Proton exchange membrane, preparation method thereof and high-temperature fuel cell

Abstract

The invention relates to a proton exchange membrane, a preparation method thereof and a high-temperature fuel cell. The proton exchange membrane comprises a cathode phosphoric acid anchoring coating, a phosphoric acid doped proton exchange membrane and an anode phosphoric acid anchoring coating which are sequentially stacked, the cathode phosphoric acid anchoring coating and the anode phosphoric acid anchoring coating are both of a porous structure; the porosity of the cathode phosphoric acid anchoring coating and the anode phosphoric acid anchoring coating is 5%-15%; the pore diameter of the porous structure ranges from 1 nm to 130 nm. The cathode phosphoric acid anchoring coating and the anode phosphoric acid anchoring coating with porous structures are constructed on the two sides of the phosphoric acid doped PBI membrane, the coatings with the porous structures remarkably improve the content of free phosphoric acid in a local area and the connectivity between the free phosphoric acid, anchor the free phosphoric acid, prevent the free phosphoric acid from being lost towards a catalyst layer, improve the performance of a membrane electrode, and improve the performance of the membrane electrode. The proton exchange membrane life is prolonged.

Description

Technical Field

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

[0002] Proton exchange membrane fuel cells (PEMFCs) are a new energy technology considered extremely promising for automotive applications due to their low operating temperature, high power density, and rapid startup capabilities. However, lifespan is a major factor limiting the commercialization of PEMFCs. Currently, perfluorosulfonic acid ionomer membranes such as Nafion are the most widely used membranes in PEMFCs. Traditional Nafion membranes are susceptible to dehydration at temperatures above 95°C, significantly increasing their resistance. Consequently, most standard perfluorosulfonic acid-based membranes have a maximum operating temperature of 95°C, requiring additional cooling to maintain a reasonable operating temperature.

[0003] Increasing the operating temperature of fuel cells is a key approach to reducing the complexity and overall cost of fuel cell systems. Furthermore, the electrochemical reaction kinetics of proton exchange membrane fuel cells are directly related to the cell's operating temperature. Increasing the operating temperature can effectively improve the kinetics of these reactions. High-temperature operation can also effectively improve the resistance of the catalysts at the anode and cathode to poisoning by byproduct gases such as carbon monoxide and hydrogen sulfide. Furthermore, increasing the operating temperature of fuel cells vaporizes water produced at the cathode, facilitating water management.

[0004] Therefore, high operating temperatures for proton exchange membrane fuel cells have the advantages of improving the reaction kinetics of the cell's catalyst layer, reducing catalyst poisoning, and simplifying system water management. Therefore, increasing the operating temperature of fuel cells has become a development trend in fuel cells. However, due to the rapid attenuation of the proton conductivity of Nafion membranes due to dehydration at high temperatures, the performance of the proton exchange membranes decreases. This high temperature directly hinders the further application of Nafion membranes in high-temperature proton exchange membrane fuel cells.

[0005] To ensure stable operation of proton exchange membrane materials in high-temperature proton exchange membrane fuel cells, currently commercial high-temperature proton exchange membranes primarily utilize phosphoric acid-doped polybenzimidazole membranes. When the phosphoric acid doping level is too high, the polybenzimidazole membrane exhibits significant volume swelling, resulting in a dramatic degradation of mechanical properties. Conversely, at lower phosphoric acid doping levels, the membrane fails to provide adequate high-temperature proton conductivity. Furthermore, as the fuel cell operates, phosphoric acid dissolves, contaminating the catalyst layer, reducing the proton conductivity of the proton exchange membrane and degrading membrane electrode performance.

