Inorganic material, and preparation method therefor and use thereof

Abstract

Provided in the embodiments of the present application is an inorganic material. The inorganic material comprises an iridium oxide nanomaterial, the iridium oxide nanomaterial being of a hexagonal crystal phase structure. The inorganic material has a relatively high intrinsic catalytic activity, and when being used in the field of proton exchange membrane water electrolysis, the inorganic material has a more obvious catalytic effect and is beneficial for reducing catalyst costs. Further provided in the embodiments of the present application are a preparation method for and the related use of the inorganic material.

Description

Inorganic materials and their preparation methods and applications

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on August 31, 2023, with application number 202311127335.5 and application name “Inorganic materials, preparation methods and applications thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of electrocatalysis technology, and specifically to an inorganic material, a preparation method, and an application thereof. Background Art

[0003] Hydrogen production by water electrolysis is the main method for producing renewable hydrogen energy. Among them, proton exchange membrane (PEM) water electrolysis hydrogen production technology is considered to be a hydrogen production technology with higher practical value compared to alkaline water electrolysis hydrogen production technology because of its advantages such as high working current density, high energy conversion efficiency and high purity of hydrogen produced.

[0004] Because the oxygen evolution reaction on the anode side of water electrolysis is kinetically slower than the hydrogen evolution reaction on the cathode side, an anode catalyst is needed to reduce the overpotential of the oxygen evolution reaction. Furthermore, because the anode catalyst of the PEM electrolysis device is in an acidic environment with local proton exchange, the anode catalyst suitable for PEM water electrolysis technology should be able to be used stably in an acidic environment. Currently, the anode catalysts used in commercial PEM electrolysis devices are generally iridium and / or its oxides, which have good acid resistance. However, the catalytic activity of iridium-based catalysts for the oxygen evolution reaction still needs to be improved. The amount of iridium used on the anode side is large, and the amount of precious metal iridium used is also correspondingly large, which limits the large-scale application of PEM hydrogen production technology. Therefore, the development of iridium-based oxygen evolution catalysts with higher catalytic activity is crucial to improving the operating efficiency of PEM hydrogen production technology and reducing hydrogen production costs.

[0005] Summary of the Invention

[0006] In view of this, the embodiments of the present application provide an inorganic material, a preparation method and application thereof, to solve the problem of low catalytic activity of the existing anode catalyst for PEM water electrolysis.

[0007] In a first aspect, an embodiment of the present application provides an inorganic material, wherein the inorganic material includes an iridium oxide nanomaterial having a hexagonal crystal structure.

[0008] The inorganic material includes a hexagonal iridium oxide nanomaterial. Compared with the commercial IrO2 catalyst used for water electrolysis, the hexagonal crystal structure can make the intrinsic catalytic activity of the inorganic material higher, and its effect of reducing the overpotential of the oxygen evolution reaction is more obvious. Moreover, its loading can be reduced, which is conducive to reducing costs.

[0009] In the embodiment of the present application, the crystal structure of the iridium oxide nanomaterial includes iridium oxide octahedra, which are connected to form the hexagonal crystal structure through shared edges. In this case, the inorganic material containing the iridium oxide nanomaterial is more resistant to high current and has good stability when used as an anode catalyst for water electrolysis.

[0010] In the embodiment of the present application, the iridium oxide nanomaterial has two crystal planes with an angle of 59.5°-60.5°, which can reflect to some extent that the iridium oxide nanosheets of the present application have a hexagonal crystal structure.

[0011] In the embodiment of the present application, the XRD spectrum of the inorganic material has crystal plane diffraction peaks at 2θ of 32.9°-33.9° and 35.5°-36.5°. These crystal plane diffraction peaks are unique to the hexagonal iridium oxide nanomaterial of the embodiment of the present application.

[0012] In the embodiment of the present application, the inorganic material contains a single crystal iridium oxide nanomaterial in the hexagonal phase structure. The single crystal iridium oxide nanomaterial has good electronic properties, better catalytic performance, and better acid resistance and stability.

[0013] In an embodiment of the present application, the iridium oxide nanomaterial comprises iridium oxide nanosheets. The nanosheet-shaped iridium oxide material has a large specific surface area and active area, thereby enhancing the catalytic activity of the inorganic material. A single iridium oxide nanosheet is formed by stacking multiple atomically thin sheets.

[0014] In the embodiment of the present application, the thickness of the iridium oxide nanosheet is 0.2-50 nm, and the lateral size of the iridium oxide nanosheet is 0.01 μm-10 μm.

[0015] In the embodiment of the present application, at least a plurality of the iridium oxide nanomaterials are assembled into a three-dimensional cluster structure. The three-dimensional cluster structure generally has certain gaps, which can ensure that there is an open and large atomic surface between the iridium oxide nanomaterials, thereby increasing the specific surface area of ​​the inorganic material and improving the catalytic performance.

[0016] In an embodiment of the present application, the average particle size of the three-dimensional cluster structure is 0.03 μm-20 μm.

[0017] In the embodiment of the present application, the specific surface area of ​​the inorganic material is 50-100m 2The specific surface area of ​​the inorganic material containing iridium oxide nanosheets is much larger than that of commercial IrO2 catalysts, and its catalytic utilization rate is high, thereby improving the catalytic activity while reducing the cost of the catalyst.

[0018] In the embodiment of the present application, the loading of the inorganic material on the working electrode in the three-electrode electrolytic cell is 0.1-1 mg / cm 2 , current density is 10mA / cm 2 Under the conditions of , the overpotential of the inorganic material is below 240 mV. A lower overpotential reflects that the catalytic performance of the inorganic material is better.

[0019] A second aspect of the present invention provides a method for preparing an inorganic material, comprising the following steps:

[0020] placing a reaction raw material comprising a solid alkali metal hydroxide and a solid iridium salt in a microwave reaction apparatus for microwave reaction to obtain a reaction material; wherein the product of the power in watts and the reaction time in minutes in the microwave reaction is within a range of 3,000 to 30,000;

[0021] The obtained reaction materials are dispersed in water, and solids are obtained by solid-liquid separation. The obtained solidified material is an inorganic material; wherein the inorganic material includes iridium oxide nanomaterial, and the iridium oxide nanomaterial has a hexagonal crystal structure.

[0022] The above preparation method, through the solid-phase melting reaction of an alkali metal hydroxide and an iridium salt under the action of a specific microwave, can produce a hexagonal iridium oxide nanomaterial with high intrinsic catalytic activity. The preparation method is also simple to operate, short in time, and easily scalable.

[0023] In the embodiment of the present application, the microwave reaction power is 500-1000W, and the reaction time is 5-60min. Under the condition that the power and time product of the microwave reaction are satisfied, controlling the microwave reaction power and time within this range can better ensure the production of single-crystal nano-sheet iridium oxide material with higher catalytic activity.

[0024] In the embodiment of the present application, the molar ratio of the alkali metal hydroxide to the iridium element in the iridium salt is (100-5000): 1. This ensures good dispersion of the iridium salt in the molten potassium hydroxide, maintains a suitable reaction concentration for product formation, and ensures that the obtained iridium oxide is in the form of hexagonal nanosheets.

