Enhanced integral membrane electrode, preparation method thereof and electrochemical reaction device

Abstract

The invention relates to an enhanced integral membrane electrode, a preparation method thereof and an electrochemical reaction device. The preparation method comprises the following steps: dissolving ion exchange resin in a solvent to obtain a polymer membrane casting solution; taking a polymer microporous membrane as a support body, and enabling the polymer membrane casting solution to enter micropores of the support body to form a wet ionic membrane; placing the wet ionic membrane on the surface of one catalytic electrode, and then placing the other catalytic electrode on the other side of the wet ionic membrane to obtain a wet component; and clamping and heating the wet component, and removing the solvent to obtain the enhanced integral membrane electrode. The invention also provides the enhanced integral membrane electrode obtained by the method. The technical scheme of the invention can overcome the defects of the membrane electrode in the prior art that the interface bonding between the catalyst layer and the membrane material is not firm, the interface mass transfer resistance is large, and the mechanical stability needs to be improved.

Description

Technical Field

[0001] This invention relates to an enhanced monolithic membrane electrode, its preparation method, and an electrochemical reaction device, belonging to the field of membrane electrode technology. Background Technology

[0002] With the rapid growth of the photovoltaic and wind power industries, large-scale consumption and efficient utilization of renewable clean energy are crucial. Hydrogen, as a sustainable clean energy source, boasts high energy density and its only byproduct after energy release is water. Hydrogen can serve as a long-term energy storage medium and can be transported over long distances via pipelines, potentially enabling large-scale energy conversion, storage, and efficient utilization at the grid level. Electrolysis of water to produce hydrogen, a key component of "green hydrogen," is constrained by the development of membrane electrode assembly (MEA) performance. MEA, a core component of electrochemical process devices, mainly consists of a catalyst layer, a gas diffusion layer, and membrane materials. It is the central site for matter and energy conversion in electrochemical processes, responsible for the transport of multiphase substances (such as water, hydrogen, oxygen, electrons, and ions) within the entire system. The performance and cost of MEA directly affect the overall cost, lifespan, and performance of the device. For example, in fuel cells, MEA costs account for approximately 30% of the total system cost. Furthermore, the gas-liquid-solid three-phase interface between the catalyst layer, gas diffusion layer, and membrane materials within the MEA, along with issues such as limited interfacial reactive sites and high mass transfer resistance, consistently hinders the development of electrochemical process devices.

[0003] Based on different scenarios and historical development, membrane electrode technology has evolved into three types: CCS (Catalyst Coated Substrate), CCM (Catalyst Coated Membrane), and ordered membrane electrodes. CCS type membrane electrodes are prepared by coating the catalyst onto a gas diffusion electrode and then bonding the catalytic electrode to the membrane material via hot pressing. Its advantages include a relatively mature preparation process, while its main disadvantages include low catalyst utilization and high mass transfer resistance at the catalyst-membrane interface and within the membrane. CCM type membrane electrodes are prepared by directly fabricating the catalyst on both sides of the membrane material through transfer printing or coating, followed by hot pressing the gas diffusion layer onto both sides of the membrane material. This process significantly alleviates the interface problem between the catalyst and the membrane material, thereby significantly reducing the membrane material thickness and catalyst dosage; however, because the bonding between the catalyst and the gas diffusion layer is not tight, and the interface problem near the membrane material has not been completely resolved, there is still considerable room for improvement in CCM type membrane electrodes.

[0004] Existing membrane electrode assemblies (MEAs) suffer from problems such as a perpetually disordered internal catalytic layer, low internal space utilization, and disordered three-phase interfaces. Developing MEAs with specific orientation structures, enabling ordered gas-liquid-solid three-phase transport, holds promise for improving the overall performance and stability of MEAs during use. Furthermore, overcoming the complexity of ordered MEA fabrication processes and simplifying preparation steps are crucial for reliable manufacturing and cost reduction, and are also essential issues that must be addressed in MEA development.

[0005] Furthermore, especially in the application scenario of alkaline anion exchange membrane (AEM) water electrolysis to produce hydrogen, membrane electrode assemblies face severe challenges that are completely different from those of traditional fuel cells (such as PEMFC).

