A fuel cell carbon-supported platinum-based anti-reversal catalyst modified with a small amount of highly dispersed iridium surface, and its preparation method and application

Abstract

The present invention discloses a fuel cell platinum-based anti-reverse polarity catalyst with a small amount of highly dispersed iridium surface modification, as well as its preparation method and application. The method comprises the following steps: impregnating the platinum-based catalyst with an iridium complex organic solvent, and then subjecting the catalyst to heat treatment under a specific atmosphere to highly disperse the iridium atoms on the surface of the platinum-based catalyst; dissolving the iridium precursor in a mixed solution of water and alcohol, adding a complexing agent, and stirring evenly at room temperature; weighing the platinum-based catalyst, wetting it with deionized water, mixing it with the solution obtained in step one, and ultrasonicating it; transferring the above mixture to a constant temperature water bath, and evaporating the solvent; transferring the material after evaporation of the solvent to a quartz boat, placing it in a tube furnace, and subjecting it to reduction heat treatment under a specific atmosphere to obtain a platinum-based catalyst with a small amount of highly dispersed iridium surface modification. The present invention not only solves the anti-reverse polarity problem of fuel cells, but also significantly reduces the amount of precious metal iridium used, which is of great significance for promoting the large-scale commercialization of fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy proton exchange membrane fuel cells, and relates to a fuel cell carbon-supported platinum-based anti-reverse polarity catalyst modified with a small amount of highly dispersed iridium surface, as well as a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer key advantages such as high energy conversion efficiency, zero emissions, and fast startup times, holding them promising applications in transportation, communications, aviation / aerospace, and submarine applications. Currently, cost and durability are the two main technical barriers to PEMFC commercialization. Durability refers to the ability of a material or product to withstand long-term damage from both its own internal and environmental factors. In addition to factors such as material aging and deactivation, fuel cell operating conditions are also a significant factor influencing durability. These include start-stop, freezing / thawing, high voltage, variable load, and wet / dry cycling. When a PEMFC anode fuel gas is deficient due to start-stop, variable load, and environmental conditions, water electrolysis and carbon corrosion often occur simultaneously on the membrane electrode. These reactions serve as sources of electrons and protons, creating a phenomenon known as electrode reversal. Membrane electrode reversal can cause serious problems. Corrosion of the carbon support can lead to the rapid growth of platinum nanoparticles and a rapid decrease in catalyst activity. Simultaneously, the reversal process generates a large amount of heat, causing perforation of the proton membrane and subsequent membrane electrode short circuit, ultimately leading to catastrophic battery failure. Optimizing system control strategies is a common and effective method for fuel cell vehicle development to avoid reversal, but a more popular and recognized approach is to develop catalysts with reversal resistance. The active ingredients of currently widely used reversal catalysts are primarily iridium or iridium oxides. Once reversal occurs, the iridium catalyst prioritizes the decomposition of water molecules and releases oxygen and hydrogen, thereby inhibiting carbon oxidation and protecting the carbon support from oxidation.

[0003] The current anti-reverse polarity technology mainly involves adding iridium-containing catalyst substances to the platinum-carbon catalyst layer, or directly preparing and using carbon-supported platinum-based catalysts containing iridium. The amount of iridium used is usually as high as one-third to one-fifth of platinum, which increases the manufacturing cost of fuel cells.

[0004] Chinese patent application CN113178582A discloses a proton exchange membrane fuel cell (PEMFC) anti-reversal anode catalyst comprising a carbon nanotube-supported platinum-iridium alloy. This catalyst eliminates the need for an additional anti-reversal additive in the anode catalyst layer, thus avoiding agglomeration caused by direct addition of iridium or iridium oxide. However, the Pt / I molar ratio in the anti-reversal catalyst provided by this invention is 6 to 1:1, resulting in a relatively high iridium dosage and low iridium utilization. Consequently, membrane electrodes prepared using this catalyst lack significantly enhanced reverse polarity tolerance.

