Porous base membrane, catalyst-coated membrane electrode, and use thereof

Abstract

The application provides a porous substrate membrane, a catalyst coating membrane electrode and application thereof, and relates to the technical field of fuel cells. The porous substrate membrane is mainly prepared by laminating an expanded polytetrafluoroethylene porous membrane on a substrate layer; the expanded polytetrafluoroethylene porous membrane layer has micropores; after coating of a catalyst coating, the ionomer in the catalyst ink is affected by gravity and capillary force and penetrates into the pores of the porous substrate membrane, and thus the structure that the ionomer content of the catalyst coating membrane electrode prepared by transfer printing is higher in the catalyst layer part close to the proton exchange membrane side and lower in the catalyst layer part close to the gas diffusion layer is realized. Meanwhile, the substrate layer has higher strength and heat resistance, and the adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane is greater than 2 N / m, so that the demolding phenomenon in the transfer printing process is effectively avoided, and the deformation problem of the porous substrate membrane in the transfer printing process is also avoided.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a porous substrate membrane, a catalyst-coated membrane electrode, and their applications. Background Technology

[0002] The catalyst-coated membrane (CCM) is a core component of a proton exchange membrane fuel cell (PEMFC), primarily composed of a proton exchange membrane (PEM), a cathode catalyst layer, and an anode catalyst layer. The preparation of the catalyst-coated membrane and the optimization of the catalyst layer structure are key technologies for PEMFCs. Their structure and preparation process directly determine the performance of the fuel cell and are crucial for reducing production costs, increasing specific power, and accelerating commercialization.

[0003] In the preparation of catalyst-coated membranes, the substrate membrane is the material used for coating the ink. Fluid catalyst ink is uniformly coated onto the substrate membrane, then dried in an oven to form a solid catalyst layer. Subsequently, the catalyst layer on the substrate membrane is transferred to a proton exchange membrane via a hot-pressing process to form a catalyst-coated membrane electrode. Typically, the substrate membrane is a smooth plastic film, such as PTFE, PET, PEN, or PP. However, the plastic film used as the substrate membrane needs to maintain flatness during coating, without bending, curling, deformation, or wrinkles. Furthermore, it needs sufficient heat resistance during the transfer process, preventing deformation caused by temperature rise during hot pressing at approximately 160°C.

[0004] The porous substrate membrane consists of a plastic film (substrate layer, such as PET, PI, PEN, POM) and an e-PTFE layer laminated on the substrate layer. Because the e-PTFE layer has micropores of controllable size and shape, this structure has the advantage that the ionomers in the ink printed on the substrate membrane are subjected to gravity and capillary forces, causing the ionomers in the catalyst ink to penetrate downwards into the pores of the porous substrate membrane, forming a gradient change in ionomer concentration.

[0005] However, as Figure 1 As shown, due to the low adhesion between the e-PTFE layer and the substrate layer, film detachment often occurs during the transfer process, meaning that the e-PTFE is transferred to the proton exchange membrane along with the catalyst layer. Simultaneously, the existing substrate layer plastic film also has poor thermal stability, making it prone to shrinkage and deformation during hot-press transfer. Therefore, these two conditions result in significant technical defects in existing catalyst-coated membrane electrodes made from porous substrate membranes.

[0006] Therefore, it is both necessary and urgent to research and develop a porous base film that is not easily detached during the transfer process and has good heat resistance and is not easily deformed in order to overcome the above problems.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The first objective of this invention is to provide a porous substrate membrane that achieves a structure in which the catalyst coating membrane electrode prepared by transfer printing has a higher content of ionomers in the catalyst layer near the proton exchange membrane (PEM) and a lower content of ionomers in the catalyst layer near the gas diffusion layer (GDL). At the same time, the porous substrate membrane also has high strength and heat resistance.

[0009] The second objective of this invention is to provide a method for preparing a porous base membrane.

[0010] A third objective of the present invention is to provide a catalyst-coated membrane electrode, wherein the catalyst layer of the catalyst-coated membrane electrode is mainly obtained by transfer from the above-mentioned porous substrate membrane.

