Iridium oxide-based catalyst, its production method and application, and a catalyst-coated membrane, its production method and application

Abstract

Provided are an iridium-oxide-based catalyst and a preparation method therefor and the use thereof, and a membrane electrode and a preparation method therefor and the use thereof. The catalyst comprises an oxide of iridium, wherein the oxide of iridium comprises an oxide of iridium having vacancies, the vacancies comprising iridium vacancies or oxygen vacancies; and iridium oxide comprises metastable-phase iridium oxide. A hydrogen-oxygen flame method is used as the preparation method for the catalyst, and can respectively regulate and control vacancies and crystal phases. The catalyst has both high-activity defect vacancies and stable high-activity crystal phases, and has a low overpotential and a high oxygen evolution catalyzing activity when being applied to water electrolysis.

Description

Iridium oxide-based catalyst, preparation method and application thereof, membrane electrode, preparation method and application thereof

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on November 24, 2023, with application number 202311587661.4 and invention name “Iridium Oxide-Based Catalyst and Preparation Method and Application Thereof” and the Chinese patent application filed with the Patent Office of China on November 24, 2023, with application number 202311587657.8 and invention name “Membrane Electrode and Application Thereof”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of catalysts, and in particular to an iridium oxide-based catalyst, a preparation method and application thereof, and a membrane electrode, a preparation method and application thereof. Background Art

[0003] Proton exchange membrane (PEM) water electrolysis technology offers advantages such as high current density, high hydrogen purity, a wide load range, and flexible operation. It is an advanced hydrogen production technology that can adapt to the volatility of renewable energy generation and is currently in the initial commercialization stage. As the core of the PEM stack, the membrane electrode assembly (MEA) typically consists of a gas diffusion layer, a catalyst layer, and a proton exchange membrane. Because the anodic oxygen evolution reaction (OER) involves a complex four-electron transfer process and the electrocatalyst has a high overpotential, designing and developing anode catalysts that are both highly active and stable is a major challenge in this technology. Vacancy engineering is an effective method for modulating the electronic structure of electrocatalysts and the adsorption / desorption of reactants on their surfaces, and its important role in the electrocatalytic oxygen evolution reaction (OER) has been demonstrated. Recent studies have discovered that metastable iridium oxide materials possess unique crystal phases and surface structures, exhibiting superior electrocatalytic oxygen evolution performance compared to stable iridium oxide, and are considered to be highly promising PEM anode catalysts. Vacancy engineering of these unconventional iridium oxide-based catalysts is expected to yield even better iridium oxide catalysts. Existing technology can use microwave heat treatment to introduce iridium vacancies in 3R-IrO2 to form rapid proton transport channels, thereby significantly improving the acidic oxygen evolution activity and stability of 3R-IrO2. However, vacancy engineering of metastable iridium oxide through simple high-temperature heat treatment has the problem that the highly active metastable phase is easily transformed into a low-activity thermodynamically stable phase. Existing technology can also use a mechanical-thermal reactor to prepare 1T phase IrO2 under strong alkaline conditions. Compared with the thermally stable rutile phase IrO2, the 1T phase IrO2 shows significantly increased oxygen evolution activity and stability. However, the disadvantage of this technology is that although the crystallinity of the 1T phase IrO2 increases and the 2D morphology becomes more obvious with increasing reaction temperature, when the reaction temperature is increased to 900°C, the thermally stable rutile phase IrO2 appears, indicating that this method cannot achieve vacancy control while maintaining a highly active crystalline phase.

[0004] Therefore, it is necessary to provide an iridium oxide-based catalyst with adjustable vacancy and stable crystal phase, and a membrane electrode related thereto.

[0005] Summary of the Invention

[0006] In order to solve the above problems, the present invention aims to provide an iridium oxide-based catalyst and its preparation method and application. The iridium oxide-based catalyst contains both highly active defect vacancies and a stable, highly active crystal phase, and has high catalytic activity.

[0007] In order to achieve the above-mentioned object, the present invention provides an iridium oxide-based catalyst, which includes an iridium oxide, wherein the iridium oxide includes an iridium oxide with vacancies, and the type of the vacancies includes iridium vacancies or oxygen vacancies; the iridium oxide contains a metastable phase of iridium oxide.

[0008] According to a specific embodiment of the present invention, the crystal phase of the metastable iridium oxide may specifically include one or a combination of two or more of the following: 1T phase, 3R phase, and monoclinic phase.

[0009] According to a specific embodiment of the present invention, the catalyst may further comprise an oxide of a stable phase iridium, and the oxide of the stable phase iridium and the oxide of the metastable phase iridium may form an iridium oxide heterogeneous catalyst. In some specific embodiments, the crystalline phase of the oxide of the stable phase iridium comprises a rutile phase (R phase).

[0010] According to a specific embodiment of the present invention, the valence state of the iridium in the iridium oxide in the catalyst is mainly tetravalent. Further, the iridium oxide in the catalyst includes an iridium oxide with vacancies, or a combination of iridium oxides with and without vacancies.

[0011] According to a specific embodiment of the present invention, the chemical formula of the iridium oxide containing no vacancies in the catalyst is IrO2 (iridium dioxide).