[0006] The working principles of water electrolysis for hydrogen production and fuel cells determine their different mass transfer characteristics. In the water electrolysis process, hydrogen and oxygen are continuously and intensely generated in situ on the electrode surface. The nucleation, growth, and desorption processes of bubbles exert severe, cyclical mechanical shocks and shear stresses on the MEA (electrode-membrane interface). Crucially, the formation of microbubbles at the electrode / membrane interface generates extremely high local high pressure (potentially far exceeding the system operating pressure). This poses a severe challenge to the membrane's puncture resistance and the interfacial bonding strength between the catalyst layer and the membrane, easily leading to MEA mechanical failure (such as delamination or perforation). AEM (Alkaline Electrolysis Membrane) systems operate in strongly alkaline electrolytes and often use glassy polymers as membrane materials. Their mechanical properties and swelling behavior are fundamentally different from the mainstream acidic membranes such as Nafion used in fuel cells, and they require extremely high alkali resistance and stability. The "supersaturated dissolution-diffusion" phenomenon of hydrogen and oxygen in the electrolyte significantly increases the driving force for gas to pass through the membrane. The risks of gas crossover are far greater than those of fuel cells. This not only brings serious safety risks due to the local high pressure generated by the combined gas bubbles, but the crossover gases may also trigger the generation of a large number of active free radicals (such as ·OH), accelerating the chemical degradation of the polymer membrane. Existing MEA structures and preparation technologies, which are mainly optimized for fuel cells, have not fully considered these extreme mechanical stresses and chemical environments in AEM water electrolysis, and often exhibit rapid performance degradation and structural failure in practical applications.

[0007] In summary, existing membrane electrode assemblies (MEAs) technologies still face challenges in terms of interfacial bonding strength, mass transfer efficiency, and ease of fabrication. In particular, in emerging applications such as AEM water electrolysis for hydrogen production, effectively addressing the extreme mechanical stress caused by bubble impacts, suppressing severe gas cross-linking and its resulting chemical degradation, while ensuring a highly efficient and stable three-phase interface, are pressing technical problems that need to be solved in this field. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide an integral membrane electrode and its preparation method, which achieves a tight integration of the ion exchange membrane and the catalytic electrode through a simplified process, thereby improving the performance and long-term operational stability of the membrane electrode.

[0009] To achieve the above objectives, the present invention provides a method for preparing an enhanced monolithic membrane electrode, comprising the following steps:

[0010] Step 1: Dissolve the ion exchange resin in a solvent to obtain a polymer casting solution;

[0011] Step 2: Using a polymer microporous membrane as a support, the polymer casting solution enters the micropores of the support to form a wet ion membrane.

[0012] Step 3: Place the wet ion membrane on the surface of a catalytic electrode, and then place another catalytic electrode on the other side of the wet ion membrane to obtain a wet assembly;

[0013] Step 4: Clamp the wet assembly, heat it, and remove the solvent to obtain the enhanced monolithic membrane electrode.

[0014] According to a specific embodiment of the present invention, preferably, in step 2, the operation of allowing the polymer casting solution to enter the micropores of the support is performed by the following method: immersing the polymer microporous membrane in the polymer casting solution, then placing it in a vacuum environment (vacuum degree of 0.1 MPa-0.001 MPa) for 5-60 minutes, then restoring to normal pressure, and continuing immersion at normal pressure for another 5-60 minutes. This method ensures that the polymer casting solution fully and uniformly penetrates into all the micropores of the polymer microporous membrane, forming a wet ion exchange membrane.

[0015] According to a specific embodiment of the present invention, preferably, in step 3, after the catalytic electrode is combined with the wet ion membrane, it is necessary to remove the air bubbles on the contact surface between them, which can be done by means of ultrasound, rolling, vacuuming, etc.

[0016] According to a specific embodiment of the present invention, preferably, in step 4, the operation of clamping the wet component can be performed using a sealing gasket, the material of which includes, but is not limited to, polyphenylene sulfide, polyimide, polytetrafluoroethylene, etc.

[0017] According to a specific embodiment of the present invention, preferably, the content of ion exchange resin in the polymer casting solution is 1%-50% by weight, more preferably 5%-25%.

[0018] According to a specific embodiment of the present invention, preferably, the ion exchange resin is selected from one or more combinations of anion exchange resins, cation exchange resins, polybenzimidazole (PBI) resins, perfluorosulfonic acid resins, etc., more preferably anion exchange resins and / or perfluorosulfonic acid resins. The anion exchange resin preferably includes strongly basic anion exchange resins and / or weakly basic anion exchange resins, such as polyaryl piperidinium resins; the cation exchange resin preferably includes strongly acidic cation exchange resins and / or weakly acidic cation exchange resins, etc.

[0019] According to a specific embodiment of the present invention, preferably, the thickness of the polymer microporous membrane is 5-100 micrometers, more preferably 15-85 micrometers.

[0020] According to a specific embodiment of the present invention, preferably, the porosity of the polymer microporous membrane is 30%-90%; more preferably, it is 70%-80%.

[0021] According to a specific embodiment of the present invention, preferably, the material of the polymer microporous membrane is selected from one or more combinations of polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl chloride, polybenzimidazole, etc.