[0005] Chinese patent application CN112838224A discloses a proton exchange membrane fuel cell (PEMFC) membrane electrode (MEE) anti-reverse polarity additive and its preparation method. The additive comprises a self-supporting iridium-cobalt alloy catalyst prepared using a sodium borohydride reduction method. Introducing the anti-reverse polarity additive into the anode effectively improves the MEE's anti-reverse polarity performance and mitigates carbon corrosion of the anode catalyst layer and platinum particle agglomeration caused by reverse polarity. However, the additive has a particle size of up to 100 nm and a high loading in the anode catalyst layer. This consumes a large amount of iridium and significantly increases the thickness of the catalyst layer, leading to increased MEE mass transfer impedance at high current densities.

[0006] Chinese patent application CN111082078A discloses a method for preparing a high-performance, voltage-reversal-resistant membrane electrode assembly. The membrane electrode assembly includes a water electrolysis catalytic material, such as iridium or ruthenium, or an oxide, during the anode preparation process. The introduction of this catalytic material into the anode effectively mitigates the damage to the membrane electrode performance caused by gas depletion. However, the voltage-reversal-resistant membrane electrode described in this invention is obtained by adding a water electrolysis catalytic material to the anode. This catalytic material is difficult to disperse evenly during the preparation of the anode slurry, and the metal oxide has poor conductivity, which significantly reduces the effective utilization rate of metals such as iridium and ruthenium or metal oxides. This results in low voltage-reversal tolerance for the membrane electrode, leading to increased use of metals such as iridium and ruthenium and increased costs. Furthermore, directly adding metals or metal oxides to the catalyst layer can cause metal particles to agglomerate, resulting in reduced catalytic activity for water electrolysis.

[0007] Iridium is a precious metal element with extremely limited resources and is very expensive. In addition to being subject to resource limitations, the large-scale use of iridium in fuel cell membrane electrodes to achieve anti-reverse polarity will also greatly increase the cost of fuel cells, hindering the large-scale commercialization of fuel cells.

[0008] To address the problem of excessive iridium usage in current anti-reversal anode technology, we investigated using a small amount of iridium in the form of single atoms to surface-modify a commercial carbon-supported platinum catalyst and used this catalyst to create a reversal-resistant anode (RTA). We found that surface modification with a very small amount of highly dispersed iridium can effectively extend the electrode's reversal tolerance time. This invention not only solves the anti-reversal anode problem in fuel cells but also significantly reduces the amount of precious metal iridium used, which is of great significance for promoting the large-scale commercialization of fuel cells. Summary of the Invention

[0009] The anti-reverse polarity performance of the fuel cell membrane electrode is of great significance for ensuring the durability and stability of the fuel cell. The currently widely used anti-reverse polarity method is to add a carbon-supported platinum-based anti-reverse polarity catalyst containing metallic iridium to the catalyst layer. However, there is a common problem of large amounts of iridium metal used, which leads to increased costs of the fuel cell and general anti-reverse polarity effect. In order to significantly reduce the amount of precious metal iridium used, improve the anti-reverse polarity effect of metallic iridium, and reduce the cost of the fuel cell, the present invention proposes a method for preparing a carbon-supported platinum-based anti-reverse polarity catalyst using a small amount of highly dispersed iridium surface-modified carbon-supported platinum-based catalyst. The prepared catalyst has important advantages such as good anti-reverse polarity effect and low iridium usage. The use of the carbon-supported platinum-based anti-reverse polarity catalyst of the present invention can effectively reduce the cost of the fuel cell while ensuring the durability and stability of the fuel cell. At the same time, the present invention also solves the problems of particle agglomeration and poor conductivity of the anti-reverse polarity catalytic material directly added to the catalyst layer. The present invention solves an important problem facing the commercialization of fuel cells and is of great significance for promoting the large-scale commercialization of fuel cells.

[0010] The present invention aims to provide a method for preparing a fuel cell carbon-supported platinum-based anti-reverse polarity catalyst with a small amount of highly dispersed iridium surface modification. When the catalyst is applied to a membrane electrode, it can significantly improve the anti-reverse polarity performance of the fuel cell and reduce the amount of iridium used.