[0012] According to a specific embodiment of the present invention, the vacancies of the iridium oxide in the above catalyst are adjustable, and the valence of iridium in the iridium oxide containing iridium vacancies is greater than tetravalent and less than pentavalent, and the chemical formula can be Ir 1-x O2 (0<x<0.2); the valence of iridium in the iridium oxide containing oxygen vacancies is less than tetravalent and greater than trivalent, and the chemical formula can be IrO 2-y (0<y<0.5). That is, the oxide of iridium having vacancies includes Ir 1-x O2 or IrO 2-y .

[0013] According to a specific embodiment of the present invention, contain vacancy in the described iridium oxide based catalyst, can reduce the resistance of catalyzer, improve the electrical conductivity of catalyzer.With respect to existing iridium oxide based catalyst, vacancy distribution is improved, vacancy concentration is improved in the iridium oxide based catalyst of the present invention, and macroscopically shows as the resistivity of catalyzer and has obvious changes with respect to the resistivity of conventional iridium oxide based catalyst.The resistivity of described iridium oxide based catalyst can be 0.13-10Ω·cm, specifically can be the specific values ​​such as 0.13Ω·cm, 0.14Ω·cm, 0.15Ω·cm, 0.16Ω·cm, 0.17Ω·cm, 0.18Ω·cm, 0.19Ω·cm, 0.20Ω·cm, 0.25Ω·cm, 0.3Ω·cm, 0.4Ω·cm, 0.5Ω·cm, 1Ω·cm, 5Ω·cm, 10Ω·cm and take any two in the above-mentioned specific values ​​as the scope of endpoints. In some specific embodiments, the resistivity of the iridium oxide-based catalyst may be 0.13-0.3 Ω·cm.

[0014] According to a specific embodiment of the present invention, when the catalyst contains both metastable iridium oxide and stable iridium oxide, the iridium oxide in each crystal phase (ie, metastable phase and stable phase) in the catalyst has the same type of defect vacancies.

[0015] The present invention also provides the use of the above-mentioned iridium oxide-based catalyst in the electrocatalytic oxygen evolution reaction, and the iridium oxide-based catalyst can be used as an oxygen evolution electrocatalyst. The iridium oxide-based catalyst provided by the present invention can make the catalyst have higher conductivity by introducing oxygen vacancies in the iridium oxide, thereby reducing the overpotential caused by electron mass transfer resistance during the electrolysis of water; by introducing iridium vacancies in the iridium oxide, the catalyst can have good proton conductivity, thereby reducing the overpotential caused by proton mass transfer resistance during the electrolysis of water. The intrinsic oxygen evolution activity of the iridium oxide in the above-mentioned catalyst provided by the present invention is improved, thereby reducing the overpotential caused by interface transfer resistance during the electrolysis of water.

[0016] According to a specific embodiment of the present invention, the iridium oxide-based catalyst may specifically include: an oxide of a metastable phase iridium with oxygen vacancies, or an oxide of a metastable phase iridium with iridium vacancies, or a combination of an oxide of a metastable phase iridium with oxygen vacancies and an oxide of a stable phase iridium with oxygen vacancies, or a combination of an oxide of a metastable phase iridium with iridium vacancies and an oxide of a stable phase iridium with iridium vacancies. Further, the iridium oxide-based catalyst may include: 1T phase Ir 1-x O2, 3R phase Ir 1-x O2, monoclinic Ir 1-x O2, 1T phase IrO 2-y , 3R phase IrO 2-y , monoclinic IrO 2-y, 1T phase Ir 1-x O2 and stable phase Ir 1-x Combination of O2, 3R phase Ir 1-x O2 and stable phase Ir 1-x Combination of O2, monoclinic Ir 1-x O2 and stable phase Ir 1-x O2 combination, 1T phase IrO 2-y and stable phase IrO 2-y Combination of 3R phase IrO 2-y and stable phase IrO 2-y Combination of monoclinic IrO 2-y and stable phase IrO 2-y One of the combinations.

[0017] The present invention also provides a method for preparing the iridium oxide-based catalyst, which comprises:

[0018] An iridium-containing precursor and a base are mixed in a solvent to form a slurry, the slurry is transferred to a substrate surface (by drip coating, doctor blade coating, screen printing, etc.), the substrate is placed in a hydrogen-oxygen flame and roasted, and the roasted product of the slurry is washed and dried to obtain the iridium oxide-based catalyst;

[0019] The hydrogen-oxygen flame is formed by the combustion of hydrogen and oxygen, and the flow ratio of the hydrogen and oxygen is (1-6):(6-1).

[0020] In the above preparation method, the iridium-containing precursor includes a metastable phase IrO2 (i.e., a metastable phase of iridium oxide without vacancies), and the crystalline phase of the metastable phase IrO2 includes one or a combination of two or more of the 1T phase, the 3R phase, and the monoclinic phase. According to a specific embodiment of the present invention, the crystalline phase of the metastable iridium oxide in the iridium oxide-based catalyst generally corresponds to the crystalline phase of the iridium-containing precursor. For example, when the iridium-containing precursor is in the 1T phase, the crystalline phase of the metastable iridium oxide in the iridium oxide-based catalyst is generally also in the 1T phase.

[0021] In the above preparation method, the base acts as a molten salt and a protective agent, which can prevent the metastable phase iridium oxide from agglomerating and preventing the metastable phase iridium oxide from being completely converted into the thermally stable phase iridium oxide. The base of the present invention refers to an aqueous solution that can directly ionize to generate OH - , or can promote the ionization of water to OH - The compound, the base includes one or a combination of two or more of KOH, NaOH, Ca(OH)2, Ba(OH)2, and NaHCO3.

