A cathode catalyst slurry for fuel cells, a cathode catalyst layer, its preparation method and application

Abstract

This invention provides a cathode catalyst slurry for fuel cells, a cathode catalyst layer, its preparation method, and its application. The cathode catalyst slurry for fuel cells comprises polyacrylic acid, a platinum-based catalyst supported on a carbon support, an ionomer, and a solvent; the polyacrylic acid has a weight-average molecular weight of 200,000 to 800,000; the solvent includes water and organic solvents. This invention introduces polyacrylic acid with a weight-average molecular weight of 200,000 to 800,000 into the cathode catalyst slurry, achieving optimized stability of the catalyst layer structure through its unique molecular configuration and interfacial interaction mechanism. This results in a significant improvement in the durability and output performance of the membrane electrode assembly, thereby enhancing the performance of the fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and relates to a cathode catalyst layer slurry, a cathode catalyst layer, its preparation method, and its application for fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered one of the most promising clean energy technologies due to their high specific energy density, zero emissions, and rapid start-up at low temperatures. As the core component of a fuel cell, the membrane electrode assembly (MEA) consists of a proton exchange membrane (PEM), a catalyst layer (CCM), and a gas diffusion layer (GDL). Its durability directly restricts the lifespan and commercialization cost of the fuel cell system. Essentially, microscopic mechanisms such as catalyst shedding, carrier corrosion, and ionomer decomposition are key factors inducing MEA durability degradation. Therefore, achieving breakthroughs in high-durability MEAs has become a critical technological bottleneck in advancing the commercialization of fuel cell technology.

[0003] In the technological path to improve the durability of membrane electrode assemblies (MEAs), the mismatch between material system characteristics and engineering requirements is particularly prominent. Regarding the optimization of intrinsic catalyst performance, while highly graphitized carbon-supported catalysts can delay activity decay caused by support collapse by enhancing corrosion resistance, their highly ordered carbon layer structure significantly reduces the anchoring site density of metal nanoparticles, leading to a decrease in the density of electrochemical active sites and severely limiting their large-scale application prospects. In terms of the control of the mesoscopic structure of the catalyst layer, current mainstream strategies such as gradient ionomer distribution design and Pt loading spatial distribution optimization can construct continuous three-phase transport channels and reduce local concentration polarization, but in practice, multi-step coating or post-processing techniques are required to achieve microstructure control. This "performance-cost-efficiency" dilemma essentially reveals the technical bottleneck of traditional preparation techniques in the precise construction of multi-scale structures.

[0004] Therefore, improving the durability of membrane electrodes is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cathode catalyst slurry, a cathode catalyst layer, a preparation method thereof, and applications for fuel cells. The present invention introduces polyacrylic acid with a weight-average molecular weight of 200,000 to 800,000 into the cathode catalyst slurry. Through its unique molecular configuration and interfacial interaction mechanism, the stability of the catalyst layer structure is optimized, resulting in a significant improvement in the durability and output performance of the membrane electrode assembly, thereby enhancing the performance of the fuel cell.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a cathode catalyst layer slurry for fuel cells, the cathode catalyst layer slurry for fuel cells comprising polyacrylic acid, a platinum-based catalyst supported on a carbon carrier, an ionomer, and a solvent; the polyacrylic acid has a weight-average molecular weight of 200,000 to 800,000; the solvent comprises water and an organic solvent.

[0008] Preferably, the polyacrylic acid accounts for 0.8wt% to 1.5wt% of the mass of the cathode catalyst layer slurry for the fuel cell.

[0009] Preferably, the mass ratio (I / C) of the ionomer to the carbon in the platinum-based catalyst supported on the carbon is 0.85 to 1.15.

[0010] Preferably, the platinum-based catalyst supported on carbon contains 30% to 70% platinum by mass.

[0011] Preferably, the solid content of the cathode catalyst slurry for the fuel cell is 8% to 13%.

[0012] In a second aspect, the present invention provides a cathode catalyst layer for a fuel cell, the cathode catalyst layer for a fuel cell being formed by coating a cathode catalyst layer slurry for a fuel cell as described in the first aspect onto the surface of a base membrane.

