An iridium catalyst and its preparation and use

Abstract

The present application relates to the technical field of catalyst, and particularly discloses an iridium catalyst and preparation and application thereof, the present application utilizes a small amount of oxalic acid to regulate and control the hydrolysis kinetics of iridium precursor, step-by-step accurately controls pH and temperature, in-situ precipitates and anchors hydrated iridium hydroxide precursor on the surface of the carrier, and ensures that the iridium species realizes uniform distribution in the subsequent precipitation process. By using the two-step heat treatment method of stabilization and ultralow-temperature reduction, sodium chloride crystals are induced to precipitate as a pore-forming agent, the active phase of elemental iridium is accurately controlled at 5-8 nm through the space confinement effect, the active point site agglomeration caused by high-temperature sintering is avoided, and the sodium chloride is removed through subsequent acid washing to construct a rich pore structure, the structure makes the catalyst have significant advantages in electrochemical impedance spectrum analysis, stability test electrochemistry and polarization performance test, and realizes high dispersion, high activity, high mass transfer efficiency and high stability.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and specifically discloses an iridium catalyst and its preparation and application. Background Technology

[0002] Proton exchange membrane electrolysis (PEMWE) has developed rapidly due to its fast response, high efficiency, and good hydrogen purity. A PEM electrolyzer mainly consists of bipolar plates, a gas diffusion layer, a proton exchange membrane, and an electrode catalyst layer. Among them, the oxygen evolution reaction (OER) at the anode is the rate-determining step, and the performance of the anode catalyst determines the hydrogen production efficiency, stability, and cost.

[0003] While iridium-based catalysts can maintain activity and stability under strong acids and high potentials, the scarcity and high cost of iridium resources have become a key bottleneck restricting the industrialization of PEMWE. Therefore, developing novel catalysts with low iridium loading, high activity, and durability has become a core research direction.

[0004] The key to improving iridium utilization lies in increasing the number of effective active sites. Preparing nano-iridium materials can significantly increase the specific surface area and the number of active sites; dispersing Ir on a support can further improve atom utilization. Therefore, synthesizing supported nano-iridium catalysts is an effective strategy to reduce Ir usage.

[0005] Liquid-phase polyol reduction and high-temperature gas-phase reduction methods are prone to particle growth and agglomeration, making it difficult to obtain highly dispersed and high-purity elemental iridium. Furthermore, additives often introduce complexity and instability. For example, in patent CN1874841A, a noble metal oxide catalyst for water electrolysis employs a deposition-precipitation method. The iridium precursor is precipitated in the presence of a high-specific-surface-area inorganic oxide support by adjusting the pH value, followed by high-temperature calcination in air. This method, using calcination at approximately 400°C, leads to severe particle sintering and growth, making precise control of the particle size at active sites impossible. The mass transfer structure of this catalyst relies solely on the passive stacking of the support particles. The accumulation of these particles is detrimental to mass transfer under high current. The precipitation process, which involves a one-step pH adjustment, is not conducive to achieving highly uniform dispersion and anchoring of active sites. Similarly, in patent CN119932605A, regarding supported noble metal-based catalysts, their preparation methods, and applications, the pH value of the support is adjusted for surface treatment, followed by the addition of an iridium precursor to ensure uniform adsorption on the surface. After drying, heat treatment is performed in a reducing atmosphere. This method uses high-temperature reduction of the precursor, which easily leads to migration and sintering of noble metal particles, making precise particle size control difficult. Furthermore, this process also fails to control the support structure, relying solely on the natural packing pores of the support particles.

[0006] Existing methods often rely on high-temperature treatment, strong reducing agents, or complex multi-step reactions, resulting in high energy consumption, difficulty in controlling particle size and distribution, and poor microscopic mass transfer behavior of the carrier. Therefore, there is an urgent need for a new method that is simple in process, mild in conditions, scalable, and can accurately generate highly active iridium species. Summary of the Invention

[0007] To address the problems existing in the prior art, the first aspect of this invention proposes a method for preparing an iridium catalyst, comprising the following steps:

[0008] Step 1: Mix sodium chloride aqueous solution, carrier, iridium precursor and oxalic acid to obtain the first mixture;

