Membrane electrode based on direct coating process and preparation method and application thereof

Abstract

The invention provides a membrane electrode based on a direct coating process and a preparation method and application thereof, and belongs to the technical field of fuel cells. The method comprises the following steps: directly coating cathode or anode catalyst slurry on one side of a proton exchange membrane with a temporary support substrate; then, the surface coated with the catalyst layer is continuously and directly coated with a proton exchange membrane functional layer and catalyst slurry, so that continuous construction of the proton exchange membrane and the catalyst layers on the two sides is achieved; finally, interface fusion and structure densification are promoted through annealing treatment, and the complete three-in-one membrane electrode is obtained. According to the method, a transfer printing film and a hot pressing transfer printing step needed in a traditional transfer printing process are completely abandoned, the manufacturing process is simplified, the material and energy consumption cost is reduced, and the production speed is remarkably increased. More importantly, by accurately controlling the coating sequence, the slurry formula and the drying-annealing process, swelling and deformation of the proton exchange membrane in the wet-dry cycle process are effectively inhibited, and it is ensured that the membrane electrode structure is smooth and the interface bonding is firm.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a membrane electrode based on a direct coating process, its preparation method, and its application. Background Technology

[0002] The membrane electrode assembly (MEA) is the core component in a proton exchange membrane fuel cell (PEMFC) stack that enables electrochemical energy conversion. Its structure directly determines the cell's output performance, operational stability, and lifespan. As the sole site of electrochemical reactions, the MEA not only needs to efficiently conduct protons and transfer electrons but also ensure the smooth diffusion of reactant gases (such as hydrogen and oxygen) and the effective removal of generated water. Therefore, its design and fabrication process have a decisive impact on the efficiency and reliability of the entire fuel cell system. Statistics show that the cost of the MEA accounts for more than 50% of the total cost of the fuel cell stack, making it one of the key factors restricting the large-scale commercial application of fuel cells.

[0003] A typical membrane electrode assembly (MEA) employs a "three-in-one" (Catalyst Coated Membrane, CCM) structure, consisting of a proton exchange membrane (such as a Nafion membrane) sandwiched between the anode and cathode catalyst layers. The catalyst layer typically comprises a noble metal catalyst (such as platinum or platinum alloys), a carbon support, an ionomer (such as perfluorosulfonic acid resin), and a suitable solvent, and is attached to the proton exchange membrane surface using a precision coating process. An ideal catalyst layer should possess high catalytic activity, a good proton / electron conductivity network, suitable porosity, and strong interfacial adhesion to the membrane. To achieve the above goals, the industry has developed a variety of membrane electrode fabrication technologies, mainly including the following three categories: First, the double-sided transfer method, in which the anode and cathode catalyst slurries are coated onto two high-temperature resistant transfer substrates (such as PTFE membranes), and after drying and curing, the proton exchange membrane is placed between the two catalyst layers. The catalyst layer is transferred from the transfer membrane to the proton exchange membrane by hot pressing; Second, the single-sided direct coating + single-sided transfer method, in which the cathode catalyst layer is usually directly coated onto one side of the proton exchange membrane, while the anode is bonded by transfer; Third, the double-sided direct coating method, in which one side of the catalyst layer is first coated on the proton exchange membrane with a temporary support substrate, the substrate is removed, and then the second catalyst layer is directly coated on the other side of the bare membrane.

[0004] While the aforementioned methods are feasible to some extent in laboratory or small-batch production, they all reveal significant shortcomings in industrial applications. The double-sided transfer method, although it can better control the morphology of the catalyst layer, has a lengthy process requiring multiple coating, drying, hot-pressing, and peeling operations. Furthermore, it relies heavily on disposable transfer films as intermediate consumables, increasing material costs and reducing production efficiency and consistency. Single-sided direct coating combined with transfer simplifies the process to some extent, but it still cannot completely eliminate dependence on transfer films, failing to fundamentally solve cost and environmental issues. While the double-sided direct coating method is theoretically the most cost-effective, it faces severe challenges in practice: the proton exchange membrane itself is soft and highly hydrophilic. When coating the second catalyst layer, the lack of rigid support makes it prone to irreversible swelling, curling, or wrinkling during the solvent wetting-drying cycle, leading to defects such as catalyst layer cracking, uneven thickness, and interfacial debonding, severely affecting the electrochemical performance and yield of the membrane electrode.