[0013] Thirdly, the present invention provides a method for preparing a cathode catalyst layer for a fuel cell as described in the second aspect, the method comprising:

[0014] The cathode catalyst layer slurry for fuel cells as described in the first aspect is coated onto the surface of the base membrane and dried to obtain the cathode catalyst layer for fuel cells.

[0015] Preferably, the platinum loading of the coating is 0.25 mg / cm³. 2 ~0.3mg / cm 2 .

[0016] Preferably, the drying process includes performing a first drying and a second drying in sequence.

[0017] Preferably, the drying temperature of the first drying process is 50℃~80℃, and the drying time of the first drying process is 10min~20min.

[0018] Preferably, the drying temperature of the second drying process is 95℃~125℃, and the drying time of the second drying process is 20min~30min.

[0019] Fourthly, the present invention provides a membrane electrode comprising a first gas diffusion layer, a cathode catalytic layer as described in the second aspect or a cathode catalytic layer prepared by the preparation method described in the third aspect, a proton exchange membrane, an anode catalytic layer, and a second gas diffusion layer stacked together.

[0020] Fifthly, the present invention also provides a fuel cell comprising a membrane electrode assembly as described in the fourth aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention introduces polyacrylic acid (PAA) with a specific weight-average molecular weight of 200,000 to 800,000 into the cathode catalyst slurry system. PAA within this weight-average molecular weight range possesses suitable molecular chain lengths, and its unique molecular configuration and interfacial interaction mechanism optimize the stability of the cathode catalyst structure. The PAA molecular chains are densely packed with carboxylic acid groups. During slurry dispersion, these carboxylic acid groups form dynamic chemical bonds with the surface of platinum (Pt) nanoparticles in the catalyst through hydrogen bonds. Simultaneously, its flexible molecular chains achieve topological entanglement on the carbon support surface through van der Waals forces, forming a synergistic "chemical anchoring-physical adsorption" mechanism. This allows a single PAA molecule to simultaneously connect with 3-5 Pt particles, constructing a three-dimensional elastic network structure spanning the micrometer scale, exhibiting a significant enhancement effect. The advantages of this enhancement effect are twofold: firstly, the electrostatic repulsion of the carboxylic acid groups inhibits the Ostwald ripening process of Pt particles; secondly, the steric hindrance formed by the polymer matrix effectively hinders particle migration and aggregation. When the cathode catalytic layer obtained from the cathode catalytic layer slurry provided by this invention is applied to the membrane electrode, it effectively improves the weak links in the durability of the membrane electrode while fully preserving the intrinsic characteristics of the catalytic active sites, truly achieving synergistic optimization of durability and output performance. Attached Figure Description

[0023] Figure 1 This is a cyclic voltammetry diagram of the MEA provided in Embodiment 1 of the present invention.

[0024] Figure 2 The cyclic voltammetry diagram of the MEA provided in Comparative Example 1 of this invention.

[0025] Figure 3 The polarization curve of the MEA provided in Embodiment 1 of the present invention is shown.

[0026] Figure 4 The polarization curve of the MEA provided in Comparative Example 1 of this invention is shown. Detailed Implementation

[0027] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0028] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0029] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0030] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0031] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0032] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0033] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0034] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0035] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0036] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0037] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0038] In one embodiment, the present invention provides a cathode catalyst layer slurry for fuel cells, the cathode catalyst layer slurry for fuel cells comprising polyacrylic acid, a platinum-based catalyst supported on a carbon support, an ionomer, and a solvent; the polyacrylic acid has a weight-average molecular weight of 200,000 to 800,000; the solvent comprises water and an organic solvent.

[0039] For example, the weight-average molecular weight of the polyacrylic acid (PAA) is 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, or 800,000.

[0040] It should be noted that the cathode catalyst slurry of the present invention does not contain conductive agents (such as carbon nanotubes, graphene, etc.) as auxiliary additives.

