A method for preparing a membrane electrode of a multi-layer catalytic layer structure

Abstract

The present application belongs to the field of fuel cell, and particularly relates to a preparation method of a membrane electrode with a multi-layer catalytic layer structure. In the method, a layer of cathode catalytic layer is prepared on a proton exchange membrane and a PTFE membrane respectively, then the two layers of cathode catalytic layer are oppositely placed, the cathode catalytic layer on the PTFE is transferred to the cathode catalytic layer on the proton exchange membrane by hot pressing transfer printing to form a two-layer structure of the cathode catalytic layer, then an anode catalytic layer is coated on the other side of the proton exchange membrane to form a membrane electrode with a multi-layer catalytic layer structure. The method can independently design the structure of the multi-layer cathode catalytic layer, and is more convenient for layering on the structure of the cathode catalytic layer, so as to optimize the mass transfer process in the cathode catalytic layer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fuel cell, and particularly relates to a preparation method of a membrane electrode with a multi-layer catalytic layer structure. BACKGROUND

[0002] The membrane electrode is the core component of the fuel cell, and the performance and durability of the membrane electrode depend to a great extent on the structure of the catalyst layer of the catalyst coated membrane (CCM) in the membrane electrode. The general CCM has a three-layer structure, with a proton exchange membrane in the middle, and an anode catalytic layer and a cathode catalytic layer on both sides of the proton exchange membrane. In terms of working principle of the fuel cell, the anode is the place where the hydrogen oxidation reaction (HOR) is completed, and the cathode is the place where the oxygen reduction reaction (ORR) is completed; the electrons generated by the anode flow to the cathode through the external circuit after doing work, and the [H + ] generated at the same time reaches the cathode through the electrolyte membrane; and then reacts with oxygen to generate water.

[0003] The performance of the membrane electrode is determined by all the membrane electrode materials such as catalysts, ionomers, proton membranes, etc. on the one hand, and by the catalytic layer structure of the membrane electrode, especially the cathode catalytic layer structure, on the other hand. The catalytic layer is not only the place of reaction, but also the place where the raw materials (air and hydrogen) of the reaction need to be transported to reach the catalytic active sites, and the water generated by the reaction needs to be diffused out of the catalytic layer for further discharge. Therefore, optimizing the structure of the catalytic layer to accelerate the transport of the reactants in the catalytic layer and the discharge of the water in the catalytic layer is a hot research field.

[0004] The design of structurally layered or gradiented catalyst layer, especially cathode catalyst layer, can optimize the mass transfer process in the catalyst layer. There are many literatures that disclose the design of multi-layer catalyst layer structure or gradiented catalyst layer design. Patent CN108063267A discloses a method for adjusting the porosity of a two-layer structure by adjusting the solid content in the slurry and using electrostatic spraying technology to enhance mass transfer. Patent CN103367768A discloses a method for preparing a double-layer catalyst layer structure, which uses a spraying process to first prepare a first catalyst layer, then sprays carbon powder onto the first catalyst layer, and then immerses the carbon powder layer in a solution of platinum precursor and weak reducing agent to obtain a two-layer structure to improve the performance of the membrane electrode. Patent CN103165915A discloses a multi-layer catalyst layer with high platinum content and ion concentration near the proton exchange membrane side and relatively low near the diffusion layer side to improve the reaction efficiency at low current density. The method for preparing the catalyst layer is spraying. Patent CN1612381A discloses a multi-layer structure that is more hydrophilic near the proton exchange membrane and more hydrophobic near the diffusion layer to improve the mass transfer capacity of the catalyst layer; the implementation is spraying. From the currently disclosed literatures, it can be seen that there are many benefits in constructing a multi-layer catalyst layer structure in the membrane electrode, especially in the cathode of the membrane electrode, such as improving the performance of the membrane electrode, improving the mass transfer capacity, and reducing the Pt loading in the membrane electrode. However, it is also noted that the usual method for preparing a double-layer catalyst layer structure or a multi-layer catalyst layer structure is to directly spray on the proton membrane or to spray two layers on the polytetrafluoroethylene (PTFE) and then transfer it to the proton exchange membrane. The spraying method for preparing a multi-layer structure catalyst layer is slow and inefficient, and is not suitable for large-scale applications. In addition, the spraying technology has high requirements for the particle size, viscosity and solid content of the slurry. Usually, small catalyst particle size, low viscosity and low solid content are required for effective spraying. The properties of the slurry have a decisive effect on the structure of the catalyst layer formed, so the use of spraying technology has great limitations on the structural design of the catalyst layer. In addition, the continuous spraying method usually affects the structure of the subsequent layer, which is not conducive to the design of independent two-layer catalyst layers. SUMMARY

[0005] In view of the defects in the above-mentioned prior art related to the construction method of double-layer or multi-layer cathode catalyst layer, the present application provides a method for preparing a membrane electrode with a multi-layer catalyst layer structure.