[0022] In the above preparation method, the mass ratio of the iridium-containing precursor to the base is (1-100):(100-1). In some specific embodiments, the mass ratio of the iridium-containing precursor to the base can be specific values ​​such as 1:100, 1:1, 3:1, 100:1, and ranges with any two of the above specific values ​​as endpoints.

[0023] In some specific embodiments, the mass ratio of the iridium-containing precursor to the base can be controlled to be (1-30):(30-1).

[0024] According to a specific embodiment of the present invention, the solvent may include one or a combination of two or more of water, methanol, ethanol, and isopropanol.

[0025] According to a specific embodiment of the present invention, the slurry may be transferred to the substrate by a method including doctor blade coating, drop coating, screen printing, spray coating, etc. In some specific embodiments, the transfer method may be drop coating.

[0026] According to a specific embodiment of the present invention, the material of the substrate includes a high-temperature resistant oxide, such as quartz.

[0027] According to a specific embodiment of the present invention, the coverage of the iridium-containing precursor in the slurry on the substrate is less than or equal to 4g / cm 2 The coverage is the ratio of the mass of the iridium-containing precursor in the slurry to the area of ​​the substrate.

[0028] The present invention adopts the hydrogen-oxygen flame method to prepare the catalyst, and the characteristics of the redox atmosphere (gas atmosphere) adjustable and high heat conduction efficiency of the method can be utilized to realize the controllable vacancy regulation of the oxide of metastable phase iridium and the oxide of stable phase iridium. For example, by controlling the flow ratio of hydrogen and oxygen forming the hydrogen-oxygen flame, the degree of oxygen deficiency or oxygen enrichment of the environment in which the substrate is located during calcination can be controlled, thereby controlling the type of vacancy in the iridium oxide. According to a specific embodiment of the present invention, the flow ratio of hydrogen and oxygen is generally controlled to be (1-6): (6-1), and can specifically be 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 and other specific values ​​and a range with any two of the above specific values ​​as endpoints. In some specific embodiments, when the flow ratio of hydrogen and oxygen is less than or equal to 1:1, the catalyst generally has iridium vacancies; when the flow ratio of hydrogen and oxygen is greater than 1:1, for example, 3:1, the catalyst generally has oxygen vacancies. The flow ratio of hydrogen to oxygen can be further controlled to be (1-3):(3-1).

[0029] According to a specific embodiment of the present invention, the calcination temperature can be controlled to be 700-1500°C, that is, the substrate is placed in a hydrogen-oxygen flame and calcined in a temperature range of 700-1500°C. In some specific embodiments, the calcination temperature can be 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, and other specific values, as well as ranges with any two of the above specific values ​​as endpoints. In some specific embodiments, the calcination temperature can be 900-1300°C or 900-1100°C.

[0030] According to a specific embodiment of the present invention, the calcination time can be controlled to be 1s-100s, that is, the calcination time of the substrate in the oxyhydrogen flame is 1s-100s. For example, the calcination time can be 1s, 3s, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s and other specific values, as well as ranges with any two of the above specific values ​​as endpoints. In some specific embodiments, the calcination time can be 3s-90s.

[0031] According to a specific embodiment of the present invention, in the above preparation method, after the calcination is completed, the substrate is generally quickly removed from the flame and cooled to room temperature.

[0032] According to a specific embodiment of the present invention, the washing process includes: completely transferring the calcined product of the slurry (located on the surface of the substrate) into deionized water, and washing with water multiple times (centrifugation, filtration, etc.) until the pH of the supernatant is neutral.

[0033] According to a specific embodiment of the present invention, the drying method includes one or a combination of two or more of vacuum drying, heat drying, and freeze drying. In some specific embodiments, the drying method can be freeze drying.

[0034] The present invention provides a membrane electrode, which comprises a proton exchange membrane, and an anode catalyst layer and a cathode catalyst layer located on both sides of the proton exchange membrane. The raw material of the anode catalyst layer comprises the above-mentioned iridium oxide-based catalyst.

[0035] According to a specific embodiment of the present invention, the anode catalyst layer may be made of an anode catalyst slurry. The anode catalyst slurry may specifically include the iridium oxide-based catalyst, a binder, and a dispersant.

[0036] In the above-mentioned anode catalyst slurry, the mass ratio of the iridium oxide-based catalyst, the binder and the dispersant can be 0.2-6:1-20:220-600. Specifically, in parts by mass, the iridium oxide-based catalyst can be 0.2-6 parts, for example, 0.2 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts and other specific values, and ranges with any two of the above specific values ​​as endpoints; the binder can be 1-20 parts, for example, 1 part, 5 parts, 10 parts, 12.5 parts, 15 parts, 20 parts and other specific values, and ranges with any two of the above specific values ​​as endpoints; the dispersant can be 220 parts, 250 parts, 300 parts, 350 parts, 400 parts, 450 parts, 500 parts, 550 parts, 600 parts and other specific values, and ranges with any two of the above specific values ​​as endpoints. In some specific embodiments, the mass ratio of the iridium oxide-based catalyst, the binder, and the dispersant may be 0.2-6:12.5:220-600.