[0011] To achieve the above objectives, the technical solution provided by the present invention is:

[0012] A method for preparing a fuel cell carbon-supported platinum-based anti-reversal catalyst with a small amount of highly dispersed iridium surface modification is disclosed. The method utilizes an iridium complex organic solvent impregnation method to highly disperse iridium atoms on the surface of the carbon-supported platinum-based catalyst.

[0013] The preparation method comprises the following steps:

[0014] Step 1: Take a small amount of metallic iridium precursor, dissolve it, add a complexing agent, and stir evenly at room temperature to prepare an iridium complex solution;

[0015] Step 2: Weigh an appropriate amount of carbon-supported platinum-based catalyst, moisten it with a small amount of deionized water, add the solvent stirred in step 1, and sonicate for 30 minutes;

[0016] Step 3: Transfer the mixed solution in step 2 to a constant temperature water bath and evaporate the solvent;

[0017] Step 4: Transfer the catalyst after evaporating the solvent in step 3 to a quartz boat, place it in a tube furnace, and perform reduction heat treatment under a specific atmosphere to obtain a small amount of carbon-supported platinum-based catalyst modified with highly dispersed iridium surface.

[0018] Preferably, the content of highly dispersed iridium loaded on the surface of the catalyst for modification is 0.1%-5wt%.

[0019] Preferably, in step 1, the precursor comprises one or two of hydrated iridium trichloride, chloroiridic acid, ammonium hexachloroiridate, and potassium chloroiridate.

[0020] Preferably, in step 1, the complexing agent comprises one or two of citric acid, tartaric acid, salicylic acid, and EDTA, and the ratio of the complexing agent to iridium is 1:1-3:1 (molar ratio).

[0021] Preferably, in step 1, the solvent used for the iridium complex comprises pure water and a mixed solvent consisting of water, alcohol, or ketone; the alcohol used comprises one or more of methanol, ethanol, ethylene glycol, and isopropanol, and the volume ratio of water to alcohol is 1:1-1:5. All ketones include acetone, cyclohexanone, etc.;

[0022] Preferably, in step 2, the carbon-supported platinum-based catalyst includes a carbon-supported platinum catalyst and an alloy catalyst formed by carbon-supported Pt and Ru, Fe, Ni, Co, Au or Pd, and the platinum or platinum alloy content in the catalyst is 20%-60%.

[0023] Preferably, the temperature of the constant temperature water bath in step 3 is controlled at 50-80°C.

[0024] Preferably, the specific atmosphere described in step 4 includes one of a hydrogen atmosphere, a hydrogen-argon mixed gas atmosphere, a hydrogen-nitrogen mixed gas atmosphere, and an air atmosphere.

[0025] Preferably, the temperature of the reduction heat treatment in step 4 is 100-800° C., and the heat treatment time is 0.5-5 hours.

[0026] Preferably, the highly dispersed iridium comprises forms of single atom dispersion, atomic cluster dispersion and sub-nanometer dispersion.

[0027] The present invention provides a fuel cell carbon-supported platinum-based anti-reverse polarity catalyst with a small amount of highly dispersed iridium surface modification, wherein the content of the highly dispersed iridium loaded on the catalyst surface modification is 0.1-5wt%; the highly dispersed iridium includes forms of single-atom dispersion, atomic cluster dispersion and sub-nanometer dispersion.

[0028] In the present invention, a membrane electrode prepared by using a carbon-supported platinum-based catalyst with a small amount of highly dispersed iridium surface modified as cathode and anode catalyst in a fuel cell has excellent anti-reverse polarity performance.

[0029] The method for evaluating the anti-reverse polarity of the fuel cell catalyst prepared by the present invention is as follows: a small amount of highly dispersed iridium surface-modified platinum-carbon catalyst is used as the anode and cathode catalyst of the membrane electrode, an external circuit is used to apply a constant current of 0.2A / cm2 to the single cell, and the anti-reverse polarity characteristics of the catalyst are evaluated by testing the reverse polarity time of the membrane electrode and the changes in the performance of the single cell before and after the reverse polarity.