[0011] The fourth objective of this invention is to provide an application of a porous substrate membrane and a catalyst-coated membrane electrode, which can be widely used in the preparation process of proton exchange membrane fuel cells.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] The present invention provides a porous substrate membrane, which is mainly made by laminating an expanded polytetrafluoroethylene porous membrane onto a substrate layer;

[0014] The adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane is >2N / m;

[0015] The properties of the substrate layer must satisfy at least one of the following:

[0016] Glass transition temperature > 90℃, crystallinity 35-39%, mechanical strength 320-355 MPa.

[0017] Furthermore, the substrate layer includes any one of PET film, PI film, PEN film, and POM film, preferably PET film.

[0018] Furthermore, the pore size of the expanded polytetrafluoroethylene porous membrane is 0.5–50 μm;

[0019] The surface tension of the expanded polytetrafluoroethylene porous membrane is <30mN / m.

[0020] The present invention provides a method for preparing the above-mentioned porous base membrane, the method comprising:

[0021] (a) Heat the substrate layer to 250-280°C and hold for 10-60 min to obtain intermediate A;

[0022] (b) When intermediate A is cooled to 200-230°C, intermediate A is laminated with expanded polytetrafluoroethylene porous membrane to obtain intermediate B.

[0023] (c) Cool intermediate B to 100-140°C and hold for 10-60 min, then cool to 20-30°C to obtain a porous basement membrane.

[0024] Furthermore, step (a) is performed under a protective gas atmosphere;

[0025] Preferably, the protective gas includes at least one of nitrogen, argon, and carbon dioxide.

[0026] Furthermore, in step (a), the heating rate of the substrate layer is 1–10 °C / min;

[0027] Preferably, the cooling rate of intermediate A in step (b) is 1–5 °C / min;

[0028] Preferably, the cooling rate of intermediate B in step (c) is 1-5 °C / min.

[0029] Furthermore, in step (b), the pressure at which intermediate A is laminated with the expanded polytetrafluoroethylene porous membrane is 1-2.5 MPa.

[0030] The present invention provides a catalyst-coated membrane electrode, wherein the catalyst layer of the catalyst-coated membrane electrode is mainly obtained by transfer from the above-mentioned porous substrate membrane.

[0031] The application of the porous substrate membrane and catalyst-coated membrane electrode provided by this invention in the preparation of proton exchange membrane fuel cells.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The porous substrate membrane provided by this invention is mainly made by laminating an expanded polytetrafluoroethylene (e-PTFE) porous membrane onto a substrate layer. The e-PTFE porous membrane layer has micropores of controllable size and shape. After the catalyst coating is applied, the ionomers in the catalyst ink are subjected to gravity and capillary forces and will penetrate downwards into the pores of the porous substrate membrane. This results in a catalyst coating membrane electrode prepared by transfer printing having a higher ionomer content in the catalyst layer near the proton exchange membrane (PEM) and a lower ionomer content in the catalyst layer near the gas diffusion layer (GDL). This gradient distribution of ionomer concentration is more conducive to constructing transport channels for protons, electrons, and reactants in the catalyst layer.

[0034] Meanwhile, the adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane in this application is >2 N / m, effectively preventing the e-PTFE layer from detaching during the transfer process. Furthermore, the substrate layer in this application satisfies at least one of the following properties: glass transition temperature >90℃, crystallinity 35-39%, and mechanical strength 320-355 MPa. Therefore, the substrate layer in this application possesses high strength and heat resistance, and also avoids the shrinkage and deformation problems during the hot-press transfer process of the porous substrate membrane.

[0035] The present invention provides a method for preparing a porous substrate membrane, wherein the method involves laminating a substrate layer with an expanded polytetrafluoroethylene (ePTFE) porous membrane during the heat treatment of the substrate layer to obtain the porous substrate membrane. The above preparation method has the advantages of simple processing and ease of operation.

