Membrane electrode, preparation method thereof and high-temperature proton exchange membrane fuel cell

Abstract

The invention discloses a membrane electrode, a preparation method thereof and a high-temperature proton exchange membrane fuel cell. The membrane electrode comprises an anode catalyst layer, a sandwich-structure proton exchange membrane and a cathode catalyst layer, the anode catalyst layer and the cathode catalyst layer are respectively arranged on two sides of the sandwich-structure proton exchange membrane; the proton exchange membrane with the sandwich structure comprises an anode side membrane, a middle side membrane and a cathode side membrane which are sequentially stacked; wherein the anode side membrane and the cathode side membrane are respectively and independently selected from any one of a polybenzimidazole membrane, a polybenzimidazole and polyvinylpyrrolidone blended membrane and a polyvinylpyrrolidone and polyethersulfone blended membrane; the middle side membrane is a phosphoric acid doped polybenzimidazole membrane, and the phosphoric acid doping amount of the middle side membrane is 400-1000% in percentage by mass. According to the invention, the acid retention capability of the proton exchange membrane is greatly improved, the interface impedance between the catalyst layer and the proton exchange membrane is effectively reduced, and the service life of a fuel cell is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature proton exchange membrane fuel cells, and in particular to a membrane electrode, a preparation method thereof, and a high-temperature proton exchange membrane fuel cell. Background Art

[0002] High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have broad prospects in the fields of mobile power, vehicle and ship propulsion, etc. due to their advantages such as high reaction kinetic efficiency at operating temperatures above 120°C, strong impurity tolerance, and simplified water and heat management. In HT-PEMFCs, the proton exchange membrane is usually doped with high concentrations of phosphoric acid (PA) to maintain proton conductivity. However, the membrane electrode based on PA-doped polybenzimidazole (PBI) membrane in the existing technology has the following key problems:

[0003] (1) Severe loss of phosphoric acid: Traditional proton exchange membranes are prone to migration of PA to the catalytic layer (including the anode catalytic layer and the cathode catalytic layer) due to concentration difference at high temperatures, resulting in a decrease in the PA content in the proton exchange membrane, a decrease in proton conductivity, an increase in ohmic impedance, and a reduction in the energy conversion efficiency and service life of the fuel cell.

[0004] (2) Insufficient stability: The "acid flooding" phenomenon caused by PA migration leads to PA blocking the active sites of the catalyst layer and membrane swelling, further limiting the service life of the fuel cell. The "acid flooding" phenomenon refers to the excessive migration of PA into the catalyst layer and occupying the active sites of the catalyst, thereby affecting the normal progress of the electrochemical reaction.

[0005] (3) Large interfacial impedance: Conventional membrane electrodes are manufactured using the GDE (Gas Diffusion Electrode) process, which involves coating a catalyst layer on a gas diffusion layer and then pressing it together with a proton exchange membrane to form a membrane electrode. This GDE process (where the catalyst layer is coated on the gas diffusion layer) can easily lead to a physical gap between the catalyst layer and the proton exchange membrane, thereby increasing interfacial impedance and reducing electrochemical reaction efficiency.

[0006] Existing improvement proposals focus on cross-linking and modifying proton exchange membranes, developing high-acid-retention proton exchange membranes, designing new ionomers, and optimizing the three-phase interface of the catalyst layer. However, these efforts have limited success in regulating the distribution of PA in the membrane electrode and optimizing the interface. Therefore, a new membrane electrode structure and fabrication process are urgently needed to synergistically address these issues.

[0007] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art. Summary of the Invention

[0008] The purpose of the present invention is to provide a membrane electrode that adopts a sandwich-structured proton exchange membrane consisting of an anode side membrane, an intermediate side membrane, and a cathode side membrane to enhance the acid retention capacity of the proton exchange membrane and solve the problems of the current HT-PEMFC membrane electrode with a phosphoric acid-doped PBI system, such as rapid loss of phosphoric acid from the proton exchange membrane and large interface impedance between the catalyst layer and the proton exchange membrane.

[0009] To achieve the above objectives, the present invention provides a membrane electrode for a high-temperature proton exchange membrane fuel cell, comprising: an anode catalyst layer, a sandwich-structured proton exchange membrane, and a cathode catalyst layer; the anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the sandwich-structured proton exchange membrane; the sandwich-structured proton exchange membrane comprises an anode side membrane, an intermediate side membrane, and a cathode side membrane stacked in sequence; wherein,

[0010] The anode side membrane and the cathode side membrane are independently selected from any one of a polybenzimidazole membrane, a polybenzimidazole and polyvinyl pyrrolidone blended membrane, and a polyvinyl pyrrolidone and polyether sulfone blended membrane;

[0011] The middle side film is a phosphoric acid-doped polybenzimidazole film, and the phosphoric acid doping amount of the middle side film is 400% to 1000%, calculated in mass percentage.

[0012] Optionally, the thickness of the intermediate side membrane is 100 μm to 400 μm; the thickness of the anode side membrane is 10 μm to 20 μm; and the thickness of the cathode side membrane is 20 μm to 40 μm.