[0025] In the embodiment of the present application, the alkali metal hydroxide is potassium hydroxide. KOH has a strong ability to absorb microwave energy, which is very helpful in ensuring the dispersion of iridium salt in its molten state and the smooth crystallization synthesis of iridium oxide nanosheets.

[0026] The third aspect of the embodiments of the present application provides a catalyst, which includes the inorganic material described in the first aspect of the embodiments of the present application or the inorganic material prepared by the preparation method described in the second aspect of the embodiments of the present application, and the catalyst also includes a binder.

[0027] The fourth aspect of the embodiments of the present application provides the application of the inorganic material described in the first aspect of the embodiments of the present application and the catalyst described in the third aspect of the embodiments of the present application in fuel cells, water electrolysis, and other electrochemical technologies.

[0028] The inorganic material or catalyst can be used in the anode catalyst layer in the water electrolysis, or in the anode catalyst layer of the fuel cell.

[0029] A fifth aspect of the present invention provides a membrane electrode, comprising a proton exchange membrane, and an anode catalyst layer and a cathode catalyst layer disposed on opposite sides of the proton exchange membrane, wherein the anode catalyst layer comprises the inorganic material described in the first aspect of the present invention or the catalyst described in the third aspect of the present invention. The membrane electrode can be used in a fuel cell, a water electrolysis device, or other electrochemical device.

[0030] When the iridium element loading in the membrane electrode originating from the inorganic material is low, the inorganic material or catalyst provided in the embodiments of the present application can still exhibit excellent electrocatalytic activity and stability.

[0031] A sixth aspect of an embodiment of the present application provides a water electrolysis device, which includes the membrane electrode described in the fifth aspect of the present application, wherein a gas diffusion layer and a bipolar plate current collector are sequentially stacked on opposite sides of the membrane electrode.

[0032] By using the inorganic material provided in the embodiments of the present application as an anode catalyst for a water electrolysis device, when the inorganic material has a lower loading, the decomposition voltage of the water electrolysis device can be lower when electrolyzing water at the same temperature and current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic structural diagram of a PEM water electrolysis device provided in an embodiment of the present application.

[0034] FIG2 is a scanning electron microscope photograph of the inorganic material prepared in Example 1 of the present application.

[0035] FIG3 is a transmission electron microscope photograph of the inorganic material prepared in Example 1 of the present application.

[0036] Figure 4 is a high-angle annular dark field scanning transmission image of a single iridium oxide nanosheet in the inorganic material prepared in Example 1 of the present application and its selected area electron diffraction pattern (Figure a), a spherical aberration electron microscope image of a single iridium oxide nanosheet (Figure b), and a crystal structure model image of a single iridium oxide nanosheet (Figure c).

[0037] FIG5 is an X-ray diffraction spectrum of the inorganic material prepared in Example 1 of the present application.

[0038] FIG6 is a test graph of nitrogen adsorption specific surface area of ​​the inorganic material prepared in Example 1 of the present application.

[0039] FIG7 is a graph showing the polarization test results of the three-electrode oxygen evolution reaction of the inorganic material prepared in Example 1 of the present application.

[0040] FIG8 is a polarization test curve of the inorganic material prepared in Example 1 of the present application as the anode catalyst of the PEM water electrolysis device.

[0041] FIG9 is an electrochemical stability curve of the inorganic material prepared in Example 1 of the present application as an anode catalyst of a PEM water electrolysis device.

[0042] FIG10 is a scanning electron microscope photograph of the inorganic material prepared in Example 4 of the present application.

[0043] FIG11 is a scanning electron microscope photograph of the inorganic material prepared in Example 6 of the present application.

[0044] FIG12 is a scanning electron microscope photograph of the inorganic material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0045] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0046] The electrochemical reactions involved in PEM water electrolysis technology include the hydrogen evolution reaction (HER) on the cathode and the oxygen evolution reaction (OER) on the anode, as shown below: + +4e - =2H2(HER); 2H2O=O2+4H + +4e - The overall reaction is: 2H2O = O2 + 2H2. Of the two half-reactions, the OER is slow, and the anode is in an acidic environment. To improve the electrochemical efficiency of water electrolysis, finding anodic oxygen evolution catalysts with good acid resistance and high catalytic activity to reduce the overpotential of the anodic oxygen evolution reaction has become a major challenge for the industrial application of water electrolysis technology.

[0047] A schematic structural diagram of a water electrolysis device commonly used in PEM water electrolysis technology is shown in Figure 1. The water electrolysis device 100 includes a membrane electrode 10, which includes a proton exchange membrane 11, and an anode catalyst layer 12 and a cathode catalyst layer 13 located on opposite sides of the proton exchange membrane 11. The anode catalyst layer 12 and the cathode catalyst layer 13 of the membrane electrode 10 are also sequentially stacked with a gas diffusion layer and a bipolar plate current collector. Among them, the anode catalyst layer 12 contains an anode catalyst for reducing the overpotential of the anode oxygen evolution reaction, and the cathode catalyst layer 13 contains a cathode catalyst for reducing the overpotential of the cathode hydrogen evolution reaction. The embodiment of the present application provides an inorganic material with high catalytic activity that can be used in the anode catalyst layer 12.

[0048] Specifically, the inorganic material provided in the embodiments of the present application includes an iridium oxide nanomaterial having a hexagonal crystal structure. The "hexagonal crystal structure" may include a conventional hexagonal crystal structure or a distorted hexagonal crystal structure in which the crystal structure is distorted due to atomic stacking.

[0049] The inorganic material provided by the present application includes a hexagonal iridium oxide nanomaterial. Compared with the commercial IrO2 catalyst (tetragonal nanoparticles) used for water electrolysis, the intrinsic catalytic activity of the iridium oxide nanomaterial with a hexagonal structure is higher, so that the catalytic activity of the inorganic material is higher, and the overpotential of the oxygen evolution reaction of water electrolysis can be reduced to a lower level; because the catalytic activity of the inorganic material is higher, its loading in the membrane electrode can be lower, which is conducive to reducing costs. When the loading of the catalyst on the membrane electrode is the same and the current density of water electrolysis is the same, the inorganic material provided by the embodiment of the present application can reduce the overpotential of the oxygen evolution reaction to a lower level; when the electrolysis potential of the oxygen evolution reaction is reduced to the same potential, the amount of the inorganic material in the embodiment of the present application can be lower and the efficiency of reducing the overpotential is higher. In addition, iridium oxide has good corrosion resistance in an acidic environment and can stably exert catalytic performance in the oxygen evolution reaction of PEM water electrolysis. Therefore, the inorganic material has good durability and long service life.

[0050] Therefore, the above-mentioned inorganic materials provided in the embodiments of the present application can solve the problems of low catalytic activity and high amount of precious metal Ir used in existing PEM water electrolysis anode catalysts.