[0006] Therefore, how to improve the high-temperature stability of proton exchange membrane fuel cells, prevent phosphoric acid from dissolving out of phosphoric acid-doped polybenzimidazole membranes, and extend the service life of proton exchange membranes has become an urgent problem to be solved. Summary of the Invention

[0007] To solve the above technical problems, the present invention aims to provide a proton exchange membrane, a preparation method thereof, and a high-temperature fuel cell. The proton exchange membrane of the present invention has a porous coating layer, which can increase the free phosphate content in the local area and the connectivity between the free phosphates, anchor the free phosphate, and thus improve the membrane electrode performance.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a proton exchange membrane, comprising a cathode phosphate anchor coating, a phosphate-doped proton exchange membrane, and an anode phosphate anchor coating stacked in sequence; the cathode phosphate anchor coating and the anode phosphate anchor coating both have porous structures; the porosity of the cathode phosphate anchor coating and the anode phosphate anchor coating is 5%-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0010] The pore size range of the porous structure is 1 nm-130 nm, for example, it can be 1 nm, 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm or 130 nm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0011] The proton exchange membrane provided by the present invention constructs a cathode phosphate anchor coating and an anode phosphate anchor coating, and the cathode phosphate anchor coating and the anode phosphate anchor coating are both porous structures, and the porous structure optimizes the spatial distribution and dynamic stability of phosphoric acid through the synergistic effect of physical confinement and chemical anchoring. On the one hand, physical confinement refers to the use of a three-dimensional continuous pore network to construct a multi-level pore structure (micropore-mesopore-macroporous synergy), wherein the micropores (<2nm) anchor a single phosphoric acid molecule, and the physical limitations of the pore wall hinder its free diffusion; phosphoric acid can freely enter the mesopores and macropores, but it needs to overcome a higher energy barrier to escape through the narrow pore throat; hydrogen bond network construction. The coating with a porous structure significantly increases the free phosphate content in the local area and the connectivity between the free phosphate, anchors the free phosphate, prevents it from flowing to the catalytic layer, and improves the membrane electrode performance.

[0012] The two endpoint values of the "pore size range of the porous structure" of the anode and cathode phosphoric acid anchor coatings defined in the present invention refer to a range of values between the pore size of the smallest pore and the pore size of the largest pore in the coating.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] Preferably, the phosphoric acid-doped proton exchange membrane comprises a phosphoric acid-doped PBI membrane (polybenzimidazole membrane).

[0015] Preferably, the thickness of the cathode phosphate anchor coating is 0.5 μm-1.5 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0016] Preferably, the thickness of the anodic phosphate anchor coating is 0.5 μm-1 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0017] In the present invention, the thickness of the cathode phosphoric acid anchor coating is further controlled to be 0.5 μm-1.5 μm, and the thickness of the anode phosphoric acid anchor coating is controlled to be 0.5 μm-1 μm. The subsequent contact resistance of the phosphoric acid anchor coating will be affected. If the thickness of the cathode / anode phosphoric acid anchor coating is too thick, gas transmission will be reduced while impedance will be increased, resulting in poor membrane electrode performance; if the thickness of the cathode / anode phosphoric acid anchor coating is too thin, the anchoring effect of phosphoric acid is poor, resulting in poor membrane electrode durability.

[0018] Preferably, the raw material compositions of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating respectively include PBI, ionomer, porous anchor agent and free radical quencher.

[0019] The present invention adds a porous anchoring agent and a free radical quencher to the cathode phosphate anchor coating and the anode phosphate anchor coating. On the one hand, PBI and the porous anchoring agent help to reduce the interfacial reaction between the proton exchange membrane and the catalytic layer, reduce the contact resistance and improve the membrane electrode performance. On the other hand, the free radical scavenger can in situ capture the free radicals generated during the operation of the fuel cell, greatly alleviating the attack of the free radicals on the proton exchange membrane, improving the chemical stability of the membrane electrode, and enhancing the life of the proton exchange membrane. The two work together to achieve the improvement of the electrochemical stability and long-cycle performance of the proton exchange membrane.

[0020] The PBI in the phosphate anchor coating of the present invention can reduce the interface effect between the coating and the PBI membrane and enhance the bonding strength of the coating and the PBI membrane. The ionomer can reduce the interface effect between the coating and the catalytic layer, reduce resistance and conduct protons at the same time.

[0021] Preferably, the porous anchor comprises a porous carbon material.