[0009] Step 2: Perform a first temperature control on the first mixture, add NaOH aqueous solution to adjust the pH of the first mixture, and perform a second temperature control on the first mixture to obtain a second mixture;

[0010] Step 3: Add NaOH solution to adjust the pH of the second mixture, precipitate to obtain the third mixture, control the temperature of the third mixture for the third time, remove the free liquid in the third mixture, and obtain the precipitate;

[0011] Step 4: After drying the precipitate in air, it is subjected to heat treatment to obtain the precursor;

[0012] Step 5: In the reducing atmosphere, the precursor is subjected to the fifth temperature control, and the precursor undergoes reduction;

[0013] Step 6: The reduced precursor is acid washed and dried to obtain the supported iridium metal catalyst.

[0014] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the aqueous solution of sodium chloride is a saturated aqueous solution of sodium chloride at 45~70°C.

[0015] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the mass of the support added to each 1L of sodium chloride aqueous solution is 20~40g.

[0016] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the support is selected from any one or a mixture of SnO2, Nb2O5, Ta2O2, and TiO2.

[0017] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the mass of the iridium precursor added to each 1L of sodium chloride aqueous solution is 40~80g.

[0018] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the mass of oxalic acid added to each 1L of sodium chloride aqueous solution is 1~5g.

[0019] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 1, the iridium precursor is selected from any one or a mixture of IrCl3 and (NH4)2IrCl6.

[0020] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 2, the temperature of the second mixture is controlled at 70~75℃.

[0021] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, the concentration of the NaOH aqueous solution is 5~40wt%.

[0022] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 2, an aqueous NaOH solution is added to adjust the pH of the first mixture to 9-10.

[0023] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 2, the temperature for second temperature control of the first mixture is 30~40℃.

[0024] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 3, NaOH solution is added to adjust the pH of the second mixture to 10-11.

[0025] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 3, after adjusting the pH of the second mixture, stirring was also performed.

[0026] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 3, the temperature for the third temperature control of the third mixture is 50~60℃.

[0027] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 3, after the third temperature control is performed on the third mixture, the third mixture is also aged.

[0028] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, the drying temperature in step 4 is 70°C to 80°C.

[0029] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, the heat treatment temperature in step 4 is 180~200℃.

[0030] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 5, the reducing atmosphere is a mixture of hydrogen and inert gas, preferably, the volume ratio of the hydrogen and inert gas mixture is 1:(2~5).

[0031] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, the inert gas is selected from any one or a mixture of nitrogen, argon, and helium.

[0032] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, in step 6, the acid used for acid washing is any one or a mixture of hydrochloric acid and nitric acid.

[0033] In some specific embodiments of the preparation method of the iridium catalyst described in the first aspect, the concentration of the acid used for acid washing is 10~30wt%.

[0034] A second aspect of the present invention provides an iridium catalyst obtained by any of the preparation methods described in the first aspect.

[0035] A third aspect of the present invention provides a membrane electrode comprising a cathode catalyst layer and an anode catalyst layer; wherein the cathode catalyst layer and the anode catalyst layer are respectively disposed on opposite sides of the proton exchange membrane, characterized in that the anode catalyst layer comprises the iridium catalyst described in the second aspect.

[0036] In some specific embodiments of the membrane electrode described in the third aspect, the iridium catalyst of the second aspect comprises: (a) a TiO2 support; (b) elemental iridium nanoparticles supported on the TiO2 support, the elemental iridium nanoparticles having a particle size range of 5 to 8 nm; and (c) a porous structure formed in the catalyst after the sacrificial template agent has been eluted.

[0037] A fourth aspect of this invention provides a method for fabricating the membrane electrode described in the third aspect, comprising the steps of:

[0038] S1: Mix the water / alcohol mixed solvent with the iridium catalyst and ionomer described in the second aspect, and grind to obtain a slurry;

[0039] S2: The slurry is coated onto the transfer film and dried to form a transfer film coated with an anode layer;

[0040] S3: The transfer film coated with Pt-based catalyst and the transfer film coated with anode layer are transferred to both sides of the proton exchange membrane to obtain the catalyst-coated film.