[0037] According to a specific embodiment of the present invention, the material of the cathode catalyst layer can be a commonly used cathode hydrogen evolution material, such as Pt / C.

[0038] According to a specific embodiment of the present invention, the binder may be a solution of an ionomeric proton conductor. The ionomeric proton conductor may include perfluorosulfonic acid resin, and the mass concentration of the ionomeric proton conductor solution is generally 5 wt%-20 wt%.

[0039] According to a specific embodiment of the present invention, the perfluorosulfonic acid resin may include one or a combination of two or more of DuPont Nafion resin, Solvay D79 series resin, Asahi Glass IC100 resin and Asahi Glass IC154 resin.

[0040] In some specific embodiments, the binder may include at least one of a Nafion resin solution with a mass concentration of 5wt%-20wt%, a Solvay D79 series resin solution with a mass concentration of 5wt%-20wt%, an Asahi Glass IC100 resin solution with a mass concentration of 5wt%-20wt%, and an Asahi Glass IC154 resin solution with a mass concentration of 5wt%-20wt%.

[0041] According to a specific embodiment of the present invention, the dispersant includes water and / or an alcoholic solvent. Specifically, the alcoholic solvent may include one or a combination of two or more of methanol, ethanol, and isopropanol. In some specific embodiments, the dispersant may be a mixture of water and an alcoholic solvent, such as a mixture of water and isopropanol.

[0042] According to a specific embodiment of the present invention, the anode catalyst layer slurry may include an iridium oxide-based catalyst, a binder (specifically, a solution of an ionomer proton conductor with a mass concentration of 5 wt% to 20 wt%), water, and isopropyl alcohol in a mass ratio of 0.2-6:1-20 (e.g., 12.5):200:20-400. For example, the anode catalyst layer slurry may include an iridium oxide-based catalyst, a Nafion resin solution with a mass concentration of 5 wt% to 20 wt% (hereinafter referred to as Nafion solution), water, and isopropyl alcohol in a mass ratio of 0.2-6:1-20 (e.g., 12.5):200:20-400.

[0043] In some specific embodiments, the anode catalyst layer slurry may include an iridium oxide-based catalyst, an ionomer proton conductor, water, and isopropyl alcohol in a mass ratio of 0.2-6:0.05-4:200:20-400.

[0044] According to a specific embodiment of the present invention, the membrane electrode provided by the present invention has good electrical conductivity and proton conductivity, which can reduce the overpotential caused by electron mass transfer resistance during water electrolysis. In some specific embodiments, the 2A / cm 2 The voltage can be controlled to be 1.8-2.15V, for example 1.9V-2.15V, and specifically can be 1.8V, 1.85V, 1.9V, 1.95V, 2.0V, 2.05V, 2.1V, 2.15V and other specific values, as well as a range with any two of the above specific values ​​as endpoints.

[0045] The present invention also provides a method for preparing the membrane electrode, which comprises:

[0046] The proton exchange membrane is placed on a substrate, and the anode catalyst slurry and the cathode catalyst slurry are respectively applied to the surfaces of the proton membrane on opposite sides, and dried to form an anode catalyst layer and a cathode catalyst layer on both sides of the proton exchange membrane, respectively, to obtain the membrane electrode. Furthermore, the above preparation method may specifically include:

[0047] The iridium oxide-based catalyst, binder and dispersant are mixed to form an anode catalyst layer slurry; a proton exchange membrane is placed on a substrate, and the anode catalyst layer slurry is covered on one side of the proton exchange membrane to form an anode catalyst layer; a cathode catalyst layer is formed on the other side of the proton exchange membrane (i.e., the opposite side of the anode catalyst layer) to obtain the membrane electrode.

[0048] According to a specific embodiment of the present invention, the mixing method of the iridium oxide-based catalyst, the binder and the dispersant may include ultrasonic treatment.

[0049] According to a specific embodiment of the present invention, the flatness of the anode catalyst layer can be controlled by controlling the temperature of the substrate, thereby improving the hydrogen evolution performance of the membrane electrode. The substrate temperature can be controlled to be between 60°C and 95°C, for example, specific values ​​such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and 95°C, as well as ranges with any two of the above specific values ​​as endpoints.

[0050] According to a specific embodiment of the present invention, the anode catalyst layer slurry may be coated on the proton exchange membrane in a manner including spraying, transfer printing, screen printing, coating, etc., or a combination of two or more thereof.

[0051] According to a specific embodiment of the present invention, when the coating method is spraying, the flow rate of the anode catalyst layer slurry can be controlled to be 0.2-20 mL / min during the spraying process. By controlling the flow rate of the anode slurry, the flatness of the anode catalyst layer can be improved in coordination with the temperature of the substrate. In some specific embodiments, the spraying method includes ultrasonic spraying.

[0052] The present invention also provides the use of the membrane electrode assembly in a proton exchange membrane water electrolysis process and / or a CO2 reduction process. The membrane electrode provided by the present invention, when used in a proton exchange membrane water electrolysis process, can effectively reduce the overpotential caused by electron mass transfer resistance and exhibit high hydrogen evolution activity.

[0053] The beneficial effects of the present invention include:

[0054] The iridium oxide-based catalyst provided by the present invention has a metastable crystalline phase, thus exhibiting high catalytic activity. Furthermore, the iridium oxide-based catalyst contains vacancies, the type and concentration of which are adjustable. This catalyst exhibits improved electrical and proton conductivity, and can reduce the overpotential caused by electron mass transfer resistance during water electrolysis.