[0022] Preferably, the porous carbon material includes any one or a combination of at least two of CNovel MH, multi-walled carbon nanotubes, CMK-3, CMK-5, OMC-100, N-doped ordered mesoporous carbon or MOF-derived ordered mesoporous carbon. Typical but non-limiting combinations include a combination of CNovel MH and CMK-3, a combination of CMK-3 and CMK-5, a combination of N-doped ordered mesoporous carbon and MOF-derived ordered mesoporous carbon, a combination of OMC-100 and N-doped ordered mesoporous carbon, a combination of CNovel MH, OMC-100, N-doped ordered mesoporous carbon and MOF-derived ordered mesoporous carbon, and a combination of CNovel MH, CMK-3, CMK-5, OMC-100, N-doped ordered mesoporous carbon and MOF-derived ordered mesoporous carbon.

[0023] Preferably, the porous anchoring agent further includes any one or a combination of at least two of SBA-15, porous silica, titania nanotubes or porous alumina. Typical but non-limiting combinations include a combination of SBA-15 and porous silica, a combination of porous silica and titania nanotubes, a combination of titania nanotubes and porous alumina, a combination of SBA-15 and porous alumina, and a combination of SBA-15, porous silica, titania nanotubes and porous alumina.

[0024] The present invention can also additionally add a porous anchoring agent, which can not only play a moisturizing role in the proton exchange membrane, but also form multiple hydrogen bonds with the P-OH groups of phosphoric acid due to its surface hydroxyl (-OH) or carboxyl (-COOH) groups. By chemically anchoring the free phosphoric acid, it prevents it from flowing into the catalyst layer, maintains the stability of the reaction interface, and thus improves the performance of the high-temperature proton exchange membrane fuel cell.

[0025] Preferably, the free radical quencher comprises any one or a combination of at least two of manganese dioxide, cerium dioxide or cobalt trioxide. Typical but non-limiting combinations include a combination of manganese dioxide and cerium dioxide, a combination of cerium dioxide and cobalt trioxide, a combination of manganese dioxide and cobalt trioxide, and a combination of manganese dioxide, cerium dioxide and cobalt trioxide.

[0026] Preferably, the ionomer comprises sulfonated PVDF and / or sulfonated PEEK.

[0027] In a second aspect, the present invention provides a method for preparing a proton exchange membrane as described in the first aspect, the preparation method comprising the following steps:

[0028] (1) uniformly mixing water, a dispersant, a PBI solution, an ionomer, a porous anchoring agent, and a free radical quencher to obtain a phosphate anchoring coating slurry;

[0029] (2) coating the phosphate anchor coating slurry obtained in step (1) on both sides of the phosphate-doped proton exchange membrane, and drying the phosphate anchor coating slurry to obtain the proton exchange membrane.

[0030] The preparation method of the present invention is simple and efficient, suitable for large-scale production, and can accurately control the thickness and uniformity of the coating while retaining the intrinsic performance of the phosphoric acid-doped proton exchange membrane. It does not change the internal structure and function of the membrane layer. The coating only acts on the membrane surface and does not interfere with the molecular chain arrangement of the proton exchange membrane, retaining its intrinsic mechanical strength. In addition, the coating confines phosphoric acid to the catalyst layer-electrolyte interface through a porous structure, avoiding membrane swelling caused by "phosphoric acid overload" caused by bulk doping. The coating method achieves precise management of phosphoric acid through the synergy of interface functionalization and structural controllability, significantly improving the overall efficiency while maintaining the performance of the matrix. Compared with the doping method, its advantages in engineering applications are reflected in higher design freedom, better long-term stability and lower scale costs. The present invention avoids the degradation of the proton membrane matrix performance through precise interface engineering preparation.

[0031] Preferably, the mass ratio of PBI solute and ionomer in the water, dispersant and PBI solution is 1:(2-10):(0.5-0.8):(0.05-0.1), for example, it can be 1:2:0.5:0.05, 1:3:0.6:0.05, 1:4:0.5:0.05, 1:2:0.6:0.05, 1:5:0.5:0.1, 1:6:0.5:0.05, 1: :2:0.5:0.06, 1:3:0.5:0.07, 1:4:0.5:0.08, 1:5:0.5:0.09, 1:6:0.5:0.1, 1:7:0.6:0.05, 1:8:0.5:0.05, 1:9:0.6:0.05, or 1:10:0.8:0.1, but not limited to the listed values, other unlisted values within the numerical range are also applicable.

[0032] Preferably, the mass fraction of the PBI solution is 5 wt%-20 wt%, for example, it can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0033] Preferably, the mixing method in step (1) includes ultrasonic dispersion.