[0013] Optionally, the anode catalyst layer comprises a carbon-supported platinum-based catalyst and polytetrafluoroethylene, with a platinum loading of 0.05 mg / cm 2 ~0.5mg / cm 2 , the content of polytetrafluoroethylene is 5% to 40%, calculated by mass percentage.

[0014] Optionally, the cathode catalyst layer comprises a carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene, and polybenzimidazole, and the platinum loading is 0.05 mg / cm 2 ~0.3mg / cm 2 , the content of polytetrafluoroethylene is 1% to 20%, and the content of polybenzimidazole is 1% to 20%, calculated in mass percentage.

[0015] The present invention also provides a method for preparing the membrane electrode for a high-temperature proton exchange membrane fuel cell, characterized by comprising:

[0016] Step 1, providing an anode side membrane, a cathode side membrane, an intermediate side membrane, an anode gas diffusion layer, an anode sealing frame, a cathode gas diffusion layer, and a cathode sealing frame;

[0017] Step 2: dissolving the carbon-supported platinum-based catalyst and polytetrafluoroethylene in a first polar solvent to prepare an anode catalyst slurry; dissolving the carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene, and polybenzimidazole in a second polar solvent to prepare the cathode catalyst slurry;

[0018] Step 3: coating the anode catalyst slurry on one side of the anode side membrane to obtain an anode catalyst coated membrane; coating the cathode catalyst slurry on one side of the cathode side membrane to obtain a cathode catalyst coated membrane;

[0019] Step 4, coating a crosslinking agent on the other side surface of the anode catalyst coating membrane and the cathode catalyst coating membrane respectively; the other side surface of the anode catalyst coating membrane and the cathode catalyst coating membrane faces the middle side membrane;

[0020] In step 5, the anode gas diffusion layer, the anode sealing frame, the anode catalyst coating membrane coated with a crosslinker, the intermediate side membrane, the cathode catalyst coating membrane coated with a crosslinker, the cathode sealing frame, and the cathode gas diffusion layer are stacked in sequence, and the membrane electrode is prepared by a hot pressing process.

[0021] Optionally, in step 1, the method for preparing the intermediate side membrane comprises:

[0022] Tetraamine monomer and dicarboxylic acid monomer are added to polyphosphoric acid, heated for reaction, cast into a film, hydrolyzed and shaped, then immersed in phosphoric acid, and dried to obtain the intermediate side film; the molar ratio of the tetraamine monomer to the dicarboxylic acid monomer is 1:1.

[0023] Optionally, the coating method in step 3 and / or step 4 includes any one of ultrasonic spray coating or slit coating.

[0024] Optionally, in step 4, the cross-linking agent comprises any one of a silane coupling agent, dichlorodimethylsilane, dichlorodiphenylsilane, 1,4-dichlorobenzene, and 1,2-dichloroethane.

[0025] Optionally, in step 5, the process parameters of the hot pressing process include: hot pressing temperature of 120° C. to 200° C., hot pressing pressure of 0.2 MPa to 2.0 MPa, and hot pressing time of 5 min to 120 min.

[0026] The present invention also provides a high-temperature proton exchange membrane fuel cell, comprising the above-mentioned membrane electrode for a high-temperature proton exchange membrane fuel cell.

[0027] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0028] (1) The membrane electrode provided by the present invention comprises a sandwich-structured proton exchange membrane consisting of an anode side membrane, an intermediate side membrane, and a cathode side membrane, wherein the intermediate side membrane is a PA-doped wet membrane (with a high PA doping amount of 400% to 1000%), which serves as the PA storage body, while the anode side membrane and the cathode side membrane are both undoped PA dry membranes, which prevent the loss of PA to the outside of the sandwich-structured proton exchange membrane through their dense structure and chemical interaction with PA. The present invention finds that the sandwich-structured proton exchange membrane can significantly improve the acid retention capacity (PA retention capacity) of the proton exchange membrane: on the one hand, since both the anode side membrane and the cathode side membrane are dense structures, a physical barrier is formed, which effectively blocks the large-scale migration of PA from the middle side membrane to the outside of the sandwich-structured proton exchange membrane, thereby significantly reducing the loss rate of phosphoric acid in the proton exchange membrane; on the other hand, the highly cross-linked molecular chain structure inside the anode side membrane and the cathode side membrane can extend the diffusion path of PA, thereby inhibiting the loss of PA driven by concentration difference; on the other hand, when PA penetrates into the anode side membrane and the cathode side membrane, the nitrogen atoms and / or carbonyl oxygen in the membrane can anchor PA through hydrogen bonding, further reducing the rate of PA loss from the proton exchange membrane, thereby avoiding the "acid flooding" phenomenon, and further contributing to a significant improvement in the energy conversion efficiency and service life of the fuel cell.

[0029] (2) Furthermore, the present invention further enhances the acid retention capacity of the proton exchange membrane by regulating the thickness of the anode side membrane, the intermediate side membrane, and the cathode side membrane. The high thickness of the intermediate side membrane (100 μm to 400 μm) provides sufficient PA storage space; the thickness of the anode side membrane is 10 μm to 20 μm, and the thickness of the cathode side membrane is 20 μm to 40 μm, which takes into account the effect of slowing down the PA loss rate and maintaining a low ohmic loss.

