Silanol-improved cathode catalyst layer of proton exchange membrane fuel cell as well as preparation method and application of silanol-improved cathode catalyst layer

Abstract

The invention discloses a silanol-improved proton exchange membrane fuel cell cathode catalyst layer, the cathode catalyst layer is loaded with platinum particles and is prepared through silanol modification, and silanol is obtained after hydrolysis of a silane coupling agent. According to the cathode catalyst layer, after Nafion is modified by silanol, the cathode catalyst layer is applied to a proton exchange membrane fuel cell cathode catalyst layer to adjust a three-phase micro-interface and is used for constructing a fuel cell electrode. Silanol formed after hydrolysis of a silane coupling agent is adopted to regulate and control the morphology and adsorption behavior of the perfluorosulfonic acid ionomer through electrostatic interaction. On the basis, the modified Nafion is sprayed on a catalyst layer of the fuel cell. The catalyst layer constructed by the silane coupling agent modified perfluorosulfonic acid ionomer has lower oxygen transmission resistance, high proton transmission efficiency and lower sulfonate radical poisoning effect. The ultra-low platinum fuel cell prepared by the method disclosed by the invention expresses very good performance.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane fuel cell technology, and particularly to a silanol-modified proton exchange membrane fuel cell cathode catalyst layer, its preparation method, and its application. Background Technology

[0002] As a key component of green energy systems, proton exchange membrane fuel cells (PEMFCs) have attracted widespread attention due to their high energy conversion efficiency and zero carbon emissions. However, despite the excellent catalytic effect of platinum catalysts in improving fuel cell performance, their high cost and scarcity have become major bottlenecks restricting their large-scale application. Therefore, exploring platinum-free or ultra-low platinum loading proton exchange membrane fuel cells has become an important direction for promoting the commercialization of fuel cell technology. With ultra-low platinum loading, the performance improvement of proton exchange membrane fuel cells is often limited by the slow oxygen reduction reaction (ORR) kinetics at the cathode. Specifically, the reduction in platinum active sites in the cathode catalyst layer (CCL) leads to limited mass transport at the three-phase interface. ORR relies on the effective synergistic effect of the platinum / ionomer interface in the CCL, which not only provides sufficient reactive active sites but also enables the rapid migration of electrons, protons, and oxygen molecules. However, the sulfonic acid side chains of PFSA (such as Nafion) ionomers often adhere firmly to the platinum surface through a cation-electron pairing transfer process, forming new adsorbates such as OH–Nafion and O–Nafion. This not only blocks some platinum surface sites but also affects the desorption kinetics of intermediates in the oxygen reduction reaction, thereby reducing the activity of the platinum catalyst. Simultaneously, this process also leads to the formation of a dense, crystalline ionomer film at the electrode interface by pulling on the polytetrafluoroethylene backbone, further increasing the local resistance to oxygen transport. Therefore, optimizing the ionomer structure to improve the three-phase environment is particularly important to maximize the activity of platinum-based catalysts.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a silanol-modified proton exchange membrane fuel cell cathode catalyst layer, its preparation method, and its application, thereby overcoming the shortcomings of existing cathode catalyst layers, such as the reduction of platinum active sites, decreased platinum catalyst activity, and reduced catalyst layer reaction kinetics and mass transfer efficiency after use.

[0005] To achieve the above objectives, the present invention provides a silanol-modified proton exchange membrane fuel cell cathode catalyst layer, wherein the cathode catalyst layer is loaded with platinum particles and prepared by silanol modification, the silanol being obtained by hydrolysis of a silane coupling agent.

[0006] Preferably, in the above technical solution, the silanol-modified proton exchange membrane fuel cell cathode catalyst layer comprises a carbon thin film with a multi-scale ordered carbon nanotube array structure, wherein platinum particles are loaded within the carbon thin film, and the platinum loading is 40-60 μg / cm³. 2 .

[0007] Preferably, in the above technical solution, the method for preparing the cathode catalyst layer includes the following steps:

[0008] (1) Using aluminum foil as the substrate for iron film deposition and iron particles as raw materials, an iron film was deposited on the aluminum foil using an electron beam deposition process to obtain a carbon nanotube array growth substrate.

[0009] (2) The substrate from step (1) was placed in the plasma chemical vapor deposition chamber, vacuumed, hydrogen was introduced, the temperature was raised, acetylene was added as a carbon source, and plasma treatment was performed to obtain carbon nanotube arrays VACNTs.

[0010] (3) The carbon nanotube array from step (2) is placed in the reaction chamber of atomic layer deposition, heated, and vacuumed. The temperature of the source bottle with the platinum source is raised to the temperature that can reach the saturated vapor pressure of the platinum source for deposition cycle. Then, platinum deposition cycle is performed. Platinum particles with different loadings are prepared by controlling the number of cycles to obtain carbon nanotube arrays with deposited platinum nanocrystals.

