Composite proton exchange membrane, preparation method thereof, membrane electrode and electrochemical device

Abstract

The invention discloses a composite proton exchange membrane and a preparation method thereof, a membrane electrode and an electrochemical device. The composite proton exchange membrane comprises a proton membrane and hydrate of solid acid dispersed in the proton membrane. A proper amount of solid acid hydrate is doped in the proton membrane, the solid acid hydrate plays a role of a micro-nano reservoir in the proton membrane, and the intelligent proton exchange membrane capable of automatically adjusting the water content according to environmental changes is constructed. When the water content of the anode side proton membrane is reduced, the hydrate of the solid acid can provide water molecules to the anode side proton membrane, and the wettability is kept; when the reverse osmosis water quantity of the cathode side is increased, the hydrate of the solid acid can absorb redundant water molecules to inhibit water logging of the anode side.

Description

Technical Field

[0001] This application relates to the field of proton exchange membrane technology, specifically to a composite proton exchange membrane and its preparation method, membrane electrode and electrochemical device. Background Technology

[0002] Electrochemical hydrogen pumps are a highly efficient hydrogen separation and purification technology that enables the purification and compression of hydrogen in a single device. Their structure is similar to that of a composite proton exchange membrane fuel cell (PEMFC), primarily consisting of key components such as the anode, cathode, and composite proton exchange membrane. Each electrode contains a gas diffusion layer (GDL) and a catalyst layer (CL), structures crucial for the effective separation and purification of hydrogen. During operation, a hydrogen-containing gas mixture is introduced to the anode side. After passing through the gas diffusion layer, the gas undergoes hydrogen oxidation (HOR) in the catalyst layer, where hydrogen molecules are oxidized into protons. These protons, under the influence of an external electric field, cross the composite proton exchange membrane and migrate to the cathode catalyst layer. At the cathode side, the protons participate in the hydrogen evolution reaction (HER), thereby achieving hydrogen separation and purification. As an advanced electrically driven hydrogen purification technology, electrochemical hydrogen pumps consume significantly less energy than traditional processes such as pressure swing adsorption (PSA) and cryogenic distillation. This technology can produce high-purity hydrogen at the product end, with a theoretical yield of up to 100%. Furthermore, the electrochemical hydrogen pump equipment offers significant advantages such as ease of maintenance and flexible operation, making it a promising candidate for widespread application in the hydrogen energy industry.

[0003] Water management of composite proton exchange membranes is crucial for maintaining stable and efficient hydrogen compression and separation purification. During proton transport, the electroosmotic drag effect causes protons to drag water molecules from the anode side to the cathode side as they pass through the membrane; this phenomenon is particularly pronounced at high current densities. When the hydrogen at the pump outlet (cathode) is unpressurized or at low pressure, water loss occurs rapidly on the anode side of the membrane electrode. Due to the low cathode hydrogen pressure, the amount of water reverse-osmotic to the anode is insufficient to meet the anode water loss, leading to gradual water loss from the catalyst layer and proton exchange membrane in the anode region. This results in a significant decrease in proton conductivity, a substantial increase in device internal resistance, and a sharp decline in performance. Conversely, when the hydrogen at the pump outlet (cathode) pressure is high, water rapidly reverse-osms from the cathode side to the anode, causing flooding of the anode catalyst layer, hindering hydrogen mass transfer at the anode, and significantly degrading device performance. Summary of the Invention

[0004] This application provides a composite proton exchange membrane and its preparation method, membrane electrode and electrochemical device, aiming to solve the problems of maintaining the wettability of the composite proton exchange membrane under high current density, preventing water loss on the anode side caused by electroosmotic dragging effect, and preventing the catalyst layer from being flooded by a large amount of reverse osmosis water under high-pressure hydrogen at the cathode.

[0005] This application provides a composite proton exchange membrane, comprising a proton membrane and a solid acid hydrate dispersed in the proton membrane.

[0006] Optionally, in some embodiments of this application, the hydrate of the solid acid includes HNb2(OH)2(PO4)3·H2O.

[0007] Optionally, in some embodiments of this application, the hydrate of the solid acid is a nanosheet.

[0008] Optionally, in some embodiments of this application, the content of the solid acid hydrate in the composite proton exchange membrane is 0.25wt%~5wt%.

[0009] Optionally, in some embodiments of this application, the content of the solid acid hydrate in the composite proton exchange membrane is 0.5wt%~1wt%.

[0010] Optionally, in some embodiments of this application, the material of the proton exchange membrane includes at least one of perfluorosulfonic acid resin, sulfonated polyethersulfone ketone resin, and sulfonated polyetherether ketone resin.