[0051] In the embodiment of the present application, in the iridium oxide nanomaterial, there are at least two crystal planes with an angle of 59.5°-60.5°. This can be known from the HAADF-STEM image of the iridium oxide nanomaterial. In the HAADF-STEM image of the iridium oxide nanomaterial, there are two crystal planes with an angle of 59.5°-60.5°, which can reflect to a certain extent that the iridium oxide nanomaterial of the present application is a hexagonal crystal phase structure. In some embodiments of the present application, in the iridium oxide nanomaterial, there are two crystal planes with an angle of 60°. In some embodiments, in the iridium oxide nanomaterial, the angle between adjacent crystal planes is 60°, for example The angle between any two is 60°. It should be noted that, due to the limitations of the detection instrument, the angle values ​​of the crystal planes in the embodiments of the present application may have detection errors allowed by the detection instruments or detection methods in the field. These detection errors should also be included in the scope of protection required by this application.

[0052] In the embodiment of the present application, lattice measurement and analytical calibration are performed on the diffraction bright spots around the transmission spot at the exact center of the selected area electron diffraction pattern of a single iridium oxide nanomaterial. It is found that the geometric shape of the basic unit expressing the symmetry of the diffraction pattern is a regular hexagon, and the crystal plane indices and crystal reciprocal lattice of the diffraction points constituting the regular hexagon conform to the hexagonal phase structure. The calibration result of the selected area electron diffraction pattern of the iridium oxide nanomaterial is consistent with the crystal plane indices of the hexagonal phase structure. This further proves that the iridium oxide nanomaterial of the present application has a hexagonal phase structure.

[0053] In the embodiment of the present application, the iridium oxide nano material comprises an iridium oxide octahedron in its crystalline structure, and the iridium oxide octahedron is connected with each other in a common edge, and is orderly expanded into the hexagonal crystalline phase structure. At this time, when the inorganic material containing the iridium oxide nano material is used as an anode catalyst for electrolysis of water, it can withstand a larger current and has better stability. Wherein, the above-mentioned crystal structure characteristics can be learned from the crystal structure simulation diagram of the iridium oxide nano material, and the iridium oxide nano material is a hexagonal Bragg unit cell. In addition, the theoretical interlayer spacing of the nano-sheet iridium oxide nano material learned based on the crystal structure simulation diagram is about 0.69nm, which is consistent with the experimental test results of follow-up XRD.

[0054] In the embodiment of the present application, in the XRD spectrum of the inorganic material, there are crystal plane diffraction peaks at 32.9°-33.9° and 35.5°-36.5° of 2θ. These crystal plane diffraction peaks are unique crystal plane diffraction peaks of the hexagonal phase of the iridium oxide nanomaterial in the embodiment of the present application, which are different from the iridium oxide material in the tetragonal phase. It should be noted that, limited by the detection method or detection instrument, the 2θ angle value of the diffraction peak in the embodiment of the present application may have the detection error allowed by the detection instrument or detection method in this field. These detection errors should also be included in the protection scope required by the present application. In some examples of the present application, in the XRD spectrum of the inorganic material, there are crystal plane diffraction peaks at 33.4° and 36° of 2θ.

[0055] In the present embodiment, the inorganic material contains a single crystal iridium oxide nanomaterial in a hexagonal phase. The iridium oxide nanomaterial with a single crystal structure has good electronic properties and better catalytic performance than polycrystalline materials due to its low grain boundary resistance, and its acid resistance and stability are better. Among them, the single crystal structure can be obtained by calibrating the selected area electron diffraction pattern of a single iridium oxide nanomaterial. The geometric feature of the selected area electron diffraction pattern of the iridium oxide nanomaterial with a single crystal structure is a speckled pattern. In some embodiments of the present application, the iridium oxide nanomaterials are all single crystal structures in a hexagonal phase.

[0056] In an embodiment of the present application, the iridium oxide nanomaterial comprises iridium oxide nanosheets. That is, the morphology of the iridium oxide nanomaterial comprises nanosheets. Nanosheet-shaped iridium oxide nanomaterials have a large specific surface area and active area, and their catalytic activity is high, thereby improving the catalytic activity of the above-mentioned inorganic material. In an embodiment of the present application, a single iridium oxide nanosheet can be formed by stacking multiple atomic layer-level sheets in sequence. The stacking direction of each sheet is parallel to the thickness direction of each sheet.

[0057] In the present application, the thickness of the iridium oxide nanosheet is less than the lateral dimension of the iridium oxide nanosheet. Here, "lateral dimension" refers to the dimension perpendicular to the thickness direction of the iridium oxide nanosheet. For example, for a nanosheet with a quadrilateral cross-section, the lateral dimension may include the length and width of the cross-section; for a nanosheet with a circular cross-section, the lateral dimension may refer to the diameter of the circle; when the cross-section is polygonal (such as a hexagon), the lateral dimension may refer to the diameter of the circumscribed circle of the polygon.

[0058] In embodiments of the present application, the iridium oxide nanosheets have a thickness of 0.2-50 nm, for example, 0.5 nm, 1 nm, 2 nm, 3 nm, 5 nm, 6 nm, 8 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, etc. In some embodiments, the iridium oxide nanosheets have a thickness of 0.2-10 nm. Thinner iridium oxide nanosheets ensure a higher total specific surface area of ​​the inorganic material on the membrane electrode, thereby improving catalytic activity.

[0059] In the embodiment of the present application, the lateral size of the iridium oxide nanosheets is 0.01 μm-10 μm, for example, specifically 0.02 μm, 0.03 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc. In some embodiments, the lateral size of the iridium oxide nanosheets is 0.5 μm-10 μm. The lateral size of the iridium oxide nanosheets is in the micron level, which can provide more active surface area, thereby improving its catalytic activity.

[0060] In the embodiment of the present application, the inorganic material includes a three-dimensional cluster structure, and the three-dimensional cluster structure is assembled by several iridium oxide nanomaterials. There are generally gaps in the three-dimensional cluster structure. The presence of the gap can further increase the specific surface area of ​​the inorganic material and improve its electrocatalytic performance. In some embodiments, the three-dimensional cluster structure is assembled by several iridium oxide nanosheets. This can effectively avoid the mutual stacking between the nanosheets, which is conducive to ensuring that there is an open and larger atomic surface between the nanosheets, and there are generally gaps in the three-dimensional cluster structure. The presence of the gaps and the multiple iridium oxide nanosheets constituting the three-dimensional cluster structure can further increase the specific surface area of ​​the inorganic material, and facilitate the entry of reactants (water to be electrolyzed), thereby improving its catalytic ability to reactants, and is conducive to the membrane electrode prepared by the inorganic material showing good electrocatalytic performance. In the present application, the inorganic material can be a three-dimensional cluster structure assembled by the iridium oxide nanosheets, or it can simultaneously contain iridium oxide nanosheets and the three-dimensional cluster structure. In some embodiments, the inorganic material is a three-dimensional cluster structure, which is assembled by several iridium oxide nanosheets.

[0061] In the embodiment of the present application, the average particle size of the three-dimensional cluster structure is 0.03 μm-20 μm. The particle size refers to the maximum cross-sectional width of the three-dimensional cluster structure, that is, the maximum lateral dimension (the distance between the two points with the largest dimensions on the cross section). For spherical or spherical cluster structures, the particle size refers to the diameter of their cross section; for polygonal cross sections, the particle size is the diameter of the circumscribed circle of the polygon.