[0041] This invention introduces polyacrylic acid (PAA) with a specific weight-average molecular weight (MAM) of 200,000 to 800,000 into the cathode catalyst slurry system. PAA within this MAM range possesses suitable molecular chain lengths, achieving optimized stability of the cathode catalyst structure through its unique molecular configuration and interfacial interaction mechanism. The PAA molecular chains are densely packed with carboxylic acid groups. During slurry dispersion, this MAM polyacrylic acid also exhibits good water solubility and significant hydrogen bonding within the slurry system. These carboxylic acid groups form dynamic chemical bonds with the surface of platinum (Pt) nanoparticles in the catalyst through hydrogen bonds. Simultaneously, its flexible molecular chains achieve topological entanglement on the carbon support surface through van der Waals forces, forming a synergistic "chemical anchoring-physical adsorption" mechanism. This allows a single PAA molecule to simultaneously connect with 3-5 Pt particles, constructing a three-dimensional elastic structure spanning the micrometer scale. The network structure exhibits a significant enhancement effect. This enhancement effect has two advantages: firstly, the electrostatic repulsion of the carboxylic acid groups inhibits the Ostwald ripening process of Pt particles; secondly, the steric hindrance formed by the polymer matrix effectively hinders particle migration and aggregation. When the cathode catalyst layer obtained from the cathode catalyst layer slurry provided by this invention is applied to the membrane electrode, it effectively improves the weak points of membrane electrode durability while fully preserving the intrinsic characteristics of the catalytic active sites, truly achieving synergistic optimization of durability and output performance. It breaks through the limitations of traditional gradient and ordered electrode preparation processes that require multiple coating / spraying steps, innovatively integrating PAA interface control technology into the cathode catalyst layer slurry process in a one-step manner. This scheme achieves in-situ self-assembly through molecular structure optimization, significantly improving the construction efficiency of the three-phase interface of the catalyst layer while maintaining the stability of the slurry system. Compared to existing technologies, this process does not require additional production equipment or complex procedures, possesses excellent process compatibility and scalability, and supports continuous and batch production, providing a solution with both technological innovation and industrial applicability for the large-scale commercialization of hydrogen fuel cells.

[0042] In the cathode catalyst slurry provided by this invention, the weight-average molecular weight of polyacrylic acid is crucial; when it is below 200,000, the synergistic effect of "chemical anchoring-physical adsorption" cannot be achieved. When the molecular weight is above 800,000, the slurry viscosity is too high, which is not conducive to coating and film formation.

[0043] In some embodiments, the polyacrylic acid comprises 0.8wt% to 1.5wt% of the cathode catalyst layer slurry for the fuel cell, for example, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, or 1.5wt%.

[0044] In the cathode catalyst layer slurry of the present invention, the mass proportion of polyacrylic acid in the cathode catalyst layer slurry for fuel cells is controlled to be 0.8wt%~1.5wt%, which effectively balances the slurry viscosity and CCM performance. This ensures that the PAA molecular chains are fully extended to form a stable three-dimensional network and play a good anchoring role, while avoiding excessive introduction that could lead to pore blockage or increased proton transport resistance.

[0045] In some embodiments, the mass ratio (I / C) of the ionomer to the carbon in the platinum-based catalyst supported on the carbon is 0.85 to 1.15, for example, 0.85, 0.88, 0.9, 0.93, 0.95, 0.98, 1, 1.03, 1.05, 1.08, 1.1, 1.13, or 1.15.

[0046] It is understood that the ionomer in this invention is the ionomer of solid dry material, rather than an ionomer solution system.

[0047] The present invention limits the mass ratio (I / C) of the ionomer to the carbon in the platinum-based catalyst supported by the carbon to be 0.85~1.15, thereby controlling the amount of ionomer and catalyst. An I / C ratio of 0.85~1.15 ensures that there is enough ionomer in the catalyst layer system for proton conduction, without blocking the gas transport channels in the catalyst layer, thus achieving a balance between catalytic activity and proton conduction optimization.

[0048] In some embodiments, the platinum-based catalyst supported on carbon contains 30% to 70% platinum by mass, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0049] The platinum-based catalyst with carbon support provided by this invention can be a pure platinum-carbon system catalyst or an alloy carbon catalyst of platinum and other transition metals. This invention does not make specific limitations, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0050] For example, but not limitingly, the platinum-carbon catalyst includes a platinum-carbon catalyst with a platinum mass content of 40% to 70%, such as 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0051] For example, but not limitingly, the platinum-alloyed carbon catalyst with other transition metals, etc., includes a platinum-based alloy catalyst with a platinum mass content of 40% to 60% (e.g., 40%, 45%, 50%, 55%, or 60%, etc.).