[0022] According to a specific embodiment of the present invention, the average pore size of the polymer microporous membrane has a significant impact on the wetting effect and the performance of the final membrane electrode. Preferably, the average pore size of the polymer microporous membrane is 0.02 µm to 0.5 µm. The selection of the pore size requires balancing two aspects: on the one hand, the pore size needs to be large enough to allow the polymer casting solution to spontaneously penetrate under a low energy barrier via capillary forces, and to ensure that the ion exchange resin can fill the pores to form a continuous ion transport network. Too small a pore size will significantly increase the wetting resistance, making complete filling difficult even under vacuum assistance. On the other hand, the pore size should not be too large, as excessively large pore sizes may lead to insufficient mechanical strength of the filled ion exchange membrane and may increase the risk of cross-permeation of gases (such as hydrogen and oxygen) in applications such as water electrolysis. The pore size range (0.02 µm to 0.5 µm) selected in this invention ensures effective wetting of the casting solution and formation of ion channels, while maintaining the membrane's excellent mechanical support and gas permeation inhibition capabilities. The depth of the micropores is the thickness of the membrane, and the present invention has limited it to a preferred range of 5-100 micrometers.

[0023] According to a specific embodiment of the present invention, preferably, the polymer microporous membrane is a polyethylene microporous membrane with a thickness of 5-100 micrometers; more preferably, the polymer microporous membrane is a polyethylene microporous membrane with a thickness of 25 micrometers. The polyethylene microporous membrane has good compatibility with the polymer casting solution and offers the following advantages: 1. Superior mechanical properties and durability: PE materials have high mechanical strength and toughness. In applications such as water electrolysis for hydrogen production, PE-reinforced membrane electrodes exhibit excellent puncture resistance and dimensional stability, effectively resisting severe bubble impacts, significantly improving device reliability, and achieving mechanical reinforcement; 2. Significant cost-effectiveness and environmental value: PE membranes (such as lithium-ion battery separators) have achieved large-scale industrial application at a low cost. Furthermore, using non-fluorinated PE materials offers better environmental friendliness.

[0024] According to a specific embodiment of the present invention, preferably, the catalytic electrode is a self-supporting structure; the self-supporting structure is a structure in which a catalyst (e.g., an electrochemical reduction catalyst or an electrochemical oxidation catalyst) is loaded on a conductive current collector; more preferably, the conductive current collector is selected from one or more combinations of foam metal, metal mesh, metal felt, etc.

[0025] According to a specific embodiment of the present invention, preferably, the catalyst is selected from one or more combinations of oxygen evolution catalyst, hydrogen evolution catalyst, hydroxide catalyst, oxygen reduction catalyst, carbon dioxide electroreduction catalyst, nitrogen electroreduction catalyst, nitrate electroreduction catalyst, etc.

[0026] According to a specific embodiment of the present invention, preferably, in step 4, during the clamping process, an appropriate pressure (preferably 1 MPa-3 MPa) is applied to the wet component for clamping, while heat curing is performed simultaneously. Preferably, the heating temperature is lower than the glass transition temperature of the ion exchange resin and the glass transition temperature of the polymer microporous membrane material; more preferably, the heating temperature is 60-95°C.

[0027] According to a specific embodiment of the present invention, preferably, the enhanced monolithic membrane electrode includes a chemical enhancement component, which is selected from free radical scavengers, recombining catalysts, or a combination of both.

[0028] According to a specific embodiment of the present invention, the chemical reinforcing component can be added using a pre-loading process, which allows the chemical reinforcing component to be more concentratedly distributed in the interface region between the membrane and the electrode. Preferably, the chemical reinforcing component is added as follows: before step 2, the chemical reinforcing component is loaded onto one or both surfaces of the polymer microporous membrane by coating. The coating method is preferably ultrasonic spraying; more preferably, the coating is performed by spraying (e.g., ultrasonic spraying) a slurry (with a concentration of 0.1%-5%) containing the chemical reinforcing component (such as nanocatalytic particles) and an appropriate amount of casting solution onto the surface of the polymer microporous membrane; subsequently, in step 2, the loaded polymer microporous membrane is impregnated with the polymer casting solution. Compared with direct addition to the casting solution, this pre-spraying method can achieve better results and more effective chemical protection and reinforcement at the interface.

[0029] According to a specific embodiment of the present invention, the chemical reinforcing component can be blended more easily. Preferably, in step 1, the chemical reinforcing component is directly added to the polymer casting solution for mixing, so that it is uniformly dispersed throughout the ion exchange membrane phase.

[0030] According to a specific embodiment of the present invention, the chemical enhancement component can be an effective substance proven in the fields of fuel cells and PEM water electrolysis. Preferably, the chemical enhancement component comprises cerium oxide and / or manganese oxide, wherein the cerium oxide can be selected from CeO2, CeO2, etc. x One or a combination of two of them, manganese oxide can be selected from one or a combination of two of MnO2 and MnOx.

[0031] According to a specific embodiment of the present invention, preferably, the chemical reinforcing component exists in the form of nanoparticles, and the free radical scavenger and the recombinant catalyst are combined in the form of a core-shell structure, a support-supported structure, or mutual doping, thereby obtaining a synergistic effect.

[0032] According to a specific embodiment of the present invention, preferably, the total loading of the chemically reinforcing components is 1 μg / cm², based on the surface area of ​​the polymer microporous membrane. 2 Up to 1000 μg / cm 2 By controlling the loading amount within the aforementioned range, the chemical enhancement effect can be achieved while avoiding adverse effects on ion conduction. More preferably, the total loading amount is 10 μg / cm³. 2 -100 μg / cm 2 .