[0006] To achieve the above-mentioned purpose, the specific technical solutions include the following:

[0007] A method for preparing a membrane electrode with a multi-layer catalyst layer structure, comprising the following steps,

[0008] (1) preparing catalyst slurry A and catalyst slurry B;

[0009] (2) The catalyst slurry A is coated on one side of the proton exchange membrane, and after drying, it serves as the cathode catalyst layer A to obtain a proton exchange membrane containing the cathode catalyst layer A; the catalyst slurry B is coated on one side of the polytetrafluoroethylene film, and after drying, it serves as the cathode catalyst layer B to obtain a polytetrafluoroethylene film containing the cathode catalyst layer B; the proton exchange membrane containing the cathode catalyst layer A and / or the polytetrafluoroethylene film containing the cathode catalyst layer B also undergoes wetting treatment;

[0010] (3) The side of the cathode catalyst layer A on the proton exchange membrane in step (2) is placed in correspondence with the side of the cathode catalyst layer B on the polytetrafluoroethylene film, and then heat pressing and transfer printing are performed, and after the heat pressing and transfer printing, the polytetrafluoroethylene film is removed to obtain a proton exchange membrane containing a double-layer cathode catalyst layer;

[0011] (4) At least one anode catalyst layer is coated on the side of the proton exchange membrane containing the double-layer cathode catalyst layer in step (3) without a catalyst layer, and after drying, a membrane electrode with a multi-layer catalyst layer structure is obtained.

[0012] The present application constructs a double-layer structure of the cathode catalyst layer of the membrane electrode by the method of heat pressing and transfer printing a single-layer catalyst layer. A layer of cathode catalyst layer is first prepared on the proton exchange membrane and the PTFE film, respectively, then the two layers of cathode catalyst layer are placed opposite to each other, and through heat pressing and transfer printing, the cathode catalyst layer on the PTFE is transferred to the cathode catalyst layer on the proton exchange membrane to form a two-layer cathode catalyst layer, and then a catalyst layer is coated on the other side of the proton exchange membrane to form a membrane electrode with a multi-layer cathode catalyst layer structure. It is particularly worth noting that transferring another layer of cathode catalyst layer to the cathode catalyst layer is not as easy as transferring the catalyst layer to the proton exchange membrane, because the adhesion of the catalyst layer to another layer of catalyst layer is much lower than the adhesion of the proton exchange membrane to the catalyst layer, and direct transfer can easily cause incomplete transfer and poor bonding of the two layers of catalyst layer. As mentioned in patent document CN113684458A, the technology of transferring a multi-walled disordered carbon nanotube thin layer to the catalyst layer also needs to spray a thin layer of Nafion on the transferred carbon nanotube thin layer as an adhesive. However, this method is not suitable for use in a two-layer catalyst layer system, because the sprayed thin layer of Nafion has strong water absorption capacity, which can easily cause flooding of the catalyst layer. In order to overcome the difficulty of transferring another layer of catalyst layer to the catalyst layer, we further optimize the transfer method and add a pretreatment step of surface treatment of the catalyst layer. Through research, it is found that by pre-wetting the catalyst layer before transfer, the transfer quality can be greatly improved.

[0013] At least one of the following properties of the two layers of cathode catalyst layers on the proton exchange membrane and the PTFE membrane is different: pore structure, type and content of ionomer, type and content of catalyst, content and type of surfactant, content and type of additive, platinum loading, thickness of the catalyst layer, roughness of the catalyst layer, and surface hydrophobicity.

[0014] As a preferred embodiment of the present application, the solvent for the wetting treatment in step (2) is water or a mixture of an organic solvent and water; the organic solvent is at least one of alcohol or ether with a boiling point lower than 150 DEG C; and the mass percentage of the organic solvent in the mixture of the organic solvent and water is 0-40%.