[0052] It is also understood that the platinum-based catalyst with carbon support of the present invention can be directly purchased from commercial sources or prepared by conventional existing technologies.

[0053] In some embodiments, the solid content of the cathode catalyst layer slurry for the fuel cell is 8% to 13%, such as 8%, 9%, 10%, 11%, 12%, or 13%.

[0054] In some embodiments, the mass ratio of the water to the organic solvent is (3~7):(7~3), for example, 3:7, 4:6, 5:5, 6:4 or 7:3, etc.

[0055] In one embodiment, the present invention does not specifically limit the preparation method of the cathode catalyst slurry for fuel cells described in the above embodiments. Conventional catalyst slurry preparation methods are applicable to the present invention without departing from the overall technical concept of the present invention.

[0056] Example, but not limitation, of the present invention provides a method for preparing a cathode catalyst slurry for a fuel cell, the method comprising:

[0057] A method for preparing the cathode catalyst slurry for fuel cells is obtained by mixing polyacrylic acid, a platinum-based catalyst supported on a carbon support, an ionomer solution, and a solvent.

[0058] Optionally, polyacrylic acid is first dissolved and dispersed in an aqueous solvent to obtain a polyacrylic acid solution; then, the polyacrylic acid solution is added to a platinum-based catalyst supported on a carbon support and ultrasonically stirred, followed by the addition of an ionomer solution and an organic solvent, and ultrasonic stirring is continued. Then, ball milling and homogenization are performed to obtain a uniformly dispersed cathode catalyst slurry for fuel cells.

[0059] Optionally, during the mixing process, in addition to the solvent in the ionomer solution, the mass ratio of the aqueous solvent to the organic solvent is (3~7):(7~3), for example, 3:7, 4:6 or 7:3, etc.

[0060] Optionally, during the preparation of the cathode catalyst slurry, the ionomer is usually added in the form of an ionomer solution, such as an ionomer solution containing 10% to 20% by mass of the ionomer. The ionomer includes perfluorosulfonic acid resin, and the ionomer solution includes, but is not limited to, one or more of DuPont Nafion solution, Aquivion D72-25BS resin solution, or Aquivion D79-25BS resin solution.

[0061] Optionally, the organic solvent includes, but is not limited to, at least one of n-propanol, isopropanol, ethanol, or glycerol.

[0062] Optionally, the diameter of the grinding beads used in the ball mill is 5mm to 10mm, such as 5mm, 6mm, 7mm, 8mm, 9mm or 10mm.

[0063] Optionally, the homogenization can be carried out using a high-speed homogenizer, with a homogenization speed of 30m / s to 40m / s, such as 30m / s, 35m / s, or 40m / s.

[0064] In one embodiment, the present invention provides a cathode catalyst layer for a fuel cell, the cathode catalyst layer for a fuel cell being formed by coating a cathode catalyst layer slurry for a fuel cell as described in the above embodiments onto the surface of a base membrane.

[0065] In one embodiment, the present invention provides a method for preparing a cathode catalyst layer for a fuel cell as described in the above embodiments, the method comprising:

[0066] The cathode catalyst layer slurry for fuel cells as described in the first aspect is coated onto the surface of the base membrane and dried to obtain the cathode catalyst layer for fuel cells.

[0067] In some embodiments, the platinum loading of the coating is 0.25 mg / cm³. 2 ~0.3mg / cm 2 For example, 0.25 mg / cm³ 2 0.26 mg / cm 2 0.27 mg / cm 2 0.28 mg / cm 2 0.29 mg / cm 2 Or 0.3 mg / cm 2 wait.

[0068] In some embodiments, the drying includes performing a first drying and a second drying in sequence.

[0069] In some embodiments, the drying temperature of the first drying is 50°C to 80°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C; and the drying time of the first drying is 10 min to 20 min, such as 10 min, 15 min, or 20 min.

[0070] In some embodiments, the drying temperature of the second drying is 95°C to 125°C, such as 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, or 125°C; and the drying time of the second drying is 20 min to 30 min, such as 20 min, 25 min, or 30 min.