[0011] Accordingly, this application also provides a method for preparing a composite proton exchange membrane, used to prepare the above-mentioned composite proton exchange membrane, the method comprising: Preparation of solid acid hydrates using a hydrothermal method; A resin for preparing a proton exchange membrane is provided, wherein the hydrate of the solid acid and the resin are ball-milled and blended with a solvent to obtain a dispersion; The dispersion was prepared into a composite proton exchange membrane by solution casting.

[0012] This application also provides a membrane electrode comprising a composite proton exchange membrane, a cathode, and an anode. The cathode comprises a cathode catalytic layer, and the anode comprises an anode catalytic layer. The cathode catalytic layer and the anode catalytic layer are respectively disposed on opposite sides of the composite proton exchange membrane. The composite proton exchange membrane is the aforementioned composite proton exchange membrane or a composite proton exchange membrane prepared by the aforementioned method.

[0013] Optionally, in some embodiments of this application, the cathode further includes a cathode diffusion layer, and the anode further includes an anode diffusion layer. The cathode diffusion layer is disposed on the side of the cathode catalyst layer opposite to the composite proton exchange membrane, and the anode diffusion layer is disposed on the side of the anode catalyst layer opposite to the composite proton exchange membrane.

[0014] In addition, this application also provides an electrochemical device, which includes the above-described membrane electrode.

[0015] Optionally, in some embodiments of this application, the electrochemical device further includes a cathode current plate and an anode current plate, wherein the cathode current plate is disposed on the side of the cathode away from the composite proton exchange membrane, and the anode current plate is disposed on the side of the anode away from the composite proton exchange membrane.

[0016] Optionally, in some embodiments of this application, the electrochemical device is an electrochemical hydrogen pump.

[0017] By doping a suitable amount of solid acid hydrate into the proton exchange membrane (PEM), both the proton conductivity and the bound water content within the membrane can be increased. The solid acid hydrate acts as a "micro-nano reservoir" within the PEM, creating an intelligent proton exchange membrane capable of autonomously adjusting its water content according to environmental changes. When the water content on the anode side decreases, the solid acid hydrate provides water molecules to maintain its wettability; when the reverse osmosis flow on the cathode side increases, the solid acid hydrate absorbs excess water molecules, preventing flooding on the anode side. Based on these principles, the solid acid hydrate-doped PEM significantly improves the operational durability and efficiency of the electrochemical device. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an electrochemical hydrogen pump provided in an exemplary embodiment of this application; Figure 2 This is the X-ray diffraction pattern of HNb2(OH)2(PO4)3·H2O provided in step S1 of Example 1 of this application and NbOPO4 formed after calcination of HNb2(OH)2(PO4)3·H2O; Figure 3 This is a scanning electron microscope image of the HNb2(OH)2(PO4)3·H2O nanosheets in step S2 of Example 1 of this application; Figure 4 This is the attenuated total reflectance infrared spectrum of HNb2(OH)2(PO4)3·H2O provided in step S1 of Embodiment 1 of this application; Figure 5 These are graphs showing the proton conductivity test results of the proton exchange membranes provided in the various embodiments and comparative examples of this application; Figure 6 These are tensile stress-strain curves of the proton exchange membranes provided in the various embodiments and comparative examples of this application; Figure 7 These are graphs showing the test results of the hydrogen permeation resistance of the membrane electrodes provided in the various embodiments and comparative examples of this application; Figure 8 These are polarization curve test results of electrochemical hydrogen pumps made from membrane electrodes provided in the various embodiments and comparative examples of this application; Figure 9 This is a graph showing the stability test results of the electrochemical hydrogen pumps made from membrane electrodes provided in the various embodiments and comparative examples of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] This application provides a composite proton exchange membrane and its preparation method, membrane electrode, and electrochemical device. These are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in a range format; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0022] Please see Figure 1 This application provides an electrochemical device 100, which includes a membrane electrode 10. Typically, the membrane electrode 10 includes a proton exchange membrane 1, a cathode, and an anode, with the cathode and anode respectively disposed on opposite sides of the proton exchange membrane 1.

[0023] A proton exchange membrane (PEM), also known as a proton membrane or hydrogen ion exchange membrane, is a special type of ion-selective permeable membrane. A PEM is an electronic insulator but allows protons (H+) to pass through it. +() Free passage. In the membrane electrode 10, the proton exchange membrane 1 can play the role of conducting protons, isolating gases, and blocking electrons between the cathode and the anode.

[0024] In some embodiments of this application, the electrochemical device 100 is a proton exchange membrane fuel cell (PEMFC). The PEMFC converts hydrogen and oxygen into electrical energy through an electrochemical reaction. Specifically, hydrogen (H2) undergoes an oxidation reaction at the anode, where it is decomposed into positively charged protons (H+). + ) and electrons (e Protons pass through the proton exchange membrane to reach the cathode, while electrons are blocked by the proton exchange membrane and can only flow to the cathode through the external circuit. Oxygen (O2) combines with protons and electrons at the anode, undergoing a reduction reaction to produce water (H2O), thus completing the electrochemical cycle.