[0015] The solvent for the wetting treatment is pure water, an organic solvent or a mixture containing part of the organic solvent, and the content of the organic solvent in the mixture is less than 40wt%. The organic solvent used can be alcohol such as methanol, ethanol, n-(iso)propanol, butanol, and ether with a boiling point lower than 150 DEG C such as methyl ether, ethyl ether, ethoxy ethanol, and methoxy ethanol.

[0016] As a preferred embodiment of the present application, the wetting treatment in step (2) includes at least one of dipping, spraying, and humidification.

[0017] At least one of the cathode catalyst layers on the proton exchange membrane and the PTFE membrane is subjected to wetting treatment before hot pressing. The wetting treatment can be dipping the cathode catalyst layer into a solvent, spraying the solvent onto the surface of the cathode catalyst layer, or humidifying the cathode catalyst layer.

[0018] As a preferred embodiment of the present application, the temperature for the hot pressing transfer printing in step (3) is 120-250 DEG C, the pressure is 0.2-5 MPa, and the time is 10-360 s.

[0019] As a further preferred embodiment of the present application, the temperature for the hot pressing transfer printing in step (3) is 150-190 DEG C, the pressure is 0.5-1 MPa, and the time is 30-120 s.

[0020] As a preferred embodiment of the present application, in steps (2) and (4), the coating includes at least one of ultrasonic spraying, electrostatic spraying, doctor blade coating, slot coating, and screen printing.

[0021] The method for preparing the catalyst layer on the PTFE can be ultrasonic spraying, electrostatic spraying, doctor blade coating, slot coating, screen printing, or the like, and the slot coating is preferred.

[0022] The method for preparing the catalytic layer on the proton exchange membrane can be ultrasonic spraying, electrostatic spraying, doctor blade coating, slot coating, screen printing, thermal transfer printing and the like, and is preferably slot coating.

[0023] As a preferred embodiment of the present application, the catalyst slurry A in step (1) comprises the following components: catalyst, resin, solvent; the catalyst slurry B in step (1) comprises the following components: catalyst, perfluorosulfonic acid resin, solvent.

[0024] As a preferred embodiment of the present application, the catalyst comprises at least one of Pt / C catalyst, PtM / C catalyst, Fe-N-C catalyst, M in the PtM / C catalyst is at least one metal comprising Co, Fe, Cu, Ni, Mn, Cr, Pd, Ir, Au, Ag, Ru; the resin is perfluorosulfonic acid resin; the solvent is a mixed solution of alcohol and water, the alcohol comprises at least one of methanol, ethanol, propanol, butanol.

[0025] As a preferred embodiment of the present application, the mass ratio of the catalyst to the resin is 1: (0.1-3).

[0026] As a further preferred embodiment of the present application, the mass ratio of the catalyst to the resin is 1: (0.3-0.8).

[0027] As a preferred embodiment of the present application, the thickness of the cathode catalytic layer A is 0.1-30 μm, and the loading of active substances in the cathode catalytic layer A is 10-500 μg / cm 2 ; the thickness of the cathode catalytic layer B is 0.1-30 μm, and the loading of active substances in the cathode catalytic layer B is 10-500 μg / cm 2 .

[0028] As a further preferred embodiment of the present application, the thickness of the cathode catalytic layer A is 3.5 μm, and the loading of active substances in the cathode catalytic layer A is 100 μg / cm 2 ; the thickness of the cathode catalytic layer B is 3.5 μm, and the loading of active substances in the cathode catalytic layer B is 100 μg / cm 2 .

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] (1) The process steps involved in the preparation method of the present application, such as coating process, thermal transfer printing process and the like, are relatively mature and widely used, so the steps involved in the method of the present application are simple and easy to implement, can be applied to large-scale applications, and the prepared multi-layer catalytic layer structure membrane electrode has excellent performance.

[0031] (2) The method of the present application can independently design the structure of the multi-layer catalytic layer, and is more convenient for layering on the structure of the catalytic layer, thereby optimizing the mass transfer process in the catalytic layer.

[0032] (3) The slurry used in the method of the present application can not be limited to the coating equipment, and can more desirably prepare the ideal catalytic layer structure according to the design. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The appearance effect pictures obtained by a camera before and after the transfer of Examples 1 and Comparative Examples 1 to 3 are shown in each example, and four small pictures are contained in the frame line, in which the left side is the PTFE coated with the catalytic layer before (upper) and after (lower) the transfer, and the right side is the proton exchange membrane coated with the catalytic layer before (upper) and after (lower) the transfer.