[0055] 2. The preparation method of the iridium oxide-based catalyst provided by the present invention utilizes a hydrogen-oxygen flame preparation method with an adjustable redox atmosphere and high thermal conductivity. This method enables the regulation of vacancies and crystalline phases in the metastable and thermostable phases of iridium oxide, which facilitates the regulation of the adsorption and desorption energies of active species on the catalyst surface, thereby significantly improving the intrinsic oxygen evolution activity of iridium oxide. The membrane electrode containing the iridium oxide-based catalyst has high activity and stability, and significantly improves the water electrolysis performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG1 is an XRD diagram of the iridium oxide-based catalysts prepared in Example 1 and Comparative Example 1.

[0057] FIG2 is a XANES (X-ray Absorption Near Edge Spectroscopy) graph of the iridium oxide-based catalyst prepared in Example 1 and a 1T-IrO2 standard sample.

[0058] FIG3 shows the polarization curves of the iridium oxide-based catalyst of Example 1 and the 1T-IrO2 standard sample.

[0059] FIG4 shows the membrane electrode polarization curves of the iridium oxide-based catalyst of Example 1 and the 1T-IrO2 standard sample. DETAILED DESCRIPTION

[0060] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0061] In the following examples and comparative examples, the mass concentration of the Nafion solution used was 5%.

[0062] Example 1

[0063] This embodiment provides an iridium oxide-based catalyst, the preparation method of which includes:

[0064] Disperse 1g of 1T phase IrO2 and 9g of KOH in 10mL of ethanol at a mass ratio of 1:9 to prepare a slurry. Apply the slurry dropwise on a quartz plate so that the coverage of the 1T phase IrO2 on the quartz plate reaches 0.2g / cm 2 Ignite hydrogen and oxygen to form an oxyhydrogen flame with a flow ratio of 1:1. Place the quartz plate in the 900°C temperature zone of the oxyhydrogen flame and hold for 7 seconds for calcination. After calcination, quickly remove the quartz plate and cool it to room temperature. Ultrasound is used to completely transfer the powder on the quartz plate to deionized water, and the water is washed multiple times until the pH of the supernatant is neutral. Finally, the powder is freeze-dried to obtain an iridium oxide-based catalyst.

[0065] FIG1 is an XRD pattern of the catalyst prepared in this example. As can be seen from FIG1 , the catalyst prepared in this example is 1T pure phase iridium oxide, and there is no thermally stable rutile phase in the catalyst.

[0066] Figure 2 is the XANES graph of the catalyst prepared in this example. As can be seen from Figure 2, the iridium dioxide used as the raw material is in the 1T phase and does not contain vacancies. The iridium oxide in the catalyst prepared in this example is in the 1T phase, and the 1T phase iridium oxide in the catalyst contains iridium vacancies. Therefore, the catalyst prepared in this example is a 1T-Ir with iridium vacancies. 1-x O2.

[0067] Figure 3 is a polarization curve of the catalyst prepared in this example. As can be seen from Figure 3, the 10mA / cm 2 The overpotential is 194mV. By introducing iridium vacancies through hydrogen-oxygen flame treatment, the oxygen evolution performance of iridium oxide catalyst is significantly improved, 10mA / cm 2 The overpotential was reduced to 185 mV.

[0068] This embodiment also provides a membrane electrode, the preparation method of which includes:

[0069] Spray 2mg / cm on the surface of N117 proton exchange membrane 2 The 1T phase Ir prepared above 1-x O2 catalyst was used as the anode catalyst layer. The flow rate of the slurry was controlled at 0.2 mL / min during ultrasonic spraying. Then 0.5 mg / cm 2 40% Pt / C cathode catalyst is used as the cathode catalyst layer to make a membrane electrode.

[0070] Among them, 1T phase Ir 1-x The O2 catalyst is sprayed on the surface of the proton exchange membrane in the form of an anode catalyst layer slurry. The anode catalyst layer slurry can be obtained by the following process: taking 200 mL of water, and then adding isopropanol, Nafion solution, iridium oxide-based catalyst and isopropanol in a mass ratio of 200:10:2:20, and ultrasonically treating for 60 minutes to obtain the anode catalyst layer slurry.

[0071] Titanium felt was hot pressed onto the anode surface of the membrane electrode prepared above, and carbon felt was hot pressed onto the cathode surface of the membrane electrode prepared above, thereby preparing a membrane electrode assembly MEA. Steady-state polarization curve test was carried out at a temperature of 80°C, and the test results are shown in Figure 4. As shown in Figure 4, compared with the 1T phase IrO2 as a raw material without vacancies, the catalyst obtained by introducing iridium vacancies into iridium oxide in the present invention as the anode oxygen evolution layer of the membrane electrode is significantly improved, 2A / cm 2 The voltage drops to 1.91V.

[0072] Comparative Example 1

[0073] This comparative example provides an iridium oxide-based catalyst, the preparation method of which is similar to the preparation method of the iridium oxide-based catalyst in Example 1, except that: in this comparative example, the quartz plate covered with the slurry is placed in a muffle furnace at 900°C and held for 7 seconds before being taken out, and the atmosphere in the muffle furnace is air.

