Iridium-based catalyst, and preparation method therefor and use thereof

Abstract

The present invention relates to an iridium-based catalyst. The catalyst comprises elemental iridium and optionally present iridium oxide. With respect to the entire catalyst, the content of iridium is 70% or above in terms of mass fraction, and the apparent mass-volume ratio of the catalyst is not higher than 0.55 g / cm3. The catalyst has a large specific surface area, a high porosity and a low apparent mass-volume ratio, and therefore has excellent mass transfer performance and an apparent catalytic activity. A three-dimensional porous structure of the catalyst can improve the utilization rate of iridium, such that the loading of iridium in a membrane electrode is reduced, and the catalyst has excellent stability. The preparation method for the catalyst is simple and convenient, and has a relatively high economy.

Description

Iridium-based catalyst and its preparation method and application Technical Field

[0001] The present disclosure relates to the field of water electrolysis, and specifically to an iridium-based catalyst, a preparation method and application thereof, and more specifically to a metallic iridium catalyst, a preparation method and application thereof; or to a composite catalyst comprising metallic iridium and iridium oxide, a preparation method and application thereof. Background Art

[0002] Hydrogen's high-quality energy properties will give it a crucial role in the future global energy landscape. Proton exchange membrane water electrolysis (PEMWE) technology offers advantages such as compact size, flexible operation, fast start-up and shutdown, a wide load regulation range, and high hydrogen purity. It is well-suited to the volatility of renewable energy and is a key research and development focus in the field of green hydrogen production.

[0003] Anode catalysts are key in PEMWE hydrogen production technology. Water oxidation occurs at the anode to generate oxygen. Since it is an ascending reaction process of four-electron coupled protons, it exhibits a higher overpotential and slow oxygen evolution reaction kinetics. At the same time, the strong oxidizing conditions and strong acidic medium at the anode lead to very high requirements for catalyst stability. Therefore, the actual available active metal elements are very limited. Currently, the active metal element of commercial anode catalysts is mainly iridium. However, iridium is very expensive, and its production and reserves are far lower than those of platinum. This is currently the bottleneck restricting the large-scale commercialization of PEMWE hydrogen production technology.

[0004] Due to the acidic environment, high anode potential, and good conductivity of PEMWE hydrogen production, the current commercial PEMWE anode catalyst is mainly composed of iridium or its oxides. The iridium content in the membrane electrode is generally higher than 2 mg / cm 2 Current research on reducing iridium content in membrane electrodes focuses on improving catalyst performance and applying doping and loading. Catalysts based on pure iridium or its oxides are generally non-porous or slightly porous nanopowders, creating a conflict between increasing specific surface area and inhibiting nanoparticle agglomeration. Reducing the iridium content of the catalyst through doping or loading still presents the challenge of maintaining the conductivity and corrosion resistance of the catalyst layer.

[0005] Commonly used PEMWE anode catalysts include iridium black and iridium oxide. They are generally non-porous powder catalysts. Conventional synthesis methods require the use of surfactants, reducing agents, templates, organic solvents, nitrates, etc., resulting in high preparation costs and the generation of organic wastewater, NO x and other harmful substances.

[0006] The information disclosed in the foregoing background section is only for enhancing understanding of the background of the present disclosure, and it may include information that is not known to one of ordinary skill in the art. Summary of the Invention

[0007] As mentioned above, in order to reduce the cost of using catalysts, in the prior art, it is necessary not only to further improve the electrochemical activity and stability of electrocatalysts; but also to consider how to adapt to the membrane electrode manufacturing process to give full play to the performance of electrocatalysts, and the dispersion of existing electrocatalysts in catalyst membrane slurry is not ideal; in addition, it is necessary to consider the microstructure of the electrocatalyst, how to make the electrocatalyst better transfer mass when facing large current to exert electrochemical performance, how to make the generated gas leave the electrode more quickly, and at the same time make water more easily transported to the active center. In addition, there are many shortcomings in the current synthesis of catalysts with novel micromorphology, such as the need to use surfactants, reducing agents, nitrates, templates and organic solvents, which will result in high production costs and produce a large amount of harmful three waste byproducts; for example, the pore walls of the products obtained by the molten salt method and the soft / hard template method are thick, some with holes and some without holes, and the pore structure is not ideal; and the porosity is not high enough, the specific surface area is not large enough, the apparent mass volume ratio is high, and the dispersion in the catalyst membrane slurry is poor.

[0008] In view of the above problems of the prior art, the inventors of the present disclosure have conducted in-depth research and found that the iridium-based catalyst of the present disclosure, by having specific physical properties, can fully exert the excellent catalytic activity and conductivity of the iridium-based catalyst. Moreover, by having a specific morphology and structure, the catalyst can exhibit the high catalytic activity of the nanomaterial while suppressing the aggregation and deactivation of the catalyst nanoparticles. The mass transfer effect and apparent mass-to-volume ratio of the catalyst are greatly improved, and the catalyst has excellent dispersibility in the slurry. In addition, the iridium-based catalyst of the present disclosure can be easily prepared by the specific method of the present disclosure.

[0009] Specifically, the present disclosure provides the following iridium-based catalysts.

[0010] The first aspect of the present disclosure provides an iridium-based catalyst, characterized in that the iridium content is 70% or more, preferably 77-95% by mass, relative to the entire catalyst, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0011] In the first aspect of the present disclosure, in the XRD spectrum of the iridium-based catalyst, a characteristic peak exists between 2θ of 30° and 40°.

[0012] In the first aspect of the present disclosure, in the XRD spectrum of the iridium-based catalyst, there are no characteristic peaks of metallic iridium and / or crystalline iridium oxide (rutile iridium oxide) except for the range of 2θ of 30 to 40°.

[0013] In the first aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst shows a broadened characteristic peak near 2θ=33.6°, and the half-peak width of the characteristic peak is 5-6°, preferably 5.2-5.6°.

[0014] A second aspect of the present disclosure provides an iridium-based catalyst, wherein the iridium in the catalyst is in the form of crystalline iridium dioxide, and the content of iridium element is 70% or more by mass, preferably 74% to 88%, more preferably 76% to 84% by mass, relative to the entire catalyst, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0015] In the second aspect of the present disclosure, the XRD spectrum of the iridium dioxide catalyst contains characteristic peaks of rutile iridium dioxide.

[0016] In the second aspect of the present disclosure, the XRD spectrum of the iridium dioxide catalyst does not have a characteristic peak of elemental iridium.

[0017] In the second aspect of the present disclosure, the XRD spectrum of the iridium dioxide catalyst only has the characteristic peak of rutile iridium dioxide.

[0018] In the second aspect of the present disclosure, in the XRD spectrum of the iridium dioxide catalyst, a characteristic peak of rutile iridium dioxide with obvious peak broadening appears near 2θ=34.8°.

[0019] In the second aspect of the present disclosure, in the XRD spectrum of the iridium dioxide catalyst, the 101 crystal plane diffraction peak is a characteristic peak, and its half-peak width is 1.5 to 3°, preferably 1.6 to 2.4°.

[0020] According to a third aspect of the present disclosure, there is provided an iridium-based catalyst, characterized in that the catalyst comprises elemental iridium and optionally iridium oxide, wherein the content of iridium element is 70% or more by mass, preferably 80-95%, and more preferably 80-90% by mass, relative to the entire catalyst, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm3 .

[0021] In the third aspect of the present disclosure, the iridium-based catalyst has a characteristic peak of elemental iridium in its XRD spectrum.

[0022] In the third aspect of the present disclosure, in addition to the characteristic peak of elemental iridium, the XRD spectrum of the iridium-based catalyst may also contain or not contain a characteristic peak of iridium oxide.

[0023] In the iridium-based catalyst of the third aspect of the present disclosure, the iridium oxide is rutile iridium dioxide and / or amorphous iridium oxide.

[0024] In the third aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst shows an obvious characteristic peak of elemental iridium near 2θ=40.7°. The characteristic peak is the (111) crystal plane diffraction peak of elemental iridium. The (111) crystal plane diffraction peak has a large intensity and a sharp peak shape. Furthermore, the half-peak width of the (111) crystal plane diffraction peak is 0.8~2.0°, preferably 0.85~1.0°.

[0025] In the third aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst shows a characteristic peak of rutile iridium dioxide ((101) crystal plane) near 2θ=34.8°, and the half-peak width is 1.5-2.0°.

[0026] In the third aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst shows a characteristic peak of amorphous iridium oxide near 2θ=33.6°, with a half-peak width of 5-6°, preferably 5.2-5.6°.

[0027] A fourth aspect of the present disclosure provides a method for preparing an iridium-based catalyst, the method comprising the following steps:

[0028] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water to obtain an iridium source solution;

[0029] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0030] (3) calcining the aerogel;

[0031] Optionally (4), wherein the product of the previous step is annealed.

[0032] By adjusting one method of preparing the iridium-based catalyst provided in the fourth aspect of the present disclosure, the iridium-based catalyst of the first aspect of the present disclosure can be prepared.

[0033] By adjusting another method of preparing the iridium-based catalyst provided in the fourth aspect of the present disclosure, the iridium-based catalyst of the second aspect of the present disclosure can be prepared.

[0034] By adjusting another method of preparing the iridium-based catalyst provided in the fourth aspect of the present disclosure, the iridium-based catalyst of the third aspect of the present disclosure can be prepared.

[0035] The fifth aspect of the present disclosure provides an iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0036] The sixth aspect of the present disclosure provides a use of the iridium-based catalyst described in the first, second or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure, in hydrogen production by electrolysis of water, wherein the use includes a membrane electrode and / or an electrolyzer.

[0037] The seventh aspect of the present disclosure provides a membrane electrode, characterized in that the membrane electrode includes a proton exchange membrane and a catalyst coated on the proton exchange membrane, and the catalyst is the iridium-based catalyst described in the first aspect, second aspect or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0038] The eighth aspect of the present disclosure provides a water electrolyzer, characterized in that the water electrolyzer includes a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is the iridium-based catalyst described in the first aspect, second aspect or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0039] Technical Effects

[0040] Through the above technical solution, the first aspect of the present disclosure provides an iridium-based catalyst and its preparation method and application. In the iridium-based catalyst of the first aspect, the content of iridium element is more than 70% by mass, preferably 77-95% by mass, relative to the whole catalyst, and the apparent mass volume ratio is not higher than 0.55g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 In addition, in the XRD spectrum of the iridium-based catalyst, there is an obvious broadened characteristic peak between 2θ of 30° and 40°, and there is no characteristic peak of crystalline iridium oxide or characteristic peak of elemental iridium.

[0041] The catalyst of the first aspect of the present disclosure has, in terms of structural morphology, a three-dimensional porous structure with large specific surface area, high porosity and continuously distributed mesopores and macropores, and therefore has excellent mass transfer performance, apparent catalytic activity and electrical conductivity.

[0042] Furthermore, the catalyst of the first aspect of the present disclosure has a very low apparent mass-to-volume ratio and a high degree of bulk, resulting in excellent dispersibility in the catalyst slurry. Thus, in electrodes prepared using the catalyst slurry, the catalyst is evenly distributed, which helps improve the conductivity of the catalyst layer and reduce the catalyst loading. Furthermore, because the catalyst of the present disclosure has a continuous mesoporous-macroporous microstructure, the catalyst can fully expose the active sites within the material, improving the utilization rate of the iridium element, thereby reducing the iridium loading in the membrane electrode and lowering the cost of the catalyst.

[0043] Furthermore, the catalyst of the first aspect of the present disclosure has a three-dimensional porous structure formed by connecting porous nanosheets. Therefore, it not only has the high catalytic activity of nanomaterials, but also can inhibit the aggregation and deactivation of catalyst nanoparticles, so that the catalyst maintains high catalytic activity while having excellent stability, thereby solving the activity and stability problems of nanomaterials.

[0044] Furthermore, for the catalyst of the first aspect of the present disclosure, in terms of chemical composition, in the XRD spectrum of the catalyst, there is an obvious broadened characteristic peak between 2θ of 30 and 40°, and there is no characteristic peak of crystalline iridium oxide or characteristic peak of elemental iridium. Therefore, the surface oxidation state of the catalyst is controlled, and the comprehensive performance of the catalyst can be significantly improved on the basis of the aforementioned nanosheets connecting to form a three-dimensional porous structure.

[0045] Therefore, when applied to hydrogen production by water electrolysis, the catalyst of the first aspect of the present disclosure exhibits superior oxygen evolution activity, a low initial overpotential, and a low Tafel slope. In particular, the catalyst of the present disclosure exhibits high stability, with the final overpotential after stability testing showing a minimal increase compared to the initial overpotential, demonstrating promising prospects for industrial application. Furthermore, the preparation method provided by the present disclosure is simple, convenient, and highly economical.

[0046] Through the above technical solution, the second aspect of the present disclosure provides an iridium-based catalyst and its preparation method and application. In the iridium-based catalyst of the second aspect, the iridium is in the form of crystalline iridium dioxide, and the content of iridium element is 70% or more by mass, preferably 74% to 88%, more preferably 76% to 84% relative to the whole catalyst, and the apparent mass volume ratio is not higher than 0.5g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 Furthermore, the XRD spectrum of the iridium-based catalyst shows characteristic peaks of rutile iridium dioxide. That is, the iridium-based catalyst of the second aspect of the present disclosure is substantially composed of rutile iridium dioxide.