[0005] Furthermore, as fuel cells develop towards higher power density, longer lifespan, and lower cost, higher demands are placed on the structural uniformity, interface integrity, and mass production capabilities of the membrane electrode assembly (MEA). Traditional processes are approaching their technological limits in areas such as micron-level coating control, membrane deformation suppression, and ionomer distribution optimization. Therefore, it is crucial to break through existing fabrication paradigms and develop a novel one-step molding technology. Summary of the Invention

[0006] The purpose of this invention is to provide a membrane electrode based on direct coating process, its preparation method and application, which can prepare a three-in-one membrane electrode in one step. This solves the problems of complex production process and high production cost of transfer printing process, as well as the problem of proton exchange membrane swelling in the direct coating process.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a membrane electrode based on a direct coating process, comprising the following steps: (1) Preparation of cathode or anode catalyst slurry: The catalyst particles were dispersed in ultrapure water to obtain a catalyst dispersion; the perfluorosulfonic acid resin and organic alcohol were mixed to obtain an ionomer-alcohol mixture, which was then added to the catalyst dispersion and ball-milled to obtain a cathode or anode catalyst slurry. (2) Preparation of proton membrane solution: A proton exchange membrane solution is obtained by mixing perfluorosulfonic acid resin, ultrapure water, organic alcohol, and additives. (3) Fabrication of membrane electrodes: The cathode or anode catalyst slurry is coated onto the base membrane of the proton exchange membrane, and then the proton exchange membrane layer prepared based on the proton membrane solution in step (2) and the anode or cathode catalyst slurry are directly coated on it. After each layer is dried, it is annealed to obtain the membrane electrode.

[0008] Preferably, in step (1), the solid content of the cathode or anode catalyst slurry is 10-20%, the Pt content is 10-60%, the mass ratio of ultrapure water to organic alcohol is 0.45-2:1, and the I:C mass ratio of perfluorosulfonic acid resin to catalyst is 0.7-1.4:1.

[0009] Preferably, in step (1), the organic alcohol includes one or more of n-propanol, isopropanol, and ethanol; the catalyst includes one of Pt / C catalyst and PtM / C catalyst.

[0010] Preferably, in step (2), the mass ratio of ultrapure water to organic alcohol is 0.45 to 2:1, the solid content of perfluorosulfonic acid resin in the proton exchange membrane solution is 10 to 35%, and the amount of additive is 0.5 to 2% of the total solids.

[0011] Preferably, in step (2), the organic alcohol includes one or more of n-propanol, isopropanol, and ethanol.

[0012] Preferably, in step (3), the wet thickness of the cathode catalyst slurry is 120~160μm, the coating speed is 0.8~3.5m / min; the wet thickness of the anode catalyst slurry is 30~40μm, the coating speed is 0.8~3.5m / min, and the drying temperature is 80~100℃.

[0013] Preferably, in step (3), the proton exchange membrane includes a first slurry layer, an intermediate reinforcing layer, and a second slurry layer; the wet thickness of the first slurry layer is 40~60μm, the thickness of the intermediate reinforcing layer e-PTFE is 2~3μm, the wet thickness of the second slurry layer is 20~50μm, the coating speed is 0.8~3.5m / min, and the drying temperature is 120~140℃.

[0014] Preferably, the annealing temperature is 160~200℃.

[0015] The present invention also provides a membrane electrode prepared by the above preparation method.

[0016] The present invention also provides an application of the above-described membrane electrode in a fuel cell.

[0017] The beneficial effects of this invention compared to the prior art are as follows: This invention provides a method for preparing a membrane electrode based on a direct coating process. The cathode or anode catalyst slurry is directly coated onto one side of a proton exchange membrane (PEM) with a temporary support substrate. Subsequently, a PEM functional layer and catalyst slurry are directly coated onto the surface of the already coated catalyst layer, thereby achieving continuous construction of the PEM and both sides of the catalyst layer. Finally, annealing promotes interfacial fusion and structural densification, resulting in a complete three-in-one membrane electrode. This method completely eliminates the transfer film and hot-press transfer steps required in traditional transfer processes, simplifying the manufacturing process, reducing material and energy costs, and significantly increasing production speed. More importantly, by precisely controlling the coating sequence, slurry formulation, and drying-annealing process, the swelling and deformation of the PEM during wet-dry cycling are effectively suppressed, ensuring a flat membrane electrode structure and strong interfacial bonding. The resulting membrane electrode exhibits excellent catalyst layer / membrane interface compatibility, significantly improving battery performance and product consistency, combining technological advancement with industrial feasibility. Attached Figure Description

