A method for preparing a catalyst coating suitable for direct coating on the surface of an ultra-thin proton exchange membrane

Abstract

The present invention provides a slurry for slot-coating a catalyst coating on the surface of an ultra-thin proton exchange membrane. The slurry is prepared from a catalyst, water, a perfluorosulfonic acid resin solution, and a low-boiling-point organic alcohol. The catalyst coating slurry provided by the present invention is suitable for slot-coating technology on the surface of ultra-thin proton exchange membranes. By rationally controlling the slurry solid content, the solvent dielectric constant, and the process, the present invention can effectively address the structural damage to the proton membrane and the opposite catalyst layer caused by slurry diffusion during direct coating, resulting in a high-quality catalyst layer with a complete structure and stable performance. This effectively improves the quality of the finished product of slot-coated CCMs, thereby ensuring the product performance and consistency of membrane electrode and fuel cell stacks.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell membrane electrode preparation, and relates to a slurry for slit coating a catalyst coating on the surface of an ultra-thin proton exchange membrane and a preparation method for coating the catalyst coating on the surface of an ultra-thin proton exchange membrane, and in particular to a preparation method for a catalyst coating suitable for direct coating on the surface of an ultra-thin proton exchange membrane. Background Art

[0002] With continuous technological breakthroughs, proton exchange membrane products are becoming increasingly thinner, with current commercial products as thin as 8μm. Thinner proton exchange membranes can effectively improve proton conductivity and reduce ohmic polarization, offering significant advantages in increasing membrane electrode power density and fuel cell stack performance. Furthermore, their significantly reduced material costs are more conducive to the large-scale and commercial application of fuel cell products. However, ultra-thin proton exchange membrane materials less than 12μm also pose additional challenges to membrane electrode (CCM) fabrication technology, impacting membrane electrode performance and process stability. In recent years, slot-type coating technology, offering advantages of continuous and high-efficiency production, has gradually gained application in the fuel cell field, and cutting-edge manufacturing equipment suitable for direct coating of proton exchange membrane surfaces is becoming increasingly mature. At the same time, catalyst slurries also need to be improved to match the innovations in coating technology. Currently, the development of catalyst slurry processes suitable for coating ultra-thin proton exchange membranes remains a significant challenge.

[0003] Therefore, how to find a more suitable coating process for ultra-thin proton membranes and solve the technical problems existing in the coating process of ultra-thin proton membranes has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a slurry for slit-coating a catalyst coating on the surface of an ultra-thin proton exchange membrane and a method for preparing the catalyst coating on the surface of an ultra-thin proton exchange membrane, particularly a method for preparing a catalyst coating suitable for direct coating on the surface of an ultra-thin proton exchange membrane. By controlling the coating slurry and coating method, the present invention effectively solves the problem of damage to the surface structure of the catalytic layer when using the direct coating method on the surface of an ultra-thin proton exchange membrane. At the same time, the process is simple and easy to control, making it more suitable for promotion and application in large-scale industrial production.

[0005] The invention provides a slurry for slit coating a catalyst coating on the surface of an ultra-thin proton exchange membrane. The slurry is prepared from a catalyst, water, a perfluorosulfonic acid resin solution and a low-boiling-point organic alcohol.

[0006] Preferably, the catalyst comprises one or more of a carbon-supported Pt-based catalyst, a carbon-supported Pt alloy catalyst, and an oxide-supported Pt-based catalyst;

[0007] The ion equivalent of the perfluorosulfonic acid resin solution is greater than 700 and less than 1100;

[0008] The boiling point of the low-boiling-point organic alcohol is less than or equal to 100°C.

[0009] Preferably, the ratio of water to low-boiling-point organic alcohol satisfies that the dielectric constant of the mixture of water and low-boiling-point organic alcohol is greater than 60;

[0010] The mass ratio of the perfluorosulfonic acid resin solution to the catalyst carrier is (1-100):1.

[0011] Preferably, the solid content of the slurry is 3 wt% to 15 wt%;

[0012] The low boiling point organic alcohol includes one or more of methanol, ethanol, n-propanol and isopropanol.

[0013] Preferably, the thickness of the ultra-thin proton exchange membrane is 5 to 12 μm;

[0014] The viscosity of the slurry is 10 to 50,000 mPa.s;

[0015] The slurry is a catalyst coating slurry used when slit coating the catalyst coating on one side of the proton exchange membrane surface and slit coating the other side.

[0016] Preferably, the method for preparing the slurry comprises the following steps:

[0017] a) fully mixing the catalyst with deionized water, then adding the perfluorosulfonic acid resin solution and homogenizing, and then adding a low-boiling point organic alcohol and homogenizing to obtain a mixed slurry;

[0018] b) The mixed slurry obtained in the above steps is dispersed and then degassed to obtain a catalyst coating slurry for slit coating the catalyst coating on the surface of the proton exchange membrane.

[0019] Preferably, the dispersion method includes one or more of high-speed shearing, grinding, ultrasonic crushing, high-energy dispersion and stirring;

[0020] The degassing method includes vacuum degassing.

