%, and the performance degradation is less than 10% after 150 hours of operation, achieving the optimal match between functional density and structural stability.

[0016] Furthermore, the adhesive component comprises a perfluorosulfonic acid resin and a fluoropolymer, wherein the solid weight ratio of the perfluorosulfonic acid resin to the fluoropolymer is 1:1.

[0017] By adopting the above technical solution, the bonding component is a 1:1 blend of perfluorosulfonic acid resin and fluoropolymer, which combines the dual advantages of ion conduction and enhanced adhesion. The perfluorosulfonic acid resin provides a continuous proton / anion conduction channel, ensuring that the modified coating layer does not become a bottleneck for ion transport; the fluoropolymer has excellent chemical inertness and hydrophobicity, which can suppress water flooding and significantly improve the coating layer's resistance to swelling and peeling. The optimized 1:1 mass ratio of the two components achieves the best elongation at break and interfacial adhesion of the coating layer without sacrificing ionic conductivity, thereby maintaining the integrity of the membrane electrode structure during long-term high-current operation. Furthermore, the fluoropolymer is polytetrafluoroethylene, polyvinylidene fluoride, or a copolymer of polyvinylidene fluoride.

[0018] By adopting the above technical solutions, both polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) (including their copolymers) are engineering plastics resistant to strong acids, strong alkalis, and oxidation, and possess low surface energy and good film-forming properties. PTFE can significantly reduce the coefficient of friction and water absorption of the coating layer, and reduce the adsorption of impurity ions; PVDF has a high dielectric constant and piezoelectricity, which helps to stabilize the electric field distribution within the membrane. Using these fluoropolymers as binder components can protect amphoteric doped particles from electrolyte corrosion and, in conjunction with perfluorosulfonic acid resin, form a robust composite coating, enabling the membrane electrode to withstand frequent start-ups and shutdowns, current fluctuations, and long-term high-voltage operation in industrial-grade CO2 electrolyzers.

[0019] Furthermore, the thickness of the modified coating layer is 6-9 μm.

[0020] By adopting the above technical solution, a thickness of 6-9 μm can ensure sufficient functional material loading to exert water dissociation catalysis and acid-base buffering effects, while minimizing ion transport resistance, enabling the membrane electrode to operate at 1 A / cm. 2 It maintains a low and stable operating voltage. When the thickness is less than 6 μm, the loading of the amphoteric dopant is insufficient to effectively buffer the H influx from the cathode side. + Under high current, the local pH inside the membrane will still fluctuate drastically, leading to a surge in hydrogen evolution reaction; a thickness of more than 9 μm will significantly increase the ion transport path length, resulting in increased membrane resistance and cell voltage, thereby reducing energy efficiency.

[0021] Secondly, this application provides a method for preparing a membrane electrode assembly for CO2 electroreduction, employing the following technical solution: A method for preparing a membrane electrode assembly for CO2 electroreduction includes the following steps: S1. Slurry preparation: The amphoteric dopant and the binder are mixed in a solvent and dispersed to obtain a uniform composite slurry; S2. Modified film coating: The composite slurry is sprayed onto the surface of the base film to form a modified coating layer, which is then dried to obtain the composite film; S3. Membrane electrode assembly: CO2 reduction catalyst and oxygen evolution catalyst are sprayed onto the cathode side and anode side of the composite membrane, respectively, to assemble the membrane electrode assembly.

[0022] By adopting the above technical solution, this method prepares membrane electrodes through a three-step process of "slurry dispersion—membrane spraying—catalyst assembly." Compared with conventional processes, the core difference lies in the introduction of uniform dispersion of amphoteric dopants and composite spraying. Specifically, step S1 uses a combination of mechanical stirring, ultrasonication, and shearing to break up agglomerates of amphoteric nanoparticles, obtaining a uniformly dispersed slurry at the submicron or nanometer scale. Step S2 uses spraying to form a 5-10 μm thin layer, avoiding particle scratches on the membrane surface that may occur with scraping, and the drying temperature of 80-90℃ can fully remove the solvent without damaging the microstructure of the proton exchange membrane. Step S3 directly sprays the catalyst onto both sides of the composite membrane, achieving close contact between the modified layer and the catalyst layer, maximizing the regulatory effect of the amphoteric substances on the reaction interface. This method has a wide process window, strong equipment versatility, and is easy to implement for continuous industrial production.