[0034] Figure 2 The polarization curve pictures of the membrane electrode prepared in Example 1, Comparative Example 4 and Comparative Example 5 are shown, in which the test conditions are as follows: the active area of the cell is 25 cm 2 , the cell temperature is 68℃, the anode / cathode humidity is 40% / 20%, and the anode / cathode pressure is 170 / 150 kPa. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below through specific comparative examples and examples.

[0036] Example 1

[0037] S1 : Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by a Beads mill disperser, the rotation speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment, to obtain catalyst slurry A coated with a proton exchange membrane. Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by a Beads mill disperser, the rotation speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment, to obtain catalyst slurry B coated with a PTFE membrane.

[0038] S2: Use a slot coating method to coat the catalyst slurry A prepared in S1 on one side of the proton exchange membrane and dry at 80°C, wherein the Pt loading of the catalyst layer is 100 μg / cm 2 , and the thickness is 3.5 μm; use a slot coating method to coat the catalyst slurry B on the PTFE membrane and dry at 80°C, wherein the Pt loading of the catalyst layer is 100 μg / cm 2 , and the thickness is 3.5 μm.

[0039] S3: Soak the proton exchange membrane coated with the catalyst layer and the PTFE coated with the catalyst layer in water until the surface of the catalyst layer is wet, and the soaking time is 1 min.

[0040] S4: After taking out, lay the proton exchange membrane on the hot transfer substrate with the side coated with the catalyst layer facing up, and lay the PTFE coated with the catalyst layer on the proton exchange membrane, so that the two catalyst layers are opposite.

[0041] S5: After hot pressing at 170°C and 0.5 MPa for 60 s in a hot press, take out the PTFE and form a double-layer catalyst layer on the proton membrane.

[0042] S6: Coat the catalyst slurry A on the side of the proton exchange membrane in S5 which is not coated with the catalyst layer, and the loading is 100 μg / cm 2Forming CCM, further assembling to form membrane electrode and fuel cell.

[0043] Example 2

[0044] S1: Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment, to obtain catalyst slurry A coated with proton exchange membrane. Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment, to obtain catalyst slurry B coated with PTFE membrane.

[0045] S2: The catalyst slurry A prepared in S1 is coated on one side of the proton exchange membrane by the method of slot coating and dried at 80°C, wherein the Pt loading of the catalyst layer is 100 μg / cm 2 , and the thickness is 3.5 μm; the catalyst slurry B is coated on the PTFE membrane by the method of slot coating and dried at 80°C, wherein the Pt loading of the catalyst layer is 100 μg / cm 2 , and the thickness is 3.5 μm.

[0046] S3: Soak the proton exchange membrane coated with the catalyst layer and the PTFE coated with the catalyst layer in water until the surface of the catalyst layer is wet, and the soaking time is 1 min.

[0047] S4: After taking out, lay the proton exchange membrane on the hot transfer substrate with the side coated with the catalyst layer facing up, and lay the PTFE coated with the catalyst layer on the proton exchange membrane, so that the two catalyst layers are opposite.

[0048] S5: After hot pressing the assembly combined in S4 at 120°C and 0.5 MPa for 60 s, take out and remove the PTFE, to form a double-layer catalyst layer on the proton membrane.

[0049] S6: The side of the proton exchange membrane without the catalytic layer in S5 was coated with catalyst slurry A, with a loading of 100 μg / cm 2 Forming CCM, further assembling to form membrane electrode and fuel cell.

[0050] Example 3

[0051] S1: 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion was added and stirred for 2 min, then the ethanol was added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry was dispersed by a Beads mill disperser, the speed of the disperser was 3000 rpm, and the dispersion time was 30 min, then the dispersed catalyst slurry was collected for defoaming treatment to obtain catalyst slurry A coated with a proton exchange membrane. 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion was added and stirred for 2 min, then the ethanol was added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry was dispersed by a Beads mill disperser, the speed of the disperser was 3000 rpm, and the dispersion time was 30 min, then the dispersed catalyst slurry was collected for defoaming treatment to obtain catalyst slurry B coated with a PTFE membrane.