[0034] Preferably, the mass ratio of water, porous anchor and free radical quencher is 1:(0.28-0.75):(0.1-0.25), for example, it can be 1:0.28:0.1, 1:0.3:0.1, 1:0.3:0.2, 1:0.4:0.1, 1:0.4:0.25, 1:0.5:0.1, 1:0.5:0.2, 1:0.6:0.1, 1:0.6:0.15, 1:0.7:0.15, 1:0.7:0.25 or 1:0.75:0.25, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0035] The present invention further controls the mass ratio of water, porous anchoring agent and free radical quencher to be 1:(0.28-0.75):(0.1-0.25). If the amount of porous anchoring agent added is too little, the phosphate anchoring effect will be poor, resulting in poor membrane electrode durability; if the amount of free radical quencher added is too little, free radicals in the membrane electrode will attack the proton membrane more, resulting in poor membrane electrode durability; if the amount of porous anchoring agent and free radical quencher is too much, the impedance will be further increased, thereby reducing membrane electrode performance.

[0036] Preferably, the dispersant comprises any one of ethanol, isopropanol, DMAC (dimethylacetamide), NMP (N-methylpyrrolidone) or DMSO (dimethyl sulfoxide) or a combination of at least two thereof. Typical but non-limiting combinations include a combination of ethanol and isopropanol, a combination of DMAC and NMP, a combination of NMP and DMSO, a combination of ethanol, isopropanol and DMSO, a combination of ethanol, DMAC, NMP and DMSO, a combination of DMAC, NMP and DMSO, and a combination of ethanol, isopropanol, DMAC, NMP and DMSO.

[0037] Preferably, the coating method includes any one or a combination of at least two of spraying, blade coating or slot coating. Typical but non-limiting combinations include a combination of spraying and blade coating, a combination of blade coating and slot coating, a combination of spraying and slot coating, and a combination of spraying, blade coating and slot coating.

[0038] The phosphoric acid-doped proton exchange membrane used in the present invention can be prepared by methods in the prior art. For example, the preparation method of the phosphoric acid-doped proton exchange membrane includes: boiling the PBI membrane with deionized water for 1 hour to 3 hours to remove impurities in the membrane, drying, and immersing the dried PBI membrane in a 65wt%-85wt% phosphoric acid solution for 15 hours to 20 hours at a temperature of 50°C to 90°C to obtain a phosphoric acid-doped proton exchange membrane.

[0039] The mass concentration of the phosphoric acid solution is 65wt%-85wt%, for example, it can be 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt% or 85wt%, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0040] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0041] (I) The PBI membrane is boiled in deionized water for 1-3 hours to remove impurities in the membrane, dried, and then immersed in a 65wt%-85wt% phosphoric acid solution for 15-20 hours at a temperature of 50°C-90°C to obtain a phosphoric acid-doped proton exchange membrane;

[0042] (II) mixing water, dispersant, PBI solution and ionomer in a mass ratio of 1:(2-10):(0.5-0.8):(0.05-0.1), and ultrasonically dispersing the mixture at a power of 300W-1000W for 1h-3h; adding a porous anchoring agent and a free radical quencher, and ultrasonically dispersing the mixture at a power of 300W-1000W for 5h-12h to obtain a phosphate anchor coating slurry, wherein the mass ratio of water, porous anchoring agent and free radical quencher is 1:(0.28-0.75):(0.1-0.25);

[0043] (III) applying the phosphate anchor coating slurry obtained in step (II) to both sides of the phosphate-doped proton exchange membrane obtained in step (I), and drying at 60° C.-90° C. for 5 min-20 min to obtain the proton exchange membrane.

[0044] In a third aspect, the present invention provides a high-temperature fuel cell, comprising the proton exchange membrane described in the first aspect.

[0045] The high-temperature fuel cell provided by the present invention has a long cycle life and stable chemical properties, and achieves higher energy conversion efficiency.