[0074] The catalyst of this comparative example was subjected to XRD and XPS testing. XRD results showed that the catalyst was rutile IrO2, indicating that the 1T phase IrO2 was completely converted to the thermally stable rutile phase IrO2 during the preparation process. XPS results showed that the rutile IrO2 in the catalyst of this comparative example contained no vacancies.

[0075] According to the method of Example 1, the iridium oxide-based catalyst of this comparative example is used to replace the iridium oxide-based catalyst of Example 1 to prepare a membrane electrode. The performance of the membrane electrode is tested according to the method of Figure 4. The 2A / cm 2 The voltage is 2.18V.

[0076] Example 2

[0077] This embodiment provides an iridium oxide-based catalyst, the preparation method of which includes:

[0078] Disperse 1g of 1T phase IrO2 and 9g of KOH in 10mL of ethanol at a mass ratio of 1:9 to prepare a slurry. Apply the slurry dropwise on a quartz plate so that the coverage of the 1T phase IrO2 on the quartz plate reaches 0.3g / cm 2 The hydrogen and oxygen flow rates were adjusted to a 3:1 ratio, and the two gases were ignited to form a 900°C flame. The quartz wafer was then placed in the 900°C zone of the flame and held for 7 seconds for calcination. After calcination, the wafer was quickly removed and cooled to room temperature. Ultrasound was used to completely transfer the powder from the wafer to deionized water, which was then washed multiple times until the pH of the supernatant was neutral. Finally, the powder was freeze-dried to obtain the iridium oxide-based catalyst.

[0079] The catalyst of this embodiment was subjected to XRD and XPS tests. The XRD results showed that the iridium oxide in the catalyst was a pure 1T phase, indicating that the 1T phase IrO2 was not transformed into the thermally stable rutile phase IrO2 during the preparation process. The XPS results showed that the iridium oxide in the catalyst of this embodiment contained oxygen vacancies. Therefore, the catalyst prepared in this embodiment was a 1T phase IrO 2-y catalyst.

[0080] This embodiment provides a membrane electrode, the preparation method of which includes:

[0081] Take 200 mL of water, then add isopropanol, Nafion solution, and iridium oxide-based catalyst in this embodiment in a mass ratio of 200:12.5:6:400, and ultrasonicate for 60 minutes to obtain an anode catalyst layer slurry.

[0082] The N117 proton exchange membrane was placed on a substrate at 95°C. The anode catalyst layer slurry was ultrasonically sprayed onto one side of the proton exchange membrane to form the anode catalyst layer. The flow rate of the slurry during the ultrasonic spraying process was controlled at 20 mL / min. The ratio of the mass of the iridium oxide-based catalyst to the area of ​​the anode catalyst layer on the proton exchange membrane was 2 mg / cm. 2 A 40% Pt / C cathode catalyst solution was sprayed on the other side of the proton exchange membrane to form a cathode catalyst layer. The ratio of the mass of the Pt / C catalyst to the area of ​​the cathode catalyst layer on the proton exchange membrane was 0.5 mg / cm 2 Thus, a membrane electrode is obtained.

[0083] The performance of the membrane electrode was tested according to the method in FIG4 , and the 2A / cm 2 The voltage is 2.13V.

[0084] Example 3

[0085] This embodiment provides an iridium oxide-based catalyst, the preparation method of which includes:

[0086] Disperse 1g of 1T phase IrO2 and 9g of KOH in 10mL of ethanol at a mass ratio of 1:9 to prepare a slurry. Apply the slurry dropwise on a quartz plate so that the coverage of the 1T phase IrO2 on the quartz plate reaches 0.2g / cm 2 The hydrogen and oxygen flow rates were adjusted to a 1:3 ratio, and the hydrogen and oxygen were ignited to form an oxyhydrogen flame. The quartz wafer was placed in the 1100°C temperature zone of the oxyhydrogen flame and held for 10 seconds for calcination. After calcination, the quartz wafer was quickly removed and cooled to room temperature. Ultrasound was used to completely transfer the powder on the quartz wafer into deionized water, and the solution was washed multiple times until the pH of the supernatant was neutral. Finally, the powder was freeze-dried to obtain the iridium oxide-based catalyst.

[0087] The catalyst of this example was subjected to XRD and XANES tests. The XRD and XANES results showed that the iridium oxide in the catalyst was in the 1T phase and the rutile phase, indicating that some 1T phase IrO2 was transformed into the thermally stable rutile phase IrO2 during the preparation process. In addition, the XANES results showed that the IrO2 in the catalyst of this example contained iridium vacancies. Therefore, the catalyst prepared in this example is 1T-Ir 1-x O2 / R-Ir 1-x O2 heterogeneous junction catalyst.

[0088] This embodiment also provides a membrane electrode, the preparation method of which includes:

[0089] Take 200 mL of water, then add ethanol, Nafion solution, and iridium oxide catalyst in this embodiment in a mass ratio of 200:2:0.2:20, and ultrasonicate for 60 minutes to obtain an anode catalyst layer slurry.