[0047] The catalyst of the second aspect of the present disclosure has, in terms of structural morphology, a three-dimensional porous structure with large specific surface area, high porosity and continuously distributed mesopores and macropores, and therefore has excellent mass transfer performance, apparent catalytic activity and conductive properties.

[0048] Furthermore, the catalyst of the second aspect of the present disclosure has a very low apparent mass-to-volume ratio and a high degree of bulk, resulting in excellent dispersibility in the catalyst slurry. Thus, in electrodes prepared using the catalyst slurry, the catalyst is evenly distributed, which helps improve the conductivity of the catalyst layer and reduce the catalyst loading. Furthermore, because the catalyst of the present disclosure has a continuous mesoporous-macroporous microstructure, the catalyst can fully expose the active sites within the material, improving the utilization rate of the iridium element, thereby reducing the iridium loading in the membrane electrode and reducing the cost of the catalyst.

[0049] Furthermore, the second aspect of the catalyst disclosed herein has a three-dimensional porous structure formed by connecting porous nanosheets. Therefore, it not only has the high catalytic activity of nanomaterials, but also can inhibit the aggregation and deactivation of catalyst nanoparticles, so that the catalyst maintains high catalytic activity while having excellent stability, thereby solving the activity and stability problems of nanomaterials.

[0050] Furthermore, for the catalyst of the second aspect of the present disclosure, in terms of chemical composition, the XRD spectrum of the iridium dioxide catalyst contains characteristic peaks of rutile iridium dioxide, thereby improving the performance of existing iridium dioxide and being able to further improve the stability of the catalyst on the basis of the aforementioned nanosheets connecting to form a three-dimensional porous structure.

[0051] Therefore, the catalyst of the second aspect of the present disclosure, when applied to hydrogen production by water electrolysis, exhibits superior oxygen evolution activity, a low initial overpotential, and a low Tafel slope. In particular, the catalyst of the present disclosure exhibits high stability, with the final overpotential after stability testing showing a minimal increase compared to the initial overpotential, demonstrating promising prospects for industrial application. Furthermore, the preparation method provided by the present disclosure is simple, convenient, and highly economical.

[0052] Through the above technical solution, the third aspect of the present disclosure provides an iridium-based catalyst, a preparation method thereof, and an application thereof. In the iridium-based catalyst of the third aspect, the catalyst comprises elemental iridium and optionally iridium oxide, and the content of iridium element is 70% or more by mass, preferably 80-95%, more preferably 80-90%, relative to the entire catalyst, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0053] The XRD spectrum of the iridium-based catalyst of the third aspect includes characteristic peaks of elemental iridium. Furthermore, in one embodiment of the third aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst includes characteristic peaks of iridium oxide. Furthermore, in one embodiment of the third aspect of the present disclosure, the iridium oxide is amorphous iridium oxide and / or rutile iridium dioxide.

[0054] The catalyst of the third aspect of the present disclosure has, in terms of structural morphology, a three-dimensional porous structure with large specific surface area, high porosity and continuously distributed mesopores and macropores, and therefore has excellent mass transfer performance, apparent catalytic activity and conductive properties.

[0055] Furthermore, the catalyst of the third aspect of the present disclosure has a very low apparent mass-to-volume ratio and a high degree of bulk, resulting in excellent dispersibility in the catalyst slurry. Thus, in electrodes prepared using the catalyst slurry, the catalyst is evenly distributed, which helps improve the conductivity of the catalyst layer and reduce the catalyst loading. Furthermore, because the catalyst of the present disclosure has a continuous mesoporous-macroporous microstructure, the catalyst can fully expose the active sites within the material, improving the utilization rate of the iridium element, thereby reducing the iridium loading in the membrane electrode and reducing the cost of the catalyst.

[0056] Furthermore, the catalyst of the third aspect of the present disclosure has a three-dimensional porous structure formed by connecting porous two-dimensional nanosheets. Therefore, it not only has the high catalytic activity of nanomaterials, but also can inhibit the aggregation and deactivation of catalyst nanoparticles, so that the catalyst maintains high catalytic activity while having excellent stability, thereby solving the activity and stability problems of nanomaterials.

[0057] Furthermore, for the catalyst of the third aspect of the present disclosure, in terms of chemical composition, the XRD spectrum of the catalyst has characteristic peaks of elemental iridium. Thus, the catalyst exhibits excellent electrical conductivity. In addition, in one embodiment of the present disclosure, the XRD spectrum of the catalyst has characteristic peaks of amorphous iridium oxide and / or rutile iridium dioxide and characteristic peaks of elemental iridium. Thus, the catalyst has both the good electrical conductivity of iridium metal and the stability of iridium oxide, and can further improve the stability of the catalyst on the basis of the aforementioned nanosheets connecting to form a three-dimensional porous structure.

[0058] Therefore, the catalyst of the third aspect of the present disclosure, when applied to hydrogen production by water electrolysis, exhibits superior oxygen evolution activity, a low initial overpotential, and a low Tafel slope. In particular, the catalyst of the present disclosure exhibits high stability, with the final overpotential after stability testing showing a minimal increase compared to the initial overpotential, demonstrating promising prospects for industrial application. Furthermore, the preparation method provided by the present disclosure is simple, convenient, and highly economical.

[0059] In the preparation method of the fourth aspect of the present disclosure, the iridium-based catalyst of the first aspect of the present disclosure, the iridium-based catalyst of the second aspect, and the iridium-based catalyst of the third aspect can be conveniently prepared by adjusting the conditions of each step.

[0060] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0062] FIG1 is a SEM image of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0063] FIG2 is an XRD pattern of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0064] FIG3 is a TEM image of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0065] FIG4 is a BET diagram of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0066] FIG5 is an XPS spectrum of Ir 4f of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0067] FIG6 is a cyclic voltammogram of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0068] FIG7 is a diagram showing the discharge of bubbles when catalyst I-C1 prepared in Example I-1 of the present disclosure is coated on carbon paper to form an electrode for water electrolysis reaction;

[0069] FIG8 is a SEM image of commercial iridium oxide I-D2 used in Comparative Example I-2 of the present disclosure;

[0070] FIG9 is a cyclic voltammogram of commercial iridium oxide I-D2 used in Comparative Example I-2 of the present disclosure;

[0071] FIG10 is a diagram showing the discharge of bubbles when commercial iridium oxide I-D2 used in Comparative Example I-2 of the present disclosure is coated on carbon paper to prepare an electrode for water electrolysis reaction;

[0072] FIG11 is a SEM image of catalyst II-C1 prepared in Example II-1 of the present disclosure;

[0073] FIG12 is an XRD pattern of catalyst II-C1 prepared in Example II-1 of the present disclosure;

[0074] FIG13 is an XPS spectrum of Ir 4f of catalyst II-C1 prepared in Example II-1 of the present disclosure;

[0075] FIG14 is a cyclic voltammogram of catalyst II-C1 prepared in Example II-1 of the present disclosure;

[0076] FIG15 is a diagram showing the discharge of bubbles when catalyst II-C1 prepared in Example II-1 of the present disclosure is coated on carbon paper to form an electrode for water electrolysis reaction;

[0077] FIG16 is a SEM image of commercial iridium dioxide II-D2 used in Comparative Example II-2 of the present disclosure;

[0078] FIG17 is a cyclic voltammogram of commercial iridium dioxide II-D2 used in Comparative Example II-2 of the present disclosure;

[0079] FIG18 is a diagram showing the discharge of bubbles when commercial iridium dioxide II-D2 used in Comparative Example II-2 of the present disclosure is coated on carbon paper to prepare an electrode for water electrolysis reaction;

[0080] FIG19 is a SEM image of catalyst III-C1 prepared in Example III-1 of the present disclosure;

[0081] FIG20 is an XRD pattern of catalyst III-C1 prepared in Example III-1 of the present disclosure;

[0082] FIG21 is a TEM image of catalyst III-C1 prepared in Example III-1 of the present disclosure;

[0083] FIG22 is a BET diagram of catalyst III-C1 prepared in Example III-1 of the present disclosure;

[0084] FIG23 is an XPS spectrum of Ir4f of catalyst III-C1 prepared in Example III-1 of the present disclosure;

[0085] FIG24 is a diagram showing the discharge of bubbles when catalyst III-C1 prepared in Example III-1 of the present disclosure is coated on carbon paper to form an electrode for water electrolysis;

[0086] FIG25 is an XRD pattern of catalyst III-C2 prepared in Example III-2 of the present disclosure;

[0087] FIG26 is a cyclic voltammogram of catalyst III-C2 prepared in Example III-2 of the present disclosure;

[0088] FIG27 is an XRD pattern of catalyst III-C3 prepared in Example III-3 of the present disclosure;

[0089] FIG28 is a diagram showing the discharge of bubbles when the commercial iridium black III-D2 used in comparative example III-2 of the present disclosure is coated on carbon paper to prepare an electrode for water electrolysis reaction.

[0090] FIG29 is a SEM image of catalyst IV-C1 prepared in Example IV-1 of the present disclosure;

[0091] FIG30 is an XRD pattern of catalyst IV-C1 prepared in Example IV-1 of the present disclosure;

[0092] FIG31 is an XPS spectrum of Ir 4f of catalyst IV-C1 prepared in Example IV-1 of the present disclosure;

[0093] FIG32 is a cyclic voltammogram of catalyst IV-C1 prepared in Example IV-1 of the present disclosure;

[0094] FIG33 is a diagram showing the discharge of bubbles when catalyst IV-C1 prepared in Example IV-1 of the present disclosure is coated on carbon paper to form an electrode for water electrolysis reaction;

[0095] FIG34 is a SEM image of commercial rutile iridium dioxide used in Comparative Example IV-2 of the present disclosure;

[0096] FIG35 is a cyclic voltammogram of the commercial rutile iridium dioxide used in Comparative Example IV-2 of the present disclosure;

[0097] FIG36 is a diagram showing the discharge of bubbles when commercial rutile iridium dioxide, used in Comparative Example IV-2 of the present disclosure, is coated on carbon paper to prepare an electrode for water electrolysis;

[0098] FIG37 is an isothermal adsorption-desorption curve of catalyst I-C1 prepared in Example I-1 of the present disclosure;

[0099] FIG38 is a low-magnification STEM image of catalyst I-C1 prepared in Example I-1 of the present disclosure at different angles;

[0100] FIG39 is a high-magnification STEM image of catalyst I-C1 prepared in Example I-1 of the present disclosure at different angles;

[0101] FIG40 is a high-magnification STEM image at different angles of the commercial iridium oxide I-D2 used in comparative example I-2 of the present disclosure. DETAILED DESCRIPTION

[0102] The structure, principle and preparation process of the iridium-based catalyst disclosed in the present invention are further described in detail below.

[0103] In this disclosure, except for the contents explicitly described, any matters or issues not mentioned are directly applicable to the contents known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are considered part of the original disclosure or record of this disclosure and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0104] All features disclosed in this disclosure may be combined in any combination, and such combinations should be understood as disclosed or described in this disclosure. Unless a person skilled in the art deems such combinations to be obviously unreasonable, such combinations should be considered as specifically disclosed and described in this disclosure. Unless otherwise specified, the numerical values ​​disclosed in this specification include not only the numerical values ​​specifically disclosed in the examples but also the endpoints of the numerical ranges in this specification. Any combination of these numerical values ​​should be considered as the range disclosed or described in this disclosure.

[0105] Technical and scientific terms in this disclosure shall be understood according to their definitions if they are defined, and shall be understood according to their common meanings in the art if they are not defined.

[0106] Terminology Notes:

[0107] The term "mesopore" is defined as pores with a pore diameter in the range of 2 nm to 50 nm, the term "macroporous" is defined as pores with a pore diameter greater than 50 nm; and the term "micropore" is defined as pores with a pore diameter less than 2 nm.

[0108] The term "porous material" is defined as a material with a porosity greater than 15%. The shape, existence form or distribution state of the pores in the porous material is not restricted. For example, the existence form of the pores may include cross-linked pores, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0109] The term "sol" is defined as a uniform dispersion having fluidity and a viscosity greater than that of water.

[0110] The term "three-dimensional porous structure" is defined as a material with a porosity greater than 15%. The shape, existence form or distribution state of the pores in the material is not restricted. For example, it can be composed of mesopores with a pore diameter in the range of 2nm to 50nm and macropores with a pore diameter greater than 50nm. The existence form of the pores may include cross-linked pores, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0111] In the XRD spectrum, the position of each peak is represented by 2θ. Due to instrument deviation, differences in measurement environment, etc., the results may vary. In the XRD spectrum, "near" each 2θ value means the range of ±0.2° of the 2θ value.

[0112] In the present disclosure, the term "amorphous" refers to a state other than a crystalline state, including an amorphous state and a pseudo-crystalline state. In the present disclosure, amorphous iridium oxide exists in an amorphous state and / or a pseudo-crystalline state.

[0113] In the present disclosure, the contents of iridium and oxygen are obtained by XRF testing.