[0025] In some embodiments of this application, the electrochemical device 100 is an electrochemical hydrogen pump (EHP). The electrochemical hydrogen pump utilizes an electrochemical reaction to drive the directional migration of protons, thereby achieving the physical displacement and pressure increase of hydrogen gas. Specifically, hydrogen gas (H2) undergoes an oxidation reaction at the anode, where it is decomposed into positively charged protons (H+). + ) and electrons (e In this process, protons pass through the proton exchange membrane to reach the cathode, while electrons are blocked by the membrane and can only flow to the cathode through the external circuit. At the cathode, electrons combine with protons, undergoing a reduction reaction to regenerate hydrogen (H2). This completes the process of pumping hydrogen from the low-pressure end (anode side) to the high-pressure end (cathode side). Unlike traditional mechanical compressors, electrochemical hydrogen pumps achieve near-isothermal compression under ideal conditions, generating extremely low waste heat during the compression process, making them ideal for handling low-concentration or flammable hydrogen mixtures.

[0026] For some embodiments of this application, please refer to Figure 1 In the membrane electrode 10, the cathode includes a cathode catalytic layer 2, and the anode includes an anode catalytic layer 3. The cathode catalytic layer 2 and the anode catalytic layer 3 are respectively disposed on opposite sides of the proton exchange membrane 1. As an example, along the thickness direction of the proton exchange membrane 1, the proton exchange membrane 1 has a first side surface and a second side surface opposite to each other, wherein the cathode catalytic layer 2 is disposed on the first side surface, and the anode catalytic layer 3 is disposed on the second side surface. The cathode catalytic layer 2 is the main site for oxidation reactions on the membrane electrode 10, and the anode catalytic layer 3 is the main site for reduction reactions on the membrane electrode 10.

[0027] For some embodiments of this application, please refer to Figure 1In the membrane electrode 10, the cathode further includes a cathode diffusion layer 4, and the anode further includes an anode diffusion layer 5. The cathode diffusion layer 4 is disposed on the side of the cathode catalyst layer 2 facing away from the proton exchange membrane 1, and the anode diffusion layer 5 is disposed on the side of the anode catalyst layer 3 facing away from the proton exchange membrane 1. It can be seen that the cathode catalyst layer 2 is located between the cathode diffusion layer 4 and the proton exchange membrane 1, and the anode catalyst layer 3 is located between the anode diffusion layer 5 and the proton exchange membrane 1. The cathode diffusion layer 4 and the anode diffusion layer 5 provide transport channels for the reactant gases, allowing the reactant gases to rapidly diffuse to the cathode catalyst layer 2 and the anode catalyst layer 3 respectively to undergo electrochemical reactions. Simultaneously, the cathode diffusion layer 4 and the anode diffusion layer 5 serve as substrates responsible for collecting electrons generated by the cathode catalyst layer 2 and the anode catalyst layer 3, respectively.

[0028] For some embodiments of this application, please refer to Figure 1 The electrochemical device 100 further includes a cathode current plate 20 and an anode current plate 30. The cathode current plate 20 is disposed on the side of the cathode away from the proton exchange membrane 1, and the anode current plate 30 is disposed on the side of the anode away from the proton exchange membrane 1. When the cathode includes a cathode catalyst layer 2 and a cathode diffusion layer 4, and the anode includes an anode catalyst layer 3 and an anode diffusion layer 5, the cathode current plate 20 is disposed on the side of the cathode diffusion layer 4 away from the cathode catalyst layer 2, and the anode current plate 30 is disposed on the side of the anode diffusion layer 5 away from the anode catalyst layer 3.

[0029] This application also provides a composite proton exchange membrane, wherein the proton exchange membrane 1 is the composite proton exchange membrane. Specifically, the composite proton exchange membrane includes a proton membrane and a solid acid hydrate dispersed in the proton membrane.

[0030] As can be seen, the composite proton exchange membrane is based on the traditional proton exchange membrane and further incorporates solid acid hydrates, with the solid acid hydrates dispersed within the proton exchange membrane. Solid acid hydrates generally refer to strong acids or acidic substances in solid form, whose molecular structure incorporates a specific number of water molecules. For example, if the solid acid includes at least one of zirconium phosphate, zirconium tungstate, and niobium oxyphosphate, then the solid acid hydrate includes at least one of zirconium phosphate hydrate (Zr(HPO4)2·nH2O), zirconium tungstate hydrate, and niobium oxyphosphate hydrate (HNb2(OH)2(PO4)3·H2O).