[0090] The N117 proton exchange membrane was placed on a substrate at 85°C. The anode catalyst layer slurry was ultrasonically sprayed onto one side of the proton exchange membrane. The flow rate of the slurry during the ultrasonic spraying process was controlled at 5 mL / min to form the anode catalyst layer. The ratio of the mass of the iridium oxide-based catalyst to the area of ​​the anode catalyst layer on the proton exchange membrane was 2 mg / cm 2 A 40% Pt / C cathode catalyst solution was sprayed on the other side of the proton exchange membrane to form a cathode catalyst layer. The ratio of the mass of the Pt / C catalyst to the area of ​​the cathode catalyst layer on the proton exchange membrane was 0.5 mg / cm 2 Thus, a membrane electrode is obtained.

[0091] The performance of the membrane electrode was tested according to the method in FIG4 , and the 2A / cm 2 The voltage is 1.93V.

[0092] Example 4

[0093] This embodiment provides an iridium oxide-based catalyst, the preparation method of which includes:

[0094] Disperse 1g of 1T phase IrO2 and 9g of KOH in 10mL of ethanol at a mass ratio of 1:9 to prepare a slurry. Apply the slurry dropwise on a quartz plate so that the coverage of the 1T phase IrO2 on the quartz plate reaches 0.2g / cm 2 The hydrogen and oxygen flow rates were adjusted to a 3:1 ratio, and the two gases were ignited to form a 1300°C flame. The quartz wafer was then placed in the 1300°C temperature zone of the flame and held for 10 seconds for calcination. After calcination, the wafer was quickly removed and cooled to room temperature. Ultrasonication was used to completely transfer the powder from the wafer to deionized water, followed by multiple washes until the pH of the supernatant was neutral. Finally, the powder was freeze-dried to obtain the iridium oxide-based catalyst.

[0095] The catalyst of this example was subjected to XRD and XPS tests. XRD results showed that the iridium oxide in the catalyst was 1T phase and rutile phase, indicating that some 1T phase IrO2 was converted into thermally stable rutile phase IrO2 during the preparation process. XPS results showed that the IrO2 in the catalyst of this example contained oxygen vacancies. Therefore, the catalyst prepared in this example is 1T-IrO 2-y / R-IrO 2-y Heterogeneous junction catalyst.

[0096] This embodiment also provides a membrane electrode, the preparation method of which includes:

[0097] Take 200 mL of water, then add methanol, Nafion solution, and iridium oxide catalyst in sequence according to the mass ratio of water, Nafion solution, iridium oxide catalyst of this embodiment and methanol of 200:12.5:4:20, and ultrasonicate for 60 minutes to obtain an anode catalyst layer slurry.

[0098] The N117 proton exchange membrane was placed on a substrate at 85°C. The anode catalyst layer slurry was ultrasonically sprayed onto one side of the proton exchange membrane. The flow rate of the slurry during the ultrasonic spraying process was controlled at 1 mL / min to form the anode catalyst layer. The ratio of the mass of the iridium oxide-based catalyst to the area of ​​the anode catalyst layer on the proton exchange membrane was 2 mg / cm 2 A 40% Pt / C cathode catalyst solution was sprayed on the other side of the proton exchange membrane to form a cathode catalyst layer. The ratio of the mass of the Pt / C catalyst to the area of ​​the cathode catalyst layer on the proton exchange membrane was 0.5 mg / cm 2 Thus, a membrane electrode is obtained.

[0099] The performance of the membrane electrode was tested according to the method in FIG4 , and the 2A / cm 2 The voltage is 1.88V.

[0100] Example 5

[0101] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 1, except that: in this embodiment, the raw material is monoclinic IrO2, and the flame roasting time is 3s.

[0102] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0103] Example 6

[0104] This embodiment provides an iridium oxide-based catalyst, and its preparation method includes the following steps: the flame roasting time in this embodiment is 90s, and the coverage of 1T phase IrO2 on the quartz plate reaches 0.3g / cm 2 .

[0105] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0106] Example 7

[0107] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 2, except that: in this embodiment, the flame roasting time is 3 seconds, and the mass ratio of the iridium-containing precursor to the base is 100:1.

[0108] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0109] Example 8

[0110] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 2, except that: the raw material in this embodiment is monoclinic IrO2, and the flame roasting time is 90s.

[0111] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0112] Example 9

[0113] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 3, except that: in this embodiment, the raw material is 3R-IrO2 and the flame roasting time is 3s.

[0114] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0115] Example 10

[0116] This embodiment provides an iridium oxide-based catalyst, and its preparation method includes the following steps: the flame roasting time in this embodiment is 90s, and the coverage of 1T phase IrO2 on the quartz plate reaches 0.3g / cm 2 .

[0117] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0118] Example 11

[0119] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 4, except that: in this embodiment, the raw material is 3R-IrO2 and the flame roasting time is 3s.

[0120] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0121] Example 12

[0122] This embodiment provides an iridium oxide-based catalyst, and its preparation method is similar to the preparation method of the iridium oxide-based catalyst in Example 4, except that: in this embodiment, the flame roasting time is 90s, and the mass ratio of the iridium-containing precursor to the base is 1:100.

[0123] This embodiment also provides a membrane electrode. The preparation method of the membrane electrode is as follows: according to the method of Example 1, the iridium oxide-based catalyst of this embodiment is used to replace the iridium oxide-based catalyst of Example 1 to prepare the membrane electrode.

[0124] The structural characterization and performance test results of the iridium oxide-based catalysts prepared in the above examples are summarized in Table 1.