[0071] In the preparation of the cathode catalyst layer for fuel cells, this invention utilizes gradient drying with segmented temperature control to induce the ordered arrangement of PAA molecular chains and gradually enhance interfacial bonding strength. During the initial slow drying stage (50℃~80℃), the slurry maintains slight fluidity, allowing the PAA carboxylic acid groups to fully contact the Pt particle surface, and hydrogen bonds dynamically recombine to form uniform anchoring points. In the later curing stage (95℃~125℃), the PAA molecular chain configuration changes, and flexible segments topologically lock onto the carbon support surface through entropy increase, simultaneously strengthening the three-dimensional network crosslinking density, promoting residual solvent evaporation, and driving the deep formation of PAA-Pt interfacial coordination bonds.

[0072] The cathode catalyst layer for fuel cells provided by this invention can be obtained through a simple slurry coating method without the need for additional production equipment or complex processes. It has excellent process compatibility and scalability, and can support continuous and mass production, providing a solution that combines technological innovation and industrial applicability for the large-scale commercialization of hydrogen fuel cells.

[0073] In one embodiment, the present invention provides a membrane electrode comprising a first gas diffusion layer, a cathode catalytic layer as described in the above embodiments or a cathode catalytic layer prepared by the preparation method described in the above embodiments, a proton exchange membrane, an anode catalytic layer, and a second gas diffusion layer stacked together.

[0074] The membrane electrode of the present invention, under the action of the cathode catalyst slurry for fuel cells provided by the present invention, has excellent durability and high output performance.

[0075] Apart from the cathode catalyst layer, the rest of the structure, raw materials, and preparation process are all conventional technical solutions, which can be adapted and adjusted by those skilled in the art according to actual needs.

[0076] In one embodiment, the present invention also provides a fuel cell comprising a membrane electrode assembly as described in the above embodiments.

[0077] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0078] Example 1

[0079] This embodiment provides a cathode catalyst layer slurry for fuel cells, which is composed of polyacrylic acid (weight average molecular weight 450,000), a platinum-based catalyst on a carbon support (JM9100 catalyst with a platinum loading of 60%), ionomer (Nafion), water, n-propanol, and propylene glycol.

[0080] The mass percentage of polyacrylic acid in the cathode catalyst slurry for the fuel cell is 1 wt%.

[0081] The mass ratio (I / C) of the ionomer to the JM9100 catalyst is 0.85.

[0082] The solid content of the cathode catalyst slurry for the fuel cell is 12.4%.

[0083] The method for preparing the cathode catalyst layer slurry for fuel cells includes:

[0084] Weigh 0.6g of PAA powder into a beaker and dissolve it in 25.375g of deionized water to prepare a PAA solution. Weigh 5g of JM9100 catalyst into another beaker and add PAA solution, 17g of Nafion 10% membrane solution, 5.439g of n-propanol and 5.439g of 1,2-propanediol into the beaker to prepare a catalyst slurry. Stir and sonicate the catalyst slurry for 1 hour, ball mill for 12 hours, and then transfer the slurry to a high-pressure homogenizer and disperse it at 35m / s for 20 minutes to obtain a high-durability cathode catalyst layer slurry for fuel cells.

[0085] Example 2

[0086] This embodiment provides a cathode catalyst layer slurry for fuel cells, wherein the cathode catalyst layer slurry for fuel cells comprises polyacrylic acid (weight average molecular weight 450,000), a platinum-based catalyst on a carbon support (JM9100 catalyst), ionomer (Nafion), water, n-propanol and propylene glycol.

[0087] The mass percentage of polyacrylic acid in the cathode catalyst slurry for the fuel cell is 1.2 wt%.

[0088] The mass ratio (I / C) of the ionomer to the JM9100 catalyst is 0.85.

[0089] The solid content of the cathode catalyst slurry for the fuel cell is 12.5%.

[0090] The method for preparing the cathode catalyst layer slurry for fuel cells includes:

[0091] Weigh 0.7g of PAA powder into a beaker and dissolve it in 25.375g of deionized water to prepare a PAA solution. Weigh 5g of JM9100 catalyst into another beaker and add PAA solution, 17g of Nafion 10% membrane solution, 5.439g of n-propanol and 5.439g of 1,2-propanediol into the beaker to prepare a catalyst slurry. Stir and sonicate the catalyst slurry for 1 hour, ball mill for 12 hours, and then transfer the slurry to a high-pressure homogenizer and disperse it at 35m / s for 20 minutes to obtain a high-durability cathode catalyst layer slurry for fuel cells.