[0030] (3) The preparation method of the membrane electrode provided by the present invention is different from the traditional GDE process. On the one hand, the present invention directly coats the catalyst layer on the surface of the anode side membrane and the cathode side membrane to form an anode catalyst coating membrane and a cathode catalyst coating membrane, so that the catalyst layer and the proton exchange membrane are tightly combined, effectively reducing the physical gap between the catalyst layer and the proton exchange membrane, thereby reducing the interface impedance; on the other hand, the present invention coats a cross-linking agent on the surface of the anode catalyst coating membrane and the cathode catalyst coating membrane facing the middle side membrane, and uses a hot pressing process to prepare the membrane electrode, so that the cross-linking structure in the membrane electrode further realizes stable interlayer bonding, thereby improving the durability of the membrane electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of a membrane electrode for a high-temperature proton exchange membrane fuel cell provided by the present invention.

[0032] Figure 2 This is a process flow chart of a method for preparing a membrane electrode for a high-temperature proton exchange membrane fuel cell provided by the present invention.

[0033] Figure 3 These are the membrane electrode polarization characteristic curves of the embodiments and comparative examples of the present invention.

[0034] Figure 4 These are the membrane electrode voltage decay curves of the embodiments of the present invention and the comparative example.

[0035] Description of the accompanying drawings:

[0036] Anode catalyst layer 10

[0037] Sandwich structure proton exchange membrane 20

[0038] Anode side membrane 21

[0039] Intermediate lateral membrane 22

[0040] Cathode side membrane 23

[0041] Cathode catalyst layer 30 DETAILED DESCRIPTION

[0042] The following is a further detailed description of a membrane electrode for a high-temperature proton exchange membrane fuel cell, a preparation method thereof, and a high-temperature proton exchange membrane fuel cell proposed by the present invention, in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention, so they have no technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0043] As described in the background art, in the prior art, membrane electrodes have problems such as severe loss of phosphoric acid, insufficient stability, and large interface impedance, which seriously affect the service life of fuel cells.

[0044] To solve the above problems, the present invention proposes a membrane electrode based on a sandwich structure proton exchange membrane, wherein the membrane electrode adopts a sandwich structure proton exchange membrane composed of an anode side membrane, an intermediate side membrane, and a cathode side membrane. By regulating the material, acid content, and thickness of the anode side membrane, the intermediate side membrane, and the cathode side membrane, the intermediate side membrane can provide sufficient PA storage capacity. The anode side membrane and the cathode side membrane form a dense structure and chemical interaction with the PA, effectively blocking the migration of PA, thereby improving the life of the fuel cell. Furthermore, the present invention proposes a method for preparing a membrane electrode based on a sandwich structure proton exchange membrane, first by directly coating a catalyst layer on one surface of the anode side membrane and the cathode side membrane, and coating a crosslinking agent on the other surface (the surface facing the intermediate side membrane), and then by a hot pressing process, the anode catalyst coating membrane coated with the crosslinking agent, the intermediate side membrane, and the cathode catalyst coating membrane coated with the crosslinking agent are tightly bonded to achieve the preparation of the membrane electrode, effectively reducing the physical gap between the catalyst layer and the proton exchange membrane, thereby reducing the interface impedance and further improving the service life of the fuel cell.

[0045] like Figure 1 As shown, the present invention provides a membrane electrode for a high-temperature proton exchange membrane fuel cell, comprising: an anode catalyst layer 10, a sandwich-structured proton exchange membrane 20, and a cathode catalyst layer 30; the anode catalyst layer 10 and the cathode catalyst layer 30 are respectively arranged on both sides of the sandwich-structured proton exchange membrane 20; the sandwich-structured proton exchange membrane 20 includes an anode side membrane 21, an intermediate side membrane 22, and a cathode side membrane 23 stacked in sequence; wherein:

[0046] The anode side membrane 21 and the cathode side membrane 23 are independently selected from any one of a polybenzimidazole (PBI) membrane, a polyvinylpyrrolidone (PVP) and PBI blend membrane, and a PVP and polyethersulfone (PES) blend membrane. The anode side membrane 21 and the cathode side membrane 23 are both undoped PA dry membranes. The above-mentioned types of membranes have excellent thermal stability (glass transition temperature> 400°C) and can maintain structural integrity at high-temperature proton exchange membrane fuel cell operating temperatures (above 120°C). More importantly, in the present invention, the roles played by the anode side membrane 21 and the cathode side membrane 23 include at least:

[0047] (1) Both the anode side membrane 21 and the cathode side membrane 23 have a dense structure, forming a physical barrier that can effectively prevent the PA in the middle side membrane 22 from migrating in large quantities toward the anode or cathode directions.

[0048] (2) Both the anode side membrane 21 and the cathode side membrane 23 have a highly cross-linked molecular chain structure. PA needs to bypass or penetrate these chain segments. This feature is conducive to extending the diffusion path of PA, thereby inhibiting the loss of PA under concentration drive.