[0041] "Room temperature" refers to the indoor ambient temperature, which can be 12℃~37℃, 20℃~30℃, 25℃~30℃, or approximately 25℃.

[0042] The average particle size of the TiO2 used in this invention is approximately 100 nm;

[0043] The reagents used in this invention have not undergone further purification and are all purchased from the open and legal market, for example, from Shanghai Aladdin Biochemical Technology Co., Ltd., Xilong Scientific Co., Ltd., Sinopharm Chemical Reagent Co., Ltd., and Shanghai McLean Biochemical Technology Co., Ltd.

[0044] Advantages of this invention:

[0045] The first aspect of this invention utilizes a small amount of oxalic acid to regulate the hydrolysis kinetics of the iridium precursor (H2IrCl6), precisely controlling pH and temperature stepwise to precipitate and anchor the hydrated iridium hydroxide precursor in situ on the support surface, ensuring a highly uniform distribution of iridium species during subsequent precipitation. The second aspect employs a unique two-step heat treatment (stabilization at 180℃ and ultra-low temperature reduction at 80~120℃) to induce the precipitation of sodium chloride crystals as a pore-forming agent. This not only precisely controls the elemental iridium active phase to 5~8 nm through spatial confinement, effectively avoiding the aggregation of active sites caused by high-temperature sintering, but also constructs a rich pore structure after subsequent acid leaching to remove sodium chloride. This unique structure gives the catalyst significant advantages in electrochemical impedance spectroscopy (EIS) analysis, electrochemical stability testing, and polarization performance testing. The catalyst of this invention achieves a balance of high dispersion, high activity, high mass transfer efficiency, and high stability. Attached Figure Description

[0046] Figure 1 XRD pattern of the catalyst after low-temperature hydrogen reduction;

[0047] Figure 2 TEM image of the catalyst prepared in this invention;

[0048] Figure 3 PEM electrolysis performance curve of the membrane electrode of the catalyst prepared in this invention;

[0049] Figure 4 Stability test diagram of the membrane electrode of the catalyst prepared in this invention. Detailed Implementation

[0050] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0051] Example 1 Preparation of Anode Catalyst

[0052] Step 1: Under constant temperature of 60℃, 2.5g of TiO2 support, 6g of H2IrCl6 (1.0 eq.) and oxalic acid (0.05 eq.) are dispersed in 100ml of saturated sodium chloride aqueous solution. Stir continuously for 0.5~1 hour to form a uniform carrier-precursor mixed dispersion.

[0053] Step 2: Heat to 70-75℃, maintain in a water bath, and use a micro-injection pump to atomize and dropwise add 40wt% NaOH aqueous solution at a low rate to adjust the pH of the above mixture to 9-10. The dropping rate is 0.1mL / min, and the mixture is stirred at 800rpm. Then cool to 35℃ to introduce a high concentration of sodium ions to initiate the common ion effect and carry out a preliminary precipitation reaction for 2-3 hours.

[0054] Step 3: Maintain 35°C and continue to use a micro-injection pump to atomize and drop 40wt% NaOH aqueous solution at a low rate to adjust the pH of the system to 10-11. Continue stirring for 13-15 hours to complete the in-situ precipitation process of hydrated iridium hydroxide on the carrier surface. After the reaction is complete, cool down to 30°C and let stand for 12 hours to complete aging. Remove the upper free clear liquid and collect the precipitate.

[0055] Step 4: Under air atmosphere, the obtained precipitate is initially dried at 70℃~80℃, then transferred to an oven for the first heat treatment at 180~200℃, and dried overnight to stabilize the precursor structure and pre-form the sodium chloride crystals generated during the precipitation process in the catalyst matrix. The precursor is dehydrated and stabilized, and the sodium chloride crystals are completely crystallized and hardened to form a rigid salt template that coats the active components.

[0056] Step 5: After the first heat treatment, the powder is heated at 80~120℃ using a hydrogen / argon mixture (V... H2 :V Ar The 1:4 ratio was used for reduction treatment for 10-12 hours to efficiently convert the hydrated iridium hydroxide precursor into metallic iridium. At the same time, the stable sodium chloride pore-forming agent played a supporting, physical isolation and template role in this process, preventing the iridium nanoparticles from sintering and preventing the migration of iridium active sites during sintering.