[0036] The catalyst-coated membrane electrode provided by this invention has a catalyst layer mainly obtained by transfer printing from the aforementioned porous substrate membrane. Because the e-PTFE layer in the porous substrate membrane has micropores of controllable size and shape, the ionomers in the catalyst ink printed on the substrate membrane are subjected to gravity and capillary forces, penetrating downwards into the pores of the porous substrate membrane. This results in a higher ionomer content in the catalyst layer portion near the proton exchange membrane (PEM) and a lower ionomer content near the gas diffusion layer (GDL) of the catalyst layer. This gradient distribution of ionomer concentration is more conducive to constructing transport channels for protons, electrons, and reactants in the catalyst layer. This, in turn, improves the electrochemical performance of the catalyst-coated membrane electrode, optimizes the CCM structure, and increases the specific power of the proton exchange membrane fuel cell (PEMFC) to meet the requirements of fuel cell vehicles.

[0037] The porous substrate membrane and catalyst-coated membrane electrode provided by this invention can be widely used in the preparation process of proton exchange membrane fuel cells. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram illustrating the technical defects of catalyst-coated membrane electrodes prepared from existing porous substrate membranes as provided in the background art of this invention.

[0040] Figure 2 This is a schematic diagram of the porous substrate membrane prepared in Example 1 of the present invention;

[0041] Figure 3 This is a comparison chart of the electrochemical performance of the catalyst-coated membrane electrode prepared with a porous substrate membrane provided in Experimental Example 2 of the present invention and the catalyst-coated membrane electrode prepared with a conventional non-porous substrate membrane. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] According to one aspect of the present invention, a porous base membrane is provided, the porous base membrane being mainly formed by laminating an expanded polytetrafluoroethylene porous membrane onto a substrate layer;

[0044] The adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane is >2N / m;

[0045] The properties of the substrate layer must satisfy at least one of the following:

[0046] Glass transition temperature > 90℃, crystallinity 35-39%, mechanical strength 320-355 MPa.

[0047] The porous substrate membrane provided by this invention is mainly made by laminating an expanded polytetrafluoroethylene (e-PTFE) porous membrane onto a substrate layer. The e-PTFE porous membrane layer has micropores of controllable size and shape. After the catalyst coating is applied, the ionomers in the catalyst ink are subjected to gravity and capillary forces and will penetrate downwards into the pores of the porous substrate membrane. This results in a catalyst coating membrane electrode prepared by transfer printing having a higher ionomer content in the catalyst layer near the proton exchange membrane (PEM) and a lower ionomer content in the catalyst layer near the gas diffusion layer (GDL). This gradient distribution of ionomer concentration is more conducive to constructing transport channels for protons, electrons, and reactants in the catalyst layer.

[0048] Meanwhile, the adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane in this application is >2 N / m, effectively preventing the e-PTFE layer from detaching during the transfer process. Furthermore, the substrate layer in this application satisfies at least one of the following properties: glass transition temperature >90℃, crystallinity 35-39%, and mechanical strength 320-355 MPa. Therefore, the substrate layer in this application possesses high strength and heat resistance, and also avoids the shrinkage and deformation problems during the hot-press transfer process of the porous substrate membrane.

[0049] In a preferred embodiment of the present invention, the substrate layer includes any one of PET film, PI film, PEN film, and POM film, preferably PET film.

[0050] In a preferred embodiment of the present invention, the pore size of the expanded polytetrafluoroethylene porous membrane is 0.5 to 50 μm;

[0051] The surface tension of the expanded polytetrafluoroethylene porous membrane is <30mN / m.

[0052] As a preferred embodiment, since the pore size, porosity, and thickness of the e-PTFE porous substrate membrane are controllable, the catalyst layer structure can be optimized by controlling the porosity and thickness. In this application, the expanded polytetrafluoroethylene porous membrane within the aforementioned pore size and surface tension range allows the ionomers in the catalyst ink to better penetrate downwards into the pores of the porous substrate membrane under the influence of gravity and capillary forces after the catalyst coating is applied.

[0053] According to one aspect of the present invention, a method for preparing the above-mentioned porous base membrane, the method comprising:

[0054] (a) Heat the substrate layer to 250-280°C and hold for 10-60 min to obtain intermediate A;

[0055] It should be noted that step (a) can make the substrate layer viscoelastic at a temperature of 250-280°C. Maintaining this temperature for 10-60 minutes allows the polymer chains to fully extend, thereby reducing the steric hindrance of the molecular chains and forming more crystalline regions during the next cooling process.

[0056] (b) When intermediate A is cooled to 200-230°C, intermediate A is laminated with expanded polytetrafluoroethylene porous membrane to obtain intermediate B.