[0033] Infusion is a commonly used process; however, it requires a strong external force field (such as high pressure) to force the solution into the micropores, or the creation of a vacuum environment after infusion to remove tiny air bubbles. During subsequent solvent removal, due to interfacial incompatibility between polymers in the solvent environment, the solution is prone to dewetting and phase separation, resulting in uneven distribution or aggregation of the polymeric polyelectrolyte within the pores, making it difficult to form a uniform and dense ion exchange membrane. This invention employs a wetting method based on rational design in interfacial chemistry. By optimizing the surface compatibility between porous polyethylene (PE) and other base membranes and ion exchange resins and other polymeric polyelectrolytes, spontaneous wetting of the PE base membrane is achieved by controlling the surface tension of the casting solution. This material compatibility-based wetting mechanism ensures that the solution can quickly and uniformly fill all micropores through capillary forces and stably form in situ during the drying process. During the impregnation process, vacuum-assisted methods can efficiently remove air from the pores (debubbling) to accelerate filling, rather than overcoming interfacial repulsion.

[0034] Steps 3 and 4 of this invention employ an in-situ solidification approach: first, the support is impregnated to form a "wet ion exchange membrane" (not yet solidified), then immediately combined with the catalytic electrodes on both sides to form a "wet assembly," and finally, it is heated and solidified under clamping conditions. This process allows the casting solution to fully penetrate the microporous structure of the catalytic electrodes before solidification. After solidification, the ion exchange resin forms a seamless, interpenetrating network of embedded connections (structural reinforcement) between the membrane and the electrodes. This integrated structure fundamentally eliminates the risk of interfacial delamination and greatly reduces interfacial mass transfer resistance. Compared to traditional membrane electrodes, the integral membrane electrode of this invention exhibits extremely low high-frequency impedance and significantly improved stability.

[0035] The present invention provides an enhanced monolithic membrane electrode, which is prepared by the above-described preparation method.

[0036] The ion exchange membrane in the enhanced integral membrane electrode of the present invention contains a porous support, which can enhance mechanical strength, toughness and puncture resistance; the ion exchange membrane forms a strong embedded connection with the self-supporting catalytic electrodes on both sides, which can achieve structural enhancement; in addition, when the membrane electrode contains chemical enhancement components such as free radical scavengers, it can not only reduce gas permeation, but also prevent free radical corrosion, thus constituting a chemical enhancement effect.

[0037] The present invention also provides an electrochemical reaction device, wherein the electrochemical reaction device includes the enhanced monolithic membrane electrode provided by the present invention.

[0038] According to a specific embodiment of the present invention, preferably, the electrochemical reaction device is used for one or more of the following: water electrolysis for hydrogen production, fuel cells, electrochemical synthesis of ammonia, electrochemical reduction of carbon dioxide, electrochemical reduction of nitrate, flow batteries, etc.

[0039] This invention provides an enhanced monolithic membrane electrode, its preparation method, and its application, which can overcome the defects of existing membrane electrodes (especially CCS and CCM types), such as weak bonding between the catalytic layer and the membrane material interface, large interfacial mass transfer resistance, and the need to improve mechanical stability.

[0040] Compared with existing technologies, this invention brings significant technical advantages and beneficial effects through a unique "three-enhancement" design, namely mechanical enhancement, structural enhancement and chemical enhancement.

[0041] 1) Mechanical Reinforcement (High Reliability): By introducing a polymer porous support (polymer microporous membrane) in situ into the ion exchange membrane, the mechanical strength, toughness, and puncture resistance of the membrane are significantly improved. In particular, during the electrolysis of water to produce hydrogen, due to the greatly improved mechanical properties, this reinforced structure can effectively resist the impact of continuously generated bubbles and the local high pressure of microbubbles, preventing membrane perforation and internal short circuits caused by extreme mechanical stress. This also effectively prevents physical damage caused by burrs on the electrode surface or abnormal operating conditions, greatly improving the mechanical reliability and service life of the membrane electrode.

[0042] 2) Enhanced Structure (Superior Electrochemical Performance and Stability): An integrated in-situ molding process ensures a robust embedded bond between the ion-exchange membrane and the self-supporting catalytic electrodes on both sides. The casting solution fully wets and penetrates the pore structure of the catalytic electrodes before curing. This seamless interface formed after curing effectively avoids delamination or gap problems that may occur with traditional hot-pressing processes, significantly reducing interfacial contact resistance and ion transport resistance. Simultaneously, this interpenetrating network structure provides extremely high interfacial adhesion strength, effectively resisting the strong shear forces and peel stresses generated by bubble desorption during water electrolysis, ensuring the overall stability of the membrane-electrode composite structure under long-term operating conditions.