[0062] In the embodiment of the present application, the specific surface area of ​​the inorganic material is 50-100m 2 / g. The specific surface area can be measured by nitrogen adsorption method (also known as "BET method"). Compared with the currently commercial IrO2 catalyst, the inorganic material containing iridium oxide nanomaterial provided in the embodiment of the present application has a larger specific surface area (the former is generally 10-20m 2 / g), which increases the active sites and can greatly improve the utilization rate of the catalyst, thereby improving the catalytic activity while reducing the cost of the catalyst. In some embodiments, the specific surface area of ​​the inorganic material is 75-100m 2 / g, for example, 78, 80, 82, 85, 88, 90, 95 or 98m 2 / g, etc.

[0063] In some embodiments of the present application, the mass percentage of iridium oxide in the inorganic material is 100%. That is, the inorganic material is composed only of iridium oxide nanosheets. In this case, the catalytic stability of the inorganic material is higher.

[0064] In another embodiment of the present application, the inorganic material further comprises one or more of platinum oxide and ruthenium oxide. The inorganic material may contain either a platinum oxide nanomaterial or a ruthenium oxide nanomaterial; or an iridium oxide nanomaterial (e.g., iridium oxide nanosheets) may contain either one or more of platinum oxide and ruthenium oxide. Furthermore, the iridium oxide content of the inorganic material is at least 50% by weight, for example, 50-95%.

[0065] The present invention also provides a method for preparing the above-mentioned inorganic material. Specifically, the preparation method comprises the following steps:

[0066] (1) subjecting a reaction material comprising a solid alkali metal hydroxide and a solid iridium salt to a microwave reaction in a microwave reaction apparatus to obtain a reaction material; wherein the product of the power in watts and the reaction time in minutes in the microwave reaction is within a range of 3000-30000;

[0067] (2) adding water to disperse the obtained reaction materials, and performing solid-liquid separation to obtain a solid, and the obtained solidified material is an inorganic material; wherein the inorganic material includes an iridium oxide nanomaterial, and the iridium oxide nanomaterial has a hexagonal crystal structure.

[0068] In the above preparation method, the reaction raw materials - alkali metal hydroxide and iridium salt - interact with microwaves, resulting in molecular polarization, orientation, friction, collision, etc., thereby absorbing microwave energy and generating a certain thermal effect. The specific product of the power and time of the above microwave reaction can ensure that the solid alkali metal hydroxide and solid iridium salt slowly melt and react, and finally crystallize to form an iridium oxide nanomaterial with a hexagonal phase, and its intrinsic catalytic activity is high, which can show excellent catalytic activity compared with commercial iridium oxide catalysts.

[0069] This preparation method utilizes a microwave-assisted, high-temperature solid-phase melting process, which is simple, easy to operate, and suitable for large-scale production. Compared to traditional hydrothermal methods, this method is time-efficient, energy-efficient, and produces high-yield, high-purity products.

[0070] In the embodiment of the present application, the product of the power and time of the microwave reaction is in the range of 3000-24000W·min, and can further be in the range of 5000-24000W·min, for example, specifically 5000, 6000, 8000, 10000, 12000, 15000, 18000, 20000 or 24000W·min, etc. Further, in the embodiment of the present application, in step (1), the power of the microwave reaction is 500-1000W, and the reaction time can be 5-60min. Wherein, the power of the microwave reaction is controlled to be below 1000W, which can ensure that the iridium salt melts slowly, and the iridium oxide material obtained by the reaction is in a flaky rather than granular state, and the catalytic activity is higher. Specifically, the power of the microwave reaction can be 600W, 650W, 700W, 750W, 800W, 850W, 9000W, 950W, 980W, etc. The reaction time of the microwave reaction can be 10 min, 20 min, 30 min, 40 min, 45 min, 50 min, etc. In some embodiments of the present application, the microwave reaction can be carried out under a constant microwave power, which can ensure a higher yield of the iridium oxide material.

[0071] In step (1), the above-mentioned reaction raw materials do not include a liquid solvent. The reaction raw materials containing solid alkali metal hydroxide and solid iridium salt can be first placed in a corrosion-resistant microwave reaction container (such as a silicon carbide crucible), and then placed in a microwave reaction device. Wherein, the iridium salt is a salt containing iridium element, including but not limited to iridium chloride (such as IrCl3·3H2O, IrCl4), iridium acetate, iridium nitrate, (hydrated) potassium chloroiridate, (hydrated) sodium chloroiridate, etc. One or more. The alkali metal hydroxide can include one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), rubidium hydroxide (RbOH), etc. In some embodiments of the present application, the alkali metal hydroxide is KOH. KOH has a strong absorption capacity for microwave energy, which facilitates its own absorption of microwave energy and melting. It can also act as a certain "solvent" to help the iridium salt continue to melt slowly, thereby ensuring the smooth crystallization synthesis of hexagonal iridium oxide nanomaterials.

[0072] In step (1), the molar ratio of the alkali metal hydroxide to the iridium element in the iridium salt is (100-5000):1. When the relationship between the power and time of the microwave reaction meets the above conditions, controlling the molar ratio of the two reaction raw materials within this range can further ensure the good dispersibility of the iridium salt in the molten potassium hydroxide, maintain a suitable product generation reaction concentration, and control the orientation and speed of the iridium oxide crystal growth, ensuring that the obtained iridium oxide is in the form of hexagonal nanosheets rather than granules. In some embodiments, the molar ratio of the alkali metal hydroxide to the iridium element in the iridium salt is (400-1500):1.

[0073] In some embodiments of the present application, the reaction raw materials in step (1) may further include one or more of a platinum source and a ruthenium source. The platinum source and the ruthenium source may be chlorides, chlorates, nitrates, etc. of platinum or ruthenium. Accordingly, the prepared inorganic material may contain platinum oxide and / or ruthenium oxide.

[0074] After the microwave reaction is completed, the microwave reaction equipment is cooled naturally to room temperature, more precisely, the microwave reaction vessel containing the reaction material is cooled naturally to room temperature, and then the reaction material is post-treated. In step (2), the obtained reaction material is dispersed with water to dissolve the unreacted reaction raw materials (especially excess alkali metal hydroxide), and then solid-liquid separation is performed to obtain a solid, which includes the desired inorganic material.

[0075] In addition, the solid can also be subjected to the following purification treatment: the solidified material is washed and solid-liquid separated multiple times to obtain a purified solid. Finally, the solid can be dried and stored for later use. Among them, solid-liquid separation can specifically be centrifugation, filtration, etc. The washing in the purification treatment can be all deionized water washing, or multiple deionized water washings can be performed first, and then multiple anhydrous ethanol washings. In addition, after the purification treatment, the purified solid can also be dried. Among them, the specific treatment method of the drying treatment is not limited, for example, it can be a vacuum drying treatment, or a room temperature drying treatment, or a combination of the two. In some embodiments, the drying treatment is specifically a constant temperature vacuum drying treatment at 30-60°C in a vacuum heating oven, and the treated product is dried and stored at room temperature for later use.

