Vacnt-based ordered membrane electrode and preparation method and application thereof

Abstract

This invention belongs to the field of batteries, and particularly relates to an ordered membrane electrode based on VACNT, its preparation method, and its application. The membrane electrode provided by this invention includes a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact. The porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than that near the proton exchange membrane; the platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than that near the proton exchange membrane. This invention constructs an ordered cathode catalyst layer structure for the membrane electrode. The cathode catalyst layer near the proton exchange membrane has a higher platinum content and lower porosity, while the cathode catalyst layer near the cathode gas diffusion layer has a lower platinum content and higher porosity. This cathode catalyst layer structure is beneficial for improving the platinum utilization rate of the cathode catalyst layer, improving the mass transfer effect of the cathode catalyst layer, and thus enhancing the electrical performance of the membrane electrode.

Description

Technical Field

[0001] This invention belongs to the field of batteries, and particularly relates to an ordered film electrode based on VACNT, its preparation method and application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are currently the most promising clean energy source, possessing significant advantages such as high energy conversion efficiency, zero pollution, and high energy density, and have gradually been commercialized on a large scale. With the expansion of the application market and the advancement of industrialization, the performance, durability, and cost requirements for PEMFCs have increased significantly, leading to a substantial increase in the requirements for the core component, the membrane electrode assembly (MEA).

[0003] The cathode catalyst layer in traditional membrane electrodes is a disordered stacking of carbon powder catalyst and perfluorosulfonic acid resin, with tortuous pore channels, which limits the further reduction of mass transfer resistance under high electrical density and the improvement of performance under low platinum loading. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an ordered membrane electrode based on VACNT, its preparation method and application. This invention can construct an ordered membrane electrode cathode catalytic layer structure, improve the mass transfer effect of the cathode catalytic layer, increase the platinum utilization rate of the cathode catalytic layer, and thus enhance the electrical performance of the membrane electrode.

[0005] This invention provides an ordered membrane electrode based on VACNT, comprising a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact. The cathode catalyst layer comprises vertically arrayed carbon nanotubes, platinum nanoparticles supported on the vertically arrayed carbon nanotubes, and perfluorosulfonic acid resin adhered to a local region of the vertically arrayed carbon nanotubes. The adhesion region of the perfluorosulfonic acid resin is the region of the cathode catalyst layer near the proton exchange membrane, or the region of the cathode catalyst layer near the proton exchange membrane and the region near the cathode gas diffusion layer. The porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than that near the proton exchange membrane. The platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than that near the proton exchange membrane.

[0006] Preferably, the cathode catalyst layer comprises a first cathode catalyst layer and a second cathode catalyst layer in contact with each other, and a perfluorosulfonic acid resin is adhered to the second cathode catalyst layer; the first cathode catalyst layer is in contact with the cathode gas diffusion layer, and the second cathode catalyst layer is in contact with the proton exchange membrane; the porosity of the first cathode catalyst layer is greater than that of the second cathode catalyst layer; and the platinum content of the first cathode catalyst layer is less than that of the second cathode catalyst layer.

[0007] Preferably, the cathode catalyst layer comprises a first cathode catalyst layer, a second cathode catalyst layer, and a third cathode catalyst layer in sequential contact, with perfluorosulfonic acid resin adhered to the first cathode catalyst layer and the third cathode catalyst layer; the first cathode catalyst layer is in contact with the cathode gas diffusion layer, and the third cathode catalyst layer is in contact with the proton exchange membrane; the porosity of the first cathode catalyst layer is greater than that of the third cathode catalyst layer and less than that of the second cathode catalyst layer; the platinum content of the first cathode catalyst layer is less than that of the third cathode catalyst layer and greater than that of the second cathode catalyst layer.

[0008] This invention provides a method for preparing an ordered film electrode based on VACNT, comprising the following steps:

[0009] a) Using vertically arrayed carbon nanotubes carrying platinum nanoparticles as the cathode catalyst layer, a perfluorosulfonic acid resin solution is coated on one side of the catalyst layer and dried to obtain a single-sided coated cathode catalyst layer; the single-sided coated cathode catalyst layer is hot-pressed onto a proton exchange membrane; after the hot-pressing transfer is completed, the coated side of the single-sided coated cathode catalyst layer is in contact with the proton exchange membrane.