[0030] The present invention focuses on the structure of carbon-supported platinum-based anti-reverse polarity catalysts for fuel cells, and aims to use a small amount of highly dispersed iridium to surface modify the carbon-supported platinum-based catalysts. The use of a small amount of iridium effectively improves the anti-reverse polarity performance of the membrane electrode and greatly improves the utilization rate of iridium.

[0031] Compared with the prior art, the present invention has the advantages of:

[0032] 1. A very small amount of iridium is directly loaded on a commercial carbon-supported platinum-based catalyst. When preparing the electrode, there is no need to add a special iridium-based anti-reverse polarity catalyst separately, avoiding problems such as particle agglomeration and insufficient conductivity caused by direct addition.

[0033] 2. Iridium exists in a highly dispersed form on the commercial platinum-carbon catalyst, which greatly improves the utilization rate of iridium, can significantly reduce the amount of iridium used, and effectively reduces the anti-reverse polarity cost of the fuel cell.

[0034] 3. The organic solvent impregnation technology of iridium complex ensures the high dispersion of iridium on the surface of carbon-supported platinum-based catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of a carbon-supported platinum-based catalyst for a fuel cell modified with a small amount of highly dispersed iridium surface;

[0036] Figure 2 The X-ray diffraction patterns of the catalysts of Example 1, Example 2 and the comparative example are shown;

[0037] Figure 3 1 is a comparison chart of oxygen evolution (OER) activity of the catalysts of Example 1, Example 2 and the comparative example;

[0038] Figure 4 1 is a comparison chart of oxygen reduction (ORR) activity of the catalysts of Example 1, Example 2 and the comparative example;

[0039] Figure 5 1 is a comparison chart of the reverse polarity time of the catalysts of Example 1, Example 2 and the comparative example;

[0040] Figure 6This is a performance comparison chart of the membrane electrode prepared with the catalyst in Example 1 before and after reversal;

[0041] Figure 7 This is a performance comparison chart of the membrane electrode prepared with the catalyst in Example 2 before and after reversal;

[0042] Figure 8 This is a performance comparison chart of the membrane electrode prepared with the comparative example catalyst before and after polarity reversal;

[0043] Figure 9 This is a comparison diagram of the voltage decay of the membrane electrode prepared with the catalyst of Examples 1 and 2 and the comparative example before and after reversal at a current density of 0.8 A / cm2. DETAILED DESCRIPTION

[0044] Example 1

[0045] Preparation of carbon-supported platinum-based anti-reversal catalyst: Step 1: dissolve 2 mg of hydrated iridium trichloride (iridium content 54%) in 1 ml of a mixed solution of water and ethanol, with the volume ratio of water to alcohol being 1:5, add citric acid, with the molar ratio of citric acid to iridium being 2:1, and stir evenly at room temperature;

[0046] Step 2: Weigh 200 mg of JM9100 (60% Pt / C) catalyst, add a small amount of deionized water to moisten it, mix it with the solution obtained in step 1, and sonicate for 30 minutes;

[0047] Step 3: Transfer the mixture to a 50°C constant temperature water bath and evaporate the solvent;

[0048] Step 4: Transfer the catalyst obtained in step 3 to a quartz boat, place it in a tube furnace, and heat treat it in a hydrogen-argon mixed gas atmosphere at a heat treatment temperature of 300°C for 2 hours. After cooling to room temperature, a carbon-supported platinum-based catalyst with an iridium content of 0.54% (Pt / Ir mass ratio ≈110:1) is obtained.

[0049] The above catalyst was prepared into anode and cathode catalyst layers: 0.87 mg of catalyst was weighed, and an appropriate amount of 5% Nafion solution and isopropanol were prepared into catalyst slurry, wherein the anode catalyst loading was 0.1 mg / cm 2 (calculated as precious metals), the cathode catalyst loading is 0.2 mg / cm 2 (calculated as precious metals), the slurry was ultrasonically dispersed and evenly sprayed onto both sides of the Nafion211 membrane to prepare a membrane electrode.