[0011] (4) The silane coupling agent (BR, 98%) was fully mixed with water and hydrolyzed to obtain silanol and ion exchange resin solution to obtain a mixture. The mixture was then uniformly sprayed onto the carbon nanotube array deposited in step (3) and dried to obtain a multi-scale ordered carbon nanotube array loaded with platinum nanocrystal electrode material, denoted as VACNT / Pt-γMPS.

[0012] Preferably, in the above technical solution, the mass ratio of the silanol obtained after hydrolysis of the silane coupling agent to the ion exchange resin solution is 1-2:1-15, preferably 1:6; the mass ratio of the silane coupling agent to water is 1-10:1-5, preferably 3:1.

[0013] Preferably, in the above technical solution, the vacuum level maintained after evacuation in step (2) is ≤3.0×10⁻⁶. -2 mbar; hydrogen flow rate 150-250 sccm; heating temperature 550-650℃; acetylene flow rate 25-50 sccm; plasma post-treatment time 300-360s; plasma power 90-150W.

[0014] Preferably, in the above technical solution, in step (3), the atomic layer deposition reaction chamber is evacuated to a vacuum level of 7-10 mbar; the platinum source is methylcyclopentadienyl-trimethylplatinum; and the saturated vapor pressure temperature is 65-80℃.

[0015] Step (3) The platinum deposition cycle method includes opening the platinum source bottle for 200-350 ms, exposing it for 1-10 s to allow the platinum source to be adsorbed onto the carbon nanotube array VACNTs, then introducing N2 for 5-15 s to remove the unadsorbed platinum source, then introducing O2 for 1-5 s to react with the platinum source, and then immediately purifying with N2 for 10-30 s to complete one platinum deposition cycle.

[0016] Preferably, in the above technical solution, the ion exchange resin liquid in step (4) is an ion exchange resin solution diluted with an alcohol solvent to a concentration of 0.5-5 mg / ml; the spraying loading is 5-30 μg / cm³. 2 The drying temperature is 75-85℃, and the drying time is 10-60 min;

[0017] The ion exchange resin solution is one of DuPont Nafion solutions D520, D521, D1020, D1021 or D2020;

[0018] The silanol is obtained by hydrolysis of one of the silane coupling agents KH560 or KH570;

[0019] The alcohol solvent is ethanol or isopropanol.

[0020] Preferably, in the above technical solution, the silanol-modified proton exchange membrane fuel cell cathode catalyst layer is prepared by mixing silanol, Nafion solution, and platinum carbon particles, followed by ultrasonication and uniform spraying onto a gas diffusion layer to serve as the cathode of the proton exchange membrane fuel cell, denoted as Pt / C-γMPS.

[0021] The platinum loading was 150-250 μg / cm³. 2 The ion exchange resin solution is one of DuPont Nafion solutions D520, D521, D1020, D1021, or D2020; the silanol is obtained by hydrolysis of one of silane coupling agents KH560 or KH570.

[0022] A silanol-modified proton exchange membrane fuel cell cathode catalyst layer, used as the cathode of a proton exchange membrane fuel cell or as an electrode for preparing a proton exchange membrane fuel cell.

[0023] A method for preparing a proton exchange membrane fuel cell electrode includes the following steps:

[0024] (1) The above-mentioned silanol-modified proton exchange membrane fuel cell cathode catalyst layer is hot-pressed onto one side of the proton exchange membrane to serve as the cathode;

[0025] (2) The gas diffusion layer is placed on the cathode side, and the gas diffusion layer coated with Pt / c catalyst is placed on the other side of the proton exchange membrane as the anode, and the proton exchange membrane fuel cell electrode is constructed by hot pressing.

[0026] Preferably, in the above technical solution, the platinum loading in the anode is 150-250 μg / cm³. 2 The proton exchange membrane is NRE211; the gas diffusion layer is H24CX483 (FREUDENBERG).

[0027] The hot pressing transfer in step (1) includes a temperature of 120-150℃, a pressure of 20-40Mpa, and a transfer time of 5-20min;

[0028] The hot pressing in step (2) includes a temperature of 120-150℃, a pressure of 20-40Mpa, and a transfer time of 60-120 s.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) The silanol-modified proton exchange membrane fuel cell cathode catalyst layer of this invention mainly uses silanol formed after the hydrolysis of silane coupling agent. After being thoroughly mixed with ionomer, the mixed solution is uniformly sprayed onto the cathode catalyst layer deposited with platinum nanocrystals using electrostatic spraying technology. After continuous drying, an ionomer film is formed on the surface of the catalyst layer. Finally, the ultra-low platinum fuel cell membrane electrode is prepared by hot pressing transfer method. The ultra-low platinum fuel cell prepared by this method exhibits excellent performance.