[0092] Example 3

[0093] This embodiment provides a cathode catalyst layer slurry for fuel cells, wherein the cathode catalyst layer slurry for fuel cells comprises polyacrylic acid (weight average molecular weight 450,000), a platinum-based catalyst on a carbon support (JM9100 catalyst), ionomer (Nafion), water, n-propanol and propylene glycol.

[0094] The mass percentage of polyacrylic acid in the cathode catalyst slurry for the fuel cell is 1.3 wt%.

[0095] The mass ratio (I / C) of the ionomer to the JM9100 catalyst is 0.85.

[0096] The solid content of the cathode catalyst slurry for the fuel cell is 12.7%.

[0097] The method for preparing the cathode catalyst layer slurry for fuel cells includes:

[0098] Weigh 0.8g of PAA powder into a beaker and dissolve it in 25.375g of deionized water to prepare a PAA solution. Weigh 5g of JM9100 catalyst into another beaker and add PAA solution, 17g of Nafion 10% membrane solution, 5.439g of n-propanol and 5.439g of 1,2-propanediol into the beaker to prepare a catalyst slurry. Stir and sonicate the catalyst slurry for 1 hour, ball mill for 12 hours, and then transfer the slurry to a high-pressure homogenizer and disperse it at 40m / s for 20 minutes to obtain a high-durability cathode catalyst layer slurry for fuel cells.

[0099] Example 4

[0100] The difference between this embodiment and Example 1 is that the mass ratio I / C of the ionomer to the JM9100 catalyst in this embodiment is 1.

[0101] In the preparation method, the mass fraction of ionomer in the ionomer solution can be adaptively adjusted.

[0102] All other conditions remain the same as in Example 1.

[0103] Example 5

[0104] The difference between this embodiment and Embodiment 1 is that the weight-average molecular weight of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 200,000.

[0105] All other conditions remain the same as in Example 1.

[0106] Example 6

[0107] The difference between this embodiment and Embodiment 1 is that the weight-average molecular weight of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 800,000.

[0108] All other conditions remain the same as in Example 1.

[0109] Example 7

[0110] The difference between this embodiment and Embodiment 1 is that the mass percentage of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 0.8 wt%.

[0111] In the preparation method, the amount of polyacrylic acid added can be adjusted adaptively.

[0112] All other conditions remain the same as in Example 1.

[0113] Example 8

[0114] The difference between this embodiment and Embodiment 1 is that the mass percentage of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 1.5 wt%.

[0115] In the preparation method, the amount of polyacrylic acid added can be adjusted adaptively.

[0116] All other conditions remain the same as in Example 1.

[0117] Example 9

[0118] The difference between this embodiment and Embodiment 1 is that the mass percentage of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 0.5 wt%.

[0119] In the preparation method, the amount of polyacrylic acid added can be adjusted adaptively.

[0120] All other conditions remain the same as in Example 1.

[0121] Example 10

[0122] The difference between this embodiment and Embodiment 1 is that the mass percentage of polyacrylic acid in the cathode catalyst slurry for fuel cells in this embodiment is 2 wt%.

[0123] In the preparation method, the amount of polyacrylic acid added can be adjusted adaptively.

[0124] All other conditions remain the same as in Example 1.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 1 is that the cathode catalyst slurry for fuel cells in this comparative example does not contain polyacrylic acid.

[0127] PAA powder is not added in the preparation method.

[0128] All other conditions remain the same as in Example 1.

[0129] Comparative Example 2

[0130] The difference between this comparative example and Example 1 is that in the cathode catalyst slurry for fuel cells in this comparative example, polyacrylic acid is replaced with polyacrylamide of equal weight average molecular weight.

[0131] In the preparation method, the mass of polyacrylamide added is 0.6g.

[0132] All other conditions remain the same as in Example 1.

[0133] Comparative Example 3

[0134] The difference between this comparative example and Example 1 is that in the cathode catalyst slurry for fuel cells in this comparative example, polyacrylic acid is replaced with polyvinyl alcohol of equal weight and average molecular weight.

[0135] In the preparation method, the mass of polyvinyl alcohol added is 0.6g.

[0136] All other conditions remain the same as in Example 1.