[0050] The above membrane electrode was assembled into a fuel cell and the cell performance and anti-reverse polarity test were conducted. The cell performance test conditions were as follows: the anode fuel was hydrogen, the cathode oxidant was air, the cell temperature was 80°C, the relative humidity of the cathode and anode was 100%, and the anode and anode back pressure was 200kPa. The anti-reverse polarity test conditions were as follows: the cell temperature was 80°C, the relative humidity of the anode and anode was 100%, the anode and anode back pressure was 0, the anode inlet gas was high-purity hydrogen, the cathode was air, and an external constant current source was connected to ensure the current was 0.2A / cm 2 (The anode is connected to the positive electrode of the constant current source). After the membrane electrode voltage stabilizes, the high-purity hydrogen at the anode is switched to high-purity nitrogen. Other conditions remain unchanged. The cut-off voltage is set to -2V. When the cut-off voltage is reached, the simulation of reverse polarity stops and the reverse polarity time of the fuel cell is recorded.

[0051] Example 2

[0052] Preparation of a carbon-supported platinum-based anti-reversal catalyst: Step 1: Dissolve 0.74 mg of hydrated iridium trichloride in 1 ml of a mixed solution of water and methanol, with the volume ratio of water to methanol being 1:2, add salicylic acid, with the molar ratio of salicylic acid to iridium in the mixed solution being 3:1, and stir evenly at room temperature;

[0053] Step 2: Weigh 200 mg of JM9100 catalyst, moisten it with deionized water, mix it with the solution obtained in step 1, and sonicate for 30 minutes;

[0054] Step 3: Transfer the mixture to a constant temperature water bath at 80°C and evaporate the solvent;

[0055] Step 4: Transfer the catalyst obtained in step 3 to a quartz boat, place it in a tube furnace, and calcine it in an air atmosphere at a calcination temperature of 200°C for a heat treatment time of 2 hours. After cooling to room temperature, a carbon-supported platinum-based catalyst with an iridium content of 0.20% (Pt / Ir mass ratio ≈ 300:1) is obtained.

[0056] The method for preparing membrane electrode using the above catalyst and conducting fuel cell performance and anti-reverse polarity testing is the same as that in Example 1.

[0057] Comparative Example:

[0058] The same method was used as in Example 1, except that the catalysts used in the cathode and anode catalyst layers of the anti-reversal membrane electrode were both commercial JM9100 catalysts that had not been impregnated with an iridium complex.

[0059] Figure 1 This is a schematic diagram of the principle of a small amount of highly dispersed iridium surface-modified carbon-supported platinum-based anti-reversal catalyst prepared in the present invention.

[0060] Figure 22 are XRD patterns of the catalysts of Examples 1 and 2 and the comparative example. It can be seen that after being impregnated with the iridium complex organic solvent, only the particle size of the catalysts changed.

[0061] Figure 3 , Figure 4 These are the LSV test diagrams of the catalysts of Examples 1 and 2 and the comparative example. It can be seen that after the carbon-supported platinum-based catalyst is impregnated with the iridium complex organic solvent, the ORR activity and conductivity of the catalyst do not change significantly, and the OER activity is significantly enhanced.

[0062] Figure 5 The reverse polarity time curves of the catalysts of Examples 1, 2 and the comparative example were tested for anti-reverse polarity. It can be seen that after surface modification with a small amount of highly dispersed iridium, the anti-reverse polarity time of Examples 1 and 2 is 3.38 times and 2 times that of the comparative example, respectively.