[0031] (2) The present invention provides a cathode catalyst layer comprising a carbon film with a multi-scale ordered carbon nanotube array structure, wherein platinum particles are loaded within the carbon film. The carbon nanotube array is grown on aluminum foil using plasma-enhanced chemical vapor deposition, exhibiting abundant porosity and high graphitization, providing efficient mass transfer channels and excellent corrosion resistance. Platinum nanocrystals are deposited on this basis, and then silanol, obtained by hydrolyzing a silane coupling agent, is used to modify the ion exchange resin before being sprayed onto the carbon nanotube array as a catalyst layer for the fuel cell. The introduction of silanol can form a bridging effect between the perfluorosulfonic acid ion polymer and the carbon nanotube array, reducing the poisoning effect of the perfluorosulfonic acid ion polymer on the platinum nanocrystals. Furthermore, silanol can regulate the morphology and structure of the perfluorosulfonic acid ion polymer through hydrogen bonding interactions, unblocking oxygen transport pathways near the platinum nanocrystals. This increases the active sites of the platinum particles, reduces the amount of platinum used, and improves the stability of the fuel cell. The method of this invention is easy to operate, has a short preparation cycle, and relatively low platinum cost, which also reduces the production cost of the invention. At the same time, the performance of this method in ultra-low platinum fuel cells shows that it has higher power density and greater current density than commercial powder-based Pt / C catalysts and pure carbon nanotube array electrodes prepared in the same way.

[0032] (3) Another cathode catalyst layer of the present invention comprises a mixture of silanol, Nafion solution, and commercial platinum-carbon particles, which is then thoroughly ultrasonicated and uniformly sprayed onto a gas diffusion layer using electrostatic spraying as the cathode of a proton exchange membrane fuel cell. Electrodes are prepared using this cathode; that is, when using an electrode with silanol-modified Nafion coated with a commercial platinum-carbon cathode catalyst as the electrode, the cathode and anode each have a catalyst concentration of 200 μg / cm³. 2 Compared to the previous method, it can achieve a 20% performance improvement, which proves the universality of this strategy. Attached Figure Description

[0033] Figure 1 This is the silane coupling agent used in this invention; wherein, Figure 1 (a) shows the molecular structure of the silane coupling agent; Figure 1 (b) shows the molecular structure of silanol after the coupling agent has been hydrolyzed.

[0034] Figure 2 This is a schematic diagram of the process for preparing multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrode material (VACNT / Pt-γMPS) according to the present invention.

[0035] Figure 3 This is a schematic diagram of the process for preparing a commercial platinum carbon cathode (Pt / C-γMPS) with silanol-modified Nafion coating according to the present invention.

[0036] Figure 4The images are SEM images of the multi-scale ordered carbon nanotube array-supported platinum nanocrystals (VACNT / Pt-γMPS) and ordered carbon nanotube array-supported platinum nanocrystals (VACNT / Pt-Nafion) prepared in Examples 1 and 2, with a scale bar of 2 μm.

[0037] Figure 4 The middle (a) is a cross-sectional view of VACNT / Pt-γMPS under a scanning electron microscope, and the right side is the corresponding EDS image;

[0038] Figure 4 The middle (b) is a cross-sectional view of the VACNT / Pt-Nafion scanning electron microscope, and the right side is the corresponding EDS image;

[0039] Figure 4 Image (c) shows an example of transmission electron microscopy of VACNT / Pt-γMPS and the results of synchrotron radiation GIWAXS.

[0040] Figure 4 Image (d) shows an example image from a transmission electron microscope of VACNT / Pt-Nafion and the results from a synchrotron radiation GIWAXS.

[0041] Figure 5 This is an electrochemical test diagram of a fuel cell using a multi-scale ordered carbon nanotube array supported on a platinum nanocrystal electrode, as described in this invention.

[0042] Figure 5 (a) shows the polarization and power density curves of VACNT / Pt-γMPS and VACNT / Pt-Nafion as cathodes and commercial platinum carbon as anodes;

[0043] Figure 5 (b) shows the polarization curves and power density curves of VACNT / Pt-γMPS obtained by modifying Nafion with different ratios of silanol;

[0044] Figure 5 In (c), oxygen transport resistance curves are shown for VACNT / Pt-γMPS and VACNT / Pt-Nafion as cathodes and commercial platinum carbon as anodes.

[0045] Figure 6 This is a sulfonate coverage test diagram of the multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrode of the present invention.

[0046] Figure 6 (a) shows the Nyquist curves of CO adsorption measured by VACNT / Pt-γMPS under four conditions;

[0047] Figure 6(b) shows the Nyquist curves of CO adsorption measured by VACNT / Pt-Nafion under four conditions;

[0048] Figure 6 In the middle (c), the sulfonate coverage is a quantitative image calculated after the Nyquist curves of the two samples were measured to separate the variables.