[0057] It should be noted that in step (b), cooling intermediate A to 200-230°C can cause the polymer chains to shrink in an orderly manner, reducing entanglement and promoting the formation and growth of crystalline regions. Subsequently, the intermediate A is laminated with the expanded polytetrafluoroethylene porous membrane, which allows the polymer chains near the interface between the two materials to penetrate and entangle with each other. At this temperature, under the action of the roller press, the polymer chains near the interface between e-PTFE and PET will move, penetrate and entangle with each other. This can improve the mechanical properties of the interface between the two materials, while keeping the pore structure of the e-PTFE layer unaffected.

[0058] (c) Cool intermediate B to 100-140°C and hold for 10-60 min, then cool to 20-30°C to obtain a porous basement membrane.

[0059] It should be noted that step (c) of cooling intermediate B to 100-140°C and holding it for 10-60 minutes can further shrink the polymer chains, increase the crystallization area, and thus improve its mechanical strength and thermal stability.

[0060] As a preferred embodiment, the above-mentioned heat treatment process can effectively improve the crystallinity of the porous base film, increase the glass transition temperature, and thus improve its mechanical and thermal stability. It can not only ensure that the substrate layer of the porous base film can maintain flatness during coating and avoid bending, curling, deformation and wrinkling, but also give the porous base film good heat resistance and prevent deformation caused by temperature rise during hot pressing at around 160°C.

[0061] It should also be noted that the porous substrate film prepared by the above process can achieve a glass transition temperature >90℃, a crystallinity of 35-39%, and a mechanical strength of 320-355 MPa, effectively avoiding high-temperature deformation of the substrate layer during the transfer process. Furthermore, the mechanical strength of the e-PTFE layer in the porous substrate film is greatly improved. Testing shows that the mechanical strength of the e-PTFE layer meets the following conditions:

[0062] “(A) = (B) > (C)”, or “(A) > (B) > (C)”, or “(B) > (C) and (B) > (A)”;

[0063] Wherein, (A) is the interfacial adhesion force between the substrate layer and e-PTFE (2N / m);

[0064] (B) represents the mechanical strength of e-PTFE;

[0065] (C) represents the interfacial adhesion between e-PTFE and the catalyst layer.

[0066] In a preferred embodiment of the present invention, step (a) is performed under a protective gas.

[0067] Preferably, the protective gas includes at least one of nitrogen, argon, and carbon dioxide.

[0068] In a preferred embodiment of the present invention, the heating rate of the substrate layer in step (a) is 1 to 10 °C / min;

[0069] Preferably, the cooling rate of intermediate A in step (b) is 1–5 °C / min;

[0070] Preferably, the cooling rate of intermediate B in step (c) is 1-5 °C / min.

[0071] As a preferred embodiment, the above-mentioned heating is performed.

[0072] In a preferred embodiment of the present invention, the pressure at which intermediate A is laminated with expanded polytetrafluoroethylene porous membrane in step (b) is 1-2.5 MPa.

[0073] According to one aspect of the present invention, a catalyst-coated membrane electrode is provided, wherein the catalyst layer of the catalyst-coated membrane electrode is mainly obtained by transfer from the above-mentioned porous substrate membrane.

[0074] The catalyst-coated membrane electrode provided by this invention has a catalyst layer mainly obtained by transfer printing from the aforementioned porous substrate membrane. Because the e-PTFE layer in the porous substrate membrane has micropores of controllable size and shape, the ionomers in the catalyst ink printed on the substrate membrane are subjected to gravity and capillary forces, penetrating downwards into the pores of the porous substrate membrane. This results in a higher ionomer content in the catalyst layer portion near the proton exchange membrane (PEM) and a lower ionomer content near the gas diffusion layer (GDL) of the catalyst layer. This gradient distribution of ionomer concentration is more conducive to constructing transport channels for protons, electrons, and reactants in the catalyst layer. This, in turn, improves the electrochemical performance of the catalyst-coated membrane electrode, optimizes the CCM structure, and increases the specific power of the proton exchange membrane fuel cell (PEMFC) to meet the requirements of fuel cell vehicles.