[0046] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) The proton exchange membrane provided by the present invention constructs a cathode phosphate anchor coating and an anode phosphate anchor coating. The porous structure optimizes the spatial distribution and dynamic stability of phosphate through the synergistic effect of physical confinement and chemical anchoring. The porous structure coating significantly increases the free phosphate content in the local area and the connectivity between free phosphates, anchors the free phosphate, prevents it from flowing into the catalytic layer, and improves the membrane electrode performance.

[0049] (2) The present invention adds a porous anchoring agent and a free radical quencher to the cathode phosphate anchor coating and the anode phosphate anchor coating. On the one hand, PBI and the porous anchoring agent help to reduce the interfacial reaction between the proton exchange membrane and the catalytic layer, reduce the contact resistance and improve the membrane electrode performance. On the other hand, the free radical scavenger can in situ capture the free radicals generated during the operation of the fuel cell, greatly alleviate the attack of the free radicals on the proton exchange membrane, improve the chemical stability of the membrane electrode, and enhance the life of the proton exchange membrane. The two work together to achieve the improvement of the electrochemical stability and long-cycle performance of the proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic structural diagram of the proton exchange membrane provided in Example 1 of the present invention, wherein 1 is an anode phosphoric acid anchor coating, 2 is a phosphoric acid-doped PBI membrane, and 3 is a cathode phosphoric acid anchor coating. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0052] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0053] The phosphoric acid-doped PBI membrane used in the examples and comparative examples can be prepared by the following preparation method: the PBI membrane is boiled in deionized water for 1 hour to remove impurities in the membrane, and then dried. The dried PBI membrane is immersed in 80wt% phosphoric acid solution for 16 hours at an immersion temperature of 60°C to obtain a phosphoric acid-doped proton exchange membrane.

[0054] Example 1

[0055] This embodiment provides a proton exchange membrane, the structure of which is shown in FIG. Figure 1 As shown, the proton exchange membrane includes a cathode phosphoric acid anchor coating 3 with a thickness of 1 μm, a phosphoric acid-doped proton exchange membrane 2 and an anode phosphoric acid anchor coating 1 with a thickness of 0.7 μm, which are stacked in sequence;

[0056] The cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating are both porous structures; the pore size range of the porous structure is 1nm-100nm; the porosity of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating is 10%;

[0057] The method for preparing the proton exchange membrane provided in this embodiment comprises the following steps:

[0058] (1) Deionized water, isopropyl alcohol, PBI, and sulfonated PVDF were mixed in a mass ratio of 1:5:0.6:0.08, and ultrasonically dispersed at a power of 500 W for 2 h; multilayer carbon nanotubes (Aladdin) and cerium dioxide were added, and ultrasonically dispersed at a power of 500 W for 7 h to obtain a phosphate anchor coating slurry, wherein the mass ratio of deionized water, multilayer carbon nanotubes, and cerium dioxide was 1:0.5:0.15;

[0059] (2) The phosphate anchor coating slurry obtained in step (1) is applied to both sides of a phosphate-doped proton exchange membrane, and dried at 80° C. for 10 minutes to obtain the proton exchange membrane.

[0060] Example 2

[0061] This embodiment provides a proton exchange membrane, which includes a cathode phosphoric acid anchor coating with a thickness of 0.5 μm, a phosphoric acid-doped proton exchange membrane, and an anode phosphoric acid anchor coating with a thickness of 0.5 μm, which are stacked in sequence;

[0062] The cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating are both porous structures; the pore size range of the porous structure is 1.5nm-130nm; the porosity of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating is 5%;

[0063] The method for preparing the proton exchange membrane provided in this embodiment comprises the following steps:

[0064] (1) Deionized water, DMAC, PBI, and sulfonated PEEK were mixed in a mass ratio of 1:2:0.5:0.05 and ultrasonically dispersed at a power of 300 W for 3 h; CNovel MH (NECC, Japan) and manganese dioxide were added and ultrasonically dispersed at a power of 300 W for 12 h to obtain a phosphate anchor coating slurry, wherein the mass ratio of deionized water, CNovel MH (NECC, Japan) and manganese dioxide was 1:0.28:0.1;

[0065] (2) The phosphate anchor coating slurry obtained in step (1) is applied to both sides of a phosphate-doped proton exchange membrane, and dried at 90° C. for 5 minutes to obtain the proton exchange membrane.