[0049] Figure 7 This is an electrochemical polarization curve of a fuel cell using silanol-modified Nafion-coated commercial platinum-carbon cathode catalyst as the cathode and commercial platinum-carbon as the anode, according to the present invention.

[0050] Figure 8 This is a power density curve of an electrochemical test of a fuel cell using a silanol-modified Nafion-coated commercial platinum-carbon cathode catalyst as the cathode and commercial platinum-carbon as the anode. Detailed Implementation

[0051] The following detailed description of specific embodiments is provided in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0052] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0053] Unless otherwise specified, all raw materials and reagents used in the examples are commercially available.

[0054] The atomic layer deposition system (ALD) and plasma-enhanced chemical vapor deposition equipment used in the embodiments are commercially available.

[0055] The proton exchange membrane is a commercially available proton exchange membrane with model number NRE211, and the gas diffusion layer is a commercially available gas diffusion layer with model number H24XC483.

[0056] The silane coupling agent is a commercially available silane coupling agent with a purity of 98% (model KH570).

[0057] The ion exchange resin solution is a commercially available ion exchange resin solution with a content of 5%-20% (mass percentage of solute). Example 1

[0058] The preparation process flow diagram is as follows: Figure 1 and Figure 2 As shown, a method for preparing a silanol-modified proton exchange membrane fuel cell cathode catalyst layer includes the following steps:

[0059] (1) Cut the aluminum foil into 11.0 cm long and 11.0 cm wide, clean the surface with anhydrous ethanol, and use it as a substrate for iron nanoparticle deposition.

[0060] (2) Iron particles were used as the raw material for depositing iron nanoparticles, and the iron particles were placed in a crucible at the bottom of the electron beam deposition chamber. The iron particles were all cylindrical with a diameter of 0.3 cm and a height of 0.4 cm; the large end radius of the crucible was 1.43 cm, the small end radius was 1.12 cm, and the depth was 1.27 cm; the iron particles were pure iron. After evacuation, a 20 A current was passed through the crucible, causing the iron particles to evaporate onto the aluminum foil to form a nanofilm. The thickness of the iron nanofilm was controlled to be 2 nm, thus obtaining a carbon nanotube array growth substrate.

[0061] (3) The vertically aligned carbon nanotube array deposition substrate sample obtained in step (2) is cut into 5.5cm × 5.5cm pieces, then adhered to the bottom of the plasma-enhanced chemical vapor deposition equipment, and the vacuum is reduced to 3.0 × 10⁻⁶. -2 After reaching mbar, maintain a vacuum level of ≤3.0×10⁻⁶. -2 mbar; 99.99% pure hydrogen gas was introduced into the chamber; after heating to 600℃, 99.99% pure acetylene was introduced as a carbon source, followed by plasma treatment for 360s at a plasma power of 105W. This yielded a carbon nanotube array. After growth, the chamber was degassed, opened, and the resulting carbon nanotube array (VACNTs) was removed and weighed to 114.31mg.

[0062] (4) Place the VACNTs obtained in step (3) into the reaction chamber of an atomic layer deposition (ALD) system. Under ALD conditions, raise the chamber temperature to 300°C, evacuate to 8 mbar, and raise the temperature of the source bottle containing the platinum source methylcyclopentadienyl-trimethylplatinum (MeCpPtMe3, 99%) to 75°C to achieve the saturated vapor pressure of the platinum source. The deposition cycle steps are as follows: open the source bottle for 300 ms, supply the platinum source, expose for 5 s to allow the platinum source to adsorb onto the carbon nanotube array VACNTs, then introduce N2 for 10 s to remove the unadsorbed platinum source, then introduce O2 for 2 s to react with the platinum source for 2 s, and then immediately purify with N2 for 15 s to remove other substances produced by the reaction, completing one platinum deposition cycle. Perform 130 ALD platinum deposition cycles to obtain a vertically aligned carbon nanotube array with deposited platinum nanoparticles, weighing 114.56 mg, with a platinum loading of 50 μg / cm³. 2 ;

[0063] (5) Dilute the DuPont Nafion D520 solution in the ion exchange resin solution to 2 mg / mL with anhydrous ethanol; hydrolyze the silane coupling agent (BR, 98%) with water (the mass ratio of silane coupling agent to water is 3:1) to obtain silanol, wherein the water is ultrapure water and the amount added is 10 μl; then mix the silanol with the ion exchange resin solution at a mass ratio of 1:6, and then place the carbon nanotube array with platinum nanocrystals deposited in step (4) in an electrostatic sprayer, and uniformly electrostatically spray the carbon nanotube array with the diluted ion exchange resin solution, with a spray loading of 20 μg / cm. 2 Drying at 80℃ for 30 minutes yields a multi-scale ordered carbon nanotube array-supported platinum nanocrystalline electrode material (Pt / VACNT-γMPS), which is then used as a cathode.