[0049] (3) When part of the PA penetrates from the middle side membrane 22 to the anode side membrane 21 or the cathode side membrane 23, the imidazole ring in PBI and / or the carbonyl oxygen in PVP can form hydrogen bonds with the PA, playing the role of anchoring the PA. This chemical bonding effect allows the PA that migrates to this area to be dynamically captured, thereby further reducing the PA loss rate of the sandwich structure proton exchange membrane 20.

[0050] The intermediate side membrane 22 is a phosphoric acid-doped polybenzimidazole membrane, with a phosphoric acid doping level of 400% to 1000%. The PBI membrane contains a dense hydrogen bond network. The nitrogen atoms on each imidazole ring can form strong hydrogen bonds with PA, fixing the PA within the intermediate side membrane 22, thereby achieving a high PA doping level. During the membrane electrode hot pressing process, the anode side membrane 21, the intermediate side membrane 22, and the cathode side membrane 23 are stacked and combined under high temperature and high pressure (in this embodiment, the hot pressing temperature is 120°C to 200°C and the hot pressing pressure is 0.2 MPa to 2.0 MPa). Due to thermal diffusion and interlayer contact, the PA in the intermediate side membrane 22 partially penetrates into the anode side membrane 21 and the cathode side membrane 23, thereby forming a continuous proton conduction path in the anode side membrane 21, the intermediate side membrane 22, and the cathode side membrane 23, using the PA as a proton conduction carrier. To further enhance the acid retention capacity of the sandwich-structured proton exchange membrane 20, the present invention also coordinates the thicknesses of the anode-side membrane 21, the intermediate membrane 22, and the cathode-side membrane 23. In some embodiments, the thickness of the intermediate membrane 22 ranges from 100 μm to 400 μm; the thickness of the anode-side membrane 21 ranges from 10 μm to 20 μm; and the thickness of the cathode-side membrane 23 ranges from 20 μm to 40 μm. The thicker intermediate membrane 22 accommodates high concentrations of PA, providing ample pathways for proton transport. Compared to the intermediate membrane 22, the anode-side membrane 21 and the cathode-side membrane 23 are thinner. This is to achieve a balance between reducing the PA loss rate and maintaining low ohmic resistance. Research has found that the 10 μm to 20 μm thickness of the anode-side membrane 21 and the 20 μm to 40 μm thickness of the cathode-side membrane 23 effectively block PA migration due to their dense structure, extended PA diffusion pathways, and hydrogen bonding, while also maintaining low ohmic resistance due to their thin thickness. In addition, since the product of the anode reaction (H2 oxidation) is H + and electrons, and no water is directly generated, while O2 reduction reaction occurs at the cathode, and the product is water, which is easy to cause impact on the membrane structure, and liquid water may promote the dissolution of PA, causing PA to migrate more easily on the cathode side than on the anode side. Therefore, the thickness of the cathode side membrane 23 is set to be slightly larger than the thickness of the anode side membrane 21, so as to improve the acid retention capacity of the sandwich structure proton exchange membrane 20.

[0051] In some embodiments, the anode catalyst layer comprises a carbon-supported platinum-based catalyst and polytetrafluoroethylene, and the platinum loading is 0.05 mg / cm 2 ~0.5mg / cm 2 The content of polytetrafluoroethylene is 5% to 40% by mass. The carbon-supported platinum-based catalyst includes but is not limited to platinum-carbon (Pt / C) or platinum-ruthenium-carbon (PtRu / C).

[0052] In some embodiments, the cathode catalyst layer comprises a carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene (PTFE), and polybenzimidazole, with a platinum loading of 0.05 mg / cm 2 ~0.3mg / cm 2 The content of polytetrafluoroethylene is 1% to 20%, and the content of polybenzimidazole is 1% to 20%, calculated by mass percentage. The carbon-supported platinum-based alloy catalyst includes but is not limited to any one of platinum cobalt (PtCo), platinum iron (PtFe) or platinum copper (PtCu).

[0053] The present invention also provides a method for preparing a membrane electrode for a high-temperature proton exchange membrane fuel cell, such as Figure 2 As shown, the following steps are included:

[0054] Step 1: Provide an anode side membrane, a cathode side membrane, an intermediate side membrane, an anode gas diffusion layer, an anode sealing frame, a cathode gas diffusion layer, and a cathode sealing frame.

[0055] As an example, the anode side membrane and the cathode side membrane are both mPBI (modified PBI) membranes, which are commercially available from Shandong Zhengentropy Energy Technology Co., Ltd. In some embodiments, the preparation method of the intermediate side membrane comprises:

[0056] Tetraamine monomer and dicarboxylic acid monomer are added to polyphosphoric acid, heated for reaction, cast into a film, hydrolyzed and shaped, then immersed in phosphoric acid, and dried to obtain the intermediate side film; the molar ratio of the tetraamine monomer to the dicarboxylic acid monomer is 1:1.