[0066] Example 3

[0067] This embodiment provides a proton exchange membrane, which includes a cathode phosphoric acid anchor coating with a thickness of 1.5 μm, a phosphoric acid-doped proton exchange membrane, and an anode phosphoric acid anchor coating with a thickness of 1 μm, which are stacked in sequence;

[0068] The cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating are both porous structures; the pore size range of the porous structure is 1nm-80nm; the porosity of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating is 15%;

[0069] The method for preparing the proton exchange membrane provided in this embodiment comprises the following steps:

[0070] (1) Deionized water, NMP, PBI, and sulfonated PEEK were mixed in a mass ratio of 1:10:0.8:0.1, and ultrasonically dispersed at a power of 1000 W for 1 h; CMK-3, SBA-15 porous silica (Sigma-Aldrich) and cerium dioxide were added, and ultrasonically dispersed at a power of 1000 W for 5 h to obtain a phosphate anchor coating slurry, wherein the mass ratio of deionized water, multilayer carbon nanotubes, SBA-15 porous silica, and cerium dioxide was 1:0.7:0.05:0.25;

[0071] (2) The phosphate anchor coating slurry obtained in step (1) is applied to both sides of a phosphate-doped proton exchange membrane, and dried at 60° C. for 20 min to obtain the proton exchange membrane.

[0072] Example 4

[0073] This embodiment provides a proton exchange membrane, which differs from the embodiment 1 only in that the thickness of the cathode phosphoric acid anchor coating is 2.5 μm, and the thickness of the anode phosphoric acid anchor coating is 2.5 μm.

[0074] Example 5

[0075] This embodiment provides a proton exchange membrane, which differs from the embodiment 1 only in that the thickness of the cathode phosphoric acid anchor coating is 0.2 μm, and the thickness of the anode phosphoric acid anchor coating is 0.7 μm.

[0076] Example 6

[0077] This embodiment provides a proton exchange membrane, which differs from embodiment 1 only in that, when preparing the proton exchange membrane, the mass ratio of water, porous anchoring agent and free radical quencher in step (1) is 1:0.1:0.15.

[0078] Example 7

[0079] This embodiment provides a proton exchange membrane, which differs from embodiment 1 only in that, when preparing the proton exchange membrane, the mass ratio of water, porous anchoring agent and free radical quencher in step (1) is 1:1:0.15.

[0080] Example 8

[0081] This embodiment provides a proton exchange membrane, which differs from embodiment 1 only in that, when preparing the proton exchange membrane, the mass ratio of water, porous anchoring agent and free radical quencher in step (1) is 1:0.5:0.05.

[0082] Example 9

[0083] This embodiment provides a proton exchange membrane, which differs from embodiment 1 only in that, when preparing the proton exchange membrane, the mass ratio of water, porous anchoring agent and free radical quencher in step (1) is 1:0.5:0.5.

[0084] Example 10

[0085] This embodiment provides a proton exchange membrane, which differs from embodiment 1 only in that, when preparing the proton exchange membrane, in step (1), the multilayer carbon nanotubes are replaced with porous silica of equal mass.

[0086] Comparative Example 1

[0087] This comparative example provides a proton exchange membrane, which differs from Example 1 only in that both sides of the phosphoric acid-doped proton exchange membrane are not coated with the phosphoric acid anchor coating slurry.

[0088] Comparative Example 2

[0089] This comparative example provides a proton exchange membrane, which differs from Example 1 only in that one side of the phosphoric acid-doped proton exchange membrane is coated with an anode phosphoric acid anchor coating slurry, but not coated with a cathode phosphoric acid anchor coating slurry.

[0090] Comparative Example 3

[0091] This comparative example provides a proton exchange membrane, which differs from Example 1 only in that one side of the phosphoric acid-doped proton exchange membrane is coated with a cathode phosphoric acid anchor coating slurry, but not with an anode phosphoric acid anchor coating slurry.

[0092] Testing Method: The proton exchange membranes prepared in the Examples and Comparative Examples were coated with a cathode catalyst layer (platinum-carbon catalyst) and an anode catalyst layer (platinum-carbon catalyst) and assembled with other components, such as a gas diffusion layer (composed of a microporous layer and carbon paper), to form single cells for performance testing. After activation, polarization curve testing was performed at a temperature of 150°C and 150 kPa, followed by a 1000-hour endurance test and a subsequent polarization curve test. The test results are shown in Table 1 below.