[0043] 3) Chemical Enhancement (High Durability): In a preferred embodiment, by combining a free radical scavenger (such as cerium oxide) and a recombinant catalyst within the membrane layer or at the interface, harmful free radicals (such as ·OH, ·OOH, etc.) generated by gas permeation (such as cross-permeation of hydrogen and oxygen) can be synergistically eliminated. Given that the risk of hydrogen-oxygen cross-permeation due to gas supersaturation dissolution and diffusion during water electrolysis is significantly higher than in fuel cells, this enhancement mechanism is particularly important for AEM water electrolysis. This effectively inhibits the chemical attack and oxidative degradation of the polymer backbone by free radicals, thereby greatly improving the chemical durability of the membrane electrode under harsh electrochemical environments.

[0044] 4) Simplified preparation process and cost-effectiveness: The preparation process of this invention is clear, mainly including impregnation and curing steps. Even with the introduction of chemical reinforcing components (such as ultrasonic spraying), the overall process is still simple and efficient, easy to achieve large-scale production, and has good industrial application prospects and cost-effectiveness. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the enhanced monolithic membrane electrode structure.

[0046] Figure 2 This is a physical image of an enhanced monolithic membrane electrode.

[0047] Figure 3 Polarization curves of the enhanced membrane electrode and the conventional membrane electrode (1M KOH, 80°C).

[0048] Figure 4 The stress-strain curves are for an enhanced anion exchange membrane.

[0049] Figure 5 This is a comparison of the stability test results between the enhanced monolithic membrane electrode and the conventional membrane electrode.

[0050] Figure 6 The results show a comparison of the purity of hydrogen produced by water electrolysis between the enhanced integral membrane electrode and the traditional membrane electrode.

[0051] Figure 7 EIS impedance spectra before and after stability testing of traditional membrane electrodes.

[0052] Figure 8 EIS impedance spectra before and after stability testing of the enhanced monolithic membrane electrode.

[0053] Explanation of icon numbers:

[0054] 1. Anode; 2. Ion exchange membrane; 3. Cathode; 4. Ion exchange membrane transition layer. Detailed Implementation

[0055] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0056] Preparation Example 1: Preparation of Polyarylpiperidine Anion Exchange Resins

[0057] The poly(aryl piperidinium) anion exchange resin used in this embodiment of the invention is prepared as follows:

[0058] (1) Synthesis of polymer precursor: In a 500 mL three-necked flask equipped with a mechanical stirrer, a top condenser, and a nitrogen inlet, p-terphenyl (57.5 g, 0.25 mol), N-methyl-4-piperidone (28.3 g, 0.25 mol), and dichloroethane (500 mL) were added as solvents. Under nitrogen protection, the mixture was cooled to 0°C, and then trifluoromethanesulfonic acid (150 g, 1.0 mol) was slowly added dropwise. After the addition was complete, the reaction system was stirred at 25°C for 24 hours, and then the reaction was continued at 80°C for 48 hours. After the reaction was completed, the resulting viscous solution was slowly poured into methanol (3 L) for precipitation. The precipitate was collected by filtration and washed repeatedly with methanol and deionized water, and then dried in a vacuum oven at 80°C for 24 hours to obtain polymer precursor powder.

[0059] (2) Quaternization reaction: The dried polymer precursor powder (50 g) was dissolved in N-methylpyrrolidone (NMP) (450 mL). Then, methyl iodide (90 g, 0.63 mol) was added, and the mixture was reacted at 60°C for 48 hours under nitrogen protection. After the reaction was completed, the solution was cooled to room temperature and precipitated in ethyl acetate (3 L). The product was collected by filtration, washed several times with ethyl acetate, and then dried under vacuum at 60°C for 24 hours to obtain the target product: poly(aryl piperidinium) anion exchange resin powder.

[0060] Example 1

[0061] This embodiment provides a method for preparing a monolithic anion exchange membrane (AEM) water electrolysis membrane electrode, which includes:

[0062] 1. Preparation of casting solution

[0063] Polyarylpiperidine anion exchange resin powder was dissolved in dimethyl sulfoxide (DMSO) solvent and magnetically stirred at 60°C for 12 hours until the resin was completely dissolved, forming a homogeneous and transparent polymer casting solution with a mass fraction of 25 wt%. Before use, the casting solution was subjected to ultrasonic degassing treatment for 30 minutes.

[0064] 2. Wetting of the support

[0065] Select a polyethylene (PE) polymer microporous membrane with a thickness of 25 μm, an average porosity of 70%, and an average pore size of 0.2 µm, and cut it into a size of 10 cm × 10 cm;

[0066] Place the PE microporous membrane in a flat-bottomed tray, and then slowly pour in the casting solution prepared in step 1 until the microporous membrane is completely submerged. Move the entire device into a vacuum drying oven, evacuate to -0.08 MPa and maintain for 15 minutes, then restore to normal pressure and continue immersion at normal pressure for 60 minutes to ensure that the casting solution fully and uniformly penetrates into all the micropores of the PE microporous membrane to form a wet ion exchange membrane.