[0010] b) Coat the other side of the proton exchange membrane with an anode catalyst layer, and then assemble it with the cathode gas diffusion layer and the anode gas diffusion layer to obtain an ordered membrane electrode based on VACNT;

[0011] The ordered membrane electrode comprises a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact; the porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than the porosity near the proton exchange membrane; the platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than the platinum content near the proton exchange membrane.

[0012] Preferably, step a) further includes: after completing the hot pressing transfer, coating the uncoated side of the single-sided cathode catalyst layer with a perfluorosulfonic acid resin solution, and drying it to obtain a double-sided coated cathode catalyst layer;

[0013] The pressure of the hot pressing transfer in step a) is greater than the pressure of the assembly in step b).

[0014] Preferably, in step a), the coating amount of the perfluorosulfonic acid resin solution, based on dry weight, is 0.05–2 mg / cm³. 2 .

[0015] Preferably, in step a), the solid content of the perfluorosulfonic acid resin solution is 0.005 to 2 wt%.

[0016] Preferably, in step a), the platinum loading of the vertically arrayed carbon nanotubes carrying platinum nanoparticles is 0.05–0.2 mg / cm³. 2 .

[0017] Preferably, in step a), the vertically arrayed carbon nanotubes carrying platinum nanoparticles are prepared according to the following steps:

[0018] Vertically arrayed carbon nanotubes were immersed in a platinum source precursor solution, removed, dried, and reduced with hydrogen to obtain vertically arrayed carbon nanotubes loaded with platinum nanoparticles.

[0019] This invention provides a proton exchange membrane fuel cell, comprising the ordered membrane electrode described in the above technical solution or the ordered membrane electrode prepared by the preparation method described in the above technical solution.

[0020] Compared with existing technologies, this invention provides an ordered membrane electrode based on VACNT, its preparation method, and its application. The membrane electrode provided by this invention comprises a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact. The cathode catalyst layer comprises vertically arrayed carbon nanotubes, platinum nanoparticles supported on the vertically arrayed carbon nanotubes, and perfluorosulfonic acid resin adhered to a localized region of the vertically arrayed carbon nanotubes. The adhesion region of the perfluorosulfonic acid resin is either the region of the cathode catalyst layer near the proton exchange membrane, or the region of the cathode catalyst layer near the proton exchange membrane and the region near the cathode gas diffusion layer. The porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than that near the proton exchange membrane. The platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than that near the proton exchange membrane. This invention introduces vertically arrayed carbon nanotubes (VACNTs) and optimizes the addition region of perfluorosulfonic acid resin in the cathode catalyst layer. Utilizing the adhesive effect of the perfluorosulfonic acid resin, the regions where the VACNTs adhere to the resin aggregate under pressure, thereby constructing an ordered membrane electrode cathode catalyst layer structure. The cathode catalyst layer near the proton exchange membrane side has a higher platinum content and lower porosity, while the cathode catalyst layer near the cathode gas diffusion layer side has a lower platinum content and higher porosity. This cathode catalyst layer structure is beneficial for improving the platinum utilization rate of the cathode catalyst layer, enhancing the mass transfer effect of the cathode catalyst layer, and thus strengthening the electrical performance of the membrane electrode. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a cross-sectional scanning electron microscope image of the cathode catalyst layer in Example 1 provided by the present invention;

[0023] Figure 2 This is a cross-sectional scanning electron microscope image of the cathode catalyst layer in Example 2 provided by the present invention;

[0024] Figure 3 This is a polarization curve diagram provided in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0026] This invention provides an ordered membrane electrode based on VACNT, comprising a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact. The cathode catalyst layer comprises vertically arrayed carbon nanotubes, platinum nanoparticles supported on the vertically arrayed carbon nanotubes, and perfluorosulfonic acid resin adhered to a local region of the vertically arrayed carbon nanotubes. The adhesion region of the perfluorosulfonic acid resin is the region of the cathode catalyst layer near the proton exchange membrane, or the region of the cathode catalyst layer near the proton exchange membrane and the region near the cathode gas diffusion layer. The porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than that near the proton exchange membrane. The platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than that near the proton exchange membrane.

[0027] In the membrane electrode provided by the present invention, the perfluorosulfonic acid resin is viscous, and the vertical array of carbon nanotubes in its adhesion region will bond and aggregate during the preparation of the membrane electrode (under extrusion), thereby reducing the porosity of the corresponding region and increasing the platinum content in the region.