[0137] Comparative Example 4

[0138] The difference between this comparative example and Example 1 is that in the cathode catalyst slurry for fuel cells in this comparative example, polyacrylic acid is replaced with polyvinylpyrrolidone of equal weight and molecular weight.

[0139] In the preparation method, the mass of polyvinylpyrrolidone added is 0.6g.

[0140] All other conditions remain the same as in Example 1.

[0141] Comparative Example 5

[0142] The difference between this comparative example and Example 1 is that the weight-average molecular weight of polyacrylic acid in the cathode catalyst slurry for fuel cells in this comparative example is 150,000.

[0143] All other conditions remain the same as in Example 1.

[0144] Comparative Example 6

[0145] The difference between this comparative example and Example 1 is that the weight-average molecular weight of polyacrylic acid in the cathode catalyst slurry for fuel cells in this comparative example is 850,000.

[0146] All other conditions remain the same as in Example 1.

[0147] The composite structure (CCM) of the cathode catalyst layer, proton exchange membrane, and anode catalyst layer.

[0148] The anode catalyst slurry for the fuel cell consists of a platinum-based catalyst (JM9100 catalyst) supported on a carbon carrier, an ionomer (Nafion), water, n-propanol, and propylene glycol; the mass ratio (I / C) of the ionomer to the JM9100 catalyst is 0.85. The solid content of the anode catalyst slurry for the fuel cell is 8.5%.

[0149] The method for preparing the anode catalyst layer slurry for fuel cells includes:

[0150] Weigh 3g of JM9100 catalyst into a beaker, and add 20.45g of water, 10.2g of Nafion 10% membrane solution and 13.64g of n-propanol to the beaker in sequence to prepare a catalyst slurry. Stir and sonicate the catalyst slurry for 1 hour, and then ball mill it for 12 hours to obtain a high-durability fuel cell anode catalyst layer slurry.

[0151] The proton exchange membrane (PEM, perfluorosulfonic acid resin membrane) was adsorbed onto a vacuum adsorption stage, and the cathode catalyst slurry for fuel cells provided in the examples and comparative examples was coated onto the PEM surface until the Pt loading was 0.3 mg / cm³. 2 The cathode catalyst layer was obtained by first drying at 60℃ for 15 min, followed by a second drying at 110℃ for 25 min, and then subjected to gradient drying. PTFE was then adsorbed onto a vacuum adsorption stage, and the anode catalyst layer slurry was coated onto the PTFE surface until the Pt loading was 0.05 mg / cm³. 2 After drying, an anode catalyst layer is formed. The two catalyst layers are then subjected to hot pressing at 160℃ and 0.5MPa for 3 minutes to finally obtain CCM.

[0152] Performance testing

[0153] (1) Electrochemical Active Area: The CCM and gas diffusion layer provided in the examples and comparative examples were assembled, and the membrane electrode assembly (MEA) was effectively sealed around the perimeter with a frame. Polarization tests were performed on a single-cell test bench. The CV method was used for testing. The anode of the cell was purged with 100% H2 relative humidity, and the cathode was purged with 100% N2 relative humidity. The scanning range was (0.05~1.2V) vs RHE, and the scanning rate was 50mV / s. The CV curve of the membrane electrode was obtained. A square wave scan was performed in the voltage range of 0.6V-0.95V, and the number of scans was 30,000. After the scan was completed, the membrane electrode was tested again with CV, and the electrochemical active area decayed after 30,000 cycles was calculated by comparing it with the value before cycling. The results are shown in Table 1.

[0154] (2) Polarization Curves: The CCM and gas diffusion layer prepared in the examples and comparative examples were assembled and effectively sealed with a frame (MEA) around the perimeter. Polarization tests were performed on a single-cell test bench. The voltage curves of the membrane electrode under different current densities were obtained. Square wave scanning was performed in the voltage range of 0.6V-0.95V, with 30,000 scans. After the scanning was completed, the polarization test of the membrane electrode was performed again, and the voltage amplitude after 30,000 cycles was calculated by comparing it with that before cycling. The results are shown in Table 2.

[0155] Figure 1 The cyclic voltammetry diagram of the MEA provided in Embodiment 1 of the present invention is shown.

[0156] Figure 2 The cyclic voltammetry diagram of the MEA provided in Comparative Example 1 of the present invention is shown.