[0057] In some embodiments, the heating reaction is carried out under nitrogen protection, at a temperature of 180°C to 220°C, for a duration of no less than 8 hours. After the heating reaction, the solution is degassed and degassing is performed before being cast onto a mold and formed by casting, doctor blade coating, or spin coating to form a gel film. The gel film is fully hydrolyzed at room temperature. During the hydrolysis process, water molecules penetrate between the PBI chains, promoting further recombination or hydrogen bond formation of incompletely cross-linked molecular chains, enhancing the mechanical strength of the film and achieving final shape. The hydrolyzed and finalized gel film is then immersed in 85 wt.% PA at 80°C to 100°C for 1 to 3 hours. After drying, a middle side film with a PA doping level of 400% to 1000% is obtained. For example, the tetraamine monomer is 3,3',4,4'-tetraaminobiphenyl, and the dicarboxylic acid monomer is isophthalic acid.

[0058] The anode and cathode gas diffusion layers are used to uniformly transport the reactant gases (anode: H2; cathode: O2 / air) from the bipolar plate flow channels to the surfaces of the anode and cathode catalyst-coated membranes, respectively. The anode and cathode sealing frames serve as edge sealing components for the membrane electrode, securing the layers within the membrane electrode, preventing reactant gas leakage, and providing structural support.

[0059] Step 2: dissolving the carbon-supported platinum-based catalyst and polytetrafluoroethylene in a first polar solvent to prepare an anode catalyst slurry; dissolving the carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene, and polybenzimidazole in a second polar solvent to prepare the cathode catalyst slurry.

[0060] As an example, the first polar solvent includes isopropyl alcohol and water, and the isopropyl alcohol and water can be mixed in a volume ratio of 1: 1. The second polar solvent includes dimethyl sulfoxide.

[0061] Step 3: coating the anode catalyst slurry on one side surface of the anode side membrane to obtain an anode catalyst coated membrane; coating the cathode catalyst slurry on one side surface of the cathode side membrane to obtain a cathode catalyst coated membrane.

[0062] After the treatment in step 3, an anode catalyst layer is formed on one surface of the anode side membrane, and a cathode catalyst layer is formed on one surface of the cathode side membrane. In some embodiments, the coating can be performed by ultrasonic spraying or slit coating. As an example, the anode catalyst slurry is uniformly coated on the surface of the anode side membrane by slit coating; the cathode catalyst slurry is uniformly coated on the surface of the cathode side membrane by slit coating; the platinum loading on one surface of the anode side membrane or the cathode side membrane can be controlled by controlling the coating speed or slurry flow rate of the slit coating.

[0063] Step 4: coating a cross-linking agent on the other side surfaces of the anode catalyst coating membrane and the cathode catalyst coating membrane respectively; the other side surfaces of the anode catalyst coating membrane and the cathode catalyst coating membrane face the middle side membrane.

[0064] The cross-linking agent acts directly on the interface between the anode / cathode catalyst coating membrane and the intermediate side membrane to enhance the interlayer bonding of the sandwich structure proton exchange membrane. In some embodiments, the cross-linking agent is a silane coupling agent KH560 (γ-glycidyloxypropyltrimethoxysilane) or a dichloro monomer (for example, dichlorodimethylsilane, dichlorodiphenylsilane, 1,4-dichlorobenzene, 1,2-dichloroethane, etc.). When the silane coupling agent KH560 is used as a cross-linking agent, the siloxane group (-Si-OCH3) in the KH560 molecule reacts with the hydroxyl group (-OH) on the surface of the intermediate side membrane (PBI membrane) to form a stable Si-O-Si covalent bond, which significantly improves the interlayer bonding strength. When a dichloromonomer is used as a cross-linking agent, for example, dichlorodimethylsilane (Cl2Si(CH3)2) can react with the hydroxyl groups (-OH) on the surface of the intermediate side membrane (PBI membrane) through its chlorine atoms to form a stable Si-O-Si bond, thereby enhancing the interlayer bonding between the anode / cathode catalyst coating membrane and the intermediate side membrane.

[0065] Step 5: stacking the anode catalyst coating membrane coated with a cross-linking agent, the intermediate side membrane, and the cathode catalyst coating membrane coated with a cross-linking agent in sequence, and preparing the membrane electrode by a hot pressing process.

[0066] When stacked, the surfaces of the anode catalyst coated membrane and the cathode catalyst coated membrane on which the crosslinking agent is coated face the middle side membrane. The process parameters of the hot pressing process include: hot pressing temperature of 120°C to 200°C, hot pressing pressure of 0.2Mpa to 2.0MPa, and hot pressing time of 5min to 120min. Under the process conditions, the high temperature causes the crosslinker to fully react chemically with the membrane material, the pressure ensures that the layers are tightly fitted to reduce the interfacial gap, and sufficient hot pressing time ensures that the crosslinking reaction is complete. Under the action of the hot pressing process parameters and the crosslinking agent, the membrane electrode forms a strong chemical crosslinking network through covalent bonds between the layers, significantly improving the structural durability of the membrane electrode while avoiding the risk of peeling caused by physical adsorption between the layers in the traditional GDE process, and the crosslinking process does not affect the proton conduction path inside the proton exchange membrane and the reaction active sites of the catalytic layer, thereby achieving performance stability under long-term operation of the fuel cell.