[0075] It should be noted that in existing substrate membrane solutions that consist only of plastic films, after the catalyst ink fluid is coated onto the substrate membrane, the ionomer concentration near the substrate membrane is higher due to gravity. Consequently, when transferred to the PEM, the ionomer concentration near the PEM is lower than that near the substrate membrane, which is detrimental to the construction of transport channels for protons, electrons, and reactants in the catalyst layer. Under the premise of using the same materials, this type of catalyst layer structure is not conducive to the optimization of PEMFC performance.

[0076] This application, through the setting of the e-PTFE layer, allows the ionomers in the catalyst ink to penetrate downwards into the pores of the porous substrate membrane, thereby achieving a gradient change in the concentration of ionomers. This avoids the problem in the prior art where "the concentration of ionomers near the PEM side is lower than that near the gas diffusion layer (GDL)," optimizes the CCM structure, and improves the electrochemical performance of the catalyst-coated membrane electrode.

[0077] According to one aspect of the present invention, the application of porous substrate membranes and catalyst-coated membrane electrodes in the preparation of proton exchange membrane fuel cells.

[0078] The porous substrate membrane and catalyst-coated membrane electrode provided by this invention can be widely used in the preparation process of proton exchange membrane fuel cells.

[0079] The technical solution of the present invention will be further described below with reference to the embodiments.

[0080] Example 1

[0081] like Figure 2 As shown, a porous base membrane is prepared by means of the following steps:

[0082] (a) Under inert gas protection, the PET substrate layer is heated to 250°C at a heating rate of 1°C / min to make the PET substrate layer exhibit a viscoelastic state; then it is kept at this temperature for 10 min to obtain intermediate A;

[0083] (b) Intermediate A is slowly cooled at a cooling rate of 1℃ / min. When the temperature drops to 200℃, it is introduced into the e-PTFE roll. At this temperature, under the action of the roller press, the polymer chains of e-PTFE and PET will move near the contact surface, penetrate and entwine with each other to obtain intermediate B.

[0084] The expanded polytetrafluoroethylene porous membrane (e-PTFE) has a pore size of 0.5 μm and a surface tension of 28 mN / m;

[0085] (c) The intermediate B was slowly cooled at a rate of 1℃ / min to 100℃, held for 20 min, and then cooled to 20℃ to obtain a porous basement membrane.

[0086] Example 2

[0087] A porous base membrane, the method for preparing the porous base membrane includes the following steps:

[0088] (a) Under inert gas protection, the PET substrate layer was heated to 280°C at a heating rate of 10°C / min to make the PET substrate layer exhibit a viscoelastic state; then it was kept at this temperature for 60 min to obtain intermediate A.

[0089] (b) Intermediate A is slowly cooled at a cooling rate of 5℃ / min. When the temperature drops to 230℃, it is introduced into the e-PTFE roll. At this temperature, under the action of the roller press, the polymer chains of e-PTFE and PET near the contact surface will move, penetrate and entwine with each other to obtain intermediate B.

[0090] The expanded polytetrafluoroethylene porous membrane (e-PTFE) has a pore size of 50 μm and a surface tension of 10 mN / m;

[0091] (c) Intermediate B is slowly cooled at a rate of 5°C / min to 140°C, held at that temperature for 60 min, and then cooled to 30°C to obtain a porous basement membrane.

[0092] Example 3

[0093] A porous base membrane, the method for preparing the porous base membrane includes the following steps:

[0094] (a) Under inert gas protection, the PET substrate layer was heated to 270°C at a heating rate of 8°C / min to make the PET substrate layer exhibit a viscoelastic state; then it was kept at this temperature for 40 min to obtain intermediate A.

[0095] (b) Intermediate A is slowly cooled at a cooling rate of 3℃ / min. When the temperature drops to 220℃, it is introduced into the e-PTFE roll. At this temperature, under the action of the roller press, the polymer chains of e-PTFE and PET near the contact surface will move, penetrate and entwine with each other to obtain intermediate B.

[0096] The expanded polytetrafluoroethylene porous membrane (e-PTFE) has a pore size of 25 μm and a surface tension of 18 mN / m;

[0097] (c) Intermediate B is slowly cooled at a rate of 3℃ / min to 125℃, held at that temperature for 40 min, and then cooled to 25℃ to obtain a porous basement membrane.