[0157] Figure 3 The polarization curve of the MEA provided in Embodiment 1 of the present invention is shown.

[0158] Figure 4 The polarization curve of the MEA provided in Comparative Example 1 of the present invention is shown.

[0159] from Figures 1 to 4 It can be seen that after the MEA is prepared from the cathode catalyst slurry for fuel cells provided by the present invention, the MEA decay is significantly reduced after cyclic voltammetry scanning. The polarization curve results show that the voltage decay phenomenon of the MEA of the present invention has been significantly improved. This indicates that the membrane electrode has truly achieved synergistic optimization of durability and output performance.

[0160] Table 1

[0161]

[0162] Table 2

[0163]

[0164] Combining Tables 1 and 2, Figures 1 to 4 We can conclude that:

[0165] This invention introduces polyacrylic acid with a weight-average molecular weight of 200,000 to 800,000 into the cathode catalyst slurry. Through its unique molecular configuration and interfacial interaction mechanism, the stability of the catalyst layer structure is optimized, and the durability and output performance of the membrane electrode are significantly improved, thereby enhancing the performance of the fuel cell.

[0166] Data analysis of Examples 1 and 7-10 shows that, in the cathode catalyst slurry of the present invention, the mass percentage of polyacrylic acid in the cathode catalyst slurry for fuel cells is controlled to be 0.8wt%~1.5wt%, which further optimizes the uniformity of polyacrylic acid molecule distribution in the catalyst layer and significantly improves CCM durability without affecting catalytic activity.

[0167] Data analysis of Example 1 and Comparative Examples 1-5 shows that the introduction of polyacrylic acid into the cathode catalyst slurry of the present invention and the weight-average molecular weight of polyacrylic acid of 200,000 to 800,000 are both crucial. Only when both conditions are met can the problems of membrane electrode durability and output performance be truly solved.

[0168] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A cathode catalyst slurry for fuel cells, characterized in that, The cathode catalyst slurry for fuel cells includes polyacrylic acid, a platinum-based catalyst supported on a carbon carrier, an ionomer, and a solvent; the weight-average molecular weight of the polyacrylic acid is 200,000 to 800,000; the solvent includes water and organic solvents.

2. The cathode catalyst slurry for fuel cells according to claim 1, characterized in that, The polyacrylic acid comprises 0.8wt% to 1.5wt% of the cathode catalyst layer slurry for the fuel cell.

3. The cathode catalyst slurry for fuel cells according to claim 1, characterized in that, The mass ratio (I / C) of the ionomer to the carbon in the platinum-based catalyst supported on the carbon is 0.85 to 1.

15. And / or, the platinum-based catalyst supported on carbon contains 30% to 70% platinum by mass.

4. The cathode catalyst slurry for fuel cells according to claim 1, characterized in that, The solid content of the cathode catalyst layer slurry for the fuel cell is 8%~13%.

5. A cathode catalyst layer for a fuel cell, characterized in that, The cathode catalyst layer for fuel cells is formed by coating the cathode catalyst layer slurry for fuel cells as described in any one of claims 1-4 onto the surface of the base membrane.

6. A method for preparing a cathode catalyst layer for a fuel cell as described in claim 5, characterized in that, The preparation method includes: The cathode catalyst layer slurry for fuel cells as described in any one of claims 1-4 is coated onto the surface of the base membrane and dried to obtain the cathode catalyst layer for fuel cells.

7. The preparation method according to claim 6, characterized in that, The platinum loading of the coating is 0.25 mg / cm³. 2 ~0.3mg / cm 2 ; And / or, the drying includes performing a first drying and a second drying in sequence.

8. The preparation method according to claim 7, characterized in that, The drying temperature of the first drying process is 50℃~80℃, and the drying time of the first drying process is 10min~20min; And / or, the drying temperature of the second drying is 95℃~125℃, and the drying time of the second drying is 20min~30min.

9. A membrane electrode, characterized in that, The membrane electrode comprises a first gas diffusion layer, a cathode catalytic layer as described in claim 6 or a cathode catalytic layer prepared by the preparation method as described in claim 7 or 8, a proton exchange membrane, an anode catalytic layer, and a second gas diffusion layer, all stacked together.

10. A fuel cell, characterized in that, The fuel cell includes the membrane electrode assembly as described in claim 9.

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