[0067] Unless otherwise specified, the chemicals used in the present invention are all conventional commercially available chemical reagents. These chemicals can be purchased from a number of chemical reagent suppliers and do not require special preparation or synthesis.

[0068] The present invention is further described in detail below with reference to the examples, but the present invention is not limited to the following specific examples.

[0069] Example

[0070] This embodiment provides a method for preparing a membrane electrode for a high-temperature proton exchange membrane fuel cell, comprising:

[0071] Step S101, providing an anode side membrane, a cathode side membrane, an anode gas diffusion layer, an anode sealing frame, a cathode gas diffusion layer, and a cathode sealing frame; the anode side membrane is an mPBI membrane not doped with PA, with a thickness of 15 μm, purchased from Shandong Zhengentropy Energy Technology Co., Ltd.; the cathode side membrane is an mPBI membrane not doped with PA, with a thickness of 30 μm, purchased from Shandong Zhengentropy Energy Technology Co., Ltd.

[0072] Step S102, preparing an anode catalyst coating membrane: preparing an anode catalyst slurry consisting of 50% Pt / C, isopropanol, water and PTFE, wherein the mass of the solid (Pt / C and PTFE) in the anode catalyst slurry accounts for 4% of the total mass of the anode catalyst slurry, and the volume ratio of isopropanol to water is 1:1, and uniformly dispersing the anode catalyst slurry by ultrasonication and homogenization; uniformly coating the uniformly dispersed anode catalyst slurry on one side surface of the anode side membrane by slit coating, and controlling the platinum loading to 0.2 mg / cm 2 , the extreme difference of platinum loading distribution is ≤±0.05mg / cm 2 The 50% Pt / C means that the mass of Pt in the catalyst accounts for 50% of the total mass of Pt and C carrier.

[0073] Step S103, preparing a cathode catalyst coating membrane: preparing a cathode catalyst slurry consisting of 60% PtCo / C, DMSO, PBI and PTFE, wherein the mass of the solids (PtCo / C, PBI and PTFE) in the cathode catalyst slurry accounts for 3% of the total mass of the cathode catalyst slurry, and uniformly dispersing the cathode catalyst slurry by ultrasonication and homogenization; uniformly coating the uniformly dispersed cathode catalyst slurry on one side surface of the cathode side membrane by slit coating, and controlling the platinum loading to 0.4 mg / cm 2 , platinum loading distribution range ≤±0.05mg / cm 2 The cathode catalyst coating membrane is obtained. The 60% PtCo / C means that the mass of PtCo in the catalyst accounts for 60% of the total mass of PtCo and C carrier.

[0074] Step S104: Preparation of the intermediate side membrane: Tetraamine monomer (3,3',4,4'-tetraaminobiphenyl) and dicarboxylic acid monomer (isophthalic acid) are added to polyphosphoric acid at a molar ratio of 1:1. Under nitrogen, the mixture is stirred and heated at 200°C for 10 hours. After degassing, the membrane is cast. The resulting gel membrane is left in air at room temperature for 1 hour to fully hydrolyze and set. The membrane is then immersed in 100°C phosphoric acid for 1 hour, removed, cut, and dried for later use.

[0075] Step S105, preparing a membrane electrode: a layer of silane coupling agent KH560 is coated on the other side of the anode catalyst coating membrane and the cathode catalyst coating membrane (the side not coated with the catalyst), and then the anode gas diffusion layer, the anode sealing frame, the anode catalyst coating membrane coated with a crosslinker, the intermediate side membrane, the cathode catalyst coating membrane coated with a crosslinker, the cathode sealing frame, and the cathode gas diffusion layer are stacked in a mold and placed in a hot press. The mold is hot-pressed at a hot pressing temperature of 160°C, a hot pressing pressure of 0.8MPa, and a hot pressing time of 60min to prepare a membrane electrode based on a sandwich structure proton exchange membrane. It is placed in a sealed bag and stored for later use.

[0076] The active area of ​​the prepared membrane electrode is 4 cm 2 The cathode gas diffusion layer and the anode gas diffusion layer have the same composition and structure, both of which are commercial TORRAYG gas diffusion layers with a thickness of 180μm. The anode catalyst layer is composed of 50% Pt / C catalyst and PTFE, with a Pt loading of 0.2mg / cm 2 The mass percentage of PTFE is 20%. The cathode catalyst layer is composed of 60% PtCo / C, PTFE and PBI, and the Pt loading is 0.4 mg / cm 2 The weight percentage of PTFE is 10%, and the weight percentage of PBI is 10%. In the sandwich structure proton exchange membrane, the weight of the silane coupling agent KH560 coated on the anode side membrane accounts for 4% of the anode side membrane weight; the weight of the silane coupling agent KH560 coated on the cathode side membrane accounts for 3% of the cathode side membrane weight. The middle side membrane is a phosphoric acid-doped PBI membrane with a PA doping content of 600% and a thickness of 200μm.