[0028] In the membrane electrode provided by this invention, the localized adhesion of the perfluorosulfonic acid resin divides the cathode catalyst layer into a multi-layer structure, preferably a two- or three-layer structure. In one embodiment of this invention, the cathode catalyst layer is a two-layer structure, comprising a first cathode catalyst layer and a second cathode catalyst layer in contact with each other, with the perfluorosulfonic acid resin adhered to the second cathode catalyst layer; the first cathode catalyst layer is in contact with the cathode gas diffusion layer, and the second cathode catalyst layer is in contact with the proton exchange membrane; the porosity of the first cathode catalyst layer is greater than that of the second cathode catalyst layer; the platinum content of the first cathode catalyst layer is less than that of the second cathode catalyst layer; the porosity of the first cathode catalyst layer is preferably 50-60%, specifically 55.07%; the porosity of the second cathode catalyst layer is preferably 30-45%, specifically 38.645%. In another embodiment of the present invention, the cathode catalyst layer has a three-layer structure, comprising a first cathode catalyst layer, a second cathode catalyst layer, and a third cathode catalyst layer in sequential contact, with perfluorosulfonic acid resin adhered to the first and third cathode catalyst layers; the first cathode catalyst layer is in contact with the cathode gas diffusion layer, and the third cathode catalyst layer is in contact with the proton exchange membrane; the porosity of the first cathode catalyst layer is greater than that of the third cathode catalyst layer and less than that of the second cathode catalyst layer; the platinum content of the first cathode catalyst layer is less than that of the third cathode catalyst layer and greater than that of the second cathode catalyst layer; the porosity of the first cathode catalyst layer is preferably 40-50%, more preferably 46.822%; the porosity of the second cathode catalyst layer is preferably 50-55%, more preferably 53.613%; and the porosity of the third cathode catalyst layer is preferably 38-48%, more preferably 44.91%.

[0029] In the membrane electrode provided by the present invention, the overall platinum loading of the cathode catalyst layer is preferably 0.05–0.2 mg / cm³. 2 Specifically, it can be 0.05 mg / cm³. 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 0.1 mg / cm 2 0.11 mg / cm 2 0.12 mg / cm 2 0.13 mg / cm 2 0.14 mg / cm 2 0.15 mg / cm 2 0.16 mg / cm 2 0.17 mg / cm 2 0.18 mg / cm 20.19 mg / cm 2 Or 0.2 mg / cm 2 .

[0030] In the membrane electrode provided by the present invention, the proton exchange membrane includes, but is not limited to, a perfluorosulfonic acid resin membrane, preferably an enhanced perfluorosulfonic acid resin membrane.

[0031] In the membrane electrode provided by the present invention, the anode catalyst layer is preferably a platinum-carbon catalyst layer; the platinum-carbon catalyst layer is preferably formed by coating and drying a platinum-carbon slurry; the platinum-carbon slurry comprises a platinum-carbon catalyst, a binder, and a solvent, preferably including a platinum-carbon catalyst, a perfluorosulfonic acid resin solution, deionized water, and anhydrous ethanol; the solid content of the perfluorosulfonic acid resin solution is preferably 10-30 wt%, more preferably 20 wt%; the mass ratio of the platinum-carbon catalyst, the perfluorosulfonic acid resin solution, the deionized water, and the anhydrous ethanol is preferably 4:(5-15):(30-50):(10-15), more preferably 4:9:39:13; the platinum loading of the anode catalyst layer is preferably 0.01-0.1 mg / cm³. 2 Specifically, it can be 0.01 mg / cm³. 2 0.02 mg / cm 2 0.03 mg / cm 2 0.04 mg / cm 2 0.05 mg / cm 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 Or 0.1 mg / cm 2 .

[0032] In the membrane electrode provided by the present invention, the cathode gas diffusion layer and the anode gas diffusion layer are independently preferably carbon paper coated with carbon powder and hydrophobic material.