[0125] Table 1

[0126] The iridium oxide-based catalyst products prepared in the above examples were subjected to XRD and XANES tests to determine the crystalline phase of each product; the iridium oxide-based catalysts were subjected to XANES and XPS tests to determine the vacancy type of each catalyst; the iridium oxide-based catalysts were subjected to resistivity and 10 mA / cm 2 The above results are shown in Table 1.

[0127] As can be seen from Table 1, the iridium oxide-based catalysts of each embodiment contain a metastable phase of iridium oxide. Comparing the above embodiments with Comparative Example 1, it can be seen that the present invention can obtain a metastable phase of iridium oxide with vacancies by adopting a hydrogen-oxygen flame calcination method.

[0128] By comparing the overpotential of Examples 1-2, 6-7 with the raw material 1T phase IrO2 used, it can be seen that, under the same crystal phase, by introducing oxygen vacancies and iridium vacancies into iridium oxide, the conductivity of the catalyst can be improved, the overpotential in the water electrolysis process can be reduced, the oxygen evolution activity of the catalyst can be increased, and the water electrolysis hydrogen production performance of the membrane electrode made of the catalyst can be improved.

Claims

1. A method for producing a catalyst based on iridium oxide, comprising: mixing an iridium-containing precursor and a base in a solvent to form a slurry; transferring the slurry to the surface of a substrate; placing the substrate in an oxygen-hydrogen flame for calcination; and washing and drying the calcination product of the slurry to form an iridium oxide-based catalyst, in this case, the oxygen-hydrogen flame is formed as a result of the combustion of hydrogen and oxygen, and the ratio of hydrogen to oxygen consumption is (1-6):(6-1); wherein said iridium oxide-based catalyst comprises iridium oxide, including iridium oxide with vacancies, wherein the types of vacancies include iridium vacancies or oxygen vacancies; and said iridium oxide comprises metastable phase iridium oxide.

2. The method according to paragraph 1, characterized in that the ratio of hydrogen consumption to oxygen is (1-3):(3-1).

3. The method according to claim 1, characterized in that said iridium-containing precursor contains a metastable phase of IrO2, and the crystalline phase of the metastable phase of IrO2 contains one or a combination of two or more of the 1T-phase, the 3R-phase, and the monoclinic phase.

4. The method according to claim 1, characterized in that the mass ratio of the iridium-containing precursor to the base is (1-100):(100-1).

5. The method according to paragraph 4, characterized in that the mass ratio of the iridium-containing precursor to the base is (1-30):(30-1).

6. The method according to paragraph 1, characterized in that the calcination temperature is 700-1500°C, and the calcination duration is 1 s-100 s.

7. The method according to claim 1, characterized in that the calcination temperature is 900-1300°C, and the calcination duration is 3 s-90 s.

8. A catalyst based on iridium oxide obtained by the method for producing a catalyst based on iridium oxide according to any one of claims 1-7.

9. The catalyst based on iridium oxide according to claim 8, characterized in that the crystalline phase of iridium oxide of the metastable phase contains one or a combination of two or more of the 1T phase, the 3R phase and the monoclinic phase.

10. A catalyst based on iridium oxide according to claim 8, characterized in that said catalyst additionally contains a stable phase of iridium oxide of a stable phase, and the crystalline phase of the stable phase of iridium oxide contains a rutile phase.

11. A catalyst based on iridium oxide according to claim 8, characterized in that the specific resistance of the catalyst based on iridium oxide is 0.13-10 Ohm cm.

12. A catalyst based on iridium oxide according to claim 8, characterized in that the specific resistance of the catalyst based on iridium oxide is 0.13-3 Ohm cm.

13. Use of an iridium oxide-based catalyst according to any one of claims 8-12 in an electrocatalytic oxygen evolution reaction.

14. A membrane with a catalyst coating, which comprises a proton exchange membrane, an anode catalytic layer and a cathode catalytic layer, respectively located on opposite sides of the proton exchange membrane, wherein the starting material of the anode catalytic layer comprises an iridium oxide-based catalyst according to any one of paragraphs 8-12.

15. A membrane with a catalyst coating according to claim 14, characterized in that said anode catalytic layer is obtained from an anode catalyst suspension containing a catalyst based on iridium oxide, a binder, and a dispersing agent.

16. A membrane with a catalyst coating according to claim 15, characterized in that the mass ratio of the catalyst based on iridium oxide, the binder and the dispersing agent is (0.2-6):(1-20):(220-600).

17. A membrane with a catalyst coating according to claim 14, characterized in that the voltage of the membrane with a catalyst coating at 2 A / cm² is 1.8-2.15 V.

18. A method for producing a membrane with a catalyst coating according to any one of paragraphs 14-17, comprising: placing a proton exchange membrane on a substrate; applying an anode catalyst suspension and a cathode catalyst suspension to opposite surfaces of the proton exchange membrane, respectively; and drying to obtain a catalyst-coated membrane.

19. The method according to claim 18, characterized in that the temperature of the substrate is 60°C-95°C.

20. The method according to claim 18, characterized in that the anode catalyst suspension is applied to the surface of the proton exchange membrane by spraying, and the flow rate of the anode catalyst suspension during spray coating is 0.2-20 ml / min.

21. Use of a membrane coated with a catalyst according to any one of paragraphs 14-17 in a method for electrolysis of water on a proton exchange membrane and / or in a method for reducing CO2.