[0114] The first aspect of the present disclosure provides an iridium-based catalyst. The iridium-based catalyst has an iridium content of 70% or more by mass, preferably 77-95%, and an apparent mass-to-volume ratio of no more than 0.5 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0115] In the first aspect of the present disclosure, in the XRD spectrum of the iridium-based catalyst, there is an obvious broadened characteristic peak between 2θ of 30° and 40°, and there is no characteristic peak of crystalline iridium oxide.

[0116] In the first aspect of the present disclosure, the iridium-based catalyst is an amorphous iridium oxide catalyst. Specifically, the XRD spectrum of the amorphous iridium oxide catalyst exhibits a distinct peak broadening near 2θ=33.6°, with a half-width of the characteristic peak of 5 to 6°, preferably 5.2 to 5.6°.

[0117] In the iridium-based catalyst of the first aspect of the present disclosure, in the XRD spectrum of the catalyst, there is an obvious broadened characteristic peak between 2θ of 30 and 40°, and there is no characteristic peak of crystalline iridium oxide, such as the characteristic peak of rutile iridium dioxide.

[0118] In one embodiment of the first aspect of the present disclosure, the XRD spectrum of the amorphous iridium oxide catalyst substantially only has characteristic peaks of amorphous iridium oxide with broadened peaks, and does not contain characteristic peaks of elemental iridium.

[0119] In one embodiment of the first aspect of the present disclosure, the content of iridium in the amorphous iridium oxide catalyst relative to the entire catalyst can be 70% by mass or more, preferably 75% by mass or more, and more preferably 77-95% by mass.

[0120] In one embodiment of the first aspect of the present disclosure, the content of iridium in the amorphous iridium oxide catalyst can be 72%, 74%, 76%, 78%, 80% or 83% by mass relative to the catalyst as a whole, or the content of iridium is within a numerical range between any two of them. Preferably, the amorphous iridium oxide catalyst contains 75-82% iridium. In the above embodiment, by selecting the preferred content of iridium, it is beneficial to further optimize the composition and structure of the catalyst, improve the conductivity of the catalyst, and thus improve its electrocatalytic activity.

[0121] In one embodiment of the first aspect of the present disclosure, the oxygen content in the amorphous iridium oxide catalyst can be 14 to 25% by mass relative to the catalyst as a whole, for example, it can be 15%, 17%, 19%, 21% or 23%, or the content of oxygen element is within the numerical range between any two of them; preferably, it contains 14 to 20% oxygen.

[0122] The amorphous iridium oxide catalyst disclosed herein may contain a small amount or trace amount of other elements in addition to iridium and oxygen due to the presence of impurities in the synthetic raw materials, but these factors have no significant effect on the structural properties and catalytic performance of the final catalyst. The present disclosure does not intend to limit the types and contents of these impurities.

[0123] In one embodiment of the first aspect of the present disclosure, the porosity of the amorphous iridium oxide catalyst is greater than 50%, preferably 70-90%, more preferably 74-85%, and further preferably 74-80%. In the above embodiment, the amorphous iridium oxide catalyst has a large porosity, which makes the catalyst more bulky, which is conducive to promoting the mass transfer process.

[0124] In one embodiment of the first aspect of the present disclosure, the specific surface area of ​​the amorphous iridium oxide catalyst is 65 to 150 m 2 / g, preferably 70 to 135 m 2 In the above embodiment, the amorphous iridium oxide catalyst has a large specific surface area, which is beneficial to improving the mass specific activity and promoting the mass transfer process.

[0125] In one embodiment of the first aspect of the present disclosure, the specific surface area of ​​the micropores of the amorphous iridium oxide catalyst relative to the specific surface area of ​​the catalyst as a whole is not more than 35%, preferably not more than 20%, more preferably not more than 15%, and further preferably not more than 10%.

[0126] In one embodiment of the first aspect of the present disclosure, the apparent mass volume ratio of the amorphous iridium oxide catalyst is 0.15 to 0.4 g / cm 3 , preferably 0.15 to 0.3 g / cm3 , more preferably 0.18 to 0.25 g / cm 3 In one embodiment of the first aspect of the present disclosure, the total pore volume of the amorphous iridium oxide catalyst is 0.15 to 0.3 cm 3 / g, preferably 0.18 to 0.26 cm 3 / g.

[0127] In the above embodiment, the amorphous iridium oxide catalyst has a loose and porous microstructure and a high degree of fluffiness, which is not only conducive to improving the mass transfer effect of the catalyst and thus improving the electrocatalytic activity of the catalyst, but also can significantly improve the dispersion of the catalyst slurry when manufacturing the membrane electrode and reduce the catalyst loading.

[0128] In one embodiment of the first aspect of the present disclosure, the amorphous iridium oxide catalyst comprises a mesopore and a macroporous structure with a pore size range between 2nm and 1000nm, preferably a pore of 50nm to 1000nm, and more preferably a pore of 50nm to 500nm. In the above-mentioned embodiment, the pore structure of the amorphous iridium oxide catalyst is basically a multi-level pore consisting of mesopores and macropores, and the pore size of the mesopores and macropores is continuously distributed, so that the catalyst has a larger specific surface area, porosity and fluffiness. "The pore size of mesopores and macropores is continuously distributed" refers to a multi-level pore consisting of continuous macropores (pore size 50 to 200nm) and mesopores (pore size 2 to 50nm) around the macropores (pore size> 200nm), wherein "continuous" refers to the presence of pores of various pore sizes, for example, pores of various pore sizes in the range of 2nm to 200nm exist. It is believed that mesopores provide a large specific surface area, expose more reaction sites, and participate in gas transport; while macropores, especially ultra-large pores with sizes of hundreds of nanometers, are very conducive to water transport and significantly reduce the apparent mass-to-volume ratio of the catalyst.

[0129] Iridium is one of the densest elements in existence. The density of metallic iridium is as high as 22.65g / cm 3 In the first aspect of the present disclosure, an amorphous iridium oxide catalyst is provided, which has the loose and porous microstructure of the first aspect of the present disclosure. In particular, the main part of the porous structure of the iridium-based catalyst in the first aspect of the present disclosure is a mesoporous and macroporous structure formed by ultrathin nanosheets connected in three-dimensional space. Therefore, the apparent mass-to-volume ratio of the iridium-based catalyst in the first aspect of the present disclosure is much lower than the apparent mass-to-volume ratio of existing iridium-based catalysts, and even lower than the apparent mass-to-volume ratio of platinum-carbon electrocatalysts. In addition, the iridium-based catalyst in the present disclosure has the above-mentioned higher surface area. These physical properties of the iridium-based catalyst in the first aspect of the present disclosure further indicate that the catalyst in the present disclosure has a loose and porous structure.

[0130] In one embodiment of the first aspect of the present disclosure, the three-dimensional porous structure of the amorphous iridium oxide catalyst is formed by connecting a plurality of nanosheets in three-dimensional space, preferably by connecting a plurality of porous nanosheets in three-dimensional space. Specifically, the entity part of the three-dimensional porous microstructure of the amorphous iridium oxide catalyst of the present disclosure is formed by overlapping and connecting a plurality of nanosheets of flaky entities. On the one hand, the flaky nanosheets extend to form the "walls" of the pore walls of a plurality of holes. On the other hand, the flaky nanosheets overlap on other nanosheets to form a "surface" covering the holes. Thus, a plurality of different nanosheets serving as "walls" and "surfaces" overlap with each other, and the holes between the nanosheets are staggered and connected, thereby forming a porous microstructure, as shown in Figure 1. In the present disclosure, the existence of the pores may include cross-linked holes, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0131] In one embodiment of the first aspect of the present disclosure, the three-dimensional porous structure of the present disclosure includes continuously distributed mesopores and macropores, which constitute a continuous mesopore-macropore multi-level pore structure as a whole.

[0132] In one embodiment of the first aspect of the present disclosure, the nanosheets of the amorphous iridium oxide catalyst are relatively small in size and very thin. For example, the nanosheets have a size of less than 500 nm. In a preferred embodiment, the nanosheet structure substantially does not contain a portion having a thickness exceeding 10 nm, that is, the thickness of the nanosheet does not substantially exceed 10 nm. Preferably, the thickness of the nanosheet is 1.5 to 8 nm, more preferably 2 to 7 nm. Due to its ultra-thin thickness, it can be referred to as a two-dimensional nanosheet. The three-dimensional porous structure formed by connecting multiple two-dimensional nanosheets gives the catalyst a large porosity and fluffiness.

[0133] In one embodiment of the first aspect of the present disclosure, the amorphous iridium oxide catalyst of the present disclosure exhibits high catalytic activity as a nanomaterial. Furthermore, because the microscopic structure is a loose, porous structure formed by continuously extending and connecting nanosheets, it facilitates improved mass transfer and apparent activity, while preventing agglomeration and deactivation of the amorphous iridium oxide catalyst. This addresses the issues of nanomaterial activity and stability, helps reduce the amount of amorphous iridium oxide catalyst used, and improves its dispersibility. In the present disclosure, the average thickness of the nanosheets was measured using SEM and statistically analyzed using Nano Measurer 1.2 software.

[0134] In one embodiment of the first aspect of the present disclosure, the continuous nanosheets in the amorphous iridium oxide catalyst are formed by a plurality of iridium oxide nanoparticles that are closely arranged and interconnected, and the average particle size of the iridium oxide nanoparticles is 1 to 4 nm, preferably 1.2 to 2.5 nm. In the above embodiment, the iridium oxide nanoparticles are relatively small in size, and the thickness of the formed nanosheets is also relatively thin, for example, the thickness is only 1 to 6 nm, which makes the internal structure of the amorphous iridium oxide catalyst composed of nanosheets more loose. In a preferred embodiment, the nanosheets formed by the nanoparticles have a wrinkled graphene-like morphology, which is beneficial to further improve the apparent activity of the catalyst. In the present disclosure, the size of the nanoparticles can be obtained by TEM testing.

[0135] In one embodiment of the first aspect of the present disclosure, the high-resolution transmission electron microscopy image of the amorphous iridium oxide catalyst has a structure combining obvious long-range disorder with medium- and short-range order, which is conducive to exposing more coordinatively unsaturated active sites and promoting the improvement of OER performance.

[0136] The amorphous iridium oxide catalyst disclosed herein is rich in highly active Ir 4+ and Ir 3+ , which is beneficial to improving the intrinsic OER activity of the catalyst. In one embodiment of the first aspect of the present disclosure, in the XPS Ir 4f spectrum of the amorphous iridium oxide catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV; Ir 3+ 4f 7 / 2 The binding energy of the peak is 62-63 eV. In a preferred embodiment, the Ir4f spectrum obtained by fitting the XPS Ir4f spectrum of the amorphous iridium oxide catalyst is 3+ The molar percentage of Ir is 20 to 50%, preferably 25 to 40%. 3+ The ratio of the molar number of the iridium oxide to the total molar number of the Ir species is 20 to 50%, preferably 25 to 40%. This shows that the surface layer of the amorphous iridium oxide catalyst disclosed in the present invention is rich in highly active Ir 3+ , which is beneficial to improving the intrinsic OER activity of the catalyst. The "surface layer" in this disclosure refers to the area with a detection depth of less than 10nm from the outer surface of the catalyst. Specifically, it is based on the detection depth of XPS.

[0137] In one embodiment of the first aspect of the present disclosure, the specific surface area of ​​the amorphous iridium oxide catalyst is ≥65m 2 / g, porosity ≥40%, with continuous mesoporous and macroporous structure.

[0138] In one embodiment of the first aspect of the present disclosure, the porosity of the amorphous iridium oxide catalyst is 65 to 90%, preferably 65 to 85%, and more preferably 67 to 80%.

[0139] In the present disclosure, "doping" refers to the dispersion of actively introduced non-iridium metal elements in the bulk phase of the catalyst.

[0140] In one embodiment of the first aspect of the present disclosure, the amorphous iridium oxide catalyst is undoped.

[0141] In one embodiment of the first aspect of the present disclosure, in order to further improve the performance of the catalyst, the amorphous iridium oxide catalyst of the present disclosure is doped, and the doping elements include, but are not limited to, Li, Na, K, and V, which are commonly used doping elements known in the art.

[0142] The second aspect of the present disclosure provides an iridium-based catalyst. The iridium in the catalyst is in the form of crystalline iridium dioxide, and the iridium content of the catalyst as a whole is 70% or more by mass, preferably 74% to 88%, more preferably 76% to 84%, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0143] In a second aspect of the present disclosure, the iridium-based catalyst is a crystalline iridium dioxide (rutile iridium dioxide) catalyst (in the present disclosure, sometimes also referred to as an iridium dioxide catalyst). Specifically, the XRD spectrum of the iridium-based catalyst of the second aspect of the present disclosure substantially only has the characteristic peak of the rutile iridium dioxide (crystalline iridium oxide) of peak broadening, and the characteristic peak of elemental iridium does not occur. It should be noted that, in the present disclosure, "substantially only" refers to that in the XRD spectrum, the characteristic peak of the rutile iridium dioxide of peak broadening mainly occurs, but due to reasons such as measurement conditions, sample impurities, other weak diffraction peaks of the intensity of 2θ angles may occur in the XRD spectrum, but these weak diffraction peaks are obviously not considered as the characteristic peaks of the iridium-based catalyst of the present disclosure.