[0021] The present invention also provides a method for preparing a catalyst coating on the surface of an ultra-thin proton exchange membrane, comprising the following steps:

[0022] 1) coating a first catalyst slurry on a slit on one side of a proton exchange membrane, and then heating and drying the slit to obtain a proton exchange membrane having a first catalyst coating on one side;

[0023] 2) applying the side of the proton exchange membrane obtained in the above step with the first catalyst coating to the surface of a vacuum adsorption platform, slit-coating the second catalyst slurry on the other side of the proton exchange membrane, and drying to obtain a proton exchange membrane with the catalyst coating;

[0024] The second catalyst slurry includes the slurry described in any one of the above technical solutions.

[0025] Preferably, the heating and drying temperature is 80-130°C;

[0026] The heating and drying time is 1 to 10 minutes;

[0027] The drying temperature is 50-90°C;

[0028] The drying time is 10 to 120 seconds.

[0029] Preferably, the platinum loading of the first catalyst layer is 0.03-0.4 mg / cm 2 ;

[0030] The platinum loading of the second catalyst layer in the catalyst coating is 0.03 to 0.4 mg / cm 2 ;

[0031] The first catalyst layer in the catalyst coating is a cathode catalyst layer or an anode catalyst layer, and the second catalyst layer is a corresponding anode catalyst layer or a cathode catalyst layer;

[0032] The proton exchange membrane composited with a catalyst coating is a CCM membrane electrode.

[0033] The present invention provides a slurry for slit coating a catalyst coating on the surface of an ultra-thin proton exchange membrane, wherein the slurry is prepared from a catalyst, water, a perfluorosulfonic acid resin solution, and a low-boiling-point organic alcohol. Compared with the prior art, the present invention is aimed at the influence of the ultra-thin proton membrane on the membrane electrode performance and process stability during the membrane electrode preparation process. Although there are also technical solutions that have conducted corresponding adaptability studies, the currently disclosed patent technical solutions mostly focus on the control means for preventing cracks on the surface of the catalyst layer, but do not pay attention to the destructive effect of organic solvent penetration on the catalyst layer when the ultra-thin proton exchange membrane is coated. Based on this, the present invention specifically chooses this improvement direction, focusing on solving the problem of the surface structure of the catalyst layer being destroyed by controlling the slurry preparation process and the coating method when using the direct coating method on the surface of the ultra-thin proton exchange membrane.

[0034] The present invention specifically designs a slurry with a specific formula and composition for slit coating of a catalyst coating on the surface of an ultra-thin proton exchange membrane. The present invention believes that the membrane electrode catalyst layer adopts a slit coating method to directly coat the catalyst slurry on the surface of the proton exchange membrane. The specific steps are to coat the first catalytic layer on one side of the proton exchange membrane, attach the side of the proton exchange membrane covering the first catalytic layer to the surface of the vacuum adsorption platform, and coat the second catalytic layer on the other side of the proton exchange membrane. Due to the high pressure difference between the two sides of the membrane caused by vacuum adsorption and the high solvent permeability of the ultra-thin proton exchange membrane, during the coating process of the second catalytic layer, the solvent in the slurry will diffuse to the other side of the membrane in large quantities, affecting the structural stability of the first catalytic layer. Therefore, the present invention specifically improves the destructiveness of the solvent to the structure of the first catalytic layer by optimizing the second catalyst slurry, thereby effectively improving the quality of the finished product of the CCM fuel cell membrane electrode prepared by the direct coating method.

[0035] The catalyst coating slurry provided by the present invention can be adapted to the slit coating technology on the surface of ultra-thin proton exchange membranes. By reasonably controlling the slurry solid content, solvent dielectric constant and process, the present invention can effectively solve the structural damage to the proton membrane and the opposite catalyst layer caused by slurry diffusion during direct coating, thereby obtaining a high-quality catalytic layer with complete structure and stable performance, effectively improving the quality of the finished product of slit direct coating CCM, and thus ensuring the product performance and consistency of membrane electrode and fuel cell stacks. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The SEM electron microscope images of the surface structure of the first catalytic layer of the membrane electrode prepared in Example 1 and Comparative Example 1 of the present invention;

[0037] Figure 2 SEM electron microscope images of the surface structure of the first catalytic layer of the membrane electrode prepared in Example 2 of the present invention and Comparative Example 2;

[0038] Figure 3 SEM electron microscope images of the surface structure of the first catalytic layer of the membrane electrode prepared in Example 3, Example 4 and Comparative Example 3 of the present invention;

[0039] Figure 4 This is a performance comparison chart of the membrane electrode prepared in Example 1 of the present invention and Comparative Example 1;

[0040] Figure 5 This is a performance comparison chart of the membrane electrode prepared in Example 2 of the present invention and Comparative Example 2;

[0041] Figure 6 This is a performance comparison chart of the membrane electrodes prepared in Example 3, Example 4, Example 5 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0042] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0043] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0044] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity requirements in the field of fuel cell membrane electrode manufacturing.

[0045] The invention provides a slurry for slit coating a catalyst coating on the surface of an ultra-thin proton exchange membrane. The slurry is prepared from a catalyst, water, a perfluorosulfonic acid resin solution and a low-boiling-point organic alcohol.

[0046] In the present invention, the catalyst preferably includes one or more of a carbon-supported Pt-based catalyst, a carbon-supported Pt alloy catalyst and an oxide-supported Pt-based catalyst, more preferably a carbon-supported Pt-based catalyst, a carbon-supported Pt alloy catalyst or an oxide-supported Pt-based catalyst.