[0052] S2: The catalyst slurry A prepared in S1 was coated on one side of the proton exchange membrane by a slot coating method and dried at 80°C, wherein the Pt loading of the catalytic layer was 100 μg / cm 2 , and the thickness was 3.5 μm; the catalyst slurry B was coated on the PTFE membrane by a slot coating method and dried at 80°C, wherein the Pt loading of the catalytic layer was 100 μg / cm 2 , and the thickness was 3.5 μm.

[0053] S3: The proton exchange membrane coated with the catalytic layer and the PTFE coated with the catalytic layer were soaked in water until the surface of the catalytic layer was wet, and the soaking time was 1 min.

[0054] S4: After being taken out, the proton exchange membrane was laid flat on the hot transfer substrate with the side coated with the catalytic layer facing up, and the PTFE coated with the catalytic layer was laid on the proton exchange membrane, so that the two catalytic layers were opposite.

[0055] S5: The assembled components in S4 were taken out after hot pressing at 250°C, 0.5 MPa for 60 s in a hot press, and the PTFE was removed to form a double-layered structure of the catalytic layer on the proton exchange membrane.

[0056] S6: The side of the proton exchange membrane without the catalytic layer in S5 was coated with the catalyst slurry A, with a loading of 100 μg / cm 2 The CCM was formed, and further assembled to form a membrane electrode and a fuel cell.

[0057] Example 4

[0058] S1: 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion was added and stirred for 2 min, then the ethanol was added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry was dispersed by a Beads mill disperser, the speed of the disperser was 3000 rpm, and the dispersion time was 30 min, then the dispersed catalyst slurry was collected for defoaming treatment to obtain the catalyst slurry A coated with the proton exchange membrane. 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water were weighed. The Pt / C catalyst was slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion was added and stirred for 2 min, then the ethanol was added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry was dispersed by a Beads mill disperser, the speed of the disperser was 3000 rpm, and the dispersion time was 30 min, then the dispersed catalyst slurry was collected for defoaming treatment to obtain the catalyst slurry B coated with the PTFE membrane.

[0059] S2: The catalyst slurry A prepared in S1 was coated on one side of the proton exchange membrane by a slot coating method and dried at 80°C, wherein the Pt loading of the catalytic layer was 100 μg / cm 2 , and the thickness was 3.5 μm; the catalyst slurry B was coated on the PTFE membrane by a slot coating method and dried at 80°C, wherein the Pt loading of the catalytic layer was 100 μg / cm 2 , and the thickness was 3.5 μm.

[0060] S3: The proton exchange membrane coated with the catalytic layer and the PTFE coated with the catalytic layer were soaked in water until the surface of the catalytic layer was wet, and the soaking time was 1 min.

[0061] S4: After taking out, lay the proton exchange membrane on the hot transfer substrate, with the side coated with the catalytic layer facing up, and lay the PTFE coated with the catalytic layer on the proton exchange membrane, so that the two catalytic layers are opposite.

[0062] S5: After taking out the assembly combined in S4, heat press at 150°C and 1 MPa for 60 s in a hot press, and then remove the PTFE to form a double-layer catalytic layer on the proton membrane.

[0063] S6: Apply the catalyst slurry A to the side of the proton exchange membrane that is not coated with the catalytic layer in S5, with a loading of 100 μg / cm 2 Form a CCM, and further assemble to form a membrane electrode and a fuel cell.

[0064] Example 5

[0065] S1: Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by a Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment to obtain catalyst slurry A for coating with a proton exchange membrane. Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry; disperse the slurry by a Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then collect the dispersed catalyst slurry for defoaming treatment to obtain catalyst slurry B for coating with a PTFE membrane.

[0066] S2: Apply the catalyst slurry A prepared in S1 to one side of the proton exchange membrane by slot coating and dry at 80°C, wherein the Pt loading of the catalytic layer is 100 μg / cm 2 , and the thickness is 3.5 μm; apply the catalyst slurry B to the PTFE membrane by slot coating and dry at 80°C, wherein the Pt loading of the catalytic layer is 100 μg / cm 2 , and the thickness is 3.5 μm.

[0067] S3: The proton exchange membrane coated with catalytic layer and PTFE coated with catalytic layer were soaked in 5wt% n-propanol aqueous solution until the catalytic layer surface was wetted, and the soaking time was 1 min.