[0023] Thirdly, this application provides an application of a membrane electrode assembly for CO2 electroreduction, employing the following technical solution: An application of a membrane electrode assembly for CO2 electroreduction, wherein the membrane electrode assembly is used in a membrane electrode electrolyzer at 1 A / cm 2 CO2 electroreduction reaction is carried out at a high current density.

[0024] By adopting the above technical solution, the above membrane electrode assembly is applied to 1A / cm 2 The high current density CO2 electroreduction fully leverages the synergistic gain effect of the amphoteric doped coating. In this current range, conventional membrane electrodes suffer from a rapid increase in the intramembrane pH gradient, dominance of the hydrogen evolution reaction, and rapid performance degradation due to the large amount of H⁺ migrating across the membrane from the anode to the cathode. In contrast, the membrane electrode of this invention utilizes the water dissociation catalysis of the modified layer to promptly replenish OH⁻. - Neutralizing H + Meanwhile, the acid-base buffering function of the amphoteric substances suppresses pH fluctuations, maintaining the cathode surface in a slightly alkaline environment suitable for CO2 reduction. Experimental measurements show that at 1 A / cm²... 2 Under continuous operation, the CO Faraday efficiency showed no significant decay, the overall Faraday efficiency approached 1, and the operating voltage remained stable without any spikes. The energy efficiency was significantly superior to existing technologies. This application directly supports the leap from laboratory-scale CO2 electroreduction technology to industrial-scale electrolytic cells, yielding significant economic and environmental benefits.

[0025] In summary, this application has the following beneficial effects: This application introduces an amphoteric doped coating layer onto the surface of a perfluorosulfonic acid proton exchange membrane, utilizing its synergistic effects of water dissociation catalysis, acid-base buffering, and enhanced anion conduction to effectively suppress H+ ionization on the cathode side under high current conditions. + The massive influx of water causes dramatic fluctuations in membrane pH and a surge in hydrogen evolution reaction, which has significant advantages over traditional unmodified membrane electrodes and can meet the requirements of continuous industrial production. Attached Figure Description

[0026] Figure 1 Membrane electrode structure and ion transport direction; Among them, (a) is a common membrane electrode structure; and (b) is the membrane electrode structure corresponding to this application. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] Example of raw material and intermediate preparation raw material It should be noted that: in the following examples, unless otherwise specified, the conditions shall be in accordance with conventional conditions or the manufacturer's recommended conditions; and the raw materials used in the following examples, unless otherwise specified, shall be from commercially available sources. Nafion 115 membrane, thickness 127 μm, EW 1100 g / mol; Nafion D520 dispersion, 5wt%, EW 1000g / mol; PTFE emulsion, 60 wt%, average particle size 150 nm; PVDF powder, Solef 5130, with a weight-average molecular weight of approximately 500 kDa; ZrO2 nanoparticles, with an average particle size of 50 nm and a specific surface area of ​​35 m². 2 / g; Al2O3 nanoparticles, with an average particle size of 40 nm, γ phase, and a specific surface area of ​​45 m². 2 / g; Toner, Vulcan XC-72, average particle size 30nm, specific surface area 254m² 2 / g; Ag nanocatalyst, with an average particle size of 35 nm; IrO2 catalyst has a particle size of 2-5 μm and a specific surface area of ​​15 m². 2 / g.

[0029] Example Example 1 A membrane electrode assembly for CO2 electroreduction is prepared by the following method: S1. Slurry preparation: Weigh out each component according to the formula in Table 1: Table 1. Slurry Formulation for Example 1 The solid weight ratio of Nafion D520 to PTFE emulsion is 1:1, and the amphoteric dopant accounts for 30 wt% of the total solid weight. Add the above components to 20 mL of isopropanol / water mixed solvent (volume ratio 5:5), and proceed sequentially: Mechanical stirring: 400 rpm, 2 hours; Ultrasonic dispersion: power 250W, working / intermittent time 3s / 3s, total effective ultrasonic time 60min; after PTFE emulsion and Nafion D520 are premixed, amphoteric dopants are added. Gradient power is used during ultrasonic dispersion (first 200W for 30min, then 250W for 30min) to promote the forced emulsification and composite of hydrophobic PTFE and hydrophilic Nafion. Shear dispersion: shear rate 1200 rpm, 5 min.