[0093] Table 1

[0094]

[0095] The test results show that:

[0096] (1) It can be seen from Examples 1 to 3 that the present invention constructs a cathode phosphoric acid anchor coating and an anode phosphoric acid anchor coating with a porous structure on both sides of the phosphoric acid-doped PBI membrane. The porous structure optimizes the spatial distribution and dynamic stability of phosphoric acid through the synergistic effect of physical confinement and chemical anchoring. The porous coating significantly increases the free phosphoric acid content and the connectivity between free phosphoric acid in the local area, anchors the free phosphoric acid, prevents it from flowing into the catalytic layer, and improves the performance of the membrane electrode. The addition of a porous anchoring agent helps to reduce the interfacial reaction between the proton exchange membrane and the catalytic layer, reduces the contact resistance, and improves the performance of the membrane electrode. The addition of a free radical scavenger can capture the free radicals generated during the operation of the fuel cell in situ, greatly alleviating the attack of free radicals on the proton exchange membrane, improving the chemical stability of the membrane electrode, and enhancing the life of the proton exchange membrane.

[0097] (2) By comparing Example 1 with Example 4-Example 5, it can be seen that the present invention further controls the thickness of the cathode phosphate anchor coating to 0.5μm-1.5μm and the thickness of the anode phosphate anchor coating to 0.5μm-1μm. The subsequent phosphate anchor coating will affect the contact resistance. If the thickness of the cathode / anode phosphate anchor coating is too thick, the gas transmission is reduced and the impedance is increased, resulting in poor membrane electrode performance; if the thickness of the cathode / anode phosphate anchor coating is too thin, the anchoring effect of phosphoric acid is poor, resulting in poor membrane electrode durability.

[0098] (3) By comparing Example 1 with Example 6-Example 7, it can be seen that the present invention further controls the mass ratio of water, porous anchoring agent and free radical quencher to be 1: (0.28-0.75): (0.1-0.25). If the amount of porous anchoring agent added is too little, the phosphate anchoring effect will be poor, resulting in poor durability of the membrane electrode; if the amount of free radical quenching agent added is too little, the free radicals in the membrane electrode will attack the proton membrane more, and the durability of the membrane electrode will be poor; if the amount of porous anchoring agent and free radical quenching agent is too much, the impedance will be further increased, and the performance of the membrane electrode will be reduced.

[0099] (4) By comparing Example 1 with Example 8, it can be seen that if the porous carbon material is not added to the present invention, the conductivity of the porous coating will be weakened, which will affect the power density of the battery.

[0100] (5) It can be seen from Example 1 and Comparative Examples 1 to Comparative Examples 3 that the voltage and maximum power density of Example 1 are greatly improved compared with Comparative Examples 1 to Comparative Examples 3, indicating that the phosphoric acid-cured coating proton exchange membrane has better durability under high temperature conditions, and the yin and yang synergistic curing effect of phosphoric acid is better. At the same time, the free radical scavenger can capture the free radicals generated during the operation of the fuel cell in situ, greatly alleviating the attack of free radicals on the proton exchange membrane, improving the chemical stability of the membrane electrode, and enhancing the life of the proton exchange membrane.

[0101] In summary, the present invention constructs a cathode phosphoric acid anchor coating and an anode phosphoric acid anchor coating with a porous structure on both sides of the phosphoric acid-doped PBI membrane. The porous structure optimizes the spatial distribution and dynamic stability of phosphoric acid through the synergistic effect of physical confinement and chemical anchoring. The porous structure coating significantly increases the free phosphoric acid content in the local area and the connectivity between the free phosphoric acid, anchors the free phosphoric acid, prevents it from flowing to the catalytic layer, and improves the membrane electrode performance. The addition of a porous anchoring agent helps to reduce the interfacial reaction between the proton exchange membrane and the catalytic layer, reduces the contact resistance and improves the membrane electrode performance; the addition of a free radical scavenger can capture the free radicals generated during the operation of the fuel cell in situ, greatly alleviating the attack of free radicals on the proton exchange membrane, improving the chemical stability of the membrane electrode, and enhancing the life of the proton exchange membrane.