[0076] The above-mentioned preparation method provided in the present application uses a microwave-assisted high-temperature solid-phase melting reaction to prepare inorganic materials. It is simple to operate, short in time, easy to scale up and prepare in large quantities, and the yield of the prepared inorganic materials is high and the catalytic activity is high.

[0077] In the embodiment of the present application, the loading of the inorganic material on the working electrode in the three-electrode electrolytic cell is 0.1-1 mg / cm 2 , current density is 10mA / cm 2 Under the conditions of , the overpotential of the inorganic material is below 240 mV, for example, 220-240 mV. This overpotential is lower than the overpotential of commercial iridium oxide materials (about 270 mV). The lower overpotential reflects that the inorganic materials provided by the embodiments of the present application have greater advantages in catalysis.

[0078] The present embodiment further provides a catalyst comprising the aforementioned inorganic material of the present embodiment and a binder, wherein the catalyst may be a composite material comprising the inorganic material and the binder.

[0079] The embodiments of the present application also provide applications of the above-mentioned inorganic materials and catalysts in fuel cells, water electrolysis, and other electrochemical technologies.

[0080] When the inorganic material or catalyst is used in the field of water electrolysis, it can be specifically used as an anode catalyst layer in the electrolyzed water, that is, an anode catalyst for the oxygen evolution reaction in water electrolysis. Wherein, the electrolyzed water can be proton exchange membrane (PEM) electrolyzed water. The inorganic material or catalyst can be specifically used in a PEM water electrolysis method or a PEM water electrolysis device. The inorganic material is specifically used as an anode catalyst for a PEM membrane electrode, which can exhibit excellent electrocatalytic activity and stability at a low loading of the precious metal iridium element, thereby helping to improve the operating efficiency of the PEM membrane electrode device and reduce costs.

[0081] When the inorganic material or catalyst is used in a fuel cell, it can be used in the anode catalyst layer of the fuel cell, mainly for solving the reverse polarity phenomenon that occurs when the anode hydrogen supply in the fuel cell is insufficient, and plays an anti-reverse polarity role. The reverse polarity phenomenon can cause serious corrosion of the anode catalyst in the membrane electrode of the fuel cell, thereby causing the attenuation of the fuel cell output performance. In actual commercial applications, in order to prevent the anode catalyst (Pt material loaded on carbon) of the fuel cell from undergoing carbon corrosion reaction during the reverse polarity phenomenon, a water electrolysis catalyst (such as the above-mentioned inorganic material or a catalyst containing the inorganic material in the embodiment of the present application) can be added to the anode catalyst of the membrane electrode of the fuel cell. The inorganic material can increase the generation rate of protons and electrons by promoting the oxygen evolution reaction on the anode catalyst layer rather than the carbon oxidation reaction of the platinum carbon catalyst, thereby protecting the anode catalyst layer of the fuel cell, thereby effectively extending the reverse polarity time and improving the service life of the fuel cell. Among them, the fuel cell can specifically be a proton exchange membrane (PEM) fuel cell.

[0082] The present invention also provides a membrane electrode, comprising a proton exchange membrane, wherein a catalyst layer on one side of the proton exchange membrane comprises the inorganic material or catalyst described in the embodiments of the present invention. The membrane electrode can be used in a fuel cell, a water electrolysis device, or other electrochemical device.

[0083] The water electrolysis device in FIG1 shows an exemplary structure of a membrane electrode 10. The membrane electrode 10 includes a proton exchange membrane 11, and an anode catalyst layer 12 and a cathode catalyst layer 13 located on opposite sides of the proton exchange membrane 11. The anode catalyst layer 12 includes the inorganic material or catalyst described in the embodiments of the present application. Generally, the anode catalyst layer 12 includes the inorganic material described in the embodiments of the present application and a binder.

[0084] In the embodiment of the present application, the loading amount of iridium element in the inorganic material in the membrane electrode 10 is 0.1-1 mg / cm 2 . When the iridium loading is low, the inorganic material can still exhibit excellent electrocatalytic activity and stability, which helps to improve the operating efficiency of the PEM membrane electrode device and reduce costs. In addition, a lower iridium loading can reduce the use of precious metal iridium in the membrane electrode 10, which is beneficial to reduce the cost of the catalyst. Specifically, the loading of iridium in the inorganic material in the membrane electrode 10 can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.32, 0.35, 0.38 or 0.4 mg / cm 2 .

[0085] In some embodiments of the present application, as shown in FIG1 , a PEM water electrolysis device is provided. The water electrolysis device 100 includes the aforementioned membrane electrode 10. A gas diffusion layer and a bipolar plate current collector are stacked sequentially on the anode catalyst layer 12 and the cathode catalyst layer 13 of the membrane electrode 10. For details regarding the membrane electrode 10, please refer to the description of FIG1 above in this application.

[0086] Continuing with Figure 1 , the anode side of the membrane electrode 10 includes, from the inside out, an anode gas diffusion layer 21 and an anode bipolar plate 22. The cathode side of the membrane electrode 10 includes, from the inside out, a cathode gas diffusion layer 31 and a cathode bipolar plate 32. The positive electrode of an external power source is connected to the anode bipolar plate 22, and the negative electrode of the external power source is connected to the cathode bipolar plate 32.

[0087] Each gas diffusion layer is located between the flow field and catalyst layer on the bipolar plate. Its function is to support the catalyst layer, stabilize the structure of the membrane electrode, and provide proton / heat / electricity transfer. It also provides multiple reaction channels for gases, protons, electrons, and water for the membrane electrode reaction. The anode gas diffusion layer 21 and the cathode gas diffusion layer 31 can be formed from conductive porous materials. For example, the anode gas diffusion layer 21 can be made of titanium felt or titanium mesh, while the cathode gas diffusion layer 31 can be made of carbon paper or carbon fiber fabric. The anode bipolar plate 22 and the cathode bipolar plate 32 are each equipped with several flow fields for water and gas transport. Furthermore, the anode bipolar plate 22 may be equipped with an inlet port 221 for fluid inflow and a first outlet port 222 for fluid outflow. The cathode bipolar plate 32 may be equipped with a first outlet port 321 for fluid outflow or gas discharge.

[0088] The working principle of the water electrolysis device 100 is as follows: the reactant (i.e., water) flows into the anode bipolar plate 22 from the inlet port 221, diffuses through the flow channel thereon to the anode gas diffusion layer 21, and penetrates and migrates to the surface of the anode catalyst layer 12. Under the electrocatalytic action of the anode catalyst, the water molecules are decomposed into hydrogen ions (H + , that is, protons), oxygen (O2) and electrons (e - ), where H + The electrons pass through the proton exchange membrane 11 and reach the surface of the cathode catalyst layer 13. The electrons are then conducted to the cathode catalyst layer 13 through the external circuit. Under the action of the cathode catalyst, H + Combined with electrons, hydrogen (H2) is generated. O2 generated on the anode side flows through the anode gas diffusion layer 21 and the flow channels on the anode bipolar plate 22, and is discharged to the oxygen storage tank via the first outlet port 222. H2 generated on the cathode side flows through the cathode gas diffusion layer 31 and the flow channels on the cathode bipolar plate 32, and is discharged to the hydrogen storage tank via the first outlet port 321.