[0064] The fabricated multi-scale ordered carbon nanotube array-supported platinum nanocrystalline electrode (VACNT / Pt-γMPS) was subjected to scanning electron microscopy, transmission electron microscopy, GIWAXS testing, and contact angle measurement. The results are as follows: Figure 4 As shown. Example 2

[0065] This embodiment describes a method for preparing a silanol-modified proton exchange membrane fuel cell cathode catalyst layer. The difference from Example 1 is that in step (5), the silanol obtained after hydrolyzing the silane coupling agent is mixed with an ion exchange resin solution to obtain a mixed solution, and the solution is prepared according to different mass ratios. The different mass ratios of silanol to ion exchange resin solution are 1:1, 1:9, 1:15, and 2:1. The multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrodes (VACNT / Pt-γMPS) prepared under different ratios are obtained. Full-cell testing was performed on the multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrodes (VACNT / Pt-γMPS) prepared under different ratios, and the results are as follows. Figure 5 As shown. Comparative Example 1

[0066] A method for preparing a proton exchange membrane fuel cell cathode catalyst layer using a vertically aligned carbon nanotube array includes the following steps:

[0067] (1) Cut the aluminum foil into 11.0 cm long and 11.0 cm wide, clean the surface with anhydrous ethanol, and use it as a substrate for iron nanoparticle deposition.

[0068] (2) Iron particles were used as the raw material for depositing iron nanoparticles, and the iron particles were placed in a crucible at the bottom of the electron beam deposition chamber. The iron particles were all cylindrical with a diameter of 0.3 cm and a height of 0.4 cm; the crucible had a large end radius of 1.43 cm, a small end radius of 1.12 cm, and a depth of 1.27 cm; the iron particles were pure iron. After evacuation, a 20 A current was passed through the crucible, causing the iron particles to evaporate onto the aluminum foil to form a nanofilm. The thickness of the iron nanofilm was controlled to be 2 nm, thus obtaining a carbon nanotube array growth substrate.

[0069] (3) The vertically aligned carbon nanotube array deposition substrate sample obtained in step (2) is cut into 5.5cm × 5.5cm pieces, then adhered to the bottom of the plasma-enhanced chemical vapor deposition equipment, and the vacuum is reduced to 3.0 × 10⁻⁶. -2 After reaching mbar, maintain a vacuum level of ≤3.0×10⁻⁶. -2 mbar. Hydrogen gas with a purity of 99.99% was introduced into the chamber; after heating to 600℃, acetylene gas with a purity of 99.99% was introduced as the carbon source, followed by plasma treatment for 360 s at a plasma power of 105 W. This yielded a carbon nanotube array. After growth, the chamber was degassed, opened, and the resulting carbon nanotube array (VACNTs) was removed and weighed to 114.31 mg.

[0070] (4) Place the VACNTs obtained in step (3) into the reaction chamber of an atomic layer deposition (ALD) system. Under ALD conditions, raise the chamber temperature to 300°C, evacuate to 8 mbar, and raise the temperature of the source bottle containing the platinum source methylcyclopentadienyl-trimethylplatinum (MeCpPtMe3, 99%) to 75°C to achieve the saturated vapor pressure of the platinum source. The deposition cycle steps are as follows: open the source bottle for 300 ms, supply the platinum source, expose for 5 s to allow the platinum source to adsorb onto the carbon nanotube array VACNTs, then introduce N2 for 10 s to remove the unadsorbed platinum source, then introduce O2 for 2 s to react with the platinum source for 2 s, and then immediately purify with N2 for 15 s to remove other substances produced by the reaction, completing one platinum deposition cycle. Perform 130 ALD platinum deposition cycles to obtain a vertically aligned carbon nanotube array with deposited platinum nanoparticles, weighing 114.56 mg, with a platinum loading of 50 μg / cm³. 2 ;

[0071] (5) Dilute the DuPont Nafion D520 ion exchange resin solution to 2 mg / mL with anhydrous ethanol; then place the carbon nanotube array with platinum nanocrystals deposited in step (4) in an electrostatic sprayer, and uniformly electrostatically spray the carbon nanotube array with the diluted ion exchange resin solution. The spray loading is 20 μg / cm³. 2Drying at 80℃ for 30 min yields a multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrode material (VACNT / Pt-Nafion), which serves as the cathode. Example 3

[0072] The preparation process flow diagram is as follows: Figure 1 and Figure 3 As shown, a method for preparing a silanol-modified proton exchange membrane fuel cell cathode catalyst layer is described. This method prepares a silanol-modified Nafion-coated commercial platinum-carbon cathode catalyst, specifically including the following steps:

[0073] (1) 36 ml of isopropanol solution (99.99%), 873 mg of D520N Nafion solution (5%), 180 mg of platinum-carbon catalyst powder (46.1%, purchased from TANAKA Japan Honchu Precious Metals), 140 mg of silane coupling agent and 40 mg of ultrapure water were mixed (silane coupling agent was hydrolyzed in water to obtain silanol) to prepare a slurry. The slurry was then placed in an ultrasonic machine for 30 min of ultrasonic operation to obtain the modified platinum-carbon slurry.