[0031] Introducing solid acid hydrates into the proton exchange membrane offers several advantages. First, the solid acid hydrates provide an acidic environment, enhancing proton conduction and resulting in excellent proton conductivity in the composite proton exchange membrane. Second, the bound water in the solid acid hydrates is strongly bound, with water molecules directly bonded to metal ions through coordination bonds or embedded in the crystal lattice. This gives the solid acid hydrates strong water absorption and retention properties, facilitating the maintenance of the composite proton exchange membrane's moisture balance. Through this strategy, even under conditions of significant free water loss due to electroosmotic drag, the strongly bound water within the composite proton exchange membrane can still maintain the moisture required for proton transport at high current densities, ensuring effective proton conduction and addressing the issue of poor device stability at high current densities.

[0032] The core function of incorporating solid acid hydrates into proton exchange membranes is to construct an intelligent "micro-nano water reservoir." This is fundamentally different from simply adding water-retaining agents. Solid acid hydrates not only release water when the membrane dries (anode water loss) like traditional water-retaining materials, but also absorb excess water when there is too much water externally (cathode water flooding due to reverse osmosis), achieving dynamic water balance. This regulatory effect occurs within the membrane itself, a spontaneous behavior based on the hydrochemical potential gradient, requiring no external intervention, thus realizing "built-in" intelligent water management.

[0033] In summary, by doping a suitable amount of solid acid hydrate into the proton exchange membrane (PEM), both the proton conductivity and the bound water content within the PEM can be improved. The solid acid hydrate acts as a "micro-nano reservoir" within the PEM, creating an intelligent proton exchange membrane capable of autonomously adjusting its water content according to environmental changes. When the water content of the anode-side PEM decreases, the solid acid hydrate can provide water molecules to maintain its wettability; when the reverse osmosis flow on the cathode side increases, the solid acid hydrate can absorb excess water molecules, preventing flooding on the anode side. Based on these principles, the solid acid hydrate-doped PEM significantly improves the operational durability and efficiency of electrochemical devices (such as electrochemical hydrogen pumps).

[0034] By enhancing the water retention capacity and dimensional stability of the composite proton exchange membrane, the device can operate stably and efficiently for a long time under harsh conditions, thus extending its service life.

[0035] In some embodiments of this application, the solid acid hydrate includes HNb2(OH)2(PO4)3·H2O.

[0036] HNb2(OH)2(PO4)3·H2O is the hydrate of niobium oxyphosphate (NbOPO4). NbOPO4 can be obtained by dehydrating HNb2(OH)2(PO4)3·H2O through heat treatment. HNb2(OH)2(PO4)3·H2O is strongly acidic and highly hygroscopic. Its strong acidity can improve the proton conductivity of the proton exchange membrane, and its high content of bound water provides a strong intrinsic water-retention capacity for the proton exchange membrane.

[0037] To address the issue that proton exchange membranes are prone to water loss at high current densities, affecting the stable operation of electrochemical devices (such as electrochemical hydrogen pumps), this application proposes an embodiment that enhances the retention capacity of strongly bound water by introducing hydrophilic HNb2(OH)2(PO4)3·H2O into the proton exchange membrane. This results in a composite proton exchange membrane with excellent water retention performance for high current densities. Even at high current densities, proton conduction can still occur through the strongly bound water inside the composite proton exchange membrane, effectively preventing device performance degradation caused by dehydration of the composite proton exchange membrane.

[0038] HNb₂(OH)₂(PO₄)₃·H₂O, as a solid acid, not only provides a suitable acidic environment to enhance the proton conductivity of the composite proton exchange membrane, but also exhibits excellent water absorption and retention properties due to its unique physicochemical characteristics. These properties enable the composite proton exchange membrane to maintain effective proton transport through strongly bound water at high current densities, thereby ensuring the stability and efficient operation of the electrochemical device.

[0039] In addition, the introduction of HNb2(OH)2(PO4)3·H2O as an inorganic filler helps to improve the thermal stability and mechanical strength of the composite proton exchange membrane, which is crucial for maintaining the integrity and durability of the membrane under harsh operating conditions.

[0040] In some embodiments of this application, the solid acid hydrate is a nanosheet. Nanosheets possess a stable two-dimensional structure, and this two-dimensional nanosheet structure has a large specific surface area, enabling the construction of a more efficient hydrophilic network and proton transport pathway within the proton exchange membrane. Furthermore, it exhibits good chemical stability and can withstand the operating environment of the fuel cell. In addition, the nanosheet-shaped solid acid hydrate has good compatibility with the resin in the proton exchange membrane and can be uniformly dispersed within it.