[0098] Comparative Example 1

[0099] Except for the heat preservation time of 5 minutes in step (a), this embodiment is the same as embodiment 3.

[0100] Comparative Example 2

[0101] Except for the cooling rate of 10℃ / min in steps (b) and (c), this embodiment is the same as embodiment 3.

[0102] Comparative Example 3

[0103] A porous base membrane, the method for preparing the porous base membrane includes the following steps:

[0104] (a) Under inert gas protection, the PET substrate layer was heated to 270°C at a heating rate of 8°C / min to make the PET substrate layer exhibit a viscoelastic state; then it was kept at this temperature for 40 min to obtain intermediate A.

[0105] (b) Intermediate A is slowly cooled at a cooling rate of 3℃ / min. When the temperature drops to 220℃, it is introduced into the e-PTFE roll. At this temperature, under the action of the roller press, the polymer chains of e-PTFE and PET will move near the contact surface, penetrate and entwine with each other to obtain intermediate B. Then, the temperature is cooled to 25℃ to obtain a porous base film.

[0106] The expanded polytetrafluoroethylene porous membrane (e-PTFE) has a pore size of 25 μm and a surface tension of 18 mN / m;

[0107] This embodiment is the same as embodiment 3 except that step (c) of keeping warm at 125°C for 40 minutes is not included.

[0108] Comparative Example 4

[0109] A porous base membrane, the method for preparing the porous base membrane includes the following steps:

[0110] (a) When the PET substrate layer is heated to 220°C at a heating rate of 8°C / min, it is introduced into the e-PTFE roll. At this temperature, the polymer chains of e-PTFE and PET will move near the contact surface under the action of the roller press, and penetrate and entangle with each other. Then, the temperature is cooled to 25°C to obtain a porous base film.

[0111] The expanded polytetrafluoroethylene porous membrane (e-PTFE) has a pore size of 25 μm and a surface tension of 18 mN / m.

[0112] Experimental Example 1

[0113] To demonstrate that the porous substrate membrane prepared in this application can effectively avoid the problem of membrane delamination during the transfer process due to the low adhesion between the e-PTFE layer and the substrate layer, and the poor thermal stability of the existing substrate layer, which easily shrinks and deforms during hot pressing transfer, the porous substrate membranes prepared in Examples 1-3 and Comparative Examples 1-4 were coated with catalyst ink and their performance was tested. The specific results are shown in the table below:

[0114]

[0115] As shown in the above experiments, the porous substrate film prepared by the above process of this application can achieve the technical effects of a glass transition temperature >90℃, crystallinity of 35-39%, and mechanical strength of 320-355 MPa for the substrate layer, effectively avoiding high-temperature deformation of the substrate layer during the transfer process; at the same time, the mechanical strength of the e-PTFE layer in the porous substrate film can be greatly improved, and the adhesion between its substrate layer and the expanded polytetrafluoroethylene porous film is >2 N / m; according to the test, the mechanical strength of the e-PTFE layer in the technical solutions of Examples 1-3 of this application can meet the following conditions:

[0116] “(A) = (B) > (C)”, or “(A) > (B) > (C)”, or “(B) > (C) and (B) > (A)”;

[0117] Wherein, (A) is the interfacial adhesion force between the substrate layer and e-PTFE (>2N / m);

[0118] (B) represents the tear strength of e-PTFE;

[0119] (C) represents the interfacial adhesion between e-PTFE and the catalyst layer.

[0120] This effectively avoids the phenomenon of e-PTFE layer peeling off during the transfer process.

[0121] In Comparative Examples 1-4, the interfacial adhesion between the substrate layer and e-PTFE was relatively low. In particular, the interfacial adhesion between the substrate layer and e-PTFE in Comparative Examples 1, 3, and 4 was even lower than that between e-PTFE and the catalyst layer. Consequently, the e-PTFE layer was more prone to delamination during the heat transfer process. Furthermore, the glass transition temperature, crystallinity, and mechanical strength of Comparative Examples 1-4 were also poor. In particular, the embodiment of Comparative Example 4, in which the substrate layer was not heat-treated, resulted in a glass transition temperature of only 77°C, a crystallinity of only 5%, and a mechanical strength of only 75 MPa. These properties indicate that the porous substrate films prepared in Comparative Examples 1-4 were also more prone to high-temperature deformation during the heat transfer process.