[0030] A uniform and stable composite slurry was obtained, with a solid content of approximately 5 wt%. S2. Modified film coating: The Nafion 115 membrane was fixed on a 60°C heating platform, and the above slurry was uniformly sprayed onto one side of the membrane (facing the cathode) using a spraying method. Spraying parameters: Distance between spray gun and substrate: 15cm; Spray gun movement speed: 50mm / s; Coating thickness set: 8μm; Single spray volume: approximately 0.5 mL.

[0031] After spraying, the coating was transferred to a vacuum drying oven and dried at 85°C for 30 minutes to obtain a composite film. The actual coating thickness was measured to be 8±1μm by a step meter, which met the set value. S3. Membrane electrode assembly: A CO2 reduction catalyst and an oxygen evolution catalyst were sprayed onto the cathode and anode sides of the composite membrane, respectively, to assemble a membrane electrode assembly; the cathode catalyst was Ag nanoparticles (loading 0.5 mg / cm³). 2 The anode catalyst was IrO2 (loading 0.3 mg / cm³). 2 ), dispersed in isopropanol / water (1:1) and sprayed.

[0032] Reference Figure 1 (a) shows a common membrane electrode structure, in which a large amount of H +The hydrogen ion migrates across the membrane from the anode to the cathode, causing localized acidification on the cathode side and triggering a severe hydrogen evolution side reaction (H2). Simultaneously, the selectivity of the CO2 reduction product, CO, decreases. (b) shows the membrane electrode structure of this application, which utilizes an amphoteric dopant modified layer introduced on the cathode side, taking advantage of its surface acidic sites (-OH2). + ) and basic sites (-O) - This catalyzes the dissociation of water molecules and buffers local pH levels, effectively inhibiting H+ ions. + Excessive accumulation at the cathode significantly reduces the hydrogen evolution reaction, stabilizes the CO2 reduction microenvironment, and enables long-term stable operation under high current conditions. Example 2 Unlike Example 1, in Example 2, the amphoteric dopant was replaced by Al2O3 nanoparticles (average particle size 40 nm).

[0033] Example 3 Unlike Example 1, in Example 3 the amphoteric dopant is a mixture of ZrO2 and carbon powder in a weight ratio of 1:1.

[0034] Example 4 Unlike Example 1, in Example 4, the fluoropolymer was replaced by PVDF (Solef 5130, prepared as a 10wt% NMP solution before use), and the solid weight ratio of Nafion to PVDF was maintained at 1:1.

[0035] Example 5 Unlike Example 1, in Example 5, the amphoteric dopant (ZrO2) accounts for 10 wt% of the total solid content, and the binder component (Nafion:PTFE=1:1) accounts for 90 wt%.

[0036] Example 6 Unlike Example 1, in Example 6, the amphoteric dopant (ZrO2) accounts for 50 wt% of the total solid content, and the binder component (Nafion:PTFE=1:1) accounts for 50 wt%.

[0037] Example 7 Unlike Example 1, in Example 7, the amphoteric dopant accounts for 5 wt% of the total solid content, and the binder component accounts for 95 wt%.

[0038] Example 8 Unlike Example 1, in Example 8, the amphoteric dopant accounts for 60 wt% of the total solid content, and the binder component accounts for 40 wt%.

[0039] Example 9 Unlike Example 1, in Example 9 the coating parameters were set to a coating thickness of 5 μm, and the actual measured thickness was 5 ± 1 μm.

[0040] Example 10 Unlike Example 1, in Example 10 the coating parameters were set to a coating thickness of 10 μm, and the actual measured thickness was 10 ± 1 μm.

[0041] Example 11 Unlike Example 1, in Example 11, the modified coating layer was sprayed onto the anode side surface of the Nafion 115 film, while the cathode side remained unmodified.