[0077] Comparative Example

[0078] The difference between this comparative example and the embodiment is that the proton exchange membrane in the membrane electrode of this comparative example is a single-layer phosphoric acid-doped PBI membrane, and its anode catalyst layer and cathode catalyst layer are prepared by the GDE method, that is, the catalyst layer is coated on the gas diffusion layer, specifically comprising:

[0079] Step S201 , providing a single-layer phosphoric acid-doped PBI membrane, an anode gas diffusion layer, an anode sealing frame, a cathode gas diffusion layer, and a cathode sealing frame; the preparation method of the single-layer phosphoric acid-doped PBI membrane is the same as the above-mentioned step S104 .

[0080] In step S202, an anode catalyst slurry is applied to one surface of the anode gas diffusion layer to form an anode catalyst layer; and a cathode catalyst slurry is applied to one surface of the cathode gas diffusion layer to form a cathode catalyst layer. The anode catalyst slurry is prepared in the same manner as the anode catalyst slurry in step S102; the cathode catalyst slurry is prepared in the same manner as the cathode catalyst slurry in step S103.

[0081] Step S203: Prepare a membrane electrode: An anode gas diffusion layer with an anode catalyst layer formed on its surface, an anode sealing frame, a single-layer phosphoric acid-doped PBI membrane, a cathode sealing frame, and a cathode gas diffusion layer with a cathode catalyst layer formed on its surface are stacked in sequence in a mold. The mold is then placed in a hot press and hot-pressed at a temperature of 160°C, a pressure of 0.8 MPa, and a time of 60 minutes to produce a membrane electrode based on a single-layer phosphoric acid-doped PBI membrane. The membrane electrode is then placed in a sealed bag and stored for future use.

[0082] With reference to GB / T 20042.5-2009, the membrane electrode materials obtained in the examples and comparative examples were fabricated into fuel cells for polarization curve testing. The specific operating conditions were as follows: a single cell operating temperature of 160°C, pure hydrogen feed for the anode, atmospheric pressure air feed for the cathode, and a stoichiometric ratio of the cathode feed to the anode feed of 2.5 and 1.5, respectively.

[0083] With reference to GB / T 20042.5-2009, the membrane electrode obtained in the embodiment and the comparative example were respectively made into fuel cells for impedance testing. The specific operating conditions were: the single cell operating temperature was 160°C, the anode was fed with pure hydrogen, the cathode was fed with atmospheric pressure air, the cathode feed and the anode feed had a stoichiometric ratio of 2.5 and 1.5, respectively, and the discharge current density was 0.5 A / cm 2 .

[0084] See also Figure 3 , the membrane electrode polarization characteristic curves of the embodiment of the present invention and the comparative example were measured. Figure 3 It can be seen that at 0.1A / cm 2 Under the conditions of 0.4A / cm 2 Under the conditions of 0.5A / cm 2Under the conditions of 0.602V and 0.587V, the membrane electrode voltages of the embodiment of the present invention and the comparative example were measured. In the polarization characteristic curve, at the same current density, the higher the membrane electrode voltage, the smaller the polarization loss of the corresponding fuel cell at the current density, and the better the overall performance (energy conversion efficiency, service life, etc.). In the low current density region (current density ≤ 0.1A / cm 2 ), the voltages of the membrane electrodes corresponding to the embodiment and the comparative example are basically the same, but as the current density increases, the voltage difference between the two becomes larger and larger. The larger ohmic polarization of the comparative example is the main reason for its lower voltage, which fully demonstrates that compared with the conventional membrane electrode prepared by the GDE process (comparative example), the membrane electrode based on the sandwich structure proton membrane prepared by the method of the present invention (embodiment) can reduce the interface impedance between the catalytic layer and the proton exchange membrane, thereby helping to reduce ohmic polarization loss, improve energy conversion efficiency, and help reduce internal heat and extend the service life of the membrane electrode.

[0085] See also Figure 4 , the membrane electrode voltage decay curves of the embodiment of the present invention and the comparative example were measured. Figure 4 It can be seen that after the fuel cell made of the membrane electrode of the embodiment and the comparative example has experienced 5 start-stop cycles and 50 hours of operation, the membrane electrode voltage decay rate of the comparative example is 0.85 mV / h, while the membrane electrode voltage decay rate of the embodiment is 0.24 mV / h. It can be seen that compared with the comparative example, the embodiment achieves a significant reduction in the voltage decay rate, which fully proves that compared with the traditional single-layer proton exchange membrane (comparative example), the sandwich-structured proton exchange membrane (embodiment) proposed in the present invention has a higher acid retention capacity and can effectively reduce the loss rate of PA, thereby helping to significantly improve the durability of the membrane electrode.