[0144] In one embodiment of the second aspect of the present disclosure, the XRD spectrum of the rutile iridium dioxide catalyst shows a characteristic peak of rutile iridium dioxide (101 crystal plane diffraction peak) with obvious peak broadening near 2θ=34.8°, and the half-peak width of the characteristic peak is 1.5 to 3°, preferably 1.6 to 2.4°. In the above embodiment, the relatively broad half-peak width indicates that the grain size of iridium dioxide is relatively small, rich in a large number of grain boundaries, can bring more electrochemical active sites, and is conducive to the improvement of OER performance.

[0145] In one embodiment of the second aspect of the present disclosure, the content of iridium element in the iridium dioxide catalyst can be greater than 70% by mass relative to the entire catalyst, preferably greater than 75%, more preferably 74% to 88%, and further preferably 76 to 84%.

[0146] In one embodiment of the second aspect of the present disclosure, the content of oxygen element may be 14 to 20% by mass, preferably 14 to 18% by mass, relative to the entire catalyst.

[0147] In one embodiment of the second aspect of the present disclosure, the content of iridium in the iridium dioxide catalyst can be 74%, 76%, 78%, 80%, 81%, 84%, 86% or 88% by mass relative to the catalyst as a whole, or the content of iridium is within a numerical range between any two of them. Preferably, the iridium dioxide catalyst comprises 76 to 84% iridium. In the above embodiment, by selecting the preferred content of iridium, it is beneficial to further optimize the composition and structure of the catalyst, improve the conductivity of the catalyst, and thus improve its electrocatalytic activity.

[0148] In one embodiment of the second aspect of the present disclosure, the oxygen content in the iridium dioxide catalyst can be 15%, 17%, or 20% by mass relative to the catalyst as a whole, or the oxygen content is within a numerical range between any two of these, preferably comprising 14% to 18% oxygen. In the above embodiment, the oxygen in the iridium dioxide catalyst is primarily present in the form of oxides.

[0149] The iridium dioxide catalyst disclosed herein may contain a small amount or trace amount of other elements in addition to iridium and oxygen due to the presence of impurities in the synthetic raw materials, but these factors have no significant effect on the structural properties and catalytic performance of the final catalyst, and the present disclosure does not intend to limit the types and contents of these impurities.

[0150] In one embodiment of the second aspect of the present disclosure, the iridium dioxide catalyst has a relatively high porosity, for example, the porosity of the iridium dioxide catalyst is greater than 50%, preferably 65-90%, more preferably 70-90%, 70-85%, or 70-80%. In the above embodiment, the iridium dioxide catalyst has a relatively high porosity, which makes the catalyst more bulky, which is beneficial to promoting the mass transfer process.

[0151] In one embodiment of the second aspect of the present disclosure, the specific surface area of ​​the iridium dioxide catalyst is 100 to 150 m 2 / g, preferably 110 to 130 m 2 In the above embodiment, the iridium dioxide catalyst has a large specific surface area, which is beneficial to improving the mass specific activity.

[0152] In one embodiment of the second aspect of the present disclosure, the specific surface area of ​​the micropores of the iridium dioxide catalyst relative to the specific surface area of ​​the catalyst as a whole is not greater than 35%, preferably not greater than 20%, more preferably not greater than 15%, and further preferably not greater than 10%.

[0153] In one embodiment of the second aspect of the present disclosure, the apparent mass volume ratio of the iridium dioxide catalyst is 0.15 to 0.4 g / cm 3 , preferably 0.2 to 0.34 g / cm 3 , more preferably 0.22 to 0.30 g / cm 3 In one embodiment of the second aspect of the present disclosure, the total pore volume of the iridium dioxide catalyst is 0.1 to 0.3 cm 3 / g, preferably 0.16 to 0.26 cm 3 / g. In the above embodiment, the iridium dioxide catalyst has a loose and porous microstructure with a high degree of bulk, which is beneficial for improving the mass transfer effect of the catalyst, thereby improving the electrocatalytic activity of the catalyst, while also reducing the iridium loading of the catalyst. The total pore volume is the volume of pores with a pore size range of 2 to 200 nm as measured by the BET test. It is understandable that since the catalyst also contains macropores with a pore size greater than 200 nm, the pore volume measured here is the pore volume of the relatively small pores with a pore size of 2 to 200 nm of the catalyst.

[0154] In one embodiment of the second aspect of the present disclosure, the three-dimensional porous structure of the iridium dioxide catalyst comprises continuously distributed mesopores and macropores, which may or may not contain micropores; for example, it comprises continuously distributed mesopores and macropores with a pore size of 2 to 1000 nm, preferably 2 to 500 nm. Furthermore, the pore structure of the iridium dioxide catalyst is basically a multi-level pore composed of mesopores and macropores, and the pore size of the mesopores and macropores is continuously distributed, so that the catalyst has a larger specific surface area, porosity and fluffiness. "Continuous distribution of pore size of mesopores and macropores" refers to a multi-level pore composed of continuous macropores (pore size 50 to 200 nm) and mesopores (pore size 2 to 50 nm) around the macropores (pore size> 200 nm), wherein "continuous" refers to the presence of pores of various pore sizes, for example, pores of various pore sizes in the range of 2 nm to 200 nm exist.

[0155] Iridium is one of the densest elements in existence. The density of metallic iridium is as high as 22.65g / cm 3In the second aspect of the present disclosure, a rutile iridium dioxide catalyst is provided, which has the loose and porous microstructure of the second aspect of the present disclosure. In particular, the main part of the porous structure of the iridium-based catalyst in the second aspect of the present disclosure is a mesoporous and macroporous structure. Therefore, the apparent mass-to-volume ratio of the iridium-based catalyst in the second aspect of the present disclosure is much lower than the density of the above-mentioned metallic iridium, and the iridium-based catalyst in the present disclosure has the above-mentioned higher surface area. These physical properties of the iridium-based catalyst in the second aspect of the present disclosure further indicate that the catalyst in the present disclosure has a loose and porous structure.

[0156] In one embodiment of the second aspect of the present disclosure, the three-dimensional porous structure of the iridium dioxide catalyst is formed by connecting a plurality of nanosheets in a three-dimensional space, preferably by connecting a plurality of porous nanosheets in a three-dimensional space. Specifically, the entity part of the three-dimensional porous microstructure of the iridium dioxide catalyst of the present disclosure is formed by overlapping and connecting a plurality of nanosheets of flaky entities. On the one hand, the flaky nanosheets extend to form the "walls" of the pore walls of a plurality of holes. On the other hand, the flaky nanosheets overlap on other nanosheets to form a "surface" covering the holes. Thus, a plurality of different nanosheets serving as "walls" and "surfaces" overlap with each other, and the holes between the nanosheets are staggered and connected, thereby forming a porous microstructure, as shown in Figure 11. In the present disclosure, the existence of the pores may include cross-linked holes, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0157] In one embodiment of the second aspect of the present disclosure, the three-dimensional porous structure of the present disclosure includes continuously distributed mesopores and macropores, which constitute a continuous mesopore-macropore multi-level pore structure as a whole.

[0158] In one embodiment of the second aspect of the present disclosure, the nanosheets of the iridium dioxide catalyst are relatively small and very thin. For example, the nanosheets have a size of less than 500 nm. In a preferred embodiment, the nanosheet structure substantially does not contain a portion having a thickness exceeding 10 nm, that is, the thickness of the nanosheet does not substantially exceed 10 nm. Preferably, the thickness of the nanosheet is 1.5 to 6.5 nm, more preferably 2 to 4.5 nm. Due to its ultra-thin thickness, it can be referred to as a two-dimensional nanosheet. The three-dimensional porous structure formed by connecting multiple two-dimensional nanosheets gives the catalyst a large porosity and fluffiness.

[0159] In one embodiment of the second aspect of the present disclosure, the iridium dioxide catalyst of the present disclosure has the high catalytic activity of a nanomaterial. At the same time, because it is a three-dimensional multi-level pore structure formed by continuous extension and connection of nanosheets, with continuously distributed mesopores and macropores, and particularly contains a certain number of macropores with a pore size of 200 nm or more, it is beneficial to improve the mass transfer effect and apparent activity, and avoid the aggregation and deactivation of the iridium dioxide catalyst, thereby improving the dispersion performance of the catalyst in the slurry, thereby solving the activity and stability problems of the nanomaterial, and at the same time helping to reduce the usage of the iridium dioxide catalyst and improve its dispersibility. The average thickness of the nanosheets was measured using SEM and statistically analyzed using Nano Measurer 1.2 software.

[0160] In one embodiment of the second aspect of the present disclosure, the continuous nanosheets in the iridium dioxide catalyst are formed by closely arranging and interconnecting a plurality of small-sized nanocrystals of iridium dioxide, and the average particle size of the iridium dioxide nanocrystals is 2 to 6 nm, preferably 2 to 4 nm. In the above embodiment, the grain size of the iridium dioxide nanocrystals is relatively small, and the thickness of the formed nanosheets is also relatively thin, for example, the thickness is only 1.5 to 6.5 nm, so that the internal structure of the iridium dioxide catalyst composed of the nanosheets is looser. In a preferred embodiment, the nanosheets formed by the small-sized nanocrystals have a wrinkled graphene-like shape, which is beneficial to further improve the apparent activity of the catalyst. In the present disclosure, the size of the nanoparticles can be obtained by TEM testing.

[0161] In one embodiment of the second aspect of the present disclosure, the XPS spectrum of the iridium dioxide catalyst has characteristic peaks of iridium dioxide, that is, in the XPS Ir 4f spectrum, there are Ir 4+ and satellite peaks, but there is no Ir 3+ Characteristic peaks, specifically, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV, indicating that the surface of the rutile iridium dioxide catalyst disclosed in the present invention is rich in high-valent Ir 4+ , which helps improve the stability of the catalyst. The "surface layer" refers to the area less than 10nm deep from the outer surface of the iridium dioxide catalyst. Specifically, the XPS detection depth is used as the standard.

[0162] In the present disclosure, "doping" refers to the dispersion of actively introduced non-iridium metal elements in the bulk phase of the catalyst.

[0163] In one embodiment of the second aspect of the present disclosure, the iridium dioxide catalyst is undoped.

[0164] In one embodiment of the second aspect of the present disclosure, in order to further improve the performance of the catalyst, the iridium dioxide catalyst of the second aspect of the present disclosure is doped, and the doping elements commonly used in the art include but are not limited to Li, Na, K, and V.

[0165] The third aspect of the present disclosure provides an iridium-based catalyst, wherein the iridium-based catalyst comprises elemental iridium and optionally iridium oxide, wherein the content of iridium element is 70% or more by mass, preferably 80-95%, more preferably 80-90% by mass, relative to the entire catalyst, and the apparent mass-to-volume ratio is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 .

[0166] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst has a characteristic peak of elemental iridium in its XRD spectrum.

[0167] In one embodiment of the third aspect of the present disclosure, the XRD spectrum of the iridium-based catalyst basically only has the characteristic peak of elemental iridium, and there is no characteristic peak of the oxide, for example, there is no characteristic peak of rutile iridium dioxide and the characteristic peak of amorphous iridium oxide. At this time, the iridium-based catalyst of the third aspect of the present disclosure is an iridium metal catalyst. Specifically, the XRD spectrum of the iridium-based catalyst shows an obvious characteristic peak of elemental iridium near 2θ=40.7°. The characteristic peak is the (111) crystal plane diffraction peak of elemental iridium. The (111) crystal plane diffraction peak has a large intensity and a sharp peak shape. Furthermore, the half-peak width of the (111) crystal plane diffraction peak is 0.8~2.0°, preferably 0.85~1.0°. In the above embodiment, the crystallinity of the elemental iridium contained in the catalyst is good, and the presence of elemental iridium is conducive to enhancing the conductivity of the iridium-based catalyst and improving the OER performance.

[0168] In one embodiment of the third aspect of the present disclosure, the content of iridium in the iridium-based catalyst may be 70% or more, preferably 80 to 95% by mass relative to the entire catalyst.

[0169] In one embodiment of the third aspect of the present disclosure, the content of iridium in the iridium-based catalyst can be 80%, 82%, 84%, 86%, 88%, 91%, 94% or 97% by mass relative to the catalyst as a whole, or the content of iridium is within a numerical range between any two of these. Preferably, the iridium-based catalyst comprises 80 to 95% iridium. In the above embodiment, by selecting the preferred content of iridium, the conductivity of the catalyst is further improved, thereby improving its electrocatalytic activity.

[0170] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst may contain a certain amount of oxygen. This oxygen may be introduced as impurities containing oxygen during catalyst preparation, as part of the iridium oxidation process during calcination, or as part of the catalyst's own adsorption of oxygen. The oxygen content of the catalyst surface can be determined through XPS analysis, such as by detecting Ir-O bonds or by direct oxygen detection.

[0171] In one embodiment of the third aspect of the present disclosure, the oxygen content of the iridium-based catalyst can be 2 to 16% of oxygen element by mass fraction, preferably, it can be 2%, 3%, 5%, 7%, 9%, 12%, 14% or 16%, or the content of oxygen element is within the numerical range between any two of them; preferably, the oxygen content is 2 to 16%, and more preferably, the oxygen content is 3 to 14%.