[0042] Comparative Example Comparative Example 1 Using an unmodified Nafion 115 membrane, the cathode catalyst (Ag) and the anode catalyst (IrO2) were directly sprayed onto both sides according to the method in Example 1, with the same loading.

[0043] Comparative Example 2 Unlike Example 1, Comparative Example 2 used only Nafion (without PTFE or PVDF) as the binder component, with the total solid content remaining unchanged and the amphoteric dopant still accounting for 30 wt%.

[0044] Comparative Example 3 A quaternary ammonium-type basic polymer FAA-3 solution (10 wt% NMP solution) was sprayed onto the cathode side surface of Nafion 115 to a thickness of 8 μm, and then vacuum dried at 85 °C for 30 min. The preparation and spraying methods of the cathode and anode catalysts were the same as in Example 1.

[0045] Comparative Example 4 A ZrO2-Nafion modification layer (ZrO2 to Nafion weight ratio 1:1, total solid concentration 5 wt%, spray thickness approximately 8 μm) was pre-sprayed onto the surface of the Ag cathode catalyst. Then, the modified Ag catalyst was sprayed onto the cathode side of the Nafion 115 membrane using conventional methods. The anode side was the same as in Example 1, with the membrane itself remaining unmodified.

[0046] Performance testing The membrane electrodes prepared in the examples and comparative examples were respectively assembled into membrane electrode electrolysis cells, and the current density was 1 A / cm². 2 CO2 electroreduction reaction was tested under the following conditions: the electrolyte was 0.5 MkHCO3 solution, and the reaction temperature was room temperature. Polarization curve testing: The membrane electrode assembly was assembled in a single-cell test fixture, and polarization curves were measured at 1 A / cm. 2 The circuit was continuously operated at the current density for 150 hours. The initial voltage and the voltage after 150 hours were measured according to the polarization curve test method specified in GB / T20042.5-2024, and the voltage increase was calculated.

[0047] Faraday efficiency (FE) determination: Gas chromatography (according to GB / T8984-2008) was used to analyze the gas phase products (CO, H2) at the cathode outlet, and high performance liquid chromatography (HPLC) was used to analyze the liquid phase products (formic acid, ethanol). The Faraday efficiency of each product was calculated according to Faraday's law; Total Faraday efficiency = FE(CO) + FE(H2) + ∑FE(other products).

[0048] Interfacial adhesion test: A cross-cut test was conducted according to GB / T9286-2021 "Paints and Varnishes - Cross-cut Test". A right-angled grid pattern (1-2 mm spacing) was drawn on the surface of the modified coating using a cross-cut knife. After adhering with tape, it was quickly peeled off at a 90° angle. The coating adhesion grade was evaluated according to the standard grading method, or the adhesion retention rate was calculated based on the percentage of squares retained.

[0049] Solvent water specifications: Solvent water used for preparing electrolytes and catalyst inks shall meet the Class I or Class II water specifications in GB / T6682-2008.

[0050] CO Faraday efficiency decay: The percentage decrease in CO Faraday efficiency compared to the initial value after 150 hours of operation.

[0051] The test results are as follows: Table 2 Comparison of electrochemical performance of membrane electrode assemblies (continuous operation for 150 h) Examples 1-4 all exhibited current retention rates ≥89% and performance degradation rates ≤11%, significantly outperforming all comparative examples. Comparative example 1 collapsed after 20 hours and experienced a 75% performance degradation after 150 hours. Comparative example 4 placed an amphoteric substance within the catalyst layer, which could locally buffer pH but could not effectively block H⁺ transmembrane migration; therefore, its modification effect was weaker than direct coating on the membrane surface.

[0052] Table 3 Comparison of modified coating thickness optimization (continuous operation for 150 hours) A thickness of 5μm is insufficient for buffering (attenuation of 12%), a thickness of 10μm slightly increases resistance, and 8μm is the optimal balance point.

[0053] Table 4 Comparison of optimized content of amphoteric dopant (continuous operation for 150 h) When the content is <<10%, the buffering effect is insufficient; when it is >50%, the adhesion decreases, leading to cracking. 30% is the optimal ratio.