[0033] This invention also provides a method for preparing an ordered film electrode based on VACNT, comprising the following steps:

[0034] a) Using vertically arrayed carbon nanotubes carrying platinum nanoparticles as the cathode catalyst layer, a perfluorosulfonic acid resin solution is coated on one side of the catalyst layer and dried to obtain a single-sided coated cathode catalyst layer; the single-sided coated cathode catalyst layer is hot-pressed onto a proton exchange membrane; after the hot-pressing transfer is completed, the coated side of the single-sided coated cathode catalyst layer is in contact with the proton exchange membrane.

[0035] b) Coat the other side of the proton exchange membrane with an anode catalyst layer, and then assemble it with the cathode gas diffusion layer and the anode gas diffusion layer to obtain an ordered membrane electrode based on VACNT;

[0036] The ordered membrane electrode comprises a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact; the porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than the porosity near the proton exchange membrane; the platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than the platinum content near the proton exchange membrane.

[0037] In the preparation method provided by this invention, in step a), the platinum loading of the vertically arrayed carbon nanotubes carrying platinum nanoparticles is preferably 0.05–0.2 mg / cm³. 2 Specifically, it can be 0.05 mg / cm³. 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 0.1 mg / cm 2 0.11 mg / cm 2 0.12 mg / cm 2 0.13 mg / cm 2 0.14 mg / cm 2 0.15 mg / cm 2 0.16 mg / cm 2 0.17 mg / cm 2 0.18 mg / cm 2 0.19 mg / cm 2 Or 0.2 mg / cm 2 The vertically arrayed carbon nanotubes carrying platinum nanoparticles are preferably prepared according to the following steps:

[0038] Vertically arrayed carbon nanotubes were immersed in a platinum source precursor solution, removed, dried, and reduced with hydrogen to obtain vertically arrayed carbon nanotubes loaded with platinum nanoparticles.

[0039] In the preparation steps of the vertically arrayed carbon nanotubes loaded with platinum nanoparticles provided by the present invention, the vertically arrayed carbon nanotubes (VACNTs) include, but are not limited to, VACNTs prepared by floating and fixed methods, as well as VACNTs with hydrophilic or hydrophobic surface treatment or inorganic element doping; the substrate material of the VACNTs includes, but is not limited to, silicon plates, stainless steel sheets, aluminum foil, etc.; the height of the VACNTs is preferably 40-300 μm, specifically 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 170 μm, 200 μm, 230 μm, 250 μm, 270 μm or 300 μm.

[0040] In the preparation steps of the vertically arrayed carbon nanotubes loaded with platinum nanoparticles provided by the present invention, the platinum source precursor in the platinum source precursor solution includes, but is not limited to, one or more of chloroplatinic acid, potassium chloroplatinate, potassium chloroplatinate, and dinitrosodiammineplatinum; the platinum source concentration of the platinum source precursor solution is preferably 0.5–1 g. Pt / L, specifically 0.5g Pt / L, 0.55g Pt / L, 0.6g Pt / L, 0.65g Pt / L, 0.7g Pt / L, 0.75g Pt / L, 0.8g Pt / L, 0.85g Pt / L, 0.9g Pt / L, 0.95g Pt / L or 1g Pt / L.

[0041] In the preparation steps of the vertical array carbon nanotubes loaded with platinum nanoparticles provided by the present invention, the impregnation temperature is preferably 15-35°C, more preferably 25°C (room temperature); the impregnation time is preferably 12-48h, specifically 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h or 48h.

[0042] In the preparation method provided by this invention, in step a), the solvent in the perfluorosulfonic acid resin solution includes, but is not limited to, one or more of water, n-propanol, isopropanol, and ethanol; the solid content of the perfluorosulfonic acid resin solution is preferably 0.005–2 wt%, specifically 0.005 wt%, 0.007 wt%, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.07 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt%, or 2 wt%; the coating amount of the perfluorosulfonic acid resin solution, based on dry weight, is preferably 0.05–2 mg / cm³. 2 Specifically, it can be 0.05 mg / cm³. 2 0.07 mg / cm 2 0.1 mg / cm 2 0.165 mg / cm 2 0.2 mg / cm 2 0.33 mg / cm 2 0.5 mg / cm 2 0.7 mg / cm 2 1mg / cm 2 1.2 mg / cm2 1.5 mg / cm 2 1.7 mg / cm 2 Or 2mg / cm 2 .

[0043] In the preparation method provided by the present invention, in step a), the coating method is preferably immersion or spraying.