[0067] 3. Assembly of membrane electrodes

[0068] Anode (catalytic electrode A): NiFe bimetallic layered hydroxide (LDH) grown in situ on a 300 μm thick nickel fiber felt current collector is used as the catalyst, with a catalyst loading of approximately 3 mg / cm². 2 .

[0069] Cathode (catalytic electrode B): Prepared by uniformly coating a PtRu / C catalyst slurry (40 wt% Pt, 20 wt% Ru) onto carbon paper, with a catalyst loading of 1 mg / cm³. 2 .

[0070] The catalytic electrode A, which serves as the anode, is laid flat on a clean polytetrafluoroethylene plate. Then, the wet ion membrane prepared in step 2 is removed from the casting solution and placed on the surface of the catalyst layer of the anode. Subsequently, the cathode is placed on top of the wet ion membrane, and a soft rubber roller is used to perform bidirectional rolling on the back layer of the cathode with gentle pressure to completely remove residual air bubbles between the membrane and the electrode interface, thus forming a wet membrane electrode precursor.

[0071] 4. Curing and molding

[0072] The wet membrane electrode precursor obtained in step 3 was placed in a flatbed press and pressed under a pressure of 1 MPa while simultaneously curing at 80°C for 12 hours. During this process, the DMSO solvent was completely evaporated and removed, and the ion exchange resin was cured in situ at the interface of the catalytic electrode under the support of the PE microporous membrane framework. After cooling to room temperature, the integrated reinforced monolithic membrane electrode was obtained.

[0073] The structure of this enhanced monolithic membrane electrode is as follows: Figure 1 As shown, it includes an anode 1, an ion exchange membrane 2, a cathode 3, and an ion exchange membrane transition layer 4. The anode 1, the ion exchange membrane 2, and the cathode 3 form a sandwich structure, and the two ends of the ion exchange membrane 2 extend out from the sides of the anode 1 and the cathode 3 to form the ion exchange membrane transition layer 4.

[0074] Actual image of the enhanced monolithic membrane electrode is shown below. Figure 2 As shown.

[0075] 5. Performance Testing

[0076] The prepared enhanced monolithic membrane electrode (with nickel as the anode and platinum-carbon as the cathode) was assembled into a single-cell electrolyzer. Using 1M KOH as the electrolyte, the water electrolysis performance was tested at a test temperature of 80℃. The test results are as follows: Figure 3 As shown. By Figure 3 It can be seen that when using the enhanced monolithic membrane electrode of Example 1 for water electrolysis, the current density reaches as high as 3.1 A / cm³ when the voltage reaches 1.8 V. 2 .

[0077] EIS impedance spectroscopy analysis was performed on the single cells before and after the test, and the test results are as follows: Figure 8 As shown. By Figure 8 It can be seen that, before the test, the high-frequency impedance of the single cell fabricated with the enhanced monolithic membrane electrode device of Example 1 was only 0.0361 Ω·cm. 2 After testing, the high-frequency internal resistance did not increase significantly, remaining at only 0.0482 Ω·cm. 2 Furthermore, no short circuit was detected by open-circuit voltage testing before and after the test, demonstrating superior device durability and structural stability.

[0078] Example 2

[0079] This embodiment provides a method for preparing an enhanced monolithic membrane electrode containing chemically reinforcing components, which includes:

[0080] Repeat steps 1, 3, and 4 of Example 1, except that: Step 2, pretreatment and impregnation of the support:

[0081] 2a. Pretreatment of the support structure

[0082] Cerium oxide (CeO2) nanoparticles with an average particle size of 50 nm (as free radical scavengers and recombination catalysts) were dispersed in a small amount of 2 wt% polyarylpiperidine polymer casting solution (i.e. the polymer casting solution obtained in step 1 of Example 1), and a stable catalytic slurry was formed by ultrasonic treatment.

[0083] Using an ultrasonic spraying device, the catalytic slurry was uniformly sprayed onto both surfaces of the PE polymer microporous membrane in Example 1, with the total loading controlled at 100 μg / cm². 2 After spraying, allow it to dry briefly at 60°C.

[0084] 2b. Wetting of the support

[0085] The PE microporous membrane coated with cerium oxide nanoparticles was then vacuum-impregnated with casting solution according to step 2 in Example 1.

[0086] Performance testing

[0087] The membrane electrode prepared in Example 2 was subjected to the same electrochemical performance test as in Example 1, and its polarization curve performance was comparable to that of Example 1.

[0088] Figure 4 The stress-strain curve is shown for the enhanced anion exchange membrane prepared in Example 2. Figure 4 It can be seen that the enhanced anion exchange membrane of Example 2 has good mechanical properties.

[0089] The stability of the membrane electrode was tested, and the test results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the membrane electrode prepared in Example 2 has a performance of 1 A / cm 2 After running continuously for 300 hours at a constant current density, the electrolysis voltage decay rate was only 68 µV / h at the end of the test.