[0057] Step 6: The reduced sample is acid-washed and purified using a 20wt% nitric acid aqueous solution. This process is repeated 2-3 times to remove free liquid. The sample is then vacuum-dried to obtain a highly dispersed, porous supported metallic iridium catalyst, namely the PEM water electrolysis anode catalyst, which is designated as Cat-1.

[0058] The catalyst in Example 1 utilizes a support with a well-structured pore structure constructed from sodium chloride. Highly dispersed elemental iridium is then achieved on this support, controlling the particle size of the iridium active nanoparticles to 5-8 nm. This balances the stability and efficiency of the catalyst at the PEM electrolyzer anode under harsh operating conditions. The pore structure of the support constructed with sodium chloride provides excellent transport pathways for reactants water and oxygen, as well as proton products. The advantages of the active site size and high dispersion ensure high atomic utilization of the precious metal iridium while maintaining structural stability under harsh electrolysis conditions. Overcoming the rapid dissolution and Austronesian ripening caused by the high surface energy of <3 nm ultrafine active site particles, the catalyst of this invention exhibits lower thermodynamic surface energy. Through synergistic control of pore structure and particle size / dispersion, the catalytic activity, high mass transfer efficiency, and long-term operational stability of the catalyst are balanced.

[0059] Comparative Example 1

[0060] The difference between Comparative Example 1 and Example 1 is that the support used in step 1 is different, while the other steps are the same. The resulting catalyst is denoted as Cat-2. In Comparative Example 1, an equal volume of Nb2O5 was used instead of TiO2 support.

[0061] Comparative Example 2

[0062] The difference between Comparative Example 2 and Example 1 is that oxalic acid was not added in step 1, while the other steps were the same, and the resulting catalyst was denoted as Cat-3.

[0063] Comparative Example 3

[0064] Compared to Example 1, Comparative Example 3 used an equal volume of deionized water instead of saturated sodium chloride solution, with the other steps being the same, and the resulting catalyst was designated Cat-4.

[0065] Comparative Example 4

[0066] Comparative Example 4, compared to Example 1, involves adjusting the pH to 10-11 in a single step, without pre-adjusting the pH to 9-10. The remaining steps are the same, specifically:

[0067] Step 1: Under constant temperature of 60℃, 2.5g of TiO2 support, 6g of H2IrCl6 (1.0 eq.) and oxalic acid (0.05 eq.) are dispersed in 100ml of saturated sodium chloride aqueous solution. Stir continuously for 0.5~1 hour to form a uniform carrier-precursor mixed dispersion.

[0068] Step 2: Maintain 35℃ and continue to use a micro-injection pump to atomize and drop 40wt% NaOH aqueous solution at a low rate to adjust the pH of the system to 10~11, and continue stirring for 13~15 hours to complete the in-situ precipitation process of hydrated iridium hydroxide on the carrier surface. After the reaction is completed, cool down to 30℃ and let stand for 12 hours to complete aging, remove the upper free clear liquid, and collect the precipitate.

[0069] The precipitate was then processed in the same manner as in Example 1, and the resulting catalyst was designated Cat-5.

[0070] Comparative Example 5

[0071] The difference between Comparative Example 5 and Example 1 is that the reduction temperature in step 5 is different. Step 5 is carried out at 350~450℃, while the other steps are the same. The resulting catalyst is denoted as Cat-6.

[0072] Example 2: Fabrication of membrane electrode:

[0073] Step S1, deionized water / alcohol mixture (V 水 :V 醇 PEM electrolysis anode catalyst (any of Cat-1 to Cat-6) and perfluorosulfonic acid solution (such as perfluorosulfonic acid Nafion™ D2021CS, the mass of perfluorosulfonic acid Nafion™ D2021CS is based on the mass of 20 wt% PEM electrolysis anode catalyst, purchased from Aladdin Company) are added sequentially to a mixture of 1 to 4:1 to obtain a slurry. The mass of PEM electrolysis anode catalyst accounts for 15 to 40 wt% of the total mass of the slurry. The glass bottle is placed on a magnetic stirrer and stirred to disperse the mixture. The solution is then transferred to a ball mill jar containing 2.0 to 4.5 mm ZrO2 grinding beads and ball milled at a constant temperature of 15 to 25°C at a speed of 300 to 1000 rpm for 2.0 to 12 hours.