[0047] In the present invention, the ion equivalent of the perfluorosulfonic acid resin solution is preferably greater than 700 and less than 1100, more preferably 750-1050, more preferably 800-1000, and more preferably 850-950.

[0048] In the present invention, the boiling point of the low-boiling-point organic alcohol is preferably less than or equal to 100°C.

[0049] In the present invention, the ratio of water to low-boiling-point organic alcohol satisfies that the dielectric constant of the mixed solution of water and low-boiling-point organic alcohol is preferably greater than 60, more preferably greater than or equal to 65, more preferably greater than or equal to 70, and more preferably greater than or equal to 80.

[0050] In the present invention, the mass ratio of the perfluorosulfonic acid resin solution to the catalyst carrier is preferably (1-100):1, more preferably (21-80):1, and even more preferably (41-60):1.

[0051] In the present invention, the solid content of the slurry is preferably 3 wt% to 15 wt%, more preferably 5 wt% to 12 wt%, and even more preferably 7 wt% to 10 wt%.

[0052] In the present invention, the low-boiling-point organic alcohol preferably includes one or more of methanol, ethanol, n-propanol and isopropanol, more preferably methanol, ethanol, n-propanol or isopropanol.

[0053] In the present invention, the thickness of the ultra-thin proton exchange membrane is preferably 5 to 12 μm, more preferably 6 to 11 μm, more preferably 7 to 10 μm, and more preferably 8 to 9 μm.

[0054] In the present invention, the viscosity of the slurry is preferably 10 to 50,000 mPa.s, more preferably 100 to 40,000 mPa.s, more preferably 1,000 to 30,000 mPa.s, and more preferably 10,000 to 20,000 mPa.s.

[0055] In the present invention, the slurry is preferably a catalyst coating slurry used when slit coating is performed on one side of the proton exchange membrane surface and then slit coating is performed on the other side.

[0056] In the present invention, the method for preparing the slurry preferably comprises the following steps:

[0057] a) fully mixing the catalyst with deionized water, then adding the perfluorosulfonic acid resin solution and homogenizing, and then adding a low-boiling point organic alcohol and homogenizing to obtain a mixed slurry;

[0058] b) The mixed slurry obtained in the above steps is dispersed and then degassed to obtain a catalyst coating slurry for slit coating the catalyst coating on the surface of the proton exchange membrane.

[0059] The invention firstly fully mixes the catalyst with deionized water, then adds perfluorosulfonic acid resin solution for homogeneous mixing, and then adds low-boiling point organic alcohol for homogeneous mixing to obtain a mixed slurry.

[0060] Finally, the present invention disperses the mixed slurry obtained in the above steps and then degasses it to obtain a catalyst coating slurry for slit coating the catalyst coating on the surface of the proton exchange membrane.

[0061] In the present invention, the dispersion method preferably includes one or more of high-speed shearing, grinding, ultrasonic crushing, high-energy dispersion and stirring, and more preferably includes multiple of high-speed shearing, grinding, ultrasonic crushing, high-energy dispersion and stirring.

[0062] In the present invention, the degassing method preferably includes vacuum degassing.

[0063] The present invention is a complete and detailed overall technical solution that better ensures the composition and ratio of the slurry and further improves the performance and consistency of the membrane electrode. The slurry for slit coating the catalyst coating on the surface of the ultra-thin proton exchange membrane and the preparation method thereof can be specifically as follows:

[0064] The slot-type direct coating process involves coating one side of the proton exchange membrane with a first catalyst slurry, heating and drying it to form a first catalytic layer. The proton exchange membrane, covered with the first catalytic layer, is then attached to the surface of a vacuum adsorption platform, and a second catalytic layer is applied to the other side of the proton exchange membrane.

[0065] Due to the high pressure difference between the two sides of the membrane caused by vacuum adsorption and the high solvent permeability of the ultra-thin proton exchange membrane, during the coating process of the second catalytic layer, the solvent in the slurry will diffuse to the other side of the membrane in large quantities, affecting the structural stability of the first catalytic layer.

[0066] The present invention provides a catalyst coating slurry suitable for the surface of an ultra-thin proton exchange membrane. By using the inventive slurry, structurally complete and high-performance anode and cathode catalyst layers can be coated on both sides of the ultra-thin proton exchange membrane through a slit-type direct coating technology.

[0067] The present invention provides an optimized catalyst slurry 2 (i.e., the slurry used to coat the second catalytic layer), thereby improving the destructiveness of the slurry to the structure of the first catalytic layer and effectively improving the quality of the finished product of the slot direct coating CCM.

[0068] The slurry preparation steps are as follows:

[0069] First, fully mix the catalyst with deionized water, and then add the perfluorosulfonic acid resin solution and low-boiling point organic alcohol in sequence. After each addition, they must be fully mixed and homogenized.

[0070] Specifically, the obtained mixed slurry is uniformly dispersed, and the step can be performed by using a high-speed shearing machine, a grinder, an ultrasonic pulverizer, a high-energy disperser, a stirrer, or the like to disperse and mix.

[0071] The slurry is vacuum degassed and can be used for subsequent slit coating operations.