[0041] In some embodiments of this application, the content of solid acid hydrate in the composite proton exchange membrane is 0.25 wt% to 5 wt%. Increasing the content of solid acid hydrate in the composite proton exchange membrane allows it to possess more strongly bound water to maintain its proton conductivity, making it suitable for applications with higher current densities. As examples, the content of solid acid hydrate in the composite proton exchange membrane is 0.25 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0042] In some embodiments of this application, the content of solid acid hydrate in the composite proton exchange membrane is 0.5 wt% to 1 wt%. In this case, the composite proton exchange membrane possesses both high proton conductivity and mechanical strength, as well as superior resistance to hydrogen permeation. As an example, the content of solid acid hydrate in the composite proton exchange membrane is 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%.

[0043] In some embodiments of this application, the proton exchange membrane material includes at least one selected from perfluorosulfonic acid resin (Nafion), sulfonated polyethersulfone resin (SPES), sulfonated polyaryletherketone resin (SPAEK), sulfonated polyethersulfoneketone resin (SPESK), and sulfonated polyetheretherketone resin (SPEEK). Perfluorosulfonic acid resin is an ionomer having a perfluorocarbon backbone and sulfonic acid side chains. Sulfonated polyethersulfoneketone resin is a polymer material obtained by chemically modifying the polyethersulfoneketone (PESK) backbone or side chains by introducing sulfonic acid groups. Sulfonated polyetheretherketone resin is a derivative obtained by introducing sulfonic acid groups (-SO3H) into polyetheretherketone (PEEK). The introduced sulfonic acid groups form hydrophilic microdomains, which are responsible for adsorbing water and transporting protons, and are key to the membrane's conductivity.

[0044] This application also provides a method for preparing a composite proton exchange membrane, used to prepare the aforementioned composite proton exchange membrane. The method for preparing the composite proton exchange membrane includes: S01. Preparation of solid acid hydrates by hydrothermal method; S02. Provide a resin for preparing a proton exchange membrane, wherein a dispersion is obtained by ball milling and mixing a solid acid hydrate and the resin with a solvent; S03. The dispersion is prepared into a composite proton exchange membrane by solution casting.

[0045] In some embodiments of this application, step S01 further includes: ultrasonically exfoliating the solid acid hydrate to prepare solid acid hydrate nanosheets, which are used to prepare composite proton exchange membranes.

[0046] In some embodiments of this application, the solid acid hydrate is HNb2(OH)2(PO4)3·H2O, and the raw materials used to prepare HNb2(OH)2(PO4)3·H2O can be niobium pentachloride (NbCl5) or niobium oxalate (Nb2(C2O4)5).

[0047] The following description is based on specific examples.

[0048] Example 1 Preparation of S1 and HNb2(OH)2(PO4)3·H2O: 1.34 g of ammonium niobate oxalate was dissolved in 28 mL of ultrapure water (DIH2O), and 6 mL of 98 wt% phosphoric acid (H3PO4) was added dropwise while stirring for 10 min. The mixture was transferred to a 50 mL autoclave and reacted at 110 °C for 16 h. The mixture was then centrifuged at 10000 rpm for 5 min to obtain a white solid. The solid was washed with DI H2O and ethanol until the supernatant was neutral, and then dried in an oven at 60 °C for 5 h to obtain HNb2(OH)2(PO4)3·H2O.

[0049] S2. Preparation of the composite proton exchange membrane. 5 mg of HNb₂(OH)₂(PO₄)₃·H₂O was added to 5 g of N,N-dimethylacetamide (DMAC) and sonicated for 60 min until dispersed, yielding an HNb₂(OH)₂(PO₄)₃·H₂O nanosheet dispersion. 1 g of SPEEK resin was dissolved in 4 g of DMAC to prepare a 20 wt% SPEEK resin solution. This solution was then poured into a ball mill jar along with the above dispersion and ball-milled for 12 h to obtain a highly dispersed HNb₂(OH)₂(PO₄)₃·H₂O / SPEEK dispersion. This dispersion was then poured into an 80 μm high mold using solution casting to form a 30 μm thick membrane, which was dried at 70 °C for 6 h to obtain a 0.5 wt% HNb₂(OH)₂(PO₄)₃·H₂O / SPEEK composite proton exchange membrane (denoted as NbPO / SPEEK composite proton exchange membrane).