[0086] In summary, the present invention provides a membrane electrode for a high-temperature proton exchange membrane fuel cell, which includes a sandwich-structured proton exchange membrane consisting of an anode side membrane, an intermediate side membrane and a cathode side membrane. The intermediate side membrane is a doped PA wet membrane (high PA doping amount of 400% to 1000%) as the PA storage body, and the anode side membrane and the cathode side membrane are both undoped PA dry membranes. The sandwich-structured proton exchange membrane blocks PA migration through the dense structure of the anode side membrane and the cathode side membrane, extends the PA diffusion path to inhibit concentration-driven loss, and anchors PA through hydrogen bonds with nitrogen atoms and / or carbonyl oxygen in the membrane, thereby greatly improving the acid retention capacity; the acid retention capacity is further enhanced by regulating the membrane thickness, while taking into account the effect of maintaining low ohmic loss; the preparation method of the present invention is different from the traditional GDE process. The catalyst layer is directly coated on the surface of the anode side membrane and the cathode side membrane so that the catalyst layer is tightly bonded to the proton exchange membrane to reduce the interface impedance, and the interlayer stable bonding is achieved by coating a cross-linking agent and hot pressing process, thereby improving the durability of the membrane electrode.

[0087] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0088] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A membrane electrode, characterized in that include: An anode catalyst layer, a sandwich-structured proton exchange membrane, and a cathode catalyst layer; the anode catalyst layer and the cathode catalyst layer are respectively arranged on both sides of the sandwich-structured proton exchange membrane; The sandwich structure proton exchange membrane comprises an anode side membrane, an intermediate side membrane and a cathode side membrane stacked in sequence; wherein, The anode side membrane and the cathode side membrane are independently selected from any one of a polybenzimidazole membrane, a polybenzimidazole and polyvinyl pyrrolidone blended membrane, and a polyvinyl pyrrolidone and polyether sulfone blended membrane; The middle side film is a phosphoric acid-doped polybenzimidazole film, and the phosphoric acid doping amount of the middle side film is 400% to 1000%, calculated in mass percentage.

2. The membrane electrode according to claim 1, characterized in that The thickness of the intermediate side membrane is 100 μm to 400 μm; the thickness of the anode side membrane is 10 μm to 20 μm; and the thickness of the cathode side membrane is 20 μm to 40 μm.

3. The membrane electrode according to claim 1, characterized in that The anode catalyst layer comprises a carbon-supported platinum-based catalyst and polytetrafluoroethylene, wherein the platinum loading is 0.05 mg / cm2 to 0.5 mg / cm2 and the content of polytetrafluoroethylene is 5% to 40%, calculated in mass percentage.

4. The membrane electrode according to claim 1, wherein The cathode catalyst layer comprises a carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene, and polybenzimidazole, wherein the platinum loading is 0.05 mg / cm2 to 0.3 mg / cm2, the polytetrafluoroethylene content is 1% to 20%, and the polybenzimidazole content is 1% to 20%, calculated in mass percentage.

5. A method for preparing a membrane electrode according to any one of claims 1 to 4, characterized in that: include: Step 1, providing an anode side membrane, a cathode side membrane, an intermediate side membrane, an anode gas diffusion layer, an anode sealing frame, a cathode gas diffusion layer, and a cathode sealing frame; Step 2: dissolving the carbon-supported platinum-based catalyst and polytetrafluoroethylene in a first polar solvent to prepare an anode catalyst slurry; dissolving the carbon-supported platinum-based alloy catalyst, polytetrafluoroethylene, and polybenzimidazole in a second polar solvent to prepare the cathode catalyst slurry; Step 3: coating the anode catalyst slurry on one side of the anode side membrane to obtain an anode catalyst coated membrane; coating the cathode catalyst slurry on one side of the cathode side membrane to obtain a cathode catalyst coated membrane; Step 4, coating a crosslinking agent on the other side surface of the anode catalyst coating membrane and the cathode catalyst coating membrane respectively; the other side surface of the anode catalyst coating membrane and the cathode catalyst coating membrane faces the middle side membrane; In step 5, the anode gas diffusion layer, the anode sealing frame, the anode catalyst coating membrane coated with a crosslinker, the intermediate side membrane, the cathode catalyst coating membrane coated with a crosslinker, the cathode sealing frame, and the cathode gas diffusion layer are stacked in sequence, and the membrane electrode is prepared by a hot pressing process.

6. The method for preparing a membrane electrode according to claim 5, wherein: In step 1, the method for preparing the intermediate side membrane comprises: Adding tetraamine monomer and dicarboxylic acid monomer to polyphosphoric acid, heating for reaction, casting a film, hydrolyzing and shaping, then soaking in phosphoric acid, and drying to obtain the intermediate side film; The molar ratio of the tetraamine monomer to the dicarboxylic acid monomer is 1:

1.

7. The method for preparing a membrane electrode according to claim 5, wherein: The coating method in step 3 and / or step 4 includes any one of ultrasonic spray coating or slit coating.

8. The method for preparing a membrane electrode according to claim 5, wherein: In the step 4, the cross-linking agent comprises any one of a silane coupling agent, dichlorodimethylsilane, dichlorodiphenylsilane, 1,4-dichlorobenzene, and 1,2-dichloroethane.

9. The method for preparing a membrane electrode according to claim 5, wherein: In step 5, the process parameters of the hot pressing process include: hot pressing temperature of 120° C. to 200° C., hot pressing pressure of 0.2 MPa to 2.0 MPa, and hot pressing time of 5 min to 120 min.

10. A high-temperature proton exchange membrane fuel cell, characterized in that: The membrane electrode comprises the membrane electrode according to any one of claims 1 to 4.

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