[0072] Specifically, the catalyst type in the catalyst slurry is one or more of a carbon-supported Pt-based catalyst, a carbon-supported Pt alloy catalyst, and an oxide-supported Pt-based catalyst.

[0073] Specifically, the ion equivalent of the perfluorosulfonic acid resin solution is greater than 700 and less than 1100.

[0074] Specifically, the low-boiling point organic alcohol is one or more of methanol, ethanol, n-propanol, and isopropanol.

[0075] Specifically, the present invention does not impose any special restrictions on the formulation process of the catalyst slurry 1 (ie, the slurry used to coat the first catalytic layer).

[0076] Specifically, the dielectric constant of the mixed solvent formed by deionized water and the organic solvent in the catalyst slurry 2 needs to be greater than 60.

[0077] Specifically, the solid content of the catalyst slurry 2 is controlled to be 3 wt% to 15 wt%, and the viscosity is controlled to be 10 to 50,000 mPa.s.

[0078] The present invention provides a method for preparing a catalyst coating on the surface of a proton exchange membrane, comprising the following steps:

[0079] 1) coating a first catalyst slurry on a slit on one side of a proton exchange membrane, and then heating and drying the slit to obtain a proton exchange membrane having a first catalyst coating on one side;

[0080] 2) applying the side of the proton exchange membrane obtained in the above step with the first catalyst coating to the surface of a vacuum adsorption platform, slit-coating the second catalyst slurry on the other side of the proton exchange membrane, and drying to obtain a proton exchange membrane with the catalyst coating;

[0081] The second catalyst slurry includes the slurry described in any one of the above technical solutions.

[0082] The present invention firstly applies the first catalyst slurry to the slits on one side of the proton exchange membrane, and then heats and dries it to obtain a proton exchange membrane with the first catalyst coating on one side.

[0083] In the present invention, the temperature of the heating and drying is preferably 80 to 130° C., more preferably 90 to 120° C., and even more preferably 100 to 110° C. The heating and drying is thorough drying.

[0084] In the present invention, the heating and drying time is preferably 1 to 10 minutes, more preferably 3 to 8 minutes, and even more preferably 5 to 6 minutes.

[0085] In the present invention, the platinum loading of the first catalyst layer is preferably 0.03 to 0.4 mg / cm 2 , more preferably 0.05 to 0.1 mg / cm 2 , more preferably 0.13 to 0.3 mg / cm 2 , more preferably 0.15 to 0.25 mg / cm 2 .

[0086] In the present invention, the first catalyst layer in the catalyst coating is preferably a cathode catalyst layer or an anode catalyst layer, and the second catalyst layer is preferably an anode catalyst layer or a cathode catalyst layer. That is, in the present invention, the first catalyst layer does not correspond to the cathode catalyst layer, and the second catalyst layer does not correspond to the anode catalyst layer. There is no priority order for the coating of the cathode and anode catalyst layers.

[0087] Finally, the present invention covers the side of the proton exchange membrane obtained in the above steps with the first catalyst coating on the surface of the vacuum adsorption platform, and slit-coates the second catalyst slurry on the other side of the proton exchange membrane. After drying, a proton exchange membrane with a catalyst coating is obtained.

[0088] In the present invention, the drying temperature is preferably 50 to 90°C, more preferably 55 to 85°C, more preferably 60 to 80°C, and more preferably 65 to 75°C.

[0089] In the present invention, the drying time is preferably 10 to 120 seconds, more preferably 30 to 100 seconds, and even more preferably 50 to 80 seconds.

[0090] In the present invention, the platinum loading of the second catalyst layer is preferably 0.03 to 0.4 mg / cm 2 , more preferably 0.08 to 0.35 mg / cm 2 , more preferably 0.13 to 0.3 mg / cm 2 , more preferably 0.18 to 0.25 mg / cm 2 .

[0091] In the present invention, the proton exchange membrane composited with a catalyst coating is preferably a CCM membrane electrode.

[0092] The present invention is to complete and refine the overall technical solution, better ensure the composition and ratio of the slurry, and further improve the performance and consistency of the membrane electrode. The preparation method of the catalyst coating on the surface of the proton exchange membrane can specifically be the following steps:

[0093] The membrane electrode CCM provided by the present invention includes an ultra-thin proton exchange membrane and catalyst layers coated on both sides of the membrane respectively. The cathode and anode catalyst layers have no priority in coating and are named the first catalyst layer and the second catalyst layer according to the coating order.

[0094] The actual preparation process of the membrane electrode CCM is as follows:

[0095] The slot-type direct coating process involves coating one side of the proton exchange membrane with a first catalyst slurry, heating and drying it to form a first catalytic layer. The proton exchange membrane, covered with the first catalytic layer, is then attached to the surface of a vacuum adsorption platform, and a second catalytic layer is applied to the other side of the proton exchange membrane.

[0096] Specifically, the catalyst slurry 1 coated on the surface of the proton exchange membrane needs to be fully heated and dried to form the first catalytic layer. Preferably, the drying temperature is greater than 80°C, and the drying time is greater than 1 minute, which can be 1 to 10 minutes.

[0097] Specifically, the ultra-thin proton exchange membrane used in the CCM has a thickness of 5 to 12 μm.