[0050] S3. Catalyst Layer Preparation. The catalyst layer slurry was prepared according to the following formula: 0.5g Pt / C catalyst (60wt% Pt), 3.27g deionized water, and 0.63g D2020 ionomer solution. An additional 0.07g PTFE emulsion (60wt% PTFE) was added to the anode catalyst layer slurry to enhance hydrophobicity. The above components were sequentially added to a ball mill jar, along with 0.27g isopropanol as a dispersant. Initial mixing and dispersion were achieved by ball milling at 300 rpm for 3.5 hours. Then, 0.50g isopropanol was added to adjust the slurry rheology, and the slurry was ball milled again at 250 rpm for 0.5 hours to ensure uniformity and stability. The obtained slurry was coated onto a substrate using a blade coating method, with a wet film thickness controlled at 80μm. After treatment in a 70℃ infrared drying oven for 15 minutes, a platinum loading of 0.3mg Pt / cm³ was formed. 2 The catalyst layer.

[0051] S4. Fabrication of the membrane electrode. The prepared composite proton exchange membrane was cut into 4×4cm pieces. 2 The cathode and anode catalyst layers were cut into 2×2cm pieces. 2 Using a heat transfer method, under conditions of 155℃, 2MPa, and 2min, a 2×2cm... 2 Catalytic layer transferred on 4×4cm 2 A 0.5wt% NbPO / SPEEK membrane electrode is fabricated in the center of the composite proton exchange membrane.

[0052] Example 2 The difference between Example 2 and Example 1 is that the amount of HNb2(OH)2(PO4)3·H2O used in step S2 is 50 mg, and a 5 wt% NbPO / SPEEK composite proton exchange membrane is prepared.

[0053] Example 3 The difference between Example 3 and Example 1 is that the amount of HNb2(OH)2(PO4)3·H2O used in step S2 is 10mg, and a 1wt% NbPO / SPEEK composite proton exchange membrane is prepared.

[0054] Example 4 The difference between Example 4 and Example 1 is that zirconium phosphate hydrate (Zr(HPO4)2·nH2O) is used instead of HNb2(OH)2(PO4)3·H2O. In step S1, the preparation process of zirconium phosphate hydrate (Zr(HPO4)2·nH2O) is as follows: ZrOCl2, NaH2PO4 and NaF are mixed according to n(Zr 4+ ): n( (PO4) 3- ) : n(F -The mixture was ground and transferred to a hydrothermal reactor in a ratio of 1:4.5:0.3. After being stored at 120 °C for 24 h, it was soaked in hydrochloric acid and then dried to obtain Zr(HPO4)2·nH2O (denoted as ZrPO).

[0055] Example 5 The difference between Example 5 and Example 1 is that in step S2, Nafion is used to replace SPEEK, and a 0.5wt% NbPO / Nafion composite proton exchange membrane is prepared. Example 6 The difference between Example 6 and Example 1 is that in step S2, SPES is used instead of SPEEK to prepare a 0.5wt% NbPO / SPES composite proton exchange membrane.

[0056] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that step S1 is omitted, and HNb2(OH)2(PO4)3·H2O is omitted in step S2, so that the proton exchange membrane obtained is a SPEEK proton exchange membrane.

[0057] Comparative Example 2 The difference between Comparative Example 2 and Example 5 is that step S1 is omitted, and HNb2(OH)2(PO4)3·H2O is omitted in step S2, so that the proton exchange membrane obtained is a Nafion proton exchange membrane.

[0058] Comparative Example 3 The difference between Comparative Example 3 and Example 6 is that step S1 is omitted, and HNb2(OH)2(PO4)3·H2O is omitted in step S2, so that the proton exchange membrane obtained is an SPES proton exchange membrane.

[0059] Performance testing: 1. X-ray diffraction (XRD) analysis: The crystal structure of HNb2(OH)2(PO4)3·H2O prepared in step S1 of Example 1, and NbOPO4 obtained by calcining HNb2(OH)2(PO4)3·H2O at 800℃ under Ar atmosphere for 2h were analyzed. Please refer to the XRD pattern for details. Figure 2 .from Figure 2 As can be seen from the data, the peak position of HNb2(OH)2(PO4)3·H2O prepared in step S1 of Example 1 is basically consistent with the peak position of the standard sample (PDF#00-047-0151) of HNb2(OH)2(PO4)3·H2O. The peak position of NbOPO4 obtained after calcining HNb2(OH)2(PO4)3·H2O prepared in step S1 of Example 1 is basically consistent with the peak position of the standard sample (PDF#97-002-4110) of NbOPO4.

[0060] 2. Scanning Electron Microscopy (SEM) Analysis: The microstructure of the HNb2(OH)2(PO4)3·H2O nanosheets prepared by ultrasonication in step S2 of Example 1 was observed. Please refer to the SEM images for details. Figure 3 .

[0061] 3. Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR) Characterization: The HNb2(OH)2(PO4)3·H2O prepared in step S1 of Example 1 was characterized by ATR-IR. The results are shown in [link to example]. Figure 4 .from Figure 4 As can be seen, at 1000cm -1 Characteristic peaks of Nb-O appeared nearby, corresponding to the non-bridging vibrations of Nb-O; while at 500 cm⁻¹... -1 ~800cm -1 The characteristic peak of PO appeared, corresponding to the POP bridging bond.