[0102] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A proton exchange membrane, characterized in that The proton exchange membrane comprises a cathode phosphoric acid anchor coating, a phosphoric acid-doped proton exchange membrane and an anode phosphoric acid anchor coating which are stacked in sequence; The cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating both have porous structures; The porosity of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating is 5%-15%; the pore size range of the porous structure is 1nm-130nm.

2. The proton exchange membrane according to claim 1, characterized in that The phosphoric acid-doped proton exchange membrane includes a phosphoric acid-doped PBI membrane; Preferably, the thickness of the cathode phosphoric acid anchor coating is 0.5 μm-1.5 μm; Preferably, the thickness of the anodic phosphoric acid anchor coating is 0.5 μm-1 μm.

3. The proton exchange membrane according to claim 1 or 2, characterized in that The raw materials of the cathode phosphoric acid anchor coating and the anode phosphoric acid anchor coating respectively include PBI, ionomer, porous anchor agent and free radical quencher.

4. The proton exchange membrane according to claim 3, characterized in that The porous anchoring agent comprises a porous carbon material; Preferably, the porous carbon material comprises any one or a combination of at least two of CNovel MH, multi-walled carbon nanotubes, CMK-3, CMK-5, OMC-100, N-doped ordered mesoporous carbon or MOF-derived ordered mesoporous carbon; Preferably, the porous anchoring agent further comprises any one or a combination of at least two of SBA-15, porous silica, titania nanotubes or porous alumina; Preferably, the free radical quencher comprises any one of manganese dioxide, cerium dioxide or cobalt trioxide, or a combination of at least two thereof; Preferably, the ionomer comprises sulfonated PVDF and / or sulfonated PEEK.

5. A method for preparing a proton exchange membrane according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) uniformly mixing water, a dispersant, a PBI solution, an ionomer, a porous anchoring agent, and a free radical quencher to obtain a phosphate anchoring coating slurry; (2) coating the phosphate anchor coating slurry obtained in step (1) on both sides of the phosphate-doped proton exchange membrane, and drying the phosphate anchor coating slurry to obtain the proton exchange membrane.

6. The preparation method according to claim 5, characterized in that The mass ratio of water, dispersant, PBI solute and ionomer in the PBI solution in step (1) is 1:(2-10):(0.5-0.8):(0.05-0.1); Preferably, the mass fraction of the PBI solution is 5wt%-20wt%; Preferably, the mixing method includes ultrasonic dispersion.

7. The preparation method according to claim 5 or 6, characterized in that: The mass ratio of water, porous anchoring agent and free radical quencher is 1:(0.28-0.75):(0.1-0.25); Preferably, the dispersant comprises any one of ethanol, isopropanol, DMAC, NMP or DMSO, or a combination of at least two thereof.

8. The preparation method according to any one of claims 5 to 7, characterized in that The coating method in step (2) includes any one of spraying, blade coating or slit coating, or a combination of at least two of them.

9. The preparation method according to any one of claims 5 to 8, characterized in that The preparation method comprises the following steps: (I) The PBI membrane is boiled in deionized water for 1-3 hours to remove impurities in the membrane, dried, and then immersed in a 65wt%-85wt% phosphoric acid solution for 15-20 hours at a temperature of 50°C-90°C to obtain a phosphoric acid-doped proton exchange membrane; (II) mixing water, dispersant, PBI solution and ionomer in a mass ratio of 1:(2-10):(0.5-0.8):(0.05-0.1), and ultrasonically dispersing the mixture at a power of 300W-1000W for 1h-3h; adding a porous anchoring agent and a free radical quencher, and ultrasonically dispersing the mixture at a power of 300W-1000W for 5h-12h to obtain a phosphate anchor coating slurry, wherein the mass ratio of water, porous anchoring agent and free radical quencher is 1:(0.28-0.75):(0.1-0.25); (III) applying the phosphate anchor coating slurry obtained in step (II) to both sides of the phosphate-doped proton exchange membrane obtained in step (I), and drying at 60° C.-90° C. for 5 min-20 min to obtain the proton exchange membrane.

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

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