[0074] Step S2: After ball milling and dispersion, the slurry is mixed and degassed using a degassing machine to obtain the anode catalyst layer slurry.

[0075] Step S3: Apply a slurry (loading 0.30 mg Ir / cm²) to the PTFE membrane using a slot coater. 2 After drying, XRF was used to detect whether the average iridium loading in the catalyst coating met the requirements.

[0076] Step S4: Subsequently, a coating with a loading of 0.3 mg Pt / cm² is applied to the PTFE membrane. 2 The cathode catalyst layer and the 115 proton exchange membrane were prepared into a catalyst-coated membrane (CCM) by hot pressing transfer. The membranes prepared by adding catalysts Cat-1 to Cat-6 were named CCM-1 to CCM-6, respectively.

[0077] Example 3: Multi-channel device performance testing:

[0078] The electrolytic cell was assembled in the following order: insulating end plate, cathode plate, 0.15 mm gasket, carbon paper, membrane electrode CCM-1 (prepared using the catalyst from Example 1), 2.05 mm gasket, titanium felt, titanium mesh, and anode plate. The electrolytic cell was then tightened diagonally with a torque wrench (3 N•m), and the electrode clamps were attached. Water was passed through the cell under test conditions of 80°C to perform polarization performance testing and obtain a 3 A / cm value. 2 The stability test results under current density are shown in Table 1:

[0079] Table 1

[0080]

[0081] The initial slot pressure is 3A / cm 2 Voltage tested under the specified conditions;

[0082] like Figure 4 Stability tests using a galvanostatic chronopotential method confirmed the superior performance of the Ir@TiO2 catalyst (Cat-1) at 3 A / cm². 2 The stringent industrial-grade current density and 0.3 mg / cm² 2 With a relatively low iridium loading, this catalyst not only exhibits high activity and low cell voltage at around 1.80V, but also demonstrates an extremely low voltage decay rate of 14.4μV / h during nearly 600 hours of continuous operation. The particle size optimization design of the catalyst's pore structure successfully endows the active sites with resistance to dissolution, agglomeration stability, and excellent mass transfer capabilities, achieving a balance between high efficiency and long lifespan.

[0083] Current-voltage polarization curves are shown below Figure 3 During the PEMWE operating condition test, the program was configured to sequentially record currents from a low current density of 0.025 A / cm². 2 Up to high current density 5 A / cm 2 The cell voltage of the electrolytic cell was plotted as a function of current density. The catalyst prepared in Example 1 (Ir@TiO2 curve) was at 3 A / cm. 2 At high current densities, the cell voltage is only around 1.80 V, and even at high current densities of up to 5 A / cm², the cell voltage remains relatively low. 2 It still operates efficiently under extreme conditions, and the IR-Free (dashed line) curve shows a relatively flat low slope, enabling it to operate efficiently under industrial-grade high current density.

[0084] Example 4 Electrochemical Impedance Spectroscopy (EIS) Analysis

[0085] Any of the CCM-1~6 prepared in Example 2 is stacked with porous titanium felt and carbon cloth to form a 5 cm 2 A single-cell MEA with high active area was operated at 80°C. Using an electrochemical workstation, measurements were taken at low operating conditions of 0.1 A / cm². 2 And 1.5 A / cm under high operating conditions 2 Nyquist spectra from 100 kHz to 0.1 Hz were acquired under DC bias. The spectra were fitted using a transmission line model to decouple the ion / mass transfer resistance (R_ion) and charge transfer resistance (R_ct) inside the electrode channels, as shown in Table 2.

[0086] Table 2

[0087]

[0088] The first R_ion represents 0.1 A / cm 2 Ohmic resistance measured at current density;

[0089] The second R_ion represents 1.5 A / cm 2 Ohmic resistance measured at current density.