[0062] 4. Proton Conductivity Test: The proton conductivity of the proton exchange membrane was tested using the method described in GB / T 20042.3-2022. At room temperature, a test sample with length a (cm), width b (cm), and thickness d (cm) was prepared. The sample was clamped, and 2 mL of deionized water was dropped onto the surface of the proton exchange membrane to maintain saturation. The high-frequency resistance R (Ω) was then obtained using a four-terminal AC impedance method. The proton conductivity σ (S / cm) was then calculated as a × R. -1 ×b -1 ×d -1 Please see the test results. Figure 5 .from Figure 5 The results show that, compared to SPEEK proton exchange membranes, the proton conductivity of composite proton exchange membranes formed by doping SPEEK proton exchange membranes with solid acid hydrates (NbPO4, ZrPO4) is improved. Furthermore, the proton conductivity of the composite proton exchange membrane increases further with increasing NbPO doping concentration. However, when the NbPO doping concentration reaches 5 wt%, the proton conductivity of the composite proton exchange membrane decreases. This is because excessive NbPO doping leads to NbPO aggregation, resulting in phase separation and thus affecting the proton conductivity of the composite proton exchange membrane. Similarly, doping Nafion and SPES proton exchange membranes with appropriate amounts of solid acid hydrates (NbPO4) also improves the proton conductivity of the composite proton exchange membranes. 5. Mechanical Performance Testing: The mechanical strength τ of the proton exchange membrane is obtained from the tensile stress-strain curve. It is calculated using the formula τ=F / (b·d), where τ (MPa) is the maximum tensile strength, F (N) is the maximum load, b (mm) is the sample width, and d (mm) is the sample thickness. Test results are available in [link to test results]. Figure 6 .from Figure 6 The results show that, compared to SPEEK proton exchange membranes, when SPEEK proton exchange membranes are doped with solid acid hydrates (NbPO4, ZrPO4) to form composite proton exchange membranes, the solid acid hydrates, acting as inorganic fillers, can improve the mechanical strength of the composite proton exchange membrane. However, as the doping amount of NbPO4 in the composite proton exchange membrane increases, the mechanical strength of the composite proton exchange membrane first increases and then decreases. Furthermore, when the NbPO4 doping amount in the composite proton exchange membrane reaches 5 wt%, the mechanical strength of the composite proton exchange membrane is actually worse than that of the SPEEK proton exchange membrane. This is because excessive NbPO4 doping leads to phase separation, thereby reducing the mechanical properties of the composite proton exchange membrane. Similarly, doping Nafion proton exchange membranes and SPES proton exchange membranes with appropriate amounts of solid acid hydrates (NbPO4) can also improve the mechanical strength of the composite proton exchange membranes.

[0063] 6. Hydrogen permeation resistance test: Following GB / T 20042.5-2024, the membrane electrode prepared in step S4 was assembled into an electrochemical hydrogen pump. High-purity N2 and H2, humidified with 100% RH, were introduced into the anode and cathode sides of the hydrogen pump, respectively. The H2 flow rate was controlled at 10 mL / min, and the N2 flow rate at 20 mL / min. The hydrogen side back pressure was controlled at 0-10 MPa. After the system stabilized, the anode was used as the working electrode, and the cathode as the counter electrode and reference electrode, connected to the electrochemical working system. A voltage range of 0-0.5V was applied, and the scan rate was 2 mV / s. The hydrogen permeation current change curve It over time was recorded. Subsequently, the hydrogen permeation current obtained under different pressures was plotted against the hydrogen side back pressure; the test results are shown in [link to test results]. Figure 7 .from Figure 7The results show that, compared to SPEEK proton exchange membranes, when SPEEK proton exchange membranes are doped with solid acid hydrates (NbPO4, ZrPO4) to form composite proton exchange membranes, the hydrogen permeation current density of the membrane electrode containing the composite proton exchange membrane decreases under the same cathode back pressure. This decrease in hydrogen permeation current density indicates that the hydrogen permeation resistance of the composite proton exchange membrane is improved. Furthermore, as the doping amount of NbPO in the composite proton exchange membrane increases, the hydrogen permeation current density of the membrane electrode containing the composite proton exchange membrane further decreases under the same cathode back pressure. However, when the doping amount of NbPO in the composite proton exchange membrane reaches 5 wt%, the hydrogen permeation current density of the membrane electrode containing the composite proton exchange membrane actually increases to a level greater than that of the membrane electrode containing the PEEK proton exchange membrane. This is because excessive NbPO doping leads to phase separation, which impairs the hydrogen permeation resistance of the composite proton exchange membrane. Similarly, doping Nafion proton exchange membranes with an appropriate amount of solid acid hydrate (NbPO) can also reduce the hydrogen permeation current density of the membrane electrode under the same cathode back pressure.