[0122] Experimental Example 2

[0123] To demonstrate that the catalyst-coated membrane electrode obtained by transferring the porous substrate membrane prepared in this application has a higher ionomer content in the catalyst layer near the proton exchange membrane (PEM) and a lower ionomer content in the catalyst layer near the gas diffusion layer (GDL), this ionomer concentration gradient distribution is more conducive to constructing transport channels for protons, electrons, and reactants in the catalyst layer. This, in turn, improves the electrochemical performance of the catalyst-coated membrane electrode.

[0124] The applicant now describes the solid catalyst layer formed by drying catalyst ink coated on a porous substrate membrane in Example 3, and the solid catalyst coating obtained from a conventional non-porous substrate membrane. The catalyst layer on the substrate membrane is transferred to a proton exchange membrane via a hot-pressing process to form a catalyst-coated membrane electrode. The catalyst-coated membrane electrode is then tested, and the specific results are as follows: Figure 3 As shown:

[0125] Depend on Figure 3 As can be seen, compared with the existing catalyst coating membrane electrode prepared by the porous substrate membrane in Example 3 of this application, the catalyst coating membrane electrode prepared by the porous substrate membrane has a more efficient construction of the transport channels for protons, electrons and reactants in its catalyst layer. As the current density increases, the catalyst coating membrane electrode prepared by the porous substrate membrane in this application can still maintain a higher average voltage than the existing catalyst coating membrane electrode.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A porous base membrane, characterized in that, The porous substrate membrane is mainly made by laminating an expanded polytetrafluoroethylene porous membrane onto a substrate layer. The adhesion between the substrate layer and the expanded polytetrafluoroethylene porous membrane is >2N / m; The properties of the substrate layer simultaneously satisfy the following parameters: Glass transition temperature > 90℃, crystallinity 35~39%, mechanical strength 320~355MPa; The substrate layer is either a PET film or a PEN film.

2. The porous substrate membrane according to claim 1, characterized in that, The substrate layer is a PET film.

3. The porous substrate membrane according to claim 1, characterized in that, The expanded polytetrafluoroethylene porous membrane has a pore size of 0.5~50μm; The surface tension of the expanded polytetrafluoroethylene porous membrane is <30mN / m.

4. A method for preparing a porous basement membrane according to any one of claims 1 to 3, characterized in that, The preparation method includes: (a) Heat the substrate layer to 250~280℃ and hold for 10~60 min to obtain intermediate A; (b) When intermediate A is cooled to 200~230℃, intermediate A is laminated with expanded polytetrafluoroethylene porous membrane to obtain intermediate B; (c) Cool intermediate B to 100~140℃, keep warm for 10~60min, and then cool to 20~30℃ to obtain a porous basement membrane.

5. The method for preparing a porous base membrane according to claim 4, characterized in that, Step (a) is performed under a protective gas atmosphere.

6. The method for preparing a porous base membrane according to claim 5, characterized in that, The protective gas includes at least one of nitrogen, argon, and carbon dioxide.

7. The method for preparing a porous base membrane according to claim 4, characterized in that, The heating rate of the substrate layer in step (a) is 1~10℃ / min.

8. The method for preparing a porous base membrane according to claim 4, characterized in that, In step (b), the cooling rate of intermediate A is 1~5℃ / min.

9. The method for preparing a porous base membrane according to claim 4, characterized in that, In step (c), the cooling rate of intermediate B is 1~5℃ / min.

10. The method for preparing a porous base membrane according to claim 4, characterized in that, In step (b), the pressure at which intermediate A is laminated with expanded polytetrafluoroethylene porous membrane is 1~2.5 MPa.

11. A catalyst-coated membrane electrode, characterized in that, The catalyst layer of the catalyst-coated membrane electrode is mainly obtained by transferring the porous substrate membrane as described in any one of claims 1 to 3.

12. The application of the porous substrate membrane as described in any one of claims 1 to 3 or the catalyst-coated membrane electrode as described in claim 11 in the preparation of proton exchange membrane fuel cells.

Images