[0090] The results showed that, compared with Cat2~6, the single-cell MEA constructed with PEM water electrolysis anode catalyst Cat-1 exhibited good mass transfer characteristics, with a mass transfer efficiency of 0.1 A / cm. 2 At that time, the first R_ion is 15 mΩ·cm 2 The low resistance value is achieved when the current density increases to 1.5 A / cm. 2 At that time, the second R_ion was only 22 mΩ·cm 2 Catalyst Cat-1 has a pore structure constructed using sodium chloride as a pore-forming agent, which provides an efficient transport path to reactant water and product oxygen and protons under high flux conditions, significantly suppressing concentration polarization and mass transfer bottlenecks. The catalyst of this invention can maintain a low overpotential under high current density.

[0091] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing an iridium catalyst, comprising the following steps: Step 1: Mix the aqueous solution of sodium chloride, the carrier, the iridium precursor, and oxalic acid to obtain the first mixture; The iridium precursor is H2IrCl6; the support is TiO2; Step 2: The first mixture is subjected to a first temperature control to 70~75℃, NaOH aqueous solution is added to adjust the pH of the first mixture to 9~10, and the first mixture is subjected to a second temperature control to 30~40℃ to obtain the second mixture; Step 3: Add NaOH solution to adjust the pH of the second mixture to 10-11, precipitate to obtain the third mixture, remove the free liquid in the third mixture to obtain the precipitate; Step 4: After drying the precipitate in air, heat-treat it at 180~200℃ to obtain the precursor; Step 5: In a reducing gas atmosphere, the precursor is subjected to a fifth temperature control to 80~120℃, and the precursor is reduced. Step 6: The reduced precursor is acid washed and dried to obtain the supported iridium metal catalyst.

2. The method for preparing the iridium catalyst according to claim 1, characterized in that, In step 1, the sodium chloride aqueous solution is a saturated sodium chloride aqueous solution at 45~70℃; and / or, in step 1, the mass of the carrier added to each 1L of sodium chloride aqueous solution is 20~40g; and / or, in step 1, the mass of the iridium precursor added to each 1L of sodium chloride aqueous solution is 40~80g; and / or, in step 1, the mass of oxalic acid added to each 1L of sodium chloride aqueous solution is 1~5g.

3. The method for preparing the iridium catalyst according to claim 1, characterized in that, The concentration of the NaOH aqueous solution is 5~40wt%.

4. The method for preparing the iridium catalyst according to claim 1, characterized in that, In step 3, after adjusting the pH of the second mixture, it is also stirred; and / or, in step 3, before removing the free liquid in the third mixture, the third mixture is also aged.

5. The method for preparing the iridium catalyst according to claim 1, characterized in that, In step 4, the precipitate is dried at a temperature of 70°C to 80°C; and / or, in step 5, the reducing gas atmosphere is a mixture of hydrogen and an inert gas, wherein the volume ratio of hydrogen to inert gas is 1:(2~5), and the inert gas is selected from any one or a mixture of nitrogen, argon, and helium.

6. The method for preparing the iridium catalyst according to claim 1, characterized in that, In step 6, the acid used for pickling is any one or a mixture of hydrochloric acid and nitric acid; and / or, in step 6, the concentration of the acid used for pickling is 10~30wt%.

7. An iridium catalyst, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. A membrane electrode, comprising a cathode catalyst layer and an anode catalyst layer; wherein, The cathode catalyst layer and the anode catalyst layer are respectively disposed on opposite sides of the proton exchange membrane, characterized in that the anode catalyst layer comprises the iridium catalyst of claim 7.

9. The membrane electrode according to claim 8, characterized in that, The iridium catalyst comprises, (a) a TiO2 support; (b) elemental iridium nanoparticles supported on the TiO2 support, the elemental iridium nanoparticles having a particle size range of 5-8 nm; and (c) a porous structure formed in the catalyst after the sacrificial template agent has been eluted.

10. A method for fabricating a membrane electrode, characterized in that, For fabricating a membrane electrode as described in any one of claims 8 or 9, the steps include: S1: Mix the water / alcohol mixed solvent, the ionomer and the iridium catalyst, and grind them to obtain a slurry; S2: The slurry is coated onto the transfer film and dried to form a transfer film coated with an anode layer; S3: The transfer membrane coated with Pt-based catalyst and the transfer membrane coated with anode layer are transferred to both sides of the proton exchange membrane to obtain the catalyst-coated membrane electrode.

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