[0068] S4: After taking out, the proton exchange membrane was laid on the thermal transfer substrate with the catalytic layer coated side upward, and the PTFE coated with catalytic layer was laid on the proton exchange membrane, so that the two catalytic layers were opposite.

[0069] S5: The assembly combined in S4 was taken out after hot pressing at 150°C, 1 MPa for 60 s in a hot press, and the PTFE was removed, forming a double-layer catalytic layer on the proton membrane.

[0070] S6: The side of the proton exchange membrane without catalytic layer coating in S5 was coated with catalyst slurry A, and the loading was 100 μg / cm 2 The CCM was formed, and further assembled to form a membrane electrode and a fuel cell.

[0071] Comparative Example 1

[0072] The steps of S1-S2 and S4-S6 of the present comparative example were the same as those of Example 1, and the difference was that the present comparative example did not undergo the surface wetting treatment of the proton exchange membrane coated with catalytic layer and the PTFE film in the S3 step.

[0073] Comparative Example 2

[0074] The steps of Comparative Example 2 and Example 1 were basically the same, and the difference was that the transfer pressure in the S5 step was 0.1 MPa.

[0075] Comparative Example 3

[0076] The steps of Comparative Example 3 and Example 1 were basically the same, and the difference was that the transfer temperature in the S5 step was 100°C.

[0077] Comparative Example 4

[0078] The present comparative example prepared a CCM with a single-layer catalytic layer.

[0079] S1 : Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. Slowly add the Pt / C catalyst to the water under stirring, stir for 5 min, then add the perfluorosulfonic acid resin dispersion and stir for 2 min, then add the ethanol and continue stirring for 2 min to complete the pre-dispersion of the slurry. Disperse the slurry by a Beads mill disperser at a speed of 3000 rpm for 30 min, then collect the dispersed catalyst slurry and perform defoaming treatment to obtain a catalyst slurry A coated with a proton exchange membrane.

[0080] S2: Coating the catalyst slurry A prepared in S1 on one side of the proton exchange membrane by a slot coating method and drying at 80°C, wherein the Pt loading of the catalyst layer is 350 μg / cm 2 , and the thickness is 12 μm.

[0081] S3: Coating the catalyst slurry A on the side of the proton exchange membrane in S2 without coating the catalyst layer, with a loading of 100 μg / cm 2 to form a CCM, and further assembling to form a membrane electrode and a fuel cell.

[0082] Comparative Example 5

[0083] In this comparative example, the hot press transfer printing method is replaced by spraying.

[0084] S1 : Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 12.8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. The Pt / C catalyst is slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion is added and stirred for 2 min, then the ethanol is added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry is dispersed by a Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then the dispersed catalyst slurry is collected for defoaming treatment to obtain catalyst slurry A. Take 5.1 g of Tec10F50e 50wt% Pt / C catalyst produced by TKK, 8 g of 20wt% perfluorosulfonic acid resin dispersion, 7.2 g of ethanol, and 39.0 g of ultrapure water. The Pt / C catalyst is slowly added to the water under stirring, stirred for 5 min, then the perfluorosulfonic acid resin dispersion is added and stirred for 2 min, then the ethanol is added and stirred for 2 min to complete the pre-dispersion of the slurry; the slurry is dispersed by a Beads mill disperser, the speed of the disperser is 3000 rpm, the dispersion time is 30 min, then the dispersed catalyst slurry is collected for defoaming treatment to obtain catalyst slurry B.

[0085] S2: The catalyst slurry A prepared in S1 is sprayed on one side of the proton exchange membrane using a spray pen, wherein the Pt loading of the catalyst layer is 100 μg / cm 2 , and the thickness is 3.5 μm; the catalyst slurry B is sprayed on the catalyst layer of catalyst A, the loading is 100 μg / cm 2 , and the thickness is 3.5 μm.

[0086] S3: The catalyst slurry A is coated on the side of the proton exchange membrane without a catalyst layer in S2, the loading is 100 μg / cm 2 to form a CCM, which is further assembled to form a membrane electrode and a fuel cell.