[0089] In the embodiment of the present application, the loading amount of iridium element in the inorganic material in the membrane electrode is 0.1-1 mg / cm 2 The temperature of electrolyzed water is 80℃ and the current density is 2A / cm 2 Under the conditions of , the electrolysis voltage of the water electrolysis device can be below 1.85V, for example, in the range of 1.7-1.85V.

[0090] The embodiments of the present application are further described below with reference to a number of embodiments.

[0091] Example 1

[0092] A method for preparing an inorganic material, comprising:

[0093] Weigh 10 g of KOH and 100 mg of IrCl3·3H2O (the molar ratio of KOH to Ir element in iridium salt is 629.6:1) and place them in a corrosion-resistant silicon carbide crucible in sequence. After uniform stirring, place the crucible in a microwave reactor. Set the power of the microwave reactor to 800 W, the reaction time to 30 min, and start the reactor to start the reaction.

[0094] After the reaction is completed, the crucible container containing the reaction material is naturally cooled to room temperature, the crucible is taken out, and a large amount of deionized ultrapure water is added thereto to dissolve and wash away the unreacted raw materials, and the solid is obtained by centrifugation or filtration. The solid includes an inorganic material; the solid is washed with water multiple times - centrifuged or filtered, and the pH of the washing liquid is neutral; then it is rinsed and purified with anhydrous ethanol 3 times, and finally separated by centrifugation or filtration to obtain the purified inorganic material, and placed in a constant temperature vacuum drying oven at 60°C for drying, and then dried and stored at room temperature of 25°C for use.

[0095] The inorganic material product obtained in Example 1 was characterized by scanning electron microscopy (SEM), and the results are shown in Figure 2. As can be seen from Figure 2, the product has a three-dimensional cluster morphology, with each three-dimensional cluster being assembled from a number of iridium oxide nanosheets, forming a three-dimensional self-supporting structure. The iridium oxide nanosheets have a lateral dimension of approximately 0.5-1.2 μm and a thickness of approximately 2-10 nm. The particle size of the three-dimensional cluster structure is approximately in the range of 0.5 μm to 5 μm.

[0096] The inorganic material product obtained in Example 1 was characterized by transmission electron microscope (TEM), and the results are shown in Figure 3. As can be seen from Figure 3, the product presents a significant lamellar structure, which can also help to illustrate that the product is a three-dimensional cluster assembled by nanosheets. Further, a single nanosheet was imaged and analyzed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) using a spherical aberration correction scanning transmission electron microscope. The results are shown in Figure 4 a. The interplanar spacing of the high-resolution atomic image can correspond to the hexagonal phase crystal structure. The angle between adjacent crystal planes is 60°. The selected area electron diffraction (SAED) analysis of the A region in Figure 4a is performed by Fourier transform. The results are shown in Figure 4a. * As shown in the inset, the pattern spots of electron diffraction in this selected area are consistent with the crystal plane index of the hexagonal crystal structure, such as The same phase calibration.

[0097] In addition, selected area electron diffraction analysis was performed on multiple other regions of a single iridium oxide nanosheet, and the obtained selected area electron diffraction pattern was calibrated with the electron diffraction spectrum. The results were consistent with those of A in Figure 4. * The small picture is similar. According to the Bragg law of electron diffraction of crystals, the diffraction pattern of a single crystal is a spot pattern, and the diffraction pattern of a polycrystal is a ring pattern. * The selected area electron diffraction pattern of the nanosheet in the inset shows only bright lattices, indicating a single-crystal structure. Further lattice measurement and analytical calibration of the diffraction bright spots surrounding the transmission spot near the exact center of the electron diffraction pattern revealed that the geometric shape of the basic unit expressing the symmetry of the diffraction pattern is a regular hexagon. The index calibration results of the six diffraction points that constitute this regular hexagon match the crystal plane indices of the hexagonal phase structure, and the reciprocal lattices of the two crystal planes are also essentially identical, indicating that the nanosheet sample is a single-crystal iridium oxide in the hexagonal phase.

[0098] In addition, the single nanometer sheet of the nanometer cluster inorganic material is carried out to detailed spherical aberration electron microscope characterization discovery, single nanometer sheet is by more atomic layer level ultrathin slice face to face stacking under higher magnification (as shown in Figure b in Fig. 4), and the interlamellar spacing between atomic layer ultrathin slices is about 0.686nm, this is consistent with the theoretical interlaminar spacing obtained from the crystal structure simulation diagram of the material (as shown in Figure c in Fig. 4) and the experimental test result of follow-up XRD, thus the three-dimensional cluster structure inorganic material prepared by the present embodiment is by the shape sheet iridium oxide material self-assembly of hexagonal crystalline phase. Wherein, Figure c in Fig. 4 is the unit cell structure simulation diagram of the iridium oxide nanometer sheet material constructed based on the experimental characterization test result, and the figure shows that the prepared iridium oxide nanometer sheet is a hexagonal Bragg unit cell, and its three-dimensional periodic structure is that the octahedral skeleton that is formed by iridium atom-oxygen atom connection is formed by mutual common edge connection, and periodic orderly expansion extends into iridium oxide layered nanometer sheet structure. Wherein, the red dot in the upper figure of Figure c in Fig. 4 represents oxygen atom, and the place indicated by dotted arrow in the figure below is oxygen atom.

[0099] Furthermore, the inorganic material product of Example 1 was subjected to powder X-ray diffraction (X-ray diffraction, abbreviated as XRD) analysis and test, and the resulting spectrum is shown in Figure 5. In the XRD spectrum of Figure 5, the peaks of 2θ at 33.4°, 36°, and 43° correspond to the crystal plane diffraction peaks of the hexagonal phase structure of the iridium oxide nanosheets. This result is consistent with the crystal plane calibrated by the selected area electron diffraction pattern. These are different from the 2θ diffraction peaks of the traditional tetragonal phase iridium oxide nanoparticles at 28°, 34.7°, 54°, etc. In addition, the diffraction peaks of 2θ at 13°, 26°, 39°, 52°, 65°, 78°, etc. correspond to the diffraction peaks of different interlayer spacings between the iridium oxide nanosheets in the three-dimensional cluster structure. Figure 6 is a specific surface area test diagram measured by nitrogen adsorption method for the inorganic material obtained in Example 1 of the present application. It can be seen from Figure 6 that the inorganic material exhibits a large surface area, which can reach 79.7m 2 / g.

[0100] Furthermore, the inorganic material prepared in Example 1 of the present application was subjected to a polarization test of a three-electrode oxygen evolution reaction, and a platinum-carbon electrode or carbon paper loaded with the inorganic material of Example 1 was used as a working electrode (the loading amount of the inorganic material on the working electrode was 0.5 mg cm -2 ), a graphite carbon rod was used as the counter electrode, a saturated calomel electrode was used as the reference electrode, and a 0.5 mol / L sulfuric acid solution was selected as the electrolyte to assemble a three-electrode electrolytic cell. The electrochemical data of the three-electrode electrolytic cell were tested by linear sweep voltammetry, and the test results are shown in Figure 7. As can be seen from Figure 7, the inorganic material used as the catalyst for the three electrodes in Example 1 has a high conductivity at 10 mA / cm 2At a current density of 1.5 wt %, its catalytic overpotential is only 220 mV, which is much lower than that of commercial IrO2 catalyst (about 270 mV), showing good electrocatalytic performance.