[0044] In the preparation method provided by the present invention, in step a), the temperature of the hot pressing transfer is preferably 120-160°C, specifically 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C or 160°C; the pressure of the hot pressing transfer is preferably 3-8 MPa, specifically 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa or 8 MPa.

[0045] In the preparation method provided by the present invention, in step a), the proton exchange membrane includes, but is not limited to, a perfluorosulfonic acid resin membrane, preferably an enhanced perfluorosulfonic acid resin membrane.

[0046] In the preparation method provided by the present invention, in step b), the anode catalyst layer is preferably a platinum-carbon catalyst layer; the platinum-carbon catalyst layer is formed by coating and drying a platinum-carbon slurry; the platinum-carbon slurry comprises a platinum-carbon catalyst, a binder, and a solvent, preferably including a platinum-carbon catalyst, a perfluorosulfonic acid resin solution, deionized water, and anhydrous ethanol; the solid content of the perfluorosulfonic acid resin solution is preferably 10-30 wt%, more preferably 20 wt%; the mass ratio of the platinum-carbon catalyst, the perfluorosulfonic acid resin solution, the deionized water, and the anhydrous ethanol is preferably 4:(5-15):(30-50):(10-15), more preferably 4:9:39:13; the platinum loading of the anode catalyst layer is preferably 0.01-0.1 mg / cm³. 2 Specifically, it can be 0.01 mg / cm³. 2 0.02 mg / cm 2 0.03 mg / cm 2 0.04 mg / cm 2 0.05 mg / cm 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 Or 0.1 mg / cm 2 .

[0047] In the preparation method provided by the present invention, in step b), the cathode gas diffusion layer and the anode gas diffusion layer are independently preferably carbon paper coated with carbon powder and hydrophobic material.

[0048] In the preparation method provided by the present invention, in step b), the assembly pressure is preferably 50-200 kPa, specifically 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, 110 kPa, 120 kPa, 130 kPa, 140 kPa, 150 kPa, 160 kPa, 170 kPa, 180 kPa, 190 kPa or 200 kPa.

[0049] In the preparation method provided by this invention, the cathode catalyst layer of the membrane electrode prepared by the above method has a two-layer structure. To prepare a three-layer cathode catalyst layer, step a) preferably further includes: after completing the hot-press transfer, coating the uncoated side of the single-sided cathode catalyst layer with a perfluorosulfonic acid resin solution, and drying it to obtain a double-sided coated cathode catalyst layer; wherein the composition, coating amount, and coating method of the perfluorosulfonic acid resin solution can be referred to the preceding text and will not be repeated here. In this invention, to ensure that the porosity of the three-layer cathode catalyst layer near the cathode gas diffusion layer is greater than the porosity near the proton exchange membrane, the pressure of the hot-press transfer in step a) needs to be greater than the assembly pressure in step b).

[0050] The present invention also provides a proton exchange membrane fuel cell, comprising the ordered membrane electrode described in the above technical solution or the ordered membrane electrode prepared by the preparation method described in the above technical solution.

[0051] The technical solution provided by this invention introduces vertically arrayed carbon nanotubes (VACNTs) and optimizes the addition region of perfluorosulfonic acid resin in the cathode catalyst layer. Utilizing the adhesive effect of the perfluorosulfonic acid resin, the regions where the VACNTs are adhered to the perfluorosulfonic acid resin undergo bonding and aggregation under compression, thereby constructing an ordered membrane electrode cathode catalyst layer structure. The cathode catalyst layer near the proton exchange membrane side has a higher platinum content and lower porosity, while the cathode catalyst layer near the cathode gas diffusion layer side has a lower platinum content and higher porosity. This cathode catalyst layer structure is beneficial for improving the platinum utilization rate of the cathode catalyst layer, enhancing the mass transfer effect of the cathode catalyst layer, and thus strengthening the electrical performance of the membrane electrode.