[0090] The purity of the anolyte gas produced by water electrolysis using a membrane electrode assembly was tested, and the test results are as follows: Figure 6 As shown. By Figure 6 It can be seen that the membrane electrode of Example 2 can achieve the oxygen purity of a thicker traditional membrane electrode (100 micrometers) with a thinner membrane thickness (30 micrometers) and control it within a high purity range (about 99.9%), demonstrating the effectiveness of the chemical enhancement strategy for the long-term safe operation of the membrane electrode.

[0091] Example 3

[0092] This embodiment provides a method for preparing a monolithic membrane electrode using a polytetrafluoroethylene (PTFE) microporous membrane as a support, comprising:

[0093] 1. Preparation of casting solution: Same as step 1 in Example 1.

[0094] 2. Impregnation of the support: Select a PTFE polymer microporous membrane with a thickness of 30 µm, an average porosity of 80%, and an average pore size of 0.2 µm, and cut it into a size of 10 cm × 10 cm. The subsequent impregnation operation is the same as step 2 in Example 1 to obtain a wet ion exchange membrane.

[0095] 3. Assembly and curing of membrane electrodes: The preparation, assembly, and curing processes of the anode and cathode are the same as steps 3 and 4 in Example 1.

[0096] 4. Performance Testing: The prepared membrane electrode was assembled into a single-cell electrolyzer and tested at 80℃ in 1M KOH electrolyte. When the voltage reached 1.85V, the current density reached 2.9 A / cm², showing excellent performance comparable to PE-based membranes, and exhibiting a lower long-term voltage decay rate due to the superior chemical stability of PTFE.

[0097] Example 4

[0098] This embodiment provides a method for preparing a monolithic membrane electrode containing a platinum group metal hydroxide catalyst (PtCo) as a chemical enhancement component.

[0099] 1. Preparation of catalytic slurry: 0.01 g of cerium dioxide (PtCo) nanoparticles with an average particle size of 4 nm (as a hydroxide catalyst) were dispersed in 5 g of 25 wt% polymer casting solution prepared in Example 1 and formed a stable catalytic slurry by ultrasonic treatment for 30 minutes.

[0100] 2. Pretreatment and impregnation of the support: Using an ultrasonic spraying device, the catalytic slurry prepared in step 1 was uniformly sprayed onto both surfaces of the PE polymer microporous membrane used in Example 1, with the total loading controlled at 150 µg / cm². After spraying, it was briefly dried at 60°C. Subsequently, the pretreated PE microporous membrane was impregnated with the casting solution under vacuum-atmospheric pressure according to the method in step 2 of Example 1.

[0101] 3. Assembly and curing: Subsequent steps are the same as steps 3 to 4 in Example 1.

[0102] 4. Performance Testing: The membrane electrode was subjected to stability testing. After continuous operation for 300 hours at a constant current density of 1 A / cm², the electrolysis voltage decay rate was only 65 µV / h, which is comparable to the results of Example 2 (using CeO2). This demonstrates that the recombinant catalyst that acts as a hydroxide can effectively improve the durability of the membrane electrode.

[0103] Comparative Example 1

[0104] This comparative example provides a method for preparing a membrane electrode using a conventional hot-pressing CCM method, which includes:

[0105] The 25% polyarylepiperidine polymer casting solution from Example 1 was coated onto a flat glass plate and dried at 80°C for 12 hours to prepare a homogeneous anion exchange membrane with a thickness of approximately 30 μm.

[0106] The anode and cathode from Example 1 were aligned with the anion exchange membrane prepared above, and then hot-pressed at 130°C and 2 MPa for 5 minutes to prepare the membrane electrode.

[0107] Performance testing

[0108] The membrane electrode prepared in Comparative Example 1 was subjected to the same electrochemical performance tests as in Example 1, and the test results are as follows: Figure 3 As shown. By Figure 3 It can be seen that when using the membrane electrode of Comparative Example 1 for water electrolysis, the current density is only 1.8 A / cm³ when the voltage reaches 1.8 V. 2 ; In performing 1 A / cm 2 After constant current stability testing, it was found that the voltage increased significantly, with a decay rate of 210 µV / h.

[0109] EIS impedance spectroscopy analysis was performed on the membrane electrode of Comparative Example 1 after polarization testing. The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that the ohmic impedance and charge transfer impedance of the membrane electrode in Comparative Example 1 are significantly increased, and obvious catalyst layer detachment and delamination are observed after disassembly.

[0110] By comparing Example 1 and Comparative Example 1, it can be seen that the in-situ curing integral molding method adopted in this invention, due to the formation of a tight embedded interface structure, greatly reduces the interface resistance, and its water electrolysis hydrogen production performance is far superior to that of traditional membrane electrodes, and it has superior stability.

[0111] The comparison between Example 2 and Comparative Example 1 shows that by introducing chemical reinforcing components at the interface of the supporting membrane, the chemical degradation of the membrane material can be effectively suppressed, gas cross-linking can be reduced, and the high stability and high gas purity of the reinforced membrane electrode under long-term operation can be guaranteed.