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

[0019] Figure 1 The membrane electrode prepared in Example 1 of this invention; Figure 2 The membrane electrode prepared in Example 2 of this invention. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention provides a method for preparing a membrane electrode based on a direct coating process, comprising the following steps: (1) Preparation of cathode or anode catalyst slurry: The catalyst particles are dispersed in ultrapure water to obtain a catalyst dispersion; a perfluorosulfonic acid resin is mixed with an organic alcohol to obtain an ionomer-alcohol mixture, which is then added to the catalyst dispersion and ball-milled to obtain a cathode or anode catalyst slurry; wherein the catalyst includes one of Pt / C catalyst and PtM / C catalyst, and M is one of Co, Ni, Cu, and Ru.

[0026] (2) Preparation of proton membrane solution: A proton exchange membrane solution is obtained by mixing perfluorosulfonic acid resin, ultrapure water, organic alcohol, and additives; wherein the additives are free radical quenchers or water-retaining agents. (3) Fabrication of membrane electrodes: The cathode or anode catalyst slurry is coated onto the base membrane of the proton exchange membrane, and then the proton exchange membrane layer prepared based on the proton membrane solution in step (2) and the anode or cathode catalyst slurry are directly coated on it. After each layer is dried, it is annealed to obtain the membrane electrode.

[0027] Example 1 Embodiment 1 of the present invention provides a method for preparing a membrane electrode based on a direct coating process, the specific steps of which are as follows: (1) Preparation of cathode and anode catalyst slurries: (1.1) Preparation of anode catalyst slurry: Weigh 2g Pt / C catalyst particles, 1.4g perfluorosulfonic acid resin, 12g ultrapure water, and 13.6g n-propanol; The catalyst particles were dispersed in ultrapure water to obtain a catalyst dispersion; the perfluorosulfonic acid resin and organic alcohol were mixed to obtain an ionomer-alcohol mixture, which was then added to the catalyst dispersion to obtain a preliminary dispersion slurry; the preliminary dispersion slurry was transferred to a ball mill, and grinding balls were added for ball milling. After ball milling, an anode catalyst slurry with a solid content (catalyst and perfluorosulfonic acid resin) of 11.7%, a Pt content of 17%, and an I:C mass ratio of 1.0 was obtained.

[0028] (1.2) Preparation of cathode catalyst slurry: Weigh 2.3g Pt / C catalyst particles, 1.3g perfluorosulfonic acid resin, 9.4g ultrapure water, and 17g n-propanol; The catalyst particles were dispersed in ultrapure water to obtain a catalyst dispersion; the perfluorosulfonic acid resin and organic alcohol were mixed to obtain an ionomer-alcohol mixture, which was then added to the catalyst dispersion to obtain a preliminary dispersion slurry; the preliminary dispersion slurry was transferred to a ball mill, and grinding balls were added for ball milling. After ball milling, a cathode catalyst slurry with a solid content (catalyst and perfluorosulfonic acid resin) of 12%, a Pt content of 30%, and an I:C mass ratio of 1.0 was obtained.

[0029] (2) Preparation of proton membrane solution: Weigh 9g of perfluorosulfonic acid resin, 25g of ultrapure water, 25g of isopropanol, and 1g of (free radical quencher) and mix them to obtain a proton exchange membrane solution with a perfluorosulfonic acid resin solid content of 15%. (3) Fabrication of membrane electrodes: The cathode catalyst slurry was coated onto the base membrane of the proton exchange membrane under the conditions of a wet thickness of 140 μm and a coating speed of 1 m / min, and then dried in an oven at 90 °C. After drying, a 30μm proton exchange membrane solution, a 4μm e-PTFE reinforcement layer, and a 20μm proton exchange membrane solution were directly coated on one side of the cathode catalyst layer at a coating speed of 1m / min, and then dried in an oven at 140℃. After drying, the anode catalyst slurry was directly coated on one side of the proton exchange membrane at a wet thickness of 40 μm and a coating speed of 1 m / min. The membrane electrode semi-finished product was then dried in an oven at 90°C. The membrane electrode semi-finished product is annealed at 180℃ to obtain a membrane electrode based on the direct coating process. Figure 1 ).