[0098] Specifically, the platinum loading range of the first catalytic layer and the second catalytic layer in the CCM is 0.03-0.4 mg / cm 2 .

[0099] The present invention provides a slurry for slot-coating a catalyst coating on the surface of an ultra-thin proton exchange membrane, a preparation method thereof, and a method for preparing a catalyst coating on the surface of an ultra-thin proton exchange membrane. The slurry designed by the present invention, which has a specific formula and composition, specifically optimizes the second catalyst slurry to reduce the destructive effect of the solvent on the first catalyst layer structure, thereby effectively improving the quality of the finished product of a CCM fuel cell membrane electrode produced by the direct coating method.

[0100] The catalyst coating slurry provided by the present invention can be adapted to the slit coating technology on the surface of ultra-thin proton exchange membranes. By reasonably controlling the slurry solid content, solvent dielectric constant and process, the present invention can effectively solve the structural damage to the proton membrane and the opposite catalyst layer caused by slurry diffusion during direct coating, thereby obtaining a high-quality catalytic layer with complete structure and stable performance, effectively improving the quality of the finished product of slit direct coating CCM, and thus ensuring the product performance and consistency of membrane electrode and fuel cell stacks.

[0101] In order to further illustrate the present invention, the following is a detailed description of a slurry for slit coating a catalyst coating on the surface of an ultra-thin proton exchange membrane and a method for preparing a catalyst coating on the surface of an ultra-thin proton exchange membrane provided by the present invention in combination with the embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0102] Example 1

[0103] (1) In this example, the catalyst used in the first catalytic layer is a Pt / C catalyst, in which the mass fraction of platinum is 50% and the specific surface area of ​​the catalyst is 250 m 2 / g.

[0104] (2) First, fully stir and mix the catalyst and deionized water, and then add the perfluorosulfonic acid resin solution and ethanol in sequence, stirring and mixing them thoroughly after each addition.

[0105] (3) The perfluorosulfonic acid resin solution is a commercial resin with an ion equivalent of about 900, wherein the mass ratio of the perfluorosulfonic acid resin to the mass ratio of the carbon in the catalyst is 0.8.

[0106] (4) The mass ratio of water to ethanol in the solvent in slurry 1 is 3:1, and the solid content of the slurry is 7 wt%.

[0107] (5) The mixed slurry was dispersed by ball milling for 60 min at a speed of 1500 rpm. The collected slurry after ball milling was subjected to vacuum degassing to obtain the catalyst slurry 1.

[0108] (6) The proton exchange membrane with one side covered with a PET protective substrate is placed on the vacuum adsorption platform of the coating machine, and the catalyst slurry 1 is coated on the surface of the proton exchange membrane using a slit direct coating method.

[0109] (7) The slurry was fully dried in a 90°C forced air oven for more than 2 minutes to form the first catalytic layer. The platinum loading of the catalyst was 0.3 mg / cm 2 .

[0110] (8) In this example, the catalyst used in the second catalytic layer is a Pt / C catalyst, in which the mass fraction of platinum is 50% and the specific surface area of ​​the catalyst is 350m 2 / g.

[0111] (9) The preparation steps and methods of slurry 2 in this example are the same as those of slurry 1.

[0112] (10) The water / ethanol mass ratio in the solvent of slurry 2 is 3:1, and the dielectric constant of the mixed solvent is 65. The solid content of the slurry is 6 wt%.

[0113] (11) One side of the proton exchange membrane covered with the first catalytic layer is attached to the surface of the vacuum adsorption platform, and after removing the PET protective substrate, the catalyst slurry 2 is coated on the other side.

[0114] (12) After the slurry is fully dried, the second catalytic layer is formed, wherein the platinum loading of the catalyst is 0.05 mg / cm 2 .

[0115] (13) The CCM covered with catalytic layers on both sides is removed from the vacuum adsorption platform to observe the effect of the preparation process of the second catalytic layer on the results of the first catalytic layer.

[0116] (14) The CCM is assembled with a frame and a gas diffusion layer on both sides to form a "seven-in-one" membrane electrode. The performance of the resulting membrane electrode can be tested by electrochemical methods.

[0117] Comparative Example 1

[0118] The steps for preparing CCM in this comparative example are the same as those in Example 1, except that the mass ratio of water to ethanol in the catalyst slurry 2 solvent is 1:1, and the dielectric constant of the mixed solvent is 51.

[0119] The CCM membrane electrodes prepared in Example 1 of the present invention and Comparative Example 1 were tested.

[0120] The surface structure of the first catalytic layer in Example 1 and Comparative Example 1 was observed by SEM (scanning electron microscope). Figure 1 shown. Figure 1 These are SEM images of the surface structure of the first catalytic layer of the membrane electrode prepared in Example 1 and Comparative Example 1 of the present invention. The upper image is Example 1, and the lower image is Comparative Example 1.

[0121] Depend on Figure 1 As can be seen, the surface coating of the first catalytic layer in Example 1 is complete and uniform, with no obvious defects. In contrast, the first catalytic layer in Comparative Example 1 exhibits significant mottled and uneven surface, with significantly increased surface roughness. Residual catalyst powder can be observed on the surface of the vacuum coating equipment platform. This suggests that during the coating process of Comparative Example slurry 2, the solvent with a high ethanol content permeated the ultra-thin proton exchange membrane into the first catalytic layer, causing significant damage to its structure.