[0063] Figure 6 、 Figure 7 and Figure 8 The fuel cell polarization curves of Examples 1, 2 and the comparative example before and after the polarity reversal are shown. Figure 9 The following graph compares the voltage decay of the aforementioned catalysts before and after reverse polarity testing. Before the reverse polarity test, the iridium is highly dispersed on the catalyst surface, maintaining the catalyst's activity and conductivity. After the reverse polarity test, at a current density of 800 mA / cm², the voltage decay of the comparative example is as high as 124 mV, while that of Examples 1 and 2 is only 40 mV and 45 mV, respectively.

[0064] Therefore, the carbon-supported platinum-based anti-reversal catalyst provided by the present invention can effectively improve the reversal tolerance of the fuel cell.

[0065] Example 3

[0066] Except for the following changes, the rest is the same as Example 1;

[0067] (1) The iridium precursor was changed to 0.4 mg potassium chloroiridate, the volume ratio of water to ethanol was changed to 1:4, the complexing agent was EDTA, and the molar ratio of the complexing agent to iridium was 1:1;

[0068] (2) Adjust the temperature of the constant temperature water bath to 70°C;

[0069] (3) Change the heat treatment temperature to 100°C and shorten the heat treatment time to 1h.

[0070] Consistent with Examples 1 and 2, the catalyst after impregnation treatment has significantly enhanced OER activity. It is used as the active component of the catalytic layer to prepare a membrane electrode with excellent anti-reverse polarity performance. Performance tests and anti-reverse polarity tests show that the reversal tolerance of the membrane electrode using the catalyst in the catalytic layer is significantly improved.

[0071] Example 4

[0072] Except for the following changes, the rest is the same as Example 1;

[0073] (1) The iridium precursor was changed to 11 mg of ammonium hexachloroiridate, the solvent was changed to a mixed solution of water and ethylene glycol with a volume ratio of 1:1, the complexing agent was tartaric acid, and the molar ratio of tartaric acid to iridium was 3:1;

[0074] (2) Changing the JM9100 catalyst to the JM3000 catalyst (20% Pt / C);

[0075] (3) During heat treatment, the heat treatment temperature was changed to 800°C and the heat treatment time was extended to 5h.

[0076] Consistent with Examples 1 and 2, the OER activity of the catalyst was significantly enhanced after impregnation treatment. Since sufficient iridium was highly dispersed on the catalyst surface, the membrane electrode with the catalyst as the active component had excellent anti-reverse polarity performance, and the water electrolysis time was greatly improved.

[0077] Example 5

[0078] Except for the following changes, the rest is the same as Example 1;

[0079] (1) The amount of iridium trichloride hydrate was changed to 5 mg, and the solvent was changed to a mixed solution of water and isopropanol with a volume ratio of 1:2;

[0080] (2) Changing the JM9100 catalyst to the JM4100 catalyst (40% Pt / C);

[0081] (3) During heat treatment, the hydrogen-argon atmosphere was changed to a hydrogen atmosphere, the heat treatment temperature was changed to 500°C, and the heat treatment time was extended to 2.5h.

[0082] Consistent with Examples 1 and 2, since iridium is highly dispersed on the catalyst surface, the catalyst has significantly enhanced OER activity. The membrane electrode prepared with the catalyst as the active component has excellent reversal tolerance, and the initial anti-reversal time is greatly improved.

[0083] Example 6

[0084] Except for the following changes, the rest is the same as Example 1;

[0085] (1) Replace the iridium complex with 3 mg of chloroiridic acid;

[0086] (2) Adjust the temperature of the constant temperature water bath to 60°C;

[0087] (3) During heat treatment, the hydrogen-argon atmosphere was changed to a hydrogen-nitrogen atmosphere, the heat treatment temperature was increased to 400°C, and the heat treatment temperature was extended to 3h.

[0088] Consistent with Examples 1 and 2, the catalyst after iridium complex impregnation heat treatment has almost unchanged ORR activity and significantly enhanced OER activity. Using it as the active component of the catalytic layer, the prepared membrane electrode has significantly enhanced reversal tolerance.