[0052] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0053] Example 1

[0054] Fabrication of a membrane electrode with a two-layer cathode catalytic layer:

[0055] A VACNT sample measuring 1.5 cm × 1.5 cm × 50 μm (carbon nanotube diameter approximately 20 nm, weight approximately 0.5 mg, provided by the team of Hou Xu and Wang Miao from Xiamen University, hereinafter the same) was used as the carbon support for the cathode catalyst layer, and was completely impregnated in 1 mL of 0.5 g [aluminum / carbon nanotube]. Pt The platinum source solution was immersed at room temperature for 24 hours, then removed, dried at room temperature, and then subjected to hydrogen reduction treatment in a carbonization furnace to obtain a platinum loading of approximately 0.1 mg / cm³. 2 Nanoplatinum-supported VACNT;

[0056] A 2 wt% perfluorosulfonic acid resin solution (a mixture of n-propanol and water, hereinafter the same) was sprayed onto one side of the platinum-supported VACNT nanoparticles, resulting in a resin loading of 0.33 mg / cm³ on a dry weight basis. 2 After drying, it is hot-pressed onto one side of a proton exchange membrane (type: reinforced perfluorosulfonic acid resin membrane, manufacturer: Gore, hereinafter the same). The hot-pressing temperature is 140℃ and the pressure is 5MPa. Then, an anode catalyst slurry is sprayed onto the other side of the proton exchange membrane. The anode catalyst slurry is prepared by mixing 4g of platinum-carbon catalyst (platinum content 50wt%, manufacturer: Tkk), 9g of 20wt% perfluorosulfonic acid resin solution, 39g of deionized water, and 13g of anhydrous ethanol. The spraying loading is 0.05mg. Pt / cm 2 A membrane structure with composite anode and cathode catalytic layers (CCM) was obtained;

[0057] Prepare the cathode gas diffusion layer and the anode gas diffusion layer. Both layers are made of the same material, specifically carbon paper coated with carbon powder and hydrophobic materials, from the brand Toray (hereinafter the same). Assemble the cathode gas diffusion layer, anode gas diffusion layer, and CCM into an assembly with an effective area of ​​1 cm². 2 In the single cell, the polarization performance of the membrane electrode consisting of the cathode gas diffusion layer / CCM / anode gas diffusion layer was tested. The assembly test conditions were: electrode back pressure 100 kPa, electrode temperature 80℃, electrode relative humidity 100% RH, and anode and cathode flow rates of 2 L / min for air and 1 L / min for hydrogen, respectively. After the polarization performance test, the single cell was opened, and the cross-sectional structure of the cathode catalyst layer was observed by scanning electron microscopy. The porosity and carbon nanotube area ratio of the cross-section were calculated.

[0058] Example 2

[0059] Fabrication of a membrane electrode with a three-layered cathode catalytic layer:

[0060] A VACNT sample measuring 1.5 cm × 1.5 cm × 50 μm was used as the carbon support for the cathode catalyst layer, and it was completely impregnated in 1 mL of 0.5 g [aluminum / concentrate]. PtThe platinum source solution was immersed at room temperature for 24 hours, then removed, dried at room temperature, and then subjected to hydrogen reduction treatment in a carbonization furnace to obtain a platinum loading of approximately 0.1 mg / cm³. 2 Nanoplatinum-supported VACNT;

[0061] A 2 wt% perfluorosulfonic acid resin solution was sprayed onto one side of the platinum-supported VACNT nanoparticles, resulting in a resin loading of 0.165 mg / cm³ on a dry weight basis. 2 After drying, it was hot-pressed onto one side of the proton exchange membrane at a temperature of 140℃ and a pressure of 5MPa. After the hot-pressing transfer was completed, a 2wt% perfluorosulfonic acid resin solution was sprayed onto the other side of the VACNT nanoparticle-supported surface, with a resin loading of 0.165 mg / cm³ on a dry weight basis. 2 After drying, an anode catalytic slurry is sprayed onto the other side of the proton exchange membrane. The composition of the anode catalytic slurry is the same as in Example 1, and the spraying loading is 0.05 mg. Pt / cm 2 A membrane structure (CCM) with composite anode and cathode catalytic layers was obtained;

[0062] The cathode gas diffusion layer, anode gas diffusion layer, and CCM are assembled into an effective area of ​​1 cm². 2 In the single cell, the polarization performance of the membrane electrode consisting of the cathode gas diffusion layer / CCM / anode gas diffusion layer was tested. The assembly test conditions were: electrode back pressure 100 kPa, electrode temperature 80℃, electrode relative humidity 100% RH, and anode and cathode flow rates of 2 L / min for air and 1 L / min for hydrogen, respectively. After the polarization performance test, the single cell was opened, and the cross-sectional structure of the cathode catalyst layer was observed by scanning electron microscopy. The porosity and carbon nanotube area ratio of the cross-section were calculated.