[0172] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst further comprises iridium oxide in addition to metallic iridium. In this case, the iridium-based catalyst forms a composite catalyst of metallic iridium and iridium oxide. In an XRD spectrum of the composite catalyst of iridium and iridium oxide, in addition to the characteristic peaks of elemental iridium, characteristic peaks of iridium oxide are also present.

[0173] In one embodiment of the third aspect of the present disclosure, in the composite catalyst of metallic iridium and iridium oxide, the iridium oxide is rutile iridium dioxide (crystalline iridium oxide) and / or amorphous iridium oxide.

[0174] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of elemental iridium and rutile iridium dioxide, and its XRD spectrum simultaneously contains characteristic peaks of rutile iridium dioxide and characteristic peaks of elemental iridium. Specifically, the XRD spectrum of the composite catalyst of elemental iridium and rutile iridium dioxide shows a relatively broad characteristic peak of rutile iridium dioxide ((101) crystal plane) near 2θ=34.8°, with a half-peak width of 1.5 to 2.0°, indicating that the grain size of rutile iridium dioxide is relatively small; at the same time, a sharp characteristic peak of elemental iridium ((111) crystal plane) appears near 2θ=40.8°, with a half-peak width of 0.6 to 1.2°, indicating that elemental iridium has high crystallinity.

[0175] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and rutile iridium dioxide. According to the peak area of ​​the characteristic peak of rutile iridium dioxide and the characteristic peak of elemental iridium in its XRD spectrum, the mass percentage of rutile iridium dioxide obtained by fitting is 20-80%, preferably 30-70%, and more preferably 40-65%, that is, the mass of rutile iridium dioxide accounts for 20-80% of the total mass of elemental iridium and rutile iridium dioxide, preferably 30-70%, and more preferably 40-65%. In the above embodiment, the composite structure of rutile iridium dioxide and elemental iridium can bring more electrochemical active sites, which is beneficial to the improvement of OER performance.

[0176] That is, in one embodiment of the third aspect of the present disclosure, the iridium-based catalyst comprises elemental iridium and may further comprise rutile iridium dioxide, thereby forming a composite catalyst of elemental iridium and rutile iridium dioxide. In this case, the iridium dioxide is coated on the surface of the elemental iridium to form a coated composite catalyst.

[0177] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of elemental iridium and amorphous iridium oxide, and the characteristic peaks of amorphous iridium oxide and elemental iridium are present in its XRD spectrum at the same time. Specifically, the XRD spectrum of the composite catalyst of elemental iridium and amorphous iridium oxide shows a characteristic peak with obvious peak broadening near 2θ=33.6°, and the half-peak width of the characteristic peak is 5 to 6°, preferably 5.2 to 5.6°. In the XRD spectrum of the composite catalyst of elemental iridium and amorphous iridium oxide, the characteristic peak of elemental iridium appears near 2θ=40.8°, and the half-peak width of the characteristic peak of the elemental iridium is preferably 0.6 to 1.2°.

[0178] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, wherein the content of iridium element can be 80-90% by mass relative to the entire catalyst.

[0179] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, wherein the content of iridium element relative to the catalyst as a whole can be 78%, 79%, 80%, 81%, 82%, 83%, 85%, 88% or 90% by mass fraction, or the content of iridium element is within a numerical range between any two of them, preferably, the content of iridium element in the composite catalyst is 80-90%, more preferably 80-84%. In the above embodiment, by selecting the preferred content of iridium element, it is beneficial to further optimize the composition and structure of the catalyst, improve the conductivity of the catalyst, and thus improve its electrocatalytic activity and stability.

[0180] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, wherein the oxygen content can be 6 to 16% by mass relative to the entire catalyst.

[0181] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, and the oxygen in the composite catalyst is mainly present in the form of iridium oxide (rutile iridium dioxide (crystalline iridium oxide) and / or amorphous iridium oxide). In a preferred embodiment, the oxygen content can be 6%, 7%, 9%, 11%, 14% or 18% by mass relative to the catalyst as a whole, or the content of oxygen element is within a numerical range between any two of these, preferably a mass fraction of 6 to 16%.

[0182] The iridium-based catalyst disclosed herein may contain a small amount or trace amount of other elements in addition to iridium and oxygen due to the presence of impurities in the synthetic raw materials, but these factors have no significant effect on the structural properties and catalytic performance of the final catalyst, and the present disclosure does not intend to limit the types and contents of these impurities.

[0183] In one embodiment of the third aspect of the present disclosure, the porosity of the iridium-based catalyst is greater than 40%, preferably 70-90%, 70-80%, or 75-80%. In the above embodiment, the iridium-based catalyst has a large porosity, which makes the catalyst more fluffy, which is conducive to promoting the mass transfer process.

[0184] In one embodiment of the third aspect of the present disclosure, the specific surface area of ​​the iridium-based catalyst is greater than 65 m 2 / g, preferably 70 to 95m 2 / g, 70~90m 2 / g or 70~80m 2 In the above embodiment, the iridium-based catalyst has a large specific surface area, which is beneficial to promoting the mass transfer process.

[0185] In one embodiment of the third aspect of the present disclosure, the specific surface area of ​​the micropores of the iridium-based catalyst relative to the specific surface area of ​​the entire catalyst is not more than 35%, preferably not more than 20%, more preferably not more than 15%, and further preferably not more than 10%.

[0186] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, and has a porosity of 40% or greater, preferably greater than 50%, more preferably 60-85%, and even more preferably 65-75%. In this embodiment, the composite catalyst has a large porosity, which makes the catalyst more bulky, which is beneficial to promoting mass transfer.

[0187] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, and its specific surface area is 70m 2 / g or more, preferably 70 to 90m 2 / g, more preferably 75 to 85m 2 In the above embodiment, the composite catalyst has a large specific surface area, which is beneficial to promoting the mass transfer process.

[0188] In one embodiment of the third aspect of the present disclosure, the apparent mass volume ratio of the iridium-based catalyst is 0.15 to 0.4 g / cm 3 , preferably 0.15 to 0.35 g / cm 3 , more preferably 0.20 to 0.30 g / cm 3 In one embodiment, the total pore volume of the iridium-based catalyst is 0.08 to 0.18 cm 3 / g, preferably 0.1 to 0.16 cm 3 / g. In the above embodiment, the iridium-based catalyst has a loose three-dimensional porous structure with a high degree of bulk, which is beneficial for improving the mass transfer effect and apparent activity of the catalyst, thereby improving the electrocatalytic activity of the catalyst, thereby reducing the iridium loading and usage cost of the catalyst. The total pore volume is the volume of pores with a pore size range of 2 to 200 nm as measured by the BET test. It is understandable that since the catalyst also contains macropores with a pore size greater than 200 nm, the pore volume measured here is the pore volume of the relatively small pores with a pore size of 2 to 200 nm of the catalyst.

[0189] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, and its apparent mass volume ratio is 0.18 to 0.35 g / cm 3 , preferably 0.2 to 0.3 g / cm 3 In one embodiment, the total pore volume is 0.1 to 0.2 cm 3 / g, preferably 0.1 to 0.15 cm 3 / g. In the above embodiment, the composite catalyst has a loose and porous microstructure with a high degree of bulk, which is conducive to improving the mass transfer effect of the catalyst, thereby improving the electrocatalytic activity of the catalyst, while also reducing the catalyst loading. The total pore volume is the volume of pores with a pore size range of 2 to 200 nm as measured by the BET test. It is understood that since the catalyst also contains macropores with a pore size greater than 200 nm, the pore volume measured here is the pore volume of the relatively small pores of the catalyst with a pore size of 2 to 200 nm.

[0190] In one embodiment of the third aspect of the present disclosure, the three-dimensional porous structure of the iridium-based catalyst contains continuously distributed mesopores and macropores, which is further conducive to promoting the mass transfer process, and may or may not contain micropores. For example, it contains continuously distributed mesopores and macropores with a pore size of 2 to 1000 nm, preferably 2 to 500 nm. Furthermore, the pore structure of the catalyst is basically a multi-level pore composed of mesopores and macropores, and the pore size of the mesopores and macropores is continuously distributed, so that the catalyst has a larger specific surface area, porosity and fluffiness. "Continuous distribution of pore size of mesopores and macropores" refers to a multi-level pore composed of continuous macropores (pore size 50 to 200 nm) and mesopores (pore size 2 to 50 nm) around the macropores (pore size> 200 nm), wherein "continuous" refers to the presence of pores of various pore sizes, for example, pores of various pore sizes in the range of 2 nm to 200 nm exist.

[0191] Iridium is one of the densest elements in existence. The density of metallic iridium is as high as 22.65g / cm 3 In the third aspect of the present disclosure, an amorphous iridium oxide catalyst is provided, which has the loose and porous microstructure of the third aspect of the present disclosure. In particular, the main part of the porous structure of the iridium-based catalyst in the third aspect of the present disclosure is a mesoporous and macroporous structure. Therefore, the apparent mass-to-volume ratio of the iridium-based catalyst in the third aspect of the present disclosure is much lower than the density of the above-mentioned metallic iridium, and the iridium-based catalyst in the present disclosure has the above-mentioned higher surface area. These physical properties of the iridium-based catalyst in the third aspect of the present disclosure further indicate that the catalyst in the present disclosure has a loose and porous structure.

[0192] In one embodiment of the third aspect of the present disclosure, the three-dimensional porous structure of the iridium-based catalyst is formed by connecting a plurality of nanosheets in a three-dimensional space, preferably by connecting a plurality of porous nanosheets in a three-dimensional space. Specifically, the entity part of the three-dimensional porous microstructure of the iridium-based catalyst of the present disclosure is formed by overlapping and connecting a plurality of nanosheets of flaky entities. On the one hand, the flaky nanosheets extend to form the "walls" of the pore walls of a plurality of holes. On the other hand, the flaky nanosheets overlap on other nanosheets to form a "surface" covering the holes. Thus, a plurality of different nanosheets serving as "walls" and "surfaces" overlap with each other, and the holes between the nanosheets are interconnected, thereby forming a porous microstructure, as shown in FIG19 . In the present disclosure, the existence of the pores may include cross-linked holes, through holes or blind holes, and the distribution state may include uniform or irregular distribution on the surface or inside of the material.

[0193] In one embodiment of the third aspect of the present disclosure, the three-dimensional porous structure of the present disclosure includes continuously distributed mesopores and macropores, which constitute a continuous mesopore-macroporous multi-level pore structure as a whole.

[0194] In one embodiment of the third aspect of the present disclosure, the nanosheets of the iridium-based catalyst are relatively small and thin. For example, the nanosheets are less than 500 nm in size. In a preferred embodiment, the nanosheet structure contains substantially no portion thicker than 20 nm, meaning that the nanosheet thickness does not exceed 20 nm. Preferably, the nanosheet thickness is 2 to 8 nm, and more preferably 3.5 to 6.5 nm. Therefore, these nanosheets can be referred to as two-dimensional nanosheets. The three-dimensional porous structure formed by connecting multiple two-dimensional nanosheets gives the catalyst a high porosity and bulkiness.

[0195] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst has the high catalytic activity of a nanomaterial. Furthermore, because it is a three-dimensional multi-level pore structure composed of continuously extended and connected nanosheets, with continuously distributed mesopores and macropores, and particularly contains a certain number of macropores with a pore size of 200 nm or greater, it is beneficial to improve mass transfer efficiency and apparent activity, avoid agglomeration and deactivation of the iridium-based catalyst, and improve the dispersion of the catalyst in the slurry, thereby solving the activity and stability issues of the nanomaterial, while also helping to reduce the amount of iridium-based catalyst used and improving its dispersibility. The average thickness of the nanosheets was measured using SEM and statistically analyzed using Nano Measurer 1.2 software.

[0196] In one embodiment of the third aspect of the present disclosure, the continuous nanosheets in the iridium-based catalyst are formed by a plurality of nanocrystals of elemental iridium that are closely arranged and interconnected, and the average particle size of the elemental iridium nanocrystals is 1 to 8 nm, preferably 2 to 5 nm. In the above embodiment, the grain size of elemental iridium is relatively small, and the thickness of the formed nanosheets is also relatively thin, for example, the thickness is only 2 to 8 nm, so that the internal structure of the iridium-based catalyst of the three-dimensional porous material composed of nanosheets is looser. In a preferred embodiment, the nanosheets formed by small-sized nanocrystals have a wrinkled graphene-like shape, which is beneficial to further improve the apparent activity of the catalyst. In the present disclosure, the size of the nanoparticles can be obtained by TEM testing.

[0197] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and iridium oxide, and its continuous nanosheets are formed by a plurality of iridium-based nanocrystals that are closely arranged and interconnected. The grain sizes of the iridium oxide nanocrystals and the elemental iridium nanocrystals are both relatively small. For example, the average particle size of the nanocrystals is 2 to 10 nm, preferably 2.5 to 6 nm. In the above embodiment, the grain sizes of the iridium oxide nanocrystals and the elemental iridium nanocrystals are relatively small, and the thickness of the formed nanosheets is also relatively thin, for example, the thickness is only 2 to 10 nm, so that the internal structure of the composite catalyst of iridium and iridium oxide composed of nanosheets is looser and the specific surface area is larger. In a preferred embodiment, the nanosheets formed by small-sized nanocrystals have a very rough surface, which is conducive to further improving the apparent activity of the catalyst.