[0112] Comparative Example 2

[0113] This comparative example provides a method for preparing a membrane electrode, which includes:

[0114] Repeat all the steps of Example 1, but in step 4, “Cure and Mold”, set the temperature of the flatbed press to 150°C, which is higher than the melting point of the PE microporous membrane (approximately 130-140°C).

[0115] Test Results: During the heating and pressurization process, the PE microporous membrane melted, and its microporous structure was completely destroyed. Although the resulting membrane electrode appeared macroscopically monolithic, the supporting framework had failed microscopically, leading to severe dimensional shrinkage and deformation. During performance testing, this membrane electrode quickly experienced an internal short circuit and failed to function properly. This indicates that a curing temperature lower than the glass transition temperature or melting point of the support material and ion exchange resin can maintain the integrity of the reinforcing framework, which helps achieve the "structural reinforcement" effect of this invention.

Claims

1. A method for preparing an enhanced monolithic film electrode, comprising the following steps: Step 1: Dissolve the ion exchange resin in a solvent to obtain a polymer casting solution; Step 2: Using a polymer microporous membrane as a support, the polymer casting solution enters the micropores of the support to form a wet ion membrane. Step 3: Place the wet ion membrane on the surface of a catalytic electrode, and then place another catalytic electrode on the other side of the wet ion membrane to obtain a wet assembly; Step 4: Clamp the wet assembly, heat it, and remove the solvent to obtain the enhanced monolithic membrane electrode.

2. The preparation method according to claim 1, wherein, The content of ion exchange resin in the polymer casting solution is 1%-50% by weight, preferably 5%-25%; And / or, the ion exchange resin is selected from one or more combinations of anion exchange resin, cation exchange resin, polybenzimidazole resin, and perfluorosulfonic acid resin, preferably anion exchange resin and / or perfluorosulfonic acid resin.

3. The preparation method according to claim 1, wherein, The thickness of the polymer microporous membrane is 5-100 micrometers, preferably 15-85 micrometers; And / or, the porosity of the polymer microporous membrane is 30%-90%; And / or, the material of the polymer microporous membrane is selected from one or more combinations of polyethylene, polypropylene, polytetrafluoroethylene, polyvinyl chloride, and polybenzimidazole; And / or, the average pore size of the polymer microporous membrane is 0.02 µm to 0.5 µm; Preferably, the polymer microporous membrane is a polyethylene microporous membrane with a thickness of 5-100 micrometers.

4. The preparation method according to claim 1, wherein, The catalytic electrode has a self-supporting structure; The self-supporting structure is a structure in which an electrochemical catalyst is loaded on a conductive current collector; Preferably, the conductive current collector is selected from one or more of the following: metal foam, metal mesh, and metal felt. Preferably, the electrochemical catalyst is selected from one or more of the following: oxygen evolution catalyst, hydrogen evolution catalyst, hydroxide catalyst, oxygen reduction catalyst, carbon dioxide electroreduction catalyst, nitrogen electroreduction catalyst, and nitrate electroreduction catalyst.

5. The preparation method according to claim 1, wherein, The heating temperature is lower than the glass transition temperature of the ion exchange resin and the glass transition temperature of the polymer microporous membrane material. Preferably, the heating temperature is 60-95°C.

6. The preparation method according to claim 1, wherein, The enhanced monolithic membrane electrode contains a chemical enhancement component, which is selected from free radical scavengers, recombinant catalysts, or a combination of both.

7. The preparation method according to claim 6, wherein, The chemical reinforcing component is added by coating one or two surfaces of the polymer microporous membrane before step 2. Preferably, the coating method is ultrasonic spraying; More preferably, the coating is performed by spraying a slurry containing the chemically reinforcing components and an appropriate amount of casting solution onto the surface of the polymer microporous membrane.

8. The preparation method according to claim 6, wherein, The chemical reinforcement component is added as follows: in step 1, the chemical reinforcement component is directly added to the polymer casting solution for mixing.

9. The preparation method according to any one of claims 6-8, wherein, The chemical reinforcing component comprises cerium oxide and / or manganese oxide; Preferably, the chemical enhancement component exists in the form of nanoparticles, and the free radical scavenger and the recombinant catalyst are combined in the form of a core-shell structure, a support-supported structure, or mutual doping.

10. The preparation method according to claim 6, wherein, Based on the surface area of ​​the polymer microporous membrane, the total loading of the chemically reinforcing components is 1 μg / cm³. 2 Up to 1000 μg / cm 2 .

11. An enhanced monolithic membrane electrode, which is prepared by the preparation method according to any one of claims 1-10.

12. An electrochemical reaction apparatus, wherein, The electrochemical reaction device includes the enhanced monolithic membrane electrode as described in claim 11; Preferably, the electrochemical reaction device is used for one or more of the following: water electrolysis for hydrogen production, fuel cell, electrochemical ammonia synthesis, electrochemical reduction of carbon dioxide, electrochemical reduction of nitrate, and flow battery.

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