[0122] The performance comparison of the membrane electrode obtained in Example 1 of the present invention and Comparative Example 1 is as follows: Figure 4 shown. Figure 4 This is a performance comparison chart of the membrane electrode prepared in Example 1 of the present invention and Comparative Example 1.

[0123] Depend on Figure 4 It can be seen that the structure of the first catalytic layer in Comparative Example 1 was severely damaged, a large amount of catalyst powder had been lost, and the performance of the resulting membrane electrode was significantly attenuated.

[0124] Furthermore, when the solid content in the slurry 2 decreases and the solvent ratio increases, the structure of the first catalytic layer can still be maintained, as shown in Example 2.

[0125] Example 2

[0126] (1) In this example, the catalyst used in the first catalytic layer is a PtCo / C catalyst, in which the mass fraction of platinum is 50% and the specific surface area of ​​the catalyst is 250 m 2 / g.

[0127] (2) First, fully stir and mix the catalyst and deionized water, and then add the perfluorosulfonic acid resin solution and ethanol in sequence, stirring and mixing them thoroughly after each addition.

[0128] (3) The perfluorosulfonic acid resin solution is a commercial resin with an ion equivalent of about 1000, wherein the mass ratio of the perfluorosulfonic acid resin to the mass ratio of the carbon in the catalyst is 1.0.

[0129] (4) The mass ratio of water to ethanol in the solvent in slurry 1 is 4:1, and the solid content of the slurry is 10 wt%.

[0130] (5) The mixed slurry was subjected to ultrasonic grinding and high-speed shear dispersion treatment for 120 minutes, and then the slurry was collected and subjected to vacuum degassing treatment to obtain the catalyst slurry 1.

[0131] (6) The proton exchange membrane with one side covered with a PET protective substrate is placed on the vacuum adsorption platform of the coating machine, and the catalyst slurry 1 is coated on the surface of the proton exchange membrane using a slit direct coating method.

[0132] (7) The slurry was fully dried in a forced air oven at 80°C for more than 3 minutes to form the first catalytic layer. The platinum loading of the catalyst was 0.25 mg / cm 2 .

[0133] (8) In this example, the catalyst used in the second catalytic layer is a Pt / C catalyst, in which the mass fraction of platinum is 40% and the specific surface area of ​​the catalyst is 100 m 2 / g.

[0134] (9) The preparation steps and methods of slurry 2 in this example are the same as those of slurry 1.

[0135] (10) The water / ethanol mass ratio in the solvent of slurry 2 is 3:1, and the dielectric constant of the mixed solvent is 65. The solid content of the slurry is 3 wt%.

[0136] (11) One side of the proton exchange membrane covered with the first catalytic layer is attached to the surface of the vacuum adsorption platform, and after removing the PET protective substrate, the catalyst slurry 2 is coated on the other side.

[0137] (12) After the slurry is fully dried, the second catalytic layer is formed, wherein the platinum loading of the catalyst is 0.05 mg / cm 2 .

[0138] (13) The CCM covered with catalytic layers on both sides was removed from the vacuum adsorption table to observe the effect of the preparation process of the second catalytic layer on the results of the first catalytic layer.

[0139] (14) The CCM is assembled with a frame and a gas diffusion layer on both sides to form a "seven-in-one" membrane electrode. The performance of the resulting membrane electrode can be tested by electrochemical methods.

[0140] Comparative Example 2

[0141] The steps for preparing CCM in this comparative example are the same as those in Example 2, except that the slurry 1 is dried at 50° C. for 3 minutes.

[0142] The CCM membrane electrodes prepared in Example 2 of the present invention and Comparative Example 2 were tested.

[0143] The surface structure of the first catalytic layer in Example 2 and Comparative Example 2 was observed by SEM (scanning electron microscope). Figure 2 shown. Figure 2 These are SEM images of the surface structure of the first catalytic layer of the membrane electrode prepared in Example 2 of the present invention and Comparative Example 2. The upper image is Example 2, and the lower image is Comparative Example 2.

[0144] Depend on Figure 2 It can be seen that the surface coating of the first catalytic layer in Example 2 is complete and uniform, without obvious defects. However, the surface of the first catalytic layer of Comparative Example 2 is very mottled and uneven, and the surface roughness is significantly increased. At the same time, residual catalyst powder can be observed on the surface of the vacuum coating equipment. This shows that the first catalytic layer in Comparative Example 2 that has not undergone high-temperature thermal annealing is structurally unstable. During the coating process of Slurry 2, a large amount of solvent penetrated into the first catalytic layer and caused significant damage to its structure. In contrast, in Example 2, the resin crystallinity in the catalytic layer after annealing is improved, which effectively enhances its tolerance to mixed solvents and structural stability.

[0145] The performance comparison of the membrane electrode obtained in Example 2 of the present invention and Comparative Example 2 is as follows: Figure 5 shown. Figure 5 This is a performance comparison chart of the membrane electrode prepared in Example 2 of the present invention and Comparative Example 2.