[0198] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and rutile iridium dioxide, and its high-resolution scanning transmission electron micrograph has lattice fringes of rutile iridium dioxide and lattice fringes of elemental iridium. In this embodiment, the catalyst has a composite structure of small-scale, localized, high-crystallinity rutile iridium dioxide and elemental iridium, which is conducive to exposing more active centers rich in high-valence states and promoting the activity and stability of the OER.

[0199] In one embodiment of the third aspect of the present disclosure, the high-resolution transmission electron microscopy image of the iridium-based catalyst shows that the interior of the catalyst also has a continuous mesopore-macroporous three-dimensional structure, and the pore walls are composed of small-sized nanocrystals, which is beneficial to increase the electrochemical active area and promote mass transfer effects, thereby improving catalytic activity.

[0200] In one embodiment of the third aspect of the present disclosure, the XPS spectrum of the iridium-based catalyst contains characteristic peaks of elemental iridium, wherein the Ir 0 4f 7 / 2 The binding energy of the peak is 61.0 to 61.4 eV. 0 4f 7 / 2 The peak has shifted toward the high electron binding energy direction relative to the standard position (60.9 eV), for example, by 0.1 to 0.5 eV, indicating that the surface elemental iridium disclosed herein is in a relatively electron-deficient state, which is conducive to binding and adsorbing oxygen intermediates. Optionally, there is also an Ir-O peak in the XPS spectrum of the iridium-based catalyst, indicating that there is also an iridium oxide, such as an iridium oxide layer, on the surface of the catalyst. Wherein "surface layer" refers to an area with a detection depth of less than 10 nm from the outer surface of the catalyst. Specifically, the detection depth of XPS shall prevail.

[0201] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and rutile iridium dioxide, and in its XPS Ir4f spectrum, there is Ir 0 、Ir 4+ and the characteristic peaks of satellite peaks, Ir 0 4f 7 / 2 The binding energy of the peak is 61.0~61.4eV, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61.4 to 62.0 eV. In one embodiment, according to the XPS Ir4f spectrum, 4+ 4f 7 / 2 Peak and Ir 0 4f 7 / 2 The peak area fitting analysis was based on the Ir 0 and Ir 4+The total molar number of the surface Ir is taken as the basis. 4+ The molar percentage is 20 to 90%, preferably 35 to 75%, that is, the surface Ir 4+ The molar number of surface Ir 0 and Ir 4+ The ratio of the total molar number of iridium to iridium is 20-90%, preferably 35-75%. In the above embodiment, the surface layer of the composite catalyst disclosed herein is rich in high-valent iridium species, which is beneficial for balancing the activity and stability of the catalyst. The "surface layer" refers to the area with a detection depth of less than 10 nm from the outer surface of the composite catalyst. Specifically, the detection depth of XPS shall prevail.

[0202] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is a composite catalyst of iridium and amorphous iridium oxide, wherein the amorphous iridium oxide catalyst is rich in highly active Ir 4+ and Ir 3+ , which is beneficial to improving the intrinsic OER activity of the catalyst. In one embodiment of the third aspect of the present disclosure, in the XPS Ir4f spectrum of the iridium-based catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV; Ir 3+ 4f 7 / 2 The binding energy of the peak is 62-63 eV. In a preferred embodiment, the Ir 4f spectrum obtained by fitting the XPS Ir 4f spectrum of the amorphous iridium oxide catalyst is 3+ The molar percentage of Ir is 20 to 50%, preferably 25 to 40%. 3+ The ratio of the molar number of the iridium oxide to the total molar number of the Ir species is 20 to 50%, preferably 25 to 40%. This shows that the surface layer of the amorphous iridium oxide catalyst disclosed in the present invention is rich in highly active Ir 3+ , which is beneficial to improving the intrinsic OER activity of the catalyst. The "surface layer" in this disclosure refers to the area with a detection depth of less than 10nm from the outer surface of the catalyst. Specifically, it is based on the detection depth of XPS.

[0203] In the present disclosure, "doping" refers to the dispersion of actively introduced non-iridium metal elements in the bulk phase of the catalyst.

[0204] In one embodiment of the third aspect of the present disclosure, the iridium-based catalyst is undoped.

[0205] In one embodiment of the third aspect of the present disclosure, in order to further improve the performance of the catalyst, the iridium-based catalyst of the third aspect of the present disclosure is doped, and the doping elements commonly used in the art include but are not limited to Li, Na, K, and V.

[0206] A fourth aspect of the present disclosure provides a method for preparing an iridium-based catalyst, the method comprising the following steps:

[0207] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water to obtain an iridium source solution;

[0208] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0209] (3) calcining the aerogel; and

[0210] Optional (4), wherein the product of the previous step is subjected to annealing treatment;

[0211] The complexing agent is at least one selected from polycarboxylic acids having hydroxyl groups or their salts, and the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts.

[0212] In one embodiment of the fourth aspect of the present disclosure, in step (1), the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts. Preferably, the salt of each polysaccharide can be independently an alkali metal salt or an alkaline earth metal salt. More preferably, the salt of each polysaccharide can be independently an alkali metal salt.

[0213] In one embodiment of the fourth aspect of the present disclosure, the salts of the polysaccharides may be independently sodium salts, potassium salts, calcium salts, or ammonium salts.

[0214] In one embodiment of the fourth aspect of the present disclosure, in step (1), the polysaccharide is at least one selected from sodium alginate, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, sodium hyaluronate, and potassium hyaluronate.

[0215] In one embodiment of the fourth aspect of the present disclosure, in step (1), the concentration of the polysaccharide in the first sol is not particularly limited, and those skilled in the art can make an appropriate selection as needed.

[0216] In one embodiment of the fourth aspect of the present disclosure, in step (1), the iridium source precursor can use various iridium source precursors known to those skilled in the art. Preferably, the iridium source precursor is one or more selected from anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salts of chloroiridic acid, wherein the alkali metal salts of chloroiridic acid include sodium chloroiridate and potassium chloroiridate.

[0217] In one embodiment of the fourth aspect of the present disclosure, in step (1), a non-iridium metal element source precursor, an iridium source precursor, a complexing agent, and water are mixed to obtain an iridium source solution containing the non-iridium metal element. The non-iridium metal element can be the doping element described above.

[0218] In one embodiment of the fourth aspect of the present disclosure, in step (1), the complexing agent is at least one selected from polycarboxylic acids having a hydroxyl group or salts thereof.

[0219] In the present disclosure, the polycarboxylic acid having a hydroxyl group may be a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups, and a total carbon number of 3 to 10.

[0220] In one embodiment of the fourth aspect of the present disclosure, the polycarboxylic acid having a hydroxyl group has 1 to 2 hydroxyl groups. In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group has 2 to 3 carboxyl groups. In one embodiment of the present disclosure, the polycarboxylic acid having a hydroxyl group has a total carbon number of 4 to 8.

[0221] In one embodiment of the fourth aspect of the present disclosure, the polycarboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, hydroxymalonic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonic acid.

[0222] In one embodiment of the fourth aspect of the present disclosure, the salts of the polycarboxylic acids having hydroxyl groups may each independently be an alkali metal salt or an alkaline earth metal salt. More preferably, the salts of the polycarboxylic acids having hydroxyl groups may each independently be an alkali metal salt.

[0223] In one embodiment of the fourth aspect of the present disclosure, the salts of the polycarboxylic acid having a hydroxyl group may each independently be a sodium salt, a potassium salt, a calcium salt, or an ammonium salt.

[0224] In one embodiment of the fourth aspect of the present disclosure, the complexing agent is at least one selected from sodium citrate, sodium tartrate and sodium malate.

[0225] In one embodiment of the fourth aspect of the present disclosure, when preparing the iridium source solution, the pH of the solution is adjusted to 5 to 10, preferably adjusted to 6 to 10, for example, it can be adjusted to 7.5 to 9. In the present disclosure, by adjusting the pH of the iridium source solution, it is beneficial for the iridium source solution to form a uniform and stable state, and the iridium element in the iridium source solution is evenly distributed. In one embodiment of the present disclosure, the pH of the solution is adjusted using an acidic solution or an alkaline solution conventional in the art. For example, one or more of sodium carbonate solution, sodium hydroxide solution, sodium bicarbonate solution and ammonia solution can be listed.

[0226] In one embodiment of the fourth aspect of the present disclosure, in step (1), the molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, further preferably (0.25-4):1, and more preferably (0.5-2):1.

[0227] In one embodiment of the fourth aspect of the present disclosure, in step (1), by selecting the components and contents disclosed herein, it is beneficial to synthesize a more loose and porous catalyst and improve the specific surface area and stability of the catalyst.

[0228] In one embodiment of the fourth aspect of the present disclosure, in step (2), the first sol is mixed with an iridium source solution to prepare a second sol.

[0229] In one embodiment of the fourth aspect of the present disclosure, in the preparation of the second sol, the mass ratio of the polysaccharide in the first sol to the iridium source precursor in the iridium source solution is (0.1-20):1, preferably (0.2-10):1, and further preferably (0.5-4):1.

[0230] In one embodiment of the fourth aspect of the present disclosure, in step (2), the second sol is subjected to a first drying to obtain an aerogel.

[0231] In one embodiment of the fourth aspect of the present disclosure, in step (2), the first drying method is one or more selected from supercritical drying and freeze drying. In one embodiment of the present disclosure, the drying is freeze drying, and the conditions of the freeze drying include: a temperature of -30 to 10°C, preferably -30 to 0°C, more preferably -30 to -20°C, and more preferably -25 to -20°C; a time of 24 to 48 hours, preferably 36 to 48 hours. In one embodiment of the present disclosure, the drying is freeze drying, which is conducive to obtaining an aerogel with a porous structure. In the above embodiment, by making the polysaccharide in the first sol and the iridium source precursor in the iridium source solution have a specific mass ratio, it is conducive to forming a three-dimensional aerogel intermediate with a suitable structure and accurately controlling the pyrolysis process; selecting the preferred freeze drying can obtain a more stable aerogel with a porous structure. In one embodiment of the present disclosure, after freeze drying, the temperature is further raised to 10 to 40°C for drying.

[0232] In one embodiment of the fourth aspect of the present disclosure, in step (2), the aerogel preparation is different from the existing aerogel preparation method. The aerogel of the present disclosure is directly formed by drying the flowable hydrosol, and no hydrogel is formed before the aerogel is prepared.

[0233] In one embodiment of the fourth aspect of the present disclosure, in step (3), the aerogel is calcined to prepare a calcined product. In one embodiment of the present disclosure, the calcined product is the iridium-based catalyst of the present disclosure.

[0234] In one embodiment of the fourth aspect of the present disclosure, in step (3), the calcination conditions include: the calcination temperature is above 200°C and does not destroy the three-dimensional porous structure, for example, the calcination temperature can be 200-550°C, preferably 320-500°C or 220-300°C; the time is 0.5-6h, preferably 1-4h, more preferably 2-3h; the heating rate is 1-10°C / min, preferably 2-8°C / min.

[0235] In one embodiment of the fourth aspect of the present disclosure, the calcination is performed in an air atmosphere.

[0236] In one embodiment of the fourth aspect of the present disclosure, step (4) is not present in the method for preparing the iridium-based catalyst of the present disclosure. In this case, after step (3), a post-treatment step of step (3') is optionally performed; the post-treatment includes washing and / or a second drying, wherein the calcined product of step (3) is washed and / or a second drying is performed. In one embodiment of the fourth aspect of the present disclosure, step (4) is not present in the method for preparing the iridium-based catalyst of the present disclosure, and after step (3), the post-treatment step of step (3') is not performed.

[0237] In one embodiment of the fourth aspect of the present disclosure, the preparation method of the iridium-based catalyst of the present disclosure includes step (4), wherein the product of the previous step is annealed. In this case, between step (3) and step (4), a post-treatment step of step (3') is optionally performed; the post-treatment includes washing and / or a second drying, wherein the calcined product of step (3) is washed and / or a second drying, and in step (4), the product of step (3') is annealed. In one embodiment of the fourth aspect of the present disclosure, the preparation method of the iridium-based catalyst of the present disclosure includes step (4), and between step (3) and step (4), the post-treatment step of step (3') is not performed.

[0238] In one embodiment of the fourth aspect of the present disclosure, the annealing is performed in an air atmosphere.

[0239] In the present disclosure, the composition of the obtained iridium-based catalyst can be adjusted by regulating the calcination step (3) and the annealing step (4).