[0063] Comparative Example 1

[0064] Preparation of a membrane electrode with a single-layer cathode catalyst layer:

[0065] A cathode catalytic slurry was sprayed onto a 1.5cm × 1.5cm silicon wafer substrate. The slurry was prepared by mixing 4g of platinum-carbon catalyst (50wt% platinum), 9g of 20wt% perfluorosulfonic acid resin solution, 39g of deionized water, and 13g of anhydrous ethanol. After spraying and drying, the slurry was hot-pressed onto one side of a proton exchange membrane. The platinum loading of the cathode catalytic layer was approximately 0.1mg / cm². 2 Next, an anode catalytic slurry is sprayed onto the other side of the proton exchange membrane. The composition of the anode catalytic slurry is the same as that of the cathode catalytic slurry, and the spraying loading is 0.05 mg. Pt / cm 2 A membrane structure (CCM) with composite anode and cathode catalytic layers was obtained;

[0066] The cathode gas diffusion layer, anode gas diffusion layer, and CCM are assembled into an effective area of ​​1 cm². 2 In the single cell, the polarization performance of the membrane electrode consisting of the cathode gas diffusion layer / CCM / anode gas diffusion layer was tested. The assembly test conditions were: electrode back pressure 100 kPa, electrode temperature 80℃, electrode relative humidity 100% RH, and anode and cathode flow rates of 2 L / min for air and 1 L / min for hydrogen, respectively. After the polarization performance test, the single cell was opened, and the cross-sectional structure of the cathode catalyst layer was observed by scanning electron microscopy. The porosity and carbon nanotube area ratio of the cross-section were calculated.

[0067] Analysis of Experimental Results

[0068] 1) The cross-sectional morphology of the cathode catalyst layer in Example 1 is as follows: Figure 1 As shown, Figure 1 This is a cross-sectional scanning electron microscope (SEM) image of the cathode catalyst layer in Embodiment 1 of the present invention, wherein the first layer is in contact with the cathode gas diffusion layer, and the second layer is in contact with the proton exchange membrane; through Figure 1 It can be seen that the cathode catalytic layer of the VACNT-based ordered membrane electrode prepared in Example 1 has a two-layer structure. After the side of the cathode catalytic layer in contact with the proton exchange membrane is sprayed with perfluorosulfonic acid resin solution, the cathode catalytic layer close to this side (i.e., Figure 1 The porosity of the second layer (in the cathode gas diffusion layer) is less than that of the cathode catalyst layer (i.e., the second layer) which is closer to the cathode gas diffusion layer. Figure 1 The first layer is the carbon nanotube layer. Since porosity is inversely proportional to the area ratio of carbon nanotubes (the two together are 100%), and the area ratio of carbon nanotubes is positively correlated with the platinum content under the preparation conditions of Example 1, it can be inferred that the platinum content of the second layer is greater than that of the first layer. In summary, the cathode catalytic layer of Example 1 achieves a layered distribution of porosity and platinum content. The first layer has high porosity and low platinum content, while the second layer has low porosity and high platinum content.

[0069] 2) The cross-sectional morphology of the cathode catalyst layer in Example 2 is as follows: Figure 2 As shown, Figure 2 This is a cross-sectional scanning electron microscope (SEM) image of the cathode catalyst layer in Example 2 of the present invention; through... Figure 2 It can be seen that the cathode catalytic layer of the VACNT-based ordered membrane electrode prepared in Example 2 has a three-layer structure. After the cathode catalytic layer is sprayed with perfluorosulfonic acid resin solution on both the side in contact with the cathode gas diffusion layer and the side in contact with the proton exchange membrane, the cathode catalytic layer has obvious stratification, with the upper and lower layers (i.e., Figure 2 The first and third layers have lower porosity, while the middle layer (i.e., Figure 2The second layer in the cathode catalyst layer has a relatively large porosity. The first layer has mostly large transverse pores, the second layer has mostly large longitudinal pores, and the third layer has mostly small pores. In addition, the cathode gas diffusion layer is in close contact with the first layer of the cathode catalyst layer, which can provide good interfacial contact and reduce contact resistance.