[0074] (2) Cut the gas diffusion layer into 12.7cm×12.7cm pieces, weigh them, and then place them in an electrostatic spraying device. Apply the slurry evenly to the gas diffusion layer by electrostatic spraying. To ensure uniform slurry application, the spraying rate is set to 0.1ml / min, and the loading is controlled at 200μg / cm. 2 A commercial platinum carbon cathode (Pt / C-γMPS) was obtained by coating Nafion with silanol-modified Nafion.

[0075] (3) Cut the Pt / C-γMPS obtained in step (2) into 2.3cm×2.3cm pieces to be used as cathodes. Comparative Example 2

[0076] The preparation method for Nafion-coated commercial platinum-carbon cathode catalyst includes the following steps:

[0077] Specifically, the following steps are included:

[0078] (1) 36 ml of isopropanol solution (99.99%), 873 mg of D520N Nafion solution (5%), and 180 mg of platinum-carbon catalyst powder (46.1%, purchased from TANAKA Japan Honchu Precious Metals) were placed in an ultrasonic machine for 30 min of ultrasonic operation to obtain the modified platinum-carbon slurry.

[0079] (2) Cut the gas diffusion layer into 12.7cm×12.7cm pieces, weigh them, and then place them in an electrostatic spraying device. Apply the slurry evenly to the gas diffusion layer by electrostatic spraying. To ensure uniform slurry application, the spraying rate is set to 0.1ml / min, and the loading is controlled at 200μg / cm. 2 A commercial platinum carbon cathode, Pt / C, was obtained by coating Nafion with silanol-modified Nafion.

[0080] (3) Cut the Pt / C-γMPS obtained in step (2) into 2.3cm×2.3cm pieces to be used as cathodes. Application and performance testing Application Example 1

[0081] The multi-scale ordered carbon nanotube array-supported platinum nanocrystal electrode (VACNT / Pt-γMPS) prepared in Example 1 was applied to the construction of an ultra-low platinum content fuel cell electrode. The VACNT / Pt-γMPS electrode was used as the cathode, and commercially available platinum-carbon was used as the anode. The platinum (Pt) loading of the cathode was 50 μg / cm³. 2 The platinum (Pt) loading of commercial platinum-carbon anodes is 200 μg / cm³. 2 The steps for constructing a membrane electrode are as follows:

[0082] (1) Place the VACNT / Pt-γMPS, which serves as the cathode, on one side of the proton exchange membrane (NRE211); perform hot pressing transfer at 135°C and 30 MPa for 12 minutes to transfer the VACNT / Pt-γMPS onto the proton exchange membrane; mark it as the cathode.

[0083] (2) The gas diffusion layer (H24CX483 FREUDENBERG) and the commercial platinum carbon anode are placed on both sides of the proton exchange membrane obtained after the transfer in step (1), and hot-pressed at 135℃ and 25MPa for 120 s to form the proton exchange membrane electrode, namely the ultra-low platinum loading proton exchange membrane fuel cell electrode. Application Example 2

[0084] The silanol-modified Nafion-coated commercial platinum-carbon cathode (Pt / C-γMPS) prepared in Example 3 was applied to the construction of an ultra-low platinum content fuel cell electrode. The silanol-modified Nafion-coated commercial platinum-carbon cathode (Pt / C-γMPS) was used as the cathode, and commercial platinum carbon was used as the anode. The platinum (Pt) loading of the cathode was 200 μg / cm³. 2 The platinum (Pt) loading of commercial platinum-carbon anodes is 200 μg / cm³. 2 The steps for constructing a membrane electrode are as follows:

[0085] (1) Place the Pt / C-γMPS, which serves as the cathode, on one side of the proton exchange membrane (NRE211); perform hot pressing transfer at 135°C and 30 MPa for 12 minutes to transfer the Pt / C-γMPS onto the proton exchange membrane; mark it as the cathode.

[0086] (2) The gas diffusion layer (H24CX483, Freudenberg) and the commercial platinum carbon anode are placed on both sides of the proton exchange membrane obtained after the transfer in step (1), and hot-pressed at 135°C and 25 MPa for 120 s to form a proton exchange membrane electrode. Performance testing

[0087] 1. Place the proton exchange membrane electrode (MEA) prepared in step (2) above into the battery fixture and test it on an 850e fuel cell test station. The battery is first swept from open circuit voltage to 0.2V at 80℃ in hydrogen / oxygen (400 / 400 sccm) until it reaches stability. Then, its IV polarization curve and power density curve are tested in hydrogen / air (400 / 1000 sccm) as shown in the figure. Figure 5 As shown. The cathode platinum loading was 50 μg / cm². 2 Under these conditions, it has 0.9W cm -2 Performance.