[0030] Example 2 Example 2 of this invention provides a method for preparing a membrane electrode based on a direct coating process using the cathode and anode catalyst slurries and proton exchange membrane solution prepared in Example 1. The specific steps are as follows: Fabrication of membrane electrodes: The anode catalyst slurry was coated onto the base membrane of the proton exchange membrane under the conditions of a wet thickness of 40 μm and a coating speed of 1 m / min, and then dried in an oven at 90 °C. After drying, a 30μm proton exchange membrane solution, a 4μm e-PTFE reinforcement layer, and a 20μm proton exchange membrane solution were directly coated on one side of the anode catalyst layer at a coating speed of 1m / min, and then dried in an oven at 140℃. After drying, the cathode catalyst slurry is coated onto the base membrane of the proton exchange membrane on one side of the proton exchange membrane under the conditions of a wet thickness of 140 μm and a coating speed of 1 m / min. The membrane electrode semi-finished product is then dried in an oven at 90°C. The membrane electrode semi-finished product is annealed at 180℃ to obtain a membrane electrode based on the direct coating process. Figure 2 ).

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a membrane electrode based on a direct coating process, characterized in that, Includes the following steps: (1) Preparation of cathode or anode catalyst slurry: The catalyst particles were dispersed in ultrapure water to obtain a catalyst dispersion; the perfluorosulfonic acid resin and organic alcohol were mixed to obtain an ionomer-alcohol mixture, which was then added to the catalyst dispersion and ball-milled to obtain a cathode or anode catalyst slurry. (2) Preparation of proton membrane solution: A proton exchange membrane solution is obtained by mixing perfluorosulfonic acid resin, ultrapure water, organic alcohol, and additives. (3) Fabrication of membrane electrodes: The cathode or anode catalyst slurry is coated onto the base membrane of the proton exchange membrane, and then the proton exchange membrane layer prepared based on the proton membrane solution in step (2) and the anode or cathode catalyst slurry are directly coated on it. After each layer is dried, it is annealed to obtain the membrane electrode.

2. The preparation method according to claim 1, characterized in that, In step (1), the solid content of the cathode or anode catalyst slurry is 10-20%, and the Pt content is 10-60%; the mass ratio of ultrapure water to organic alcohol is 0.45-2:1; and the I:C mass ratio of perfluorosulfonic acid resin to catalyst is 0.7-1.4:

1.

3. The preparation method according to claim 2, characterized in that, In step (1), the organic alcohol includes one or more of n-propanol, isopropanol, and ethanol; the catalyst includes one of Pt / C catalyst and PtM / C catalyst.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of ultrapure water to organic alcohol is 0.45 to 2:1, the solid content of perfluorosulfonic acid resin in the proton exchange membrane solution is 10 to 35%, and the amount of additive is 0.5 to 2% of the total solids.

5. The preparation method according to claim 1, characterized in that, In step (2), the organic alcohol includes one or more of n-propanol, isopropanol, and ethanol.

6. The preparation method according to claim 1, characterized in that, In step (3), the wet thickness of the cathode catalyst slurry is 120~160μm, the coating speed is 0.8~3.5m / min; the wet thickness of the anode catalyst slurry is 30~40μm, the coating speed is 0.8~3.5m / min, and the drying temperature is 80~100℃.

7. The preparation method according to claim 1, characterized in that, In step (3), the proton exchange membrane includes a first slurry layer, an intermediate reinforcement layer, and a second slurry layer; the wet thickness of the first slurry layer is 40~60μm, the thickness of the intermediate reinforcement layer e-PTFE is 2~4μm, the wet thickness of the second slurry layer is 20~50μm, the coating speed is 0.8~3.5m / min, and the drying temperature is 120~140℃.

8. The preparation method according to claim 7, characterized in that, The annealing temperature is 160~200℃.

9. A membrane electrode prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the membrane electrode according to claim 9 in a fuel cell.

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