[0101] Preparation of membrane electrodes and devices and device performance testing:

[0102] The inorganic material prepared in Example 1 was used as an anode catalyst and sprayed or transferred onto one side (i.e., the anode side) of a proton exchange membrane (specifically, a Nafion 115 membrane from DuPont) to form an anode catalyst layer. A cathode catalyst layer was formed on the other side (i.e., the cathode side) of the proton exchange membrane to obtain a membrane electrode. Specifically, a commercial platinum-carbon catalyst, Pt / C, was used as the cathode catalyst.

[0103] The membrane electrode was assembled with the anode / cathode gas diffusion layer, sealing gasket, bipolar plate current collector, end plate, etc. to form a PEM water electrolysis device as shown in Figure 1. The electrolysis performance of the PEM water electrolysis device was tested at 80°C, and the test results are shown in Figures 8 and 9. Among them, Figures 8 and 9 respectively summarize the polarization test curve and electrochemical stability curve of the PEM water electrolysis device prepared using the inorganic material of Example 1 as the anode catalyst of the membrane electrode. In Figures 8 and 9, "40wt% Pt / C" means that the mass proportion of Pt in the platinum carbon catalyst is 40wt%.

[0104] As can be seen from FIG8 , the Ir element loading in the membrane electrode of the inorganic material of Example 1 of the present application as the anode catalyst is as low as 0.17 mg·cm -2 Under the conditions of temperature 80℃ and current density 2A / cm 2 The electrolysis voltage under the condition of 1.78V is only 1.78V, showing excellent membrane electrode device performance, which also reflects that the inorganic material of Example 1 has high catalytic activity as an anode catalyst. As can be seen from Figure 9, the Ir element loading in the membrane electrode of the inorganic material of Example 1 of the present application as an anode catalyst is 0.857mg·cm -2 Under the conditions of 80℃ and 1500mA / cm 2 (i.e. 1.5A / cm 2 ) for more than 500 h, no device performance degradation was observed, indicating that the anode catalyst has good stability.

[0105] Example 2

[0106] A method for preparing an inorganic material, which differs from Example 1 primarily in that the amount of the raw material IrCl3·3H2O is changed from 100 mg to 130 mg. Here, the molar ratio of KOH to the Ir element in the iridium salt is 484.34:1.

[0107] The inorganic material product obtained in Example 2 was characterized by SEM, TEM, selected area electron diffraction, XRD, etc., and the results were similar to those in Example 1. The inorganic material was also a three-dimensional cluster structure assembled from hexagonal single crystal iridium oxide nanosheets.

[0108] Furthermore, the performance of the PEM water electrolysis device made of the inorganic material of Example 2 as the anode catalyst of the membrane electrode was tested. The results showed that the Ir element loading in the membrane electrode of the inorganic material of Example 2 was 0.385 mg·cm -2 , electrolysis at a temperature of 80 ° C, where the current density of the PEM water electrolysis device reaches 2A / cm 2 The electrolysis voltage is 1.8 V. This shows that the inorganic material prepared in Example 2 exhibits high OER catalytic activity in PEM water electrolysis, far exceeding the current commercial IrO2.

[0109] Example 3

[0110] A method for preparing an inorganic material, which differs from Example 1 mainly in that the amount of the raw material IrCl3·3H2O is changed from 100 mg to 60 mg (the molar ratio of KOH to the Ir element in the iridium salt is 1049.4:1), the microwave reaction power is 500 W, and the reaction time remains 30 min.

[0111] The inorganic material product obtained in Example 3 was subjected to characterization and analysis such as SEM, TEM, selected area electron diffraction, and XRD, and the results were similar to those in Example 1, indicating that the inorganic material was a three-dimensional cluster structure assembled from hexagonal single crystal iridium oxide nanosheets.

[0112] Furthermore, the performance test of the PEM water electrolysis device made of the inorganic material of Example 3 as the anode catalyst of the membrane electrode was carried out. The results showed that the Ir element loading in the membrane electrode of the inorganic material of Example 3 was 0.4 mg·cm -2 , electrolyze water at a temperature of 80°C, and the PEM water electrolysis device can achieve a current density of 2A / cm 2 The electrolysis voltage is 1.82V.

[0113] Example 4

[0114] A method for preparing an inorganic material, which is mainly different from Example 1 in that the power of the microwave reaction is 1000 W and the reaction time is 5 min.

[0115] Figure 10 is an SEM photograph of the inorganic material obtained in Example 4. It can be observed from Figure 10 that the inorganic material has a three-dimensional cluster morphology, and each three-dimensional cluster is assembled from a plurality of iridium oxide nanosheets. Among them, the lateral size of the nanosheet is about 0.2-1.0 μm, and the thickness is about 1-5 nm. The particle size of the three-dimensional cluster is about 0.3-1.5 μm. The inorganic material obtained in Example 4 was further characterized by TEM, selected area electron diffraction, XRD, etc., and the results were similar to those in Example 1, all indicating that the nanosheets constituting the three-dimensional cluster structure are single crystal iridium oxide nanosheets in the hexagonal phase.

[0116] The performance test of the PEM water electrolysis device made of the inorganic material of Example 4 as the anode catalyst of the membrane electrode was carried out. The results showed that the Ir element loading in the membrane electrode of the inorganic material of Example 4 was 0.2 mg·cm -2 , electrolyze water at a temperature of 80 ° C, and the current density of the PEM water electrolysis device reaches 2A / cm 2 The electrolysis voltage is 1.8 V. This shows that the inorganic material prepared in Example 4 exhibits high OER catalytic activity in PEM water electrolysis, far exceeding the current commercial IrO2.

[0117] Example 5

[0118] A method for preparing an inorganic material, which is mainly different from Example 1 in that the power of the microwave reaction is 900 W and the reaction time is 20 min.

[0119] The inorganic material product obtained in Example 5 was subjected to characterization and analysis such as SEM, TEM, selected area electron diffraction, and XRD, and the results were similar to those in Example 1. The inorganic material included a three-dimensional cluster structure assembled from hexagonal single crystal iridium oxide nanosheets.

[0120] Furthermore, the performance test of the PEM water electrolysis device made of the inorganic material of Example 5 as the anode catalyst of the membrane electrode was carried out. The results showed that the Ir element loading in the membrane electrode of the inorganic material of Example 5 was 0.3 mg·cm -2 , electrolyze water at a temperature of 80°C, and the PEM water electrolysis device can achieve a current density of 2A / cm 2 The electrolysis voltage is 1.81V.

[0121] Example 6

[0122] A method for preparing an inorganic material, which differs from Example 1 mainly in that the raw material IrCl3·3H2O is replaced by iridium nitrate.