[0146] Depend on Figure 5 It can be seen that the membrane electrode performance obtained in Comparative Example 2 is highly consistent with that of Example 2 in the low current density range, but decays significantly in the medium and high current density range, which indicates that the destruction of the first catalytic layer structure will seriously affect the mass transfer capacity of CCM.

[0147] Furthermore, if a low-polarity solvent (such as propanol, butanol, etc.) is used in slurry 2, it will cause varying degrees of damage to the perfluorosulfonic acid resin. During the coating process of slurry 2, it is necessary to further reduce the proportion of alcohol in the solvent and increase the polarity of the solvent, that is, to increase the dielectric constant of the solvent to inhibit its damage to the proton membrane and the catalyst layer structure, as shown in Examples 3, 4, and 5.

[0148] Example 3

[0149] (1) In this example, the catalyst used in the first catalytic layer is a Pt / C catalyst, wherein the mass fraction of platinum is 60% and the specific surface area of ​​the catalyst is 300 m 2 / g.

[0150] (2) First, fully stir and mix the catalyst and deionized water, and then add the perfluorosulfonic acid resin solution and ethanol in sequence, stirring and mixing them thoroughly after each addition.

[0151] (3) The perfluorosulfonic acid resin solution is a commercial resin with an ion equivalent of about 1000, wherein the mass ratio of the perfluorosulfonic acid resin to the mass ratio of the carbon in the catalyst is 1.0.

[0152] (4) The mass ratio of water to ethanol in the solvent in slurry 1 is 4:1, and the solid content of the slurry is 10 wt%.

[0153] (5) The mixed slurry was dispersed by high-speed grinding at a speed of 3000 rpm for 30 min. After grinding, the collected slurry was subjected to vacuum degassing to obtain the catalyst slurry 1.

[0154] (6) The proton exchange membrane with one side covered with a PET protective substrate is placed on the vacuum adsorption platform of the coating machine, and the catalyst slurry 1 is coated on the surface of the proton exchange membrane using a slit direct coating method.

[0155] (7) The slurry was fully dried in a 90°C forced air oven for more than 2 minutes to form the first catalytic layer. The platinum loading of the catalyst was 0.35 mg / cm 2 .

[0156] (8) In this example, the catalyst used in the second catalytic layer is a Pt / C catalyst, in which the mass fraction of platinum is 50% and the specific surface area of ​​the catalyst is 300 m 2 / g.

[0157] (9) The preparation steps and methods of slurry 2 in this example are the same as those of slurry 1.

[0158] (10) The mass ratio of water to ethanol in the solvent of slurry 2 is 7:3, and the dielectric constant of the mixed solvent is 62. The solid content of the slurry is 4 wt%.

[0159] (11) Place one side of the proton exchange membrane covered with the first catalyst layer on the surface of the vacuum adsorption platform, remove the PET protective substrate, and apply catalyst slurry 2.

[0160] (12) After the slurry is fully dried, the second catalytic layer is formed, wherein the platinum loading of the catalyst is 0.05 mg / cm 2 .

[0161] (13) The CCM covered with catalytic layers on both sides was removed from the vacuum adsorption table to observe the effect of the preparation process of the second catalytic layer on the results of the first catalytic layer.

[0162] (14) The CCM is assembled with a frame and a gas diffusion layer on both sides to form a "seven-in-one" membrane electrode. The performance of the resulting membrane electrode can be tested by electrochemical methods.

[0163] Example 4

[0164] The CCM preparation steps described in this embodiment are the same as those in Example 3. The CCM preparation steps described in this embodiment are the same as those in Example 3, except that the mass ratio of water / n-propanol in the catalyst slurry 2 solvent is 9:1, and the dielectric constant of the mixed solvent is 73.

[0165] Example 5

[0166] The steps for preparing CCM in this embodiment are the same as those in Example 3, except that the mass ratio of water to n-propanol in the catalyst slurry 2 solvent is 4:1, and the dielectric constant of the mixed solvent is 67.

[0167] Comparative Example 3

[0168] The CCM preparation steps in this comparative example are the same as those in Example 3, except that the mass ratio of water to n-propanol in the catalyst slurry 2 solvent is 7:3, and the dielectric constant of the mixed solvent is 60.

[0169] The CCM membrane electrodes prepared in Example 3, Example 4 and Comparative Example 1 of the present invention were tested.

[0170] The surface structure of the first catalytic layer in Example 3, Example 4, Example 5 and Comparative Example 3 was observed by SEM (scanning electron microscope). Figure 3 shown. Figure 3 The SEM images of the surface structures of the first catalytic layers of the membrane electrodes prepared in Example 3, Example 4, and Comparative Example 3 are shown. The upper left image shows Example 3, the upper right image shows Example 4, the lower left image shows Example 5, and the lower right image shows Comparative Example 3.

[0171] Depend on Figure 3 It can be seen that the surface coating of the first catalytic layer in Examples 3 and 4 is complete and uniform, with no obvious defects. The surface coating of the first catalytic layer in Example 5 is basically complete, with a few defect streaks, and the defect area accounts for a small proportion of the overall catalytic layer. However, the first catalytic layer of Comparative Example 3 has a very mottled and uneven surface, with a significantly increased surface roughness. At the same time, residual catalyst powder can be observed on the surface of the vacuum coating equipment platform.