[0089] Example 7

[0090] Except for the following changes, the rest is the same as Example 1;

[0091] (1) Change the complexing agent to EDTA;

[0092] (2) The JM9100 catalyst was replaced with a PtAu / C catalyst with a platinum content of 40%;

[0093] (3) During heat treatment, the hydrogen atmosphere was changed to air atmosphere and the heat treatment time was shortened to 1.5h.

[0094] Consistent with Examples 1 and 2, after surface modification with a small amount of highly dispersed iridium, the membrane electrode prepared with the catalyst has excellent anti-reverse polarity performance, and the water electrolysis time of the fuel cell is effectively extended.

[0095] Example 8:

[0096] Except for the following changes, the others are the same as Example 1:

[0097] (1) The solvent was changed to a mixed solution of water and ethylene glycol with a volume ratio of 1:4, and the complexing agent was changed to salicylic acid;

[0098] (2) During heat treatment, the hydrogen-argon atmosphere was changed to hydrogen atmosphere, the heat treatment temperature was increased to 600°C, and the heat treatment time was shortened to 0.5h.

[0099] Consistent with Examples 1 and 2, since a small amount of iridium exists in a highly dispersed form on the surface of the catalyst, the membrane electrode prepared with the catalyst has significantly enhanced reversal resistance.

Claims

1. A method for preparing a small amount of highly dispersed iridium surface-modified platinum-based anti-reversal catalyst for fuel cells, characterized by: The platinum-based catalyst is impregnated with an iridium complex solution, and then heat-treated under a specific atmosphere to make the reduced iridium atoms highly dispersed on the surface of the carbon-supported platinum-based catalyst; The steps include: Step 1: dissolving an iridium precursor in a solvent, adding a complexing agent, and stirring uniformly at room temperature to obtain an iridium complex solution; Step 2: Weigh a platinum-based catalyst, wet it with deionized water, mix it with the solution obtained in step 1, and sonicate to obtain a mixture; Step 3: Transfer the mixture to a constant temperature water bath and evaporate the solvent; Step 4: Transfer the material after evaporating the solvent to a quartz boat, place it in a tube furnace, and perform reduction heat treatment under a specific atmosphere to obtain a platinum-based catalyst with a small amount of highly dispersed iridium modified on the surface; In step 1, the iridium precursor includes one or a mixture of more than one of hydrated iridium trichloride, chloroiridic acid, ammonium hexachloroiridate, and potassium chloroiridate; In step 2, the carbon-supported platinum-based catalyst includes a carbon-supported platinum catalyst and a carbon-supported platinum-based alloy catalyst, and the platinum or platinum-based alloy content in the catalyst is 20% to 60%; the alloy in the carbon-supported platinum-based alloy catalyst is an alloy formed by Pt and one or more of Ru, Fe, Ni, Co, Au or Pd; In step 4, the specific atmosphere includes one of a hydrogen atmosphere, a hydrogen-argon mixed gas atmosphere, a hydrogen-nitrogen mixed gas atmosphere, and an air atmosphere; The temperature of the heat treatment step is 100-800°C, and the heat treatment time is 0.5-5 hours; The content of highly dispersed iridium modified on the catalyst surface is 0.1-5 wt%; The highly dispersed iridium forms include: single atom dispersion, atomic cluster dispersion and sub-nanometer dispersion; In step 1, the complexing agent includes one or more of citric acid, tartaric acid, salicylic acid, and EDTA, and the molar ratio of the complexing agent to iridium is 1:1-3:1; In step 1, the solvent includes pure water and a mixture of pure water, alcohol, and ketone, wherein the alcohol includes one or more of methanol, ethanol, ethylene glycol, and isopropanol, and the volume ratio of water to alcohol is 1:1 to 1:5; the ketone includes one of acetone and cyclohexanone; In step 3, the temperature of the constant temperature water bath is controlled at 50-80°C.

2. The membrane electrode prepared by the preparation method of claim 1 and using a small amount of highly dispersed iridium surface-modified carbon-supported platinum-based catalyst as cathode and anode catalyst in a fuel cell has excellent anti-reverse polarity performance.

Images