[0123] The inorganic material product obtained in Example 6 was characterized and analyzed by SEM ( FIG. 11 ), TEM, selected area electron diffraction, and XRD. The results were similar to those in Example 1. The inorganic material included a three-dimensional cluster structure assembled from hexagonal single-crystal iridium oxide nanosheets.

[0124] Furthermore, the performance test of the PEM water electrolysis device made of the inorganic material of Example 6 as the anode catalyst of the membrane electrode was carried out. The results showed that the Ir element loading in the membrane electrode of the inorganic material of Example 6 was 0.3 mg·cm -2 , electrolyze water at a temperature of 80°C, and the PEM water electrolysis device can achieve a current density of 2A / cm 2 The electrolysis voltage is 1.82V.

[0125] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0126] Comparative Example 1

[0127] A method for preparing an inorganic material, which is mainly different from Example 1 in that the power of the microwave reaction is 1100 W and the reaction time is 60 min.

[0128] The product sample prepared in Comparative Example 1 was characterized by SEM, and the results are shown in Figure 12. Figure 12 shows that the product is composed of aggregated nanoparticles with a particle size of approximately 50-200 nm. This may be due to the excessive energy of the microwave reaction used in Comparative Example 1 (the product of microwave reaction power and time in Comparative Example 1 was 60,000 W·min).

[0129] In addition, the performance test of the PEM water electrolysis device made of the product of Comparative Example 1 as the anode catalyst of the membrane electrode was carried out. The results showed that the Ir element loading in the membrane electrode in the product was 0.5 mg·cm -2 , electrolyze water at a temperature of 80°C, and the PEM water electrolysis device can achieve a current density of 2A / cm 2 The electrolysis voltage is 1.85 V. It can be seen that when the Ir loading of the product of Comparative Example 1 is higher than that of the inorganic materials of Examples 1, 4, and 5 of the present application, under the same temperature and water electrolysis current density, the water electrolysis voltage is still higher than that of the examples of the present application, which indicates that the catalytic activity of the inorganic materials provided by the examples of the present application is stronger.

[0130] The above merely represents several exemplary embodiments of the present application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art would be able to make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0131] It should be understood that the first, second and various numerical numbers involved in this document are only distinguished for the convenience of description and are not intended to limit the scope of this application.

[0132] In this application, "and / or" describes the relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the related objects are in an "or" relationship.

[0133] In this application, "at least one" means one or more, and "more than one" means greater than or equal to two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

Claims

1. An inorganic material, characterized in that: The inorganic material includes iridium oxide nanomaterial, and the iridium oxide nanomaterial has a hexagonal crystal phase structure.

2. The inorganic material according to claim 1, characterized in that The crystal structure of the iridium oxide nanomaterial includes iridium oxygen octahedrons, and the iridium oxygen octahedrons are connected to form the hexagonal crystal phase structure.

3. The inorganic material according to claim 1 or 2, characterized in that In the iridium oxide nanomaterial, there are two crystal planes with an angle of 59.5°-60.5°.

4. The inorganic material according to any one of claims 1 to 3, characterized in that In the XRD spectrum of the inorganic material, there are crystal plane diffraction peaks at 2θ of 32.9°-33.9° and 35.5°-36.5°.

5. The inorganic material according to any one of claims 1 to 4, characterized in that The inorganic material contains a single crystal iridium oxide nanomaterial having the hexagonal crystal phase structure.

6. The inorganic material according to any one of claims 1 to 5, characterized in that The iridium oxide nanomaterial comprises iridium oxide nanosheets.

7. The inorganic material according to claim 6, characterized in that The thickness of the iridium oxide nanosheet is 0.2-50 nm; the lateral size of the iridium oxide nanosheet is 0.01 μm-10 μm.

8. The inorganic material according to any one of claims 1 to 7, characterized in that At least a number of the iridium oxide nanomaterials are assembled into a three-dimensional cluster structure.

9. The inorganic material according to claim 8, characterized in that The average particle size of the three-dimensional cluster structure is 0.03 μm-20 μm.

10. The inorganic material according to any one of claims 1 to 9, characterized in that The specific surface area of ​​the inorganic material is 50-100m 2 / g.

11. The inorganic material according to any one of claims 1 to 10, characterized in that In the inorganic material, the mass percentage of the iridium oxide is 100%.

12. The inorganic material according to any one of claims 1 to 10, characterized in that The inorganic material further comprises one or more of platinum oxide and ruthenium oxide.

13. The inorganic material according to claim 12, characterized in that In the inorganic material, the mass percentage of the iridium oxide is 50-95%.

14. The inorganic material according to any one of claims 1 to 13, characterized in that: The loading of the inorganic material on the working electrode in the three-electrode electrolytic cell is 0.1-1 mg / cm 2 , current density is 10mA / cm 2 Under the conditions of , the overpotential of the inorganic material is below 240mV.

15. A method for preparing an inorganic material, characterized in that: The following steps are involved: Placing a reaction material comprising a solid alkali metal hydroxide and a solid iridium salt in a microwave reaction device for microwave reaction to obtain a reaction material; wherein the product of the power in watts and the reaction time in minutes in the microwave reaction is in the range of 3000-30000; The obtained reaction materials are dispersed in water, and solids are obtained by solid-liquid separation. The obtained solidified material is an inorganic material; wherein the inorganic material comprises iridium oxide nanomaterial, and the iridium oxide nanomaterial has a hexagonal crystal phase structure.

16. The preparation method according to claim 15, characterized in that: The power of the microwave reaction is 500-1000W, and the reaction time is 5-60min.

17. The preparation method according to claim 15 or 16, characterized in that: The molar ratio of the alkali metal hydroxide to the iridium element in the iridium salt is (100-5000):

1.

18. A catalyst, characterized in that The catalyst comprises the inorganic material according to any one of claims 1 to 14 or the inorganic material prepared by the preparation method according to any one of claims 15 to 17, and the catalyst further comprises a binder.

19. Use of the inorganic material according to any one of claims 1 to 14 and the catalyst according to claim 17 in fuel cells, water electrolysis, and other electrochemical technologies.

20. The use according to claim 19, characterized in that The inorganic material or the catalyst is used in the anode catalyst layer in the water electrolysis or in the anode catalyst layer of the fuel cell.

21. A membrane electrode, characterized in that: The membrane electrode comprises a proton exchange membrane, and an anode catalyst layer and a cathode catalyst layer arranged on opposite sides of the proton exchange membrane, wherein the anode catalyst layer comprises the inorganic material according to any one of claims 1 to 14, or the catalyst according to claim 18.

22. The membrane electrode according to claim 21, characterized in that The loading amount of iridium element in the inorganic material in the membrane electrode is 0.1-1 mg / cm 2 .

23. A water electrolysis device, characterized in that: The water electrolysis device comprises the membrane electrode as described in any one of claims 21-22, wherein a gas diffusion layer and a bipolar plate current collector are sequentially stacked on opposite sides of the membrane electrode.

24. The water electrolysis device according to claim 23, characterized in that The loading amount of iridium element in the inorganic material in the membrane electrode is 0.1-1 mg / cm 2 , current density is 2A / cm 2 Under the conditions of , the electrolysis voltage of the water electrolysis device is below 1.85V.

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