[0087] From Figure 1As can be seen, Example 1 showed the best transfer effect, completely transferring the catalyst layer on the PTFE to the catalyst layer of the proton exchange membrane. In Comparative Example 1, the catalyst layer on the PTFE with an unwetted catalyst layer surface was almost completely transferred to the catalyst layer of the proton exchange membrane. In Comparative Example 2, although the catalyst layer surface was wetted, the transfer pressure was low, and the catalyst layer on the PTFE was also almost completely transferred to the catalyst layer of the proton exchange membrane. In Comparative Example 3, the catalyst layer surface was pre-wetted, but the transfer effect at a transfer temperature of 100°C was extremely poor, and the catalyst layer on the PTFE was not transferred to the catalyst layer of the proton exchange membrane at all. Therefore, on the one hand, wetting the catalyst layer surface before transfer is key to effectively improving transfer quality; on the other hand, sufficient transfer pressure and transfer temperature are required to achieve better transfer results.

[0088] from Figure 2 As can be seen from the performance test results of Example 1 and Comparative Example 4, the membrane electrode with a bilayer structure of cathode catalyst layer using hot-press transfer exhibits good performance even with a cathode Pt loading of only 200 μg / cm³. 2 The performance of the membrane electrode is also significantly better than that of the cathode with a Pt loading of 350 μg / cm³. 2 A single-layer catalytic layer membrane electrode. This demonstrates that constructing a multi-layer catalytic layer can improve membrane electrode performance and reduce catalyst usage. A comparison of the polarization curves from Example 1 and Comparative Example 5 shows that the membrane electrode with a double-layer catalytic layer structure prepared by hot-press transfer exhibits better performance than the membrane electrode prepared by spraying.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a membrane electrode with a multilayer catalytic layer structure, characterized in that, Includes the following steps, (1) Prepare catalyst slurry A and catalyst slurry B; catalyst slurry A includes the following components: catalyst, resin, solvent, and catalyst slurry B includes the following components: catalyst, perfluorosulfonic acid resin, solvent; (2) The catalyst slurry A is coated on one side of the proton exchange membrane and dried to serve as the cathode catalyst layer A, thus obtaining a proton exchange membrane containing the cathode catalyst layer A; the catalyst slurry B is coated on one side of the polytetrafluoroethylene membrane and dried to serve as the cathode catalyst layer B, thus obtaining a polytetrafluoroethylene membrane containing the cathode catalyst layer B; the proton exchange membrane containing the cathode catalyst layer A and the polytetrafluoroethylene membrane containing the cathode catalyst layer B are also subjected to a wetting treatment; the solvent for the wetting treatment is water, or a mixture of an organic solvent and water; the organic solvent is at least one of alcohols or ethers with a boiling point below 150°C; the mass percentage of the organic solvent in the mixture of the organic solvent and water is 0-40%. (3) Place one side of the cathode catalyst layer A on the proton exchange membrane in step (2) and the other side of the cathode catalyst layer B on the polytetrafluoroethylene membrane, and then perform hot pressing transfer treatment. After the hot pressing transfer treatment, remove the polytetrafluoroethylene membrane to obtain a proton exchange membrane containing a double cathode catalyst layer. The temperature of the hot pressing transfer treatment is 150-190℃, the pressure is 0.5-1MPa, and the time is 30-120s. (4) In step (3), at least one anodic catalytic layer is coated on the side of the proton exchange membrane containing the double cathode catalytic layer that is not coated with the catalytic layer. After drying, a membrane electrode with a multilayer catalytic layer structure is obtained.

2. The preparation method according to claim 1, characterized in that, The wetting treatment method in step (2) includes at least one of impregnation, spraying, and humidification.

3. The preparation method according to claim 1 or 2, characterized in that, In steps (2) and (4), the coating includes at least one of ultrasonic spraying, electrostatic spraying, blade coating, slot coating, and screen printing.

4. The preparation method according to claim 1, characterized in that, The catalyst includes at least one of Pt / C catalyst, PtM / C catalyst, and Fe-NC catalyst, wherein M in the PtM / C catalyst is at least one metal selected from Co, Fe, Cu, Ni, Mn, Cr, Pd, Ir, Au, Ag, and Ru; the solvent is a mixed solution of alcohol and water, wherein the alcohol includes at least one of methanol, ethanol, propanol, and butanol.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the catalyst to the resin is 1:(0.1-3).

6. The preparation method according to claim 1 or 2, characterized in that, The thickness of the cathode catalyst layer A is 0.1–30 μm, and the loading of active material in the cathode catalyst layer A is 10–500 μg / cm³. 2 The thickness of the cathode catalyst layer B is 0.1–30 μm, and the loading of active material in the cathode catalyst layer B is 10–500 μg / cm³. 2 .

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