[0064] 7. Electrochemical Performance Testing: The membrane electrode prepared in step S4 was assembled into an electrochemical hydrogen pump for operating condition testing, and polarization curves and stability comparisons were performed. The test temperature was room temperature, with atmospheric pressure hydrogen gas flowing through the anode at a flow rate of 56 mL / min and a humidity of 100% RH. This experiment tested the polarization curves of different membrane electrodes at a range of 2 A / cm². 2 Stability tests were conducted at current densities, and the results are as follows: Figure 8 and Figure 9 As shown. From Figure 8 The results show that, compared to SPEEK proton exchange membranes, when a composite proton exchange membrane is formed by doping a SPEEK proton exchange membrane with solid acid hydrates (NbPO4, ZrPO4), the current density of the membrane electrode containing this composite proton exchange membrane decreases under the same cell pressure. Furthermore, when the NbPO doping amount in the composite proton exchange membrane increases from 0.5 wt% to 1 wt%, the current density of the membrane electrode further decreases, indicating that the electrochemical performance of the electrochemical hydrogen pump is improved. Figure 9 It can be seen that the cell pressure of the membrane electrode containing the SPEEK proton exchange membrane increases sharply after nearly 28 hours of operation, while the membrane electrode containing the composite proton exchange membrane can operate stably for at least 140 hours, and some can even operate stably for more than 300 hours, indicating that the stability of the electrochemical hydrogen pump is improved. Therefore, by enhancing the water retention capacity, proton conductivity and mechanical properties of the composite proton exchange membrane, devices (such as electrochemical hydrogen pumps) can operate stably and efficiently for a long time, extending their service life.

[0065] The foregoing has provided a detailed description of a composite proton exchange membrane, its preparation method, membrane electrode, and electrochemical device provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A composite proton exchange membrane, characterized in that, It includes a proton exchange membrane and a hydrate of a solid acid dispersed in the proton exchange membrane.

2. The composite proton exchange membrane according to claim 1, characterized in that, The solid acid hydrate includes HNb2(OH)2(PO4)3·H2O; and / or, the solid acid hydrate is a nanosheet.

3. The composite proton exchange membrane according to claim 1, characterized in that, In the composite proton exchange membrane, the content of the solid acid hydrate is 0.25wt%~5wt%.

4. The composite proton exchange membrane according to claim 3, characterized in that, In the composite proton exchange membrane, the content of the solid acid hydrate is 0.5wt%~1wt%.

5. The composite proton exchange membrane according to any one of claims 1 to 4, characterized in that, The proton exchange membrane is made of at least one of perfluorosulfonic acid resin, sulfonated polyethersulfone ketone resin, and sulfonated polyetherether ketone resin.

6. A method for preparing a composite proton exchange membrane, used to prepare the composite proton exchange membrane as described in any one of claims 1 to 5, characterized in that, include: Preparation of solid acid hydrates using a hydrothermal method; A resin for preparing a proton exchange membrane is provided, wherein the hydrate of the solid acid and the resin are ball-milled and blended with a solvent to obtain a dispersion; The dispersion was prepared into a composite proton exchange membrane by solution casting.

7. A membrane electrode, characterized in that, The device includes a composite proton exchange membrane, a cathode, and an anode. The cathode includes a cathode catalytic layer, and the anode includes an anode catalytic layer. The cathode catalytic layer and the anode catalytic layer are respectively disposed on opposite sides of the composite proton exchange membrane. The composite proton exchange membrane is the composite proton exchange membrane according to any one of claims 1 to 5 or the composite proton exchange membrane prepared by the method of claim 6.

8. The membrane electrode according to claim 7, characterized in that, The cathode further includes a cathode diffusion layer, and the anode further includes an anode diffusion layer. The cathode diffusion layer is disposed on the side of the cathode catalyst layer opposite to the composite proton exchange membrane, and the anode diffusion layer is disposed on the side of the anode catalyst layer opposite to the composite proton exchange membrane.

9. An electrochemical device, characterized in that, The electrochemical device includes the membrane electrode as described in claim 7 or 8.

10. The electrochemical device according to claim 9, characterized in that, The electrochemical device further includes a cathode current plate and an anode current plate, the cathode current plate being disposed on the side of the cathode facing away from the composite proton exchange membrane, and the anode current plate being disposed on the side of the anode facing away from the composite proton exchange membrane; and / or, The electrochemical device is an electrochemical hydrogen pump.

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