[0240] In one embodiment of the fourth aspect of the present disclosure, the calcination conditions include: the calcination temperature is above 200°C and does not result in the production of elemental iridium, preferably above 220°C or above 250°C and does not result in the production of elemental iridium; further preferably, the calcination temperature is 220-300°C, more preferably 250-280°C. In one embodiment of the fourth aspect of the present disclosure, the product of the previous step is not subjected to the annealing treatment of step (4). Through the calcination conditions in this embodiment, the amorphous iridium oxide catalyst of the first aspect of the present disclosure is obtained. In one embodiment of the fourth aspect of the present disclosure, after step (3), the post-treatment step of step (3') is optionally performed. In one embodiment of the fourth aspect of the present disclosure, the product of the previous step is subjected to the annealing treatment of step (4), the annealing temperature is above 200°C and does not result in the production of elemental iridium, preferably 220-300°C and does not result in the production of elemental iridium, and the annealing holding time is 0.5-2h, preferably 1-2h. The amorphous iridium oxide catalyst of the first aspect of the present disclosure is obtained by the calcination conditions and annealing conditions in this embodiment. In one embodiment of the fourth aspect of the present disclosure, between step (3) and step (4), a post-treatment step of step (3') is optionally performed. The amorphous iridium oxide catalyst of the first aspect of the present disclosure is obtained by the calcination conditions, post-treatment and annealing conditions in this embodiment.

[0241] In one embodiment of the fourth aspect of the present disclosure, the calcination conditions include: the calcination temperature is above 200°C and does not result in the production of elemental iridium, preferably above 220°C or above 250°C and does not result in the production of elemental iridium, further preferably 220-300°C, and more preferably 250-280°C. Further, the calcined product is subjected to annealing treatment in step (4), the annealing temperature is above 330°C and does not destroy the three-dimensional porous structure, preferably above 350°C and does not destroy the three-dimensional porous structure, more preferably 360-550°C, and the annealing holding time is 0.5-2h, preferably 1-2h; the microscopic three-dimensional porous structure of the material does not change significantly before and after annealing. The rutile iridium dioxide catalyst of the second aspect of the present disclosure is prepared by the calcination conditions and annealing conditions in this embodiment. In one embodiment of the fourth aspect of the present disclosure, between steps (3) and (4), a post-treatment step of step (3') is optionally performed. The rutile iridium dioxide catalyst of the second aspect of the present disclosure is prepared through the calcination conditions, post-treatment and annealing conditions in this embodiment.

[0242] In one embodiment of the fourth aspect of the present disclosure, the calcination conditions include: the calcination temperature is 320°C or above and does not destroy the three-dimensional porous structure, preferably 320-550°C, more preferably 325-420°C; and the annealing treatment of step (4) is not performed on the obtained calcined product. The iridium-based catalyst of the third aspect of the present disclosure is prepared under the calcination conditions in this embodiment, and the catalyst is an iridium metal catalyst. In one embodiment of the fourth aspect of the present disclosure, after step (3), the post-treatment step of step (3') is optionally performed. The iridium-based catalyst of the third aspect of the present disclosure is prepared under the calcination conditions and post-treatment in this embodiment, and the catalyst is an iridium metal catalyst.

[0243] In one embodiment of the fourth aspect of the present disclosure, the calcination conditions include: a calcination temperature of 320°C or higher without destroying the three-dimensional porous structure, preferably 320-500°C, more preferably 320-450°C, and more preferably 330-450°C; further, the calcined product is subjected to annealing treatment in step (4), the annealing temperature is 300°C or higher without destroying the three-dimensional porous structure, preferably 300-550°C, more preferably 300-500°C, 350-500°C or 400-500°C, and the time is 0.5-2h, preferably 1-2h; the microscopic three-dimensional porous structure of the material before and after annealing does not change significantly. Through the calcination conditions and annealing conditions in this embodiment, the iridium-based catalyst of the third aspect of the present disclosure is prepared, which is a composite catalyst of elemental iridium and iridium oxide. In one embodiment of the fourth aspect of the present disclosure, between steps (3) and (4), a post-treatment step of step (3') is optionally performed. The iridium-based catalyst of the third aspect of the present disclosure is prepared through the calcination conditions, post-treatment and annealing conditions in this embodiment. The catalyst is a composite catalyst of elemental iridium and iridium oxide.

[0244] In one embodiment of the fourth aspect of the present disclosure, the calcination conditions include: a calcination temperature of 320°C or higher without destroying the three-dimensional porous structure, preferably 320-500°C, more preferably 320-450°C, and more preferably 330-450°C; further, the calcined product is subjected to annealing treatment in step (4), the annealing temperature is 300°C or higher without destroying the three-dimensional porous structure, preferably 300-550°C, more preferably 300-500°C, 350-500°C or 400-500°C, and the time is 0.5-2h, preferably 1-2h; the microscopic three-dimensional porous structure of the material before and after annealing does not change significantly. Through the calcination conditions and annealing conditions in this embodiment, the iridium-based catalyst of the third aspect of the present disclosure is prepared, which is a composite catalyst of elemental iridium and rutile iridium dioxide. In one embodiment of the fourth aspect of the present disclosure, between steps (3) and (4), a post-treatment step of step (3') is optionally performed. The iridium-based catalyst of the third aspect of the present disclosure is prepared through the calcination conditions, post-treatment and annealing conditions in this embodiment. The catalyst is a composite catalyst of elemental iridium and rutile iridium dioxide.

[0245] As described above, in the preparation method disclosed herein, by controlling the calcination conditions in step (3) and the annealing conditions in step (4), iridium-based catalysts of different crystal forms can be prepared and their surface oxidation states can be controlled, thereby further regulating the activity and stability of the catalyst while maintaining the three-dimensional porous structure of the catalyst.

[0246] In one embodiment of the fourth aspect of the present disclosure, without the annealing step of step (4), the method further comprises a post-treatment step (3') after step (3); the post-treatment comprises washing and / or a second drying, wherein the calcined product of step (3) is washed and / or a second drying is performed.

[0247] In one embodiment of the fourth aspect of the present disclosure, in the case of the annealing step of step (4), the method further includes a post-treatment step (3') between steps (3) and (4); the post-treatment includes washing and / or a second drying, wherein the calcined product of step (3) is washed and / or a second drying is performed, and then, in step (4), the post-treated product of step (3') is annealed.

[0248] In one embodiment of the fourth aspect of the present disclosure, the washing in step (3') comprises: acid washing, water washing and alcohol washing of the calcined product of step (3).

[0249] In one embodiment of the fourth aspect of the present disclosure, the acid used for the pickling is selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. In one embodiment of the fourth aspect of the present disclosure, the solvent used for the alcohol washing is one or more selected from methanol, ethanol, and isopropanol, or at least one of them.

[0250] In one embodiment of the fourth aspect of the present disclosure, in the washing of step (3'), the order of acid washing, water washing, and alcohol washing is not particularly limited, and can be acid washing, water washing, and alcohol washing in sequence; can also be acid washing, alcohol washing, and water washing in sequence; can also be water washing, acid washing, and alcohol washing in sequence. In one embodiment of the present disclosure, in the washing of step (3'), it is preferred to carry out acid washing, water washing, and alcohol washing in sequence.

[0251] In one embodiment of the fourth aspect of the present disclosure, in step (3'), the number of times each washing solution is used for washing is not particularly limited, and those skilled in the art can appropriately select it as needed, for example, 1, 2, 3, 4 or 5 times.

[0252] In one embodiment of the fourth aspect of the present disclosure, the conditions for the second drying in step (3') include: a temperature of 40 to 60°C, preferably 45 to 55°C, and a time of 2 to 24 hours, preferably 10 to 20 hours. In the present disclosure, the washing and second drying in step (3') are sufficient to remove impurities such as inorganic salts, carbon, and metal elements remaining on the catalyst surface.

[0253] In one embodiment of the present disclosure, without the annealing step of step (4), the product obtained after the second drying is the iridium-based catalyst of the present disclosure.

[0254] In one embodiment of the present disclosure, in the case of an annealing step (4), the product after the annealing step (4) is the iridium-based catalyst of the present disclosure.

[0255] The preparation method of the fourth aspect of the present disclosure is simple and convenient, the synthesis route is green and economical, and the obtained iridium-based catalyst has a novel three-dimensional multi-level porous loose structure. The microstructure shows that the structure is composed of very thin nanosheets connected together, and has a large specific surface area. Therefore, it can have both high catalytic activity and high stability, has excellent electrochemical catalytic performance, and can be used in hydrogen production by electrolysis of water.

[0256] The fifth aspect of the present disclosure provides an iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0257] The sixth aspect of the present disclosure provides a use of the iridium-based catalyst described in the first, second or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure, in hydrogen production by electrolysis of water, wherein the use includes a membrane electrode and / or an electrolyzer.

[0258] The seventh aspect of the present disclosure provides a membrane electrode, characterized in that the membrane electrode includes a proton exchange membrane and a catalyst coated on the proton exchange membrane, and the catalyst is the iridium-based catalyst described in the first aspect, second aspect or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0259] The eighth aspect of the present disclosure provides a water electrolyzer, characterized in that the water electrolyzer includes a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is the iridium-based catalyst described in the first aspect, second aspect or third aspect of the present disclosure, or the iridium-based catalyst prepared by the method described in the fourth aspect of the present disclosure.

[0260] The iridium-based catalyst provided by the present disclosure exhibits excellent electrochemical catalytic performance when used for hydrogen production by water electrolysis, with a low initial overpotential, a low Tafel slope, and a small increase in the final overpotential after stability testing compared to the initial overpotential, showing promising prospects for industrial application. In specific embodiments of the present disclosure, the water electrolysis catalyst is used as an oxygen evolution catalyst for hydrogen production by water electrolysis, which can reduce the amount of iridium used in the membrane electrode.

[0261] In this disclosure, the directly recorded contents shall prevail first, and any other matters or issues not mentioned shall be directly applicable to the existing knowledge in the art without any change.

[0262] In general, the present invention provides the following solutions:

[0263] Scheme 1. An iridium-based catalyst characterized in that the iridium content is 70% or more, preferably 77-95% by mass, relative to the total catalyst, and the apparent mass-to-volume ratio of the catalyst is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4 g / cm 3 , further preferably not higher than 0.35g / cm 3 ;

[0264] Scheme 2. The catalyst according to Scheme 1, characterized in that the catalyst satisfies at least one of the following conditions:

[0265] The porosity of the catalyst is 40%, preferably 70-90%, more preferably 70-80%, and even more preferably 75-80%; and / or

[0266] The specific surface area of ​​the catalyst is greater than 65m 2 / g, preferably 70 to 150m 2 / g, more preferably 70 to 130m2 / g; and / or

[0267] The apparent mass volume ratio of the catalyst is 0.15 to 0.4 g / cm 3 , preferably 0.15 to 0.35 g / cm 3 , more preferably 0.20 to 0.30 g / cm 3 and / or

[0268] The total pore volume of the catalyst is 0.08 to 0.3 cm 3 / g, preferably 0.1 to 0.26 cm 3 / g; and / or

[0269] The catalyst has a three-dimensional porous structure formed by connecting multiple nanosheets in three-dimensional space, preferably the average thickness of the nanosheets does not exceed 20nm, preferably the thickness of the nanosheets is 1.5 to 8nm, more preferably 2 to 7nm;

[0270] Scheme 3. The catalyst according to Scheme 1 or 2, characterized in that the catalyst satisfies at least one of the following conditions:

[0271] In the XRD spectrum of the iridium-based catalyst, a characteristic peak exists between 2θ of 30° and 40°, preferably a characteristic peak appears near 2θ = 33.6°, and more preferably a characteristic peak appears only near 2θ = 33.6°; and / or

[0272] The half-peak width of the characteristic peak appearing near 2θ=33.6° is 5 to 6°, preferably 5.2 to 5.6°; and / or

[0273] In the XRD spectrum of the iridium-based catalyst, there is no characteristic peak of crystalline iridium oxide; and / or

[0274] In the XRD spectrum of the iridium-based catalyst, there is no characteristic peak of elemental iridium; and / or

[0275] In the XPS Ir 4f spectrum of the catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV; Ir 3+ 4f 7 / 2 The binding energy of the peak is 62 to 63 eV; and / or

[0276] The Ir 4f spectrum of the catalyst was fitted with the XPS Ir 3+ The molar percentage is 20 to 50%, preferably 25 to 40%;

[0277] Scheme 4. The catalyst according to Scheme 1 or 2, characterized in that the catalyst satisfies at least one of the following conditions:

[0278] In the XRD spectrum of the catalyst, a characteristic peak of rutile iridium dioxide appears near 2θ=34.8°;

[0279] and / or

[0280] The half-peak width of the characteristic peak of rutile iridium dioxide appearing near 2θ=34.8° is 1.5 to 3°, preferably 1.6 to 2.4°; and / or

[0281] In the XRD spectrum of the catalyst, there is no characteristic peak of elemental iridium; and / or

[0282] In the XPS Ir 4f spectrum of the catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is between 61 and 62 eV;

[0283] Scheme 5. The catalyst according to Scheme 1 or 2, characterized in that the catalyst satisfies at least one of the following conditions:

[0284] In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.7°; and / or

[0285] The half-peak width of the characteristic peak of elemental iridium appearing near 2θ=40.7° is 0.8 to 2.0°, preferably 0.85 to 1.0°;

[0286] Scheme 6. The catalyst according to Scheme 1 or 2, characterized in that the catalyst is a composite catalyst of elemental iridium and rutile iridium dioxide, and satisfies at least one of the following conditions:

[0287] In the XRD spectrum of the iridium-based catalyst, a characteristic peak of rutile iridium dioxide appears near 2θ=34.8°, and preferably the half-peak width of the characteristic peak of rutile iridium dioxide is 1.5-2.0°; and / or

[0288] In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.8°, and preferably the half-peak width of the characteristic peak of elemental iridium is 0.6 to 1.2°, and / or

[0289] In the iridium-based catalyst, the mass of rutile iridium dioxide accounts for 20 to 80% of the total mass of elemental iridium and rutile iridium dioxide, preferably 30 to 70%, and more preferably 40 to 65%; and / or

[0290] In the XPS Ir 4f spectrum of the iridium-based catalyst, Ir 0 4f 7 / 2 The binding energy of the peak is 61.0~61.4eV, Ir4+ 4f 7 / 2 The binding energy of the peak is between 61.4 and 62.0 eV; and / or

[0291] Ir on the catalyst surface 0 and Ir 4+ The total molar number of the surface Ir is taken as the basis. 4+ The molar percentage is 20 to 90%, preferably 35 to 75%;

[0292] Scheme 7. The catalyst according to Scheme 1 or 2, characterized in that the catalyst is a composite catalyst of elemental iridium and amorphous iridium oxide, and satisfies at least one of the following conditions:

[0293] In the XRD spectrum of the iridium-based catalyst, a characteristic peak of amorphous iridium oxide appears near 2θ=33.6°, and preferably the half-peak width of the characteristic peak of the amorphous iridium oxide is 5-6°, preferably 5.2-5.6°; and / or

[0294] In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.8°, and preferably the half-peak width of the characteristic peak of elemental iridium is 0.6 to 1.2°; and / or

[0295] In the XPS Ir4f spectrum of the iridium-based catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV, Ir 3+ 4f 7 / 2 The binding energy of the peak is 62 to 63 eV; and / or

[0296] Ir 3+ The ratio of the molar number of Ir to the total molar number of Ir species is 20 to 50%, preferably 25 to 40%;

[0297] Scheme 8. The catalyst according to any one of Schemes 1 to 7, wherein the catalyst satisfies at least one of the following conditions:

[0298] The content of oxygen in the catalyst as a whole may be 2-20% or 2-18% by mass, preferably 6-16% by mass; and / or

[0299] The catalyst has a three-dimensional porous structure, which is formed by multiple porous nanosheets connected in three-dimensional space;

[0300] Scheme 9. A method for preparing an iridium-based catalyst, characterized in that the preparation method comprises the following steps:

[0301] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water to obtain an iridium source solution;

[0302] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0303] (3) calcining the aerogel; and

[0304] Optional (4), wherein the product of the previous step is annealed;

[0305] Wherein, the complexing agent is at least one selected from polycarboxylic acids or salts thereof having a hydroxyl group, and the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts;

[0306] Scheme 10. The method for preparing the catalyst according to Scheme 9, characterized in that in step (1),

[0307] The polysaccharide is at least one selected from sodium alginate, sodium carboxymethyl cellulose, sodium hyaluronate, potassium alginate, potassium carboxymethyl cellulose, and potassium hyaluronate; and / or

[0308] The iridium source precursor is at least one selected from anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salt of chloroiridic acid, preferably at least one selected from sodium chloroiridate and potassium chloroiridate; and / or

[0309] The polycarboxylic acid having a hydroxyl group is a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups and a total carbon number of 3 to 10. Preferably, the polycarboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, hydroxymalonic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonic acid; the salt of the polycarboxylic acid having a hydroxyl group is a sodium salt, potassium salt, calcium salt or ammonium salt; and / or

[0310] The molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, more preferably (0.25-4):1, and more preferably (0.5-2):1; and / or

[0311] When preparing the iridium source solution, the pH of the solution is adjusted to 5 to 11, preferably to 6 to 10;

[0312] Scheme 11. The method for preparing the catalyst according to Scheme 9 or 10, characterized in that in step (2),

[0313] In the preparation of the second sol, the mass ratio of the polysaccharide in the first sol to the iridium source precursor in the iridium source solution is (0.1-20):1, preferably (0.2-10):1, and more preferably (0.5-4):1; and / or

[0314] The first drying method is one or more selected from supercritical drying and freeze drying; preferably, the drying is freeze drying, and the freeze drying conditions include: a temperature of -30 to 10°C, preferably -30 to 0°C, more preferably -30 to -20°C, and even more preferably -25 to -20°C; a time of 24 to 48 hours, preferably 36 to 48 hours, and more preferably drying at 10-40°C after freeze drying;

[0315] Scheme 12. The method for preparing the catalyst according to any one of Schemes 9 to 11, characterized in that in step (3),

[0316] The calcination conditions include: a calcination temperature of 200°C or higher, preferably 220-300°C; or a calcination temperature of 320°C or higher, preferably 320-550°C, more preferably 325-420°C;

[0317] The calcination time is 0.5 to 6 hours, preferably 1 to 4 hours, more preferably 2 to 3 hours; the heating rate is 1 to 10°C / min, preferably 2 to 8°C / min;

[0318] Scheme 13. The method for preparing a catalyst according to any one of Schemes 9 to 12, characterized in that the method further comprises a post-treatment step (3') between step (3) and step (4); the post-treatment comprises washing and / or a second drying, wherein the calcined product of step (3) is washed and / or a second drying is performed, and in step (4), the product of step (3') is annealed;

[0319] The washing comprises: performing acid washing, water washing and alcohol washing on the calcined product of step (3); preferably, the acid washing, water washing and alcohol washing are performed in sequence; preferably, the acid used in the acid washing is one or more selected from dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the solvent used in the alcohol washing is one or more selected from methanol, ethanol and isopropanol, or a mixed solvent of at least one of them and water;

[0320] The second drying conditions include: a temperature of 40 to 60°C, preferably 45 to 55°C; a time of 2 to 24 hours, preferably 10 to 20 hours;

[0321] Scheme 14. The method for preparing a catalyst according to any one of Schemes 9 to 13, characterized in that there is step (4), wherein:

[0322] The annealing temperature is 300-550°C, preferably 300-500°C, more preferably 350-500°C, and the annealing holding time is 0.5-2h, preferably 1-2h;

[0323] Scheme 15. An iridium-based catalyst prepared by the preparation method described in any one of Schemes 9-14;

[0324] Scheme 16. Use of the iridium-based catalyst according to any one of Schemes 1-8 and 15 as an anode catalyst in proton exchange membrane water electrolysis;

[0325] Solution 17. A membrane electrode, characterized in that the membrane electrode comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, wherein the catalyst is an iridium-based catalyst according to any one of Solutions 1-8 and 15;

[0326] Scheme 18. A water electrolyzer, characterized in that the water electrolyzer comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is an iridium-based catalyst described in any one of Schemes 1-8 and 15.

[0327] More specifically, one aspect of the present disclosure discloses the following scheme:

[0328] Solution 1. A water electrolysis catalyst, characterized in that the water electrolysis catalyst is a three-dimensional porous material of elemental iridium and / or iridium oxide, and its specific surface area is ≥65m 2 / g, porosity ≥40%, with mesoporous and macroporous structure;

[0329] Scheme 2. The water electrolysis catalyst according to Scheme 1, characterized in that the specific surface area of ​​the water electrolysis catalyst is 65 to 150 m 2 / g, preferably 70 to 135 m 2 / g;

[0330] Solution 3. The water electrolysis catalyst according to Solution 1, wherein the porosity of the water electrolysis catalyst is 65-90%, preferably 65-85%, and more preferably 67-80%.

[0331] Solution 4. The water electrolysis catalyst according to Solution 1, characterized in that the water electrolysis catalyst comprises a mesoporous and macroporous structure with a pore size range of 2 nm to 1000 nm, wherein the pore size range of the mesopore is 2 nm to 50 nm, and the pore size range of the macropore is greater than 50 nm, preferably 50 nm to 1000 nm, and more preferably 50 nm to 500 nm;

[0332] Solution 5. The water electrolysis catalyst according to Solution 1, wherein the iridium oxide is crystalline iridium oxide and / or amorphous iridium oxide;

[0333] Solution 6. The water electrolysis catalyst according to Solution 1, characterized in that the water electrolysis catalyst contains iridium element with a mass fraction of 75% or more, preferably contains iridium element with a mass fraction of 77-95%;

[0334] Scheme 7. The water electrolysis catalyst according to Scheme 1, characterized in that the apparent mass volume ratio of the water electrolysis catalyst is 0.15 to 0.35 g / cm 3 , preferably 0.18 to 0.27 g / cm 3 ;

[0335] Solution 8. The water electrolysis catalyst according to Solution 1, characterized in that the pore structure of the water electrolysis catalyst is formed by connecting nanosheets; the average thickness of the nanosheets constituting the pore walls of the pore structure is 1 to 10 nm, preferably 1.5 to 8 nm, and more preferably 2 to 7 nm;

[0336] Scheme 9. A method for preparing a water electrolysis catalyst, characterized in that the preparation method comprises:

[0337] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water, and adjusting the pH of the resulting mixture to 5 to 10 to obtain an iridium source solution;

[0338] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0339] (3) calcining the aerogel to obtain the water electrolysis catalyst with or without annealing the calcined product;

[0340] Wherein, the complexing agent is a polycarboxylate having a hydroxyl group, and the polysaccharide is selected from one or more of alginic acid, carboxymethyl cellulose and alkali metal salts of hyaluronic acid;

[0341] Scheme 10. The preparation method according to Scheme 9, characterized in that in step (1), the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salts of chloroiridic acid;

[0342] The complexing agent is selected from one or more alkali metal salts of citric acid, tartaric acid and malic acid;

[0343] The molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, more preferably (0.5-4):1, and more preferably (0.5-2):1;

[0344] Scheme 11. The preparation method according to Scheme 9, characterized in that in step (2), the mass ratio of the polysaccharide to the iridium source precursor in the second sol is (0.1-20):1, preferably (0.2-10):1;

[0345] The first drying includes supercritical drying and / or freeze drying, preferably freeze drying; the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours;

[0346] Scheme 12. The preparation method according to Scheme 9, characterized in that in step (3), the calcination conditions include: a calcination temperature of 200-550°C, preferably 320-500°C or 220-300°C; a calcination time of 0.5-6 hours, preferably 1-4 hours; a heating rate of 1-10°C / min, preferably 2-8°C / min;

[0347] Solution 13. The preparation method according to Solution 9, characterized in that the preparation method further includes a post-processing step, wherein the post-processing includes washing and a second drying;

[0348] The washing comprises: sequentially performing acid washing, water washing and alcohol washing on the calcined product, wherein the acid used in the acid washing is selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the alcohol used in the alcohol washing is selected from one or more of methanol, ethanol and isopropanol;

[0349] The second drying conditions include: a temperature of 40 to 60°C, preferably 45 to 55°C; a time of 2 to 24 hours, preferably 10 to 20 hours;

[0350] Scheme 14. A water electrolysis catalyst prepared by the preparation method described in any one of Schemes 9 to 13;

[0351] Scheme 15. Use of the water electrolysis catalyst according to any one of Schemes 1 to 8 and 14 as an anode catalyst in proton exchange membrane water electrolysis;

[0352] Scheme 16. A membrane electrode, characterized in that the membrane electrode comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, wherein the catalyst is the water electrolysis catalyst according to any one of Schemes 1 to 8 and 14;

[0353] Scheme 17. A water electrolyzer, characterized in that the water electrolyzer comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is the water electrolysis catalyst described in any one of Schemes 1 to 8 and 14.

[0354] Another aspect of the present disclosure discloses the following solution:

[0355] Solution 1. An iridium dioxide catalyst, characterized in that the iridium dioxide catalyst is a material having a three-dimensional porous structure, wherein the three-dimensional porous structure comprises mesopores and macropores; and the XRD spectrum of the iridium dioxide catalyst contains characteristic peaks of rutile iridium dioxide;

[0356] Option 2. The iridium dioxide catalyst according to Option 1, wherein the iridium dioxide catalyst contains iridium element at a mass fraction of 75% or more, preferably 76-84% by mass;

[0357] Option 3. The iridium dioxide catalyst according to Option 1 or 2, wherein the iridium dioxide catalyst contains 14 to 18% by mass of oxygen;

[0358] Solution 4. The iridium dioxide catalyst according to Solution 1, wherein the porosity of the iridium dioxide catalyst is 50% or more, preferably 70 to 90%;

[0359] Scheme 5. The iridium dioxide catalyst according to Scheme 1, characterized in that the specific surface area of ​​the iridium dioxide catalyst is 100 to 150 m 2 / g, preferably 110 to 130 m 2 / g;

[0360] Scheme 6. The iridium dioxide catalyst according to Scheme 1 is characterized in that the apparent mass volume ratio of the iridium dioxide catalyst is 0.2 to 0.34 g / cm 3 , preferably 0.22 to 0.3 g / cm 3 ;

[0361] Solution 7. The iridium dioxide catalyst according to Solution 1, characterized in that the three-dimensional porous structure of the iridium dioxide catalyst is formed by connecting nanosheets; the average thickness of the nanosheets constituting the pore walls of the three-dimensional porous structure is 1.5 to 6.5 nm, preferably 2 to 4.5 nm;

[