[0088] 2. The VACNT / Pt-γMPS obtained in Examples 1 and 2 was used as the cathode, with a platinum loading of 50 μg / cm³. 2 Platinum loading is 200 μg / cm 2 Commercially available platinum-carbon was used as the anode, and a proton exchange membrane electrode (MEA) was prepared according to steps (1) and (2) of Application Example 1. The VACNT / Pt-Nafion obtained in Comparative Example 1 was used as the cathode, with a platinum loading of 50 μg / cm³. 2 Platinum loading is 200 μg / cm 2 Commercially available platinum-carbon was used as the anode, and a proton exchange membrane electrode (MEA) was prepared according to steps (1) and (2) of Application Example 1. The MEA was placed in a battery fixture and tested on an 850e fuel cell test station. The battery was first swept from open-circuit voltage to 0.2 V at 80°C in hydrogen / oxygen (400 / 400 sccm) until stable, and then its IV polarization curve and power density curve were tested in hydrogen / air (400 / 1000 sccm). Figure 5 As shown, VACNT / Pt-γMPS with a cathode platinum loading of 50 μg / cm³ 2 Under these conditions, it has 0.9W cm -2 Performance is improved by 27% compared to VACNT / Pt-Nafion, and the best performance is achieved at a silanol to Nafion mass ratio of 1:6.

[0089] 3. The film electrodes made of commercial platinum-carbon in Example 3 and Comparative Example 2 had platinum loadings of 200 μg / cm³ for both the cathode and anode. 2 Proton exchange membrane electrode assembly (MEA) was prepared according to steps (1) and (2) of Application Example 2. The MEA was placed in the battery fixture and tested on an 850e fuel cell test station. The battery was first swept from open circuit voltage to 0.2 V at 80°C in hydrogen / oxygen (400 / 400 sccm) until it reached stability. Then, its IV polarization curve and power density curve were tested in hydrogen / air (400 / 1000 sccm). The results are as follows. Figure 5 As shown. From Figure 7 and Figure 8 It can be seen that when the electrode of the commercial platinum-carbon cathode catalyst modified with silanol Nafion in Example 3 of the present invention is used as the electrode, compared with the use of a commercial Pt / C catalyst, the cathode and anode each have a concentration of 200 μg / cm. 2 Compared to the previous method, it also showed a 20% performance improvement and reduced oxygen transport resistance; this demonstrates the universality of this strategy.

[0090] 4. Figure 4 The images are SEM images of the multi-scale ordered carbon nanotube array-supported platinum nanocrystals (VACNT / Pt-γMPS) and ordered carbon nanotube array-supported platinum nanocrystals (VACNT / Pt-Nafion) prepared in Example 1. Figure 4 As shown in (a) and (b), the cross-sectional images of VACNTs obtained by SEM testing and the corresponding EDS test on the right indicate that this carbon material contains Pt, S and Si elements, indicating that platinum nanocrystals and Nafion are fully covered and uniformly distributed on VACNTs. Figure 4 (c) and (d) are TEM images of both and GIWAXS synchrotron radiation. The results show that the coverage of the ionomer layer is more uniform and thinner. In addition, while keeping the average spacing of the ionomer clusters unchanged, a longer-range structural correlation and a more continuous ion conduction network are achieved, providing a structural basis for the spatial separation of oxygen and proton transport and the improvement of electrode performance.

[0091] 5. Figure 6 The EIS was measured under four different conditions using in-situ impedance detection technology. After calculating the double-layer capacitance under the conditions using the EIS, the poisoning rate of Nafion on platinum can be obtained by fitting the data. Figure 6 (a) and (b) are EIS plots under four conditions for VACNT / Pt-γMPS and VACNT / Pt-Nafion, respectively. Figure 6(c) is a quantitative graph of the poisoning rate after separating the variables. After modifying Nafion with silanol, the poisoning effect of Nafion was effectively inhibited (reduced by 42%), allowing platinum to expose more active sites and providing more oxygen reaction sites.

[0092] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A silanol-modified proton exchange membrane fuel cell cathode catalyst layer, characterized in that, The cathode catalyst layer is loaded with platinum particles and prepared by modification with silanol, which is obtained by hydrolysis of silane coupling agent.

2. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 1, characterized in that, The cathode catalyst layer comprises a carbon film with a multi-scale ordered carbon nanotube array structure, wherein platinum particles are loaded within the carbon film at a loading of 40-60 μg / cm³. 2 .

3. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 2, characterized in that, The method for preparing the cathode catalyst layer includes the following steps: (1) Using aluminum foil as the iron film deposition substrate and iron particles as raw materials, an iron film was deposited on the aluminum foil using electron beam deposition process to obtain a carbon nanotube array growth substrate. (2) The substrate from step (1) is placed in a plasma chemical vapor deposition chamber, a vacuum is drawn, hydrogen is introduced, the temperature is raised, acetylene is added as a carbon source, and plasma treatment is performed to obtain a carbon nanotube array. (3) The carbon nanotube array from step (2) is placed in the reaction chamber of atomic layer deposition, heated, and vacuumed. The temperature of the source bottle with the platinum source is raised to the temperature that can reach the saturated vapor pressure of the platinum source for deposition cycle. Then, platinum deposition cycle is performed. Platinum particles with different loadings are prepared by controlling the number of cycles to obtain carbon nanotube arrays with deposited platinum nanocrystals. (4) The silane coupling agent is fully mixed with water and hydrolyzed to obtain silanol and ion exchange resin solution to obtain a mixture. The mixture is then uniformly sprayed onto the carbon nanotube array deposited in step (3) and dried to obtain a multi-scale ordered carbon nanotube array loaded with platinum nanocrystal electrode material.

4. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 3, characterized in that, The mass ratio of the silanol obtained after hydrolysis of the silane coupling agent to the ion exchange resin solution is 1-2:1-15, preferably 1:6; the mass ratio of the silane coupling agent to water is 1-10:1-5, preferably 3:

1.

5. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 3, characterized in that, After step (2), maintain the vacuum level at ≤3.0×10⁻⁶. -2 mbar; hydrogen flow rate of 150-250 sccm; heating temperature of 550-650℃; acetylene flow rate of 25-50 sccm; plasma post-treatment time of 300-360s; plasma power of 90-150W.

6. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 3, characterized in that, Step (3) Evacuate the atomic layer deposition reaction chamber to a vacuum level of 7-10 mbar; the platinum source is methylcyclopentadienyl-trimethylplatinum; the saturated vapor pressure temperature is 65-80℃; Step (3) The platinum deposition cycle method includes opening the platinum source bottle for 200-350 ms, exposing it for 1-10 s to allow the platinum source to be adsorbed onto the carbon nanotube array, then passing N2 for 5-15 s to remove the unadsorbed platinum source, then passing O2 for 1-5 s to react with the platinum source, and then immediately purifying with N2 for 10-30 s to complete one platinum deposition cycle; The ion exchange resin liquid is an ion exchange resin solution diluted with an alcohol solvent to a concentration of 0.5-5 mg / ml; the spraying loading is 5-30 μg / cm³. 2 The drying temperature is 75-85℃, and the drying time is 10-60 min; The ion exchange resin solution is one of DuPont Nafion solutions D520, D521, D1020, D1021 or D2020; The silanol is obtained by hydrolysis of one of the silane coupling agents KH560 or KH570; The alcohol solvent is ethanol or isopropanol.

7. The silanol-modified proton exchange membrane fuel cell cathode catalyst layer according to claim 1, characterized in that, The preparation of the cathode catalyst layer includes mixing silanol, Nafion solution, and platinum carbon particles, ultrasonicating, and then uniformly spraying the mixture onto the gas diffusion layer to serve as the cathode of the proton exchange membrane fuel cell. The platinum loading was 150-250 μg / cm³. 2 ; The ion exchange resin solution is one of DuPont Nafion solutions D520, D521, D1020, D1021, or D2020; the silanol is obtained by hydrolysis of one of silane coupling agents KH560 or KH570.

8. A silanol-modified proton exchange membrane fuel cell cathode catalyst layer as described in any one of claims 1-7, used as the cathode of a proton exchange membrane fuel cell or as an electrode for preparing a proton exchange membrane fuel cell.

9. A method for preparing a proton exchange membrane fuel cell electrode, characterized in that, Includes the following steps: (1) The silanol-modified proton exchange membrane fuel cell cathode catalyst layer of any one of claims 1-7 is hot-pressed onto one side of the proton exchange membrane as a cathode; (2) The gas diffusion layer is placed on the cathode side, and the gas diffusion layer coated with Pt / c catalyst is placed on the other side of the proton exchange membrane as the anode, and the proton exchange membrane fuel cell electrode is constructed by hot pressing.

10. The method for preparing a proton exchange membrane fuel cell electrode according to claim 9, characterized in that, The platinum loading in the anode is 150-250 μg / cm³. 2 ; The hot pressing transfer in step (1) includes a temperature of 120-150℃, a pressure of 20-40Mpa, and a transfer time of 5-20min; The hot pressing in step (2) includes a temperature of 120-150℃, a pressure of 20-40Mpa, and a transfer time of 60-120 s.

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