[0172] This indicates that during the coating process of Comparative Example Slurry 2, the solvent penetrated the ultra-thin proton exchange membrane to the first catalytic layer and caused significant damage to its structure.

[0173] The performance comparison of the membrane electrode obtained in Example 3, Example 4, Example 5 and Comparative Example 3 of the present invention is shown in FIG. Figure 6 shown. Figure 6 This is a performance comparison chart of the membrane electrodes prepared in Example 3, Example 4, Example 5 and Comparative Example 3 of the present invention.

[0174] Depend on Figure 6It can be seen that the polarization curves of Example 3, Example 4 and Example 5 are highly consistent, and the membrane electrode performance obtained in Comparative Example 3 is highly consistent with that of Examples 3, 4 and 5 in the low current density range, but is significantly attenuated in the medium and high current density range, which indicates that the destruction of the first catalytic layer structure by high content of n-propanol will seriously affect the mass transfer capacity of CCM.

[0175] See Table 1, which shows the specific ratios and parameters of the mixed solvent system in the catalyst slurry 2 in the examples of the present invention and the comparative examples.

[0176] Table 1

[0177] Serial number Mixed solvent system Alcohol / water ratio Solvent dielectric constant Example 4 n-Propanol / Water 1 / 9 73 Example 5 n-Propanol / Water 1 / 4 67 Example 1 Ethanol / water 1 / 3 65 Example 2 Ethanol / water 1 / 3 65 Comparative Example 2 Ethanol / water 1 / 3 65 Example 3 Ethanol / water 3 / 7 62 Comparative Example 3 n-Propanol / Water 3 / 7 60 Comparative Example 1 Ethanol / water 1 / 1 51

[0178] The above is a detailed introduction to a method for preparing a catalyst coating suitable for direct coating on the surface of an ultra-thin proton exchange membrane provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the literal wording of the claims, or if they include equivalent structural elements that are not substantially different from the literal wording of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a catalyst coating on the surface of an ultra-thin proton exchange membrane, characterized in that: The following steps are involved: 1) coating a first catalyst slurry on a slit on one side of a proton exchange membrane, and then heating and drying the slit to obtain a proton exchange membrane having a first catalyst coating on one side; 2) applying the side of the proton exchange membrane obtained in the above step with the first catalyst coating to the surface of a vacuum adsorption platform, slit-coating the second catalyst slurry on the other side of the proton exchange membrane, and drying to obtain a proton exchange membrane with the catalyst coating; The thickness of the proton exchange membrane is 5 to 12 μm; The second catalyst slurry is prepared from a catalyst, water, a perfluorosulfonic acid resin solution and a low-boiling-point organic alcohol; The ratio of water to low-boiling-point organic alcohol satisfies that the dielectric constant of the mixed solution of water and low-boiling-point organic alcohol is greater than 60.

2. The preparation method according to claim 1, characterized in that The catalyst comprises one or more of a carbon-supported Pt-based catalyst, a carbon-supported Pt alloy catalyst, and an oxide-supported Pt-based catalyst; The ion equivalent of the perfluorosulfonic acid resin solution is greater than 700 and less than 1100; The boiling point of the low-boiling-point organic alcohol is less than or equal to 100°C.

3. The preparation method according to claim 2, characterized in that The mass ratio of the perfluorosulfonic acid resin solution to the catalyst carrier is (1-100):

1.

4. The preparation method according to claim 1, characterized in that The solid content of the slurry is 3wt% to 15wt%; The low boiling point organic alcohol includes one or more of methanol, ethanol, n-propanol and isopropanol.

5. The preparation method according to claim 1, characterized in that The viscosity of the slurry is 10 to 50,000 mPa.s; The slurry is a catalyst coating slurry used when slit coating the catalyst coating on one side of the proton exchange membrane surface and slit coating the other side.

6. The preparation method according to claim 1, characterized in that The preparation method of the slurry comprises the following steps: a) fully mixing the catalyst with deionized water, then adding the perfluorosulfonic acid resin solution and homogenizing, and then adding a low-boiling point organic alcohol and homogenizing to obtain a mixed slurry; b) The mixed slurry obtained in the above steps is dispersed and then degassed to obtain a catalyst coating slurry for slit coating the catalyst coating on the surface of the proton exchange membrane.

7. The preparation method according to claim 6, characterized in that The dispersion method includes one or more of high-speed shearing, grinding, ultrasonic crushing, high-energy dispersion and stirring; The degassing method includes vacuum degassing.

8. The preparation method according to claim 1, characterized in that The heating and drying temperature is 80-130°C; The heating and drying time is 1 to 10 minutes.

9. The preparation method according to claim 1, characterized in that The drying temperature is 50-90°C; The drying time is 10 to 120 seconds.

10. The preparation method according to claim 1, characterized in that The platinum loading of the first catalyst layer is 0.03-0.4 mg / cm 2 ; The platinum loading of the second catalyst layer in the catalyst coating is 0.03 to 0.4 mg / cm 2 ; The first catalyst layer in the catalyst coating is a cathode catalyst layer or an anode catalyst layer, and the second catalyst layer is a corresponding anode catalyst layer or a cathode catalyst layer; The proton exchange membrane composited with a catalyst coating is a CCM membrane electrode.

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