[0054] Table 5 Comparison of Modified Coating Layer Position Optimization (Continuous Operation for 150h) Coating the cathode side can directly buffer H + The influx of hydrogen ion inhibited the hydrogen evolution reaction, causing the HER concentration to drop from 25% to 8%.

[0055] Table 6. Accelerated Long-Term Stability Test of Example 1 (300h Continuous Operation) The decrease in overall Faraday efficiency is mainly attributed to energy dissipation caused by the accumulation of trace amounts of liquid phase byproducts such as formic acid and ethanol during long-term operation and the increase in interfacial resistance. For the quantitative method of liquid phase products, please refer to the HPLC method in the performance detection section. The performance degradation is only 15% after 300 hours, and the expected lifespan is >2000 hours, which is more than 10 times better than that of traditional membrane electrodes.

[0056] Table 7 Comparison of Ion Transport Performance Example 1: While maintaining high proton conductivity, OH - The conductivity increased by 4.2 times, and the water dissociation overpotential decreased from 120mV to 35mV.

[0057] In summary, this application meets the following requirements: High current stability: at 1A / cm 2 After 150 hours of continuous operation, the current retention rate is ≥89% and the performance degradation is ≤11%. Long-term selectivity stability: CO Faraday efficiency remains at 80-85%, with selectivity decay of only 3-4%; Structural integrity: interfacial adhesion retention rate ≥85%, no interlayer delamination.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A membrane electrode assembly for CO2 electroreduction, characterized in that, include: Basement membrane: perfluorosulfonic acid proton exchange membrane; A modified coating layer located on at least one surface of the base film includes an amphoteric dopant and a binder component; the surface of the amphoteric dopant simultaneously has acidic and basic sites, which are used to catalyze the dissociation of water molecules, buffer local pH, and enhance anion conduction. The cathode catalyst layer and the anode catalyst layer are respectively disposed on opposite sides of the substrate membrane.

2. The membrane electrode assembly for CO2 electroreduction according to claim 1, characterized in that, The perfluorosulfonic acid proton exchange membrane is one of Nafion 115, Nafion 117, Nafion 212, Nafion 112 or Dow perfluorosulfonic acid membrane.

3. The membrane electrode assembly for CO2 electroreduction according to claim 1, characterized in that, The amphoteric dopant is at least one of carbon powder, zirconium oxide, aluminum oxide, titanium dioxide, hydroxyapatite, zinc oxide, or heteroatom-doped carbon spheres.

4. A membrane electrode assembly for CO2 electroreduction according to claim 1, characterized in that, Based on the total weight of the solid components in the modified coating, the weight percentage of the amphoteric dopant is 10-50%, and the weight percentage of the binder component is 50-90%.

5. A membrane electrode assembly for CO2 electroreduction according to claim 1, characterized in that, The adhesive component comprises perfluorosulfonic acid resin and fluoropolymer, with a solid weight ratio of perfluorosulfonic acid resin to fluoropolymer of 1:

1.

6. A membrane electrode assembly for CO2 electroreduction according to claim 5, characterized in that, The fluoropolymer is polytetrafluoroethylene, polyvinylidene fluoride, or a copolymer of polyvinylidene fluoride.

7. A membrane electrode assembly for CO2 electroreduction according to claim 1, characterized in that, The thickness of the modified coating is 6-9 μm.

8. A method for preparing a membrane electrode assembly for CO2 electroreduction as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Slurry preparation: The amphoteric dopant and the binder are mixed in a solvent and dispersed to obtain a uniform composite slurry; S2. Modified film coating: The composite slurry is sprayed onto the surface of the base film to form a modified coating layer, which is then dried to obtain the composite film; S3. Membrane electrode assembly: CO2 reduction catalyst and oxygen evolution catalyst are sprayed onto the cathode side and anode side of the composite membrane, respectively, to assemble the membrane electrode assembly.

9. An application of a membrane electrode assembly for CO2 electroreduction as described in any one of claims 1-7, characterized in that, The membrane electrode assembly is used in a membrane electrode electrolysis cell at 1 A / cm 2 CO2 electroreduction reaction is carried out at a high current density.

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