[0070] 3) The calculated results of the cross-sectional porosity and carbon nanotube area ratio of the cathode catalyst layer in Examples 1 and 2 are shown in Table 1:

[0071] Table 1. Cross-sectional porosity and carbon nanotube area ratio of two-layer and three-layer cathode catalyst layers.

[0072]

[0073] As can be seen from Table 1, the porosity of the two-layer cathode catalytic layer prepared in Example 1 increases layer by layer along the direction from the proton exchange membrane to the cathode gas diffusion layer; although the porosity of the three-layer cathode catalytic layer prepared in Example 2 does not increase layer by layer along the direction from the proton exchange membrane to the cathode gas diffusion layer, the porosity of the cathode gas diffusion layer side and the middle layer is greater than the porosity of the proton exchange membrane side.

[0074] 4) The polarization performance test results of single cells in Examples 1, 2, and 1 are as follows: Figure 3 As shown, Figure 3 This is a polarization curve diagram provided in an embodiment of the present invention. Figure 3 In the diagram, the voltage curves include solid and dashed lines. The solid line voltage curves represent the voltage at different current densities after considering impedance, reflecting the overall performance. The dashed line voltage curves represent the voltage after impedance correction, reflecting the battery performance without considering impedance effects. The impedance HFR curves (solid lines) represent the impedance values ​​at different current densities. Figure 3 As can be seen from the solid line group of voltage curves, under the same platinum loading, when the current density is greater than 800 mA / cm², 2 At that time, the voltage performance of Example 2 was better than that of Comparative Example 1, indicating that under the same platinum loading, the ordered film electrode based on VACNT performs better than the conventional carbon powder film electrode. Furthermore, although... Figure 3 Among the solid line group of voltage curves, Example 1 had the worst performance, but the performance after impedance correction (dashed line group of voltage curves) was better than Example 2 and Example 3. Further optimization of the amount of sprayed resin is expected to achieve very good performance.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating an ordered film electrode based on VACNT, characterized in that, Includes the following steps: a) Using a vertical array of carbon nanotubes loaded with platinum nanoparticles as the cathode catalyst layer, a perfluorosulfonic acid resin solution is coated on one side of the catalyst layer and dried to obtain a single-sided coated cathode catalyst layer; the single-sided coated cathode catalyst layer is hot-pressed onto a proton exchange membrane; after the hot-pressing transfer is completed, the coated side of the single-sided coated cathode catalyst layer is in contact with the proton exchange membrane. b) Coat the other side of the proton exchange membrane with an anode catalyst layer, and then assemble it with the cathode gas diffusion layer and the anode gas diffusion layer to obtain an ordered membrane electrode based on VACNT; The ordered membrane electrode comprises a cathode gas diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode gas diffusion layer in sequential contact; the porosity of the cathode catalyst layer near the cathode gas diffusion layer is greater than the porosity near the proton exchange membrane; the platinum content of the cathode catalyst layer near the cathode gas diffusion layer is less than the platinum content near the proton exchange membrane.

2. The preparation method according to claim 1, characterized in that, Step a) further includes: after completing the hot pressing transfer, coating the uncoated side of the single-sided cathode catalyst layer with a perfluorosulfonic acid resin solution, drying it, and obtaining a double-sided coated cathode catalyst layer. The pressure of the hot pressing transfer in step a) is greater than the pressure of the assembly in step b).

3. The preparation method according to claim 1, characterized in that, In step a), the coating amount of the perfluorosulfonic acid resin solution, based on dry weight, is 0.05~2 mg / cm². 2 .

4. The preparation method according to claim 1, characterized in that, In step a), the solid content of the perfluorosulfonic acid resin solution is 0.005~2wt%.

5. The preparation method according to claim 1, characterized in that, In step a), the platinum loading of the vertically arrayed carbon nanotubes carrying platinum nanoparticles is 0.05~0.2 mg / cm³. 2 .

6. The preparation method according to claim 1, characterized in that, In step a), the vertically arrayed carbon nanotubes carrying platinum nanoparticles are prepared according to the following steps: Vertically arrayed carbon nanotubes were immersed in a platinum source precursor solution, removed, dried, and reduced with hydrogen to obtain vertically arrayed carbon nanotubes loaded with platinum nanoparticles.

7. A proton exchange membrane fuel cell, characterized in that, Including the ordered film electrode prepared by the preparation method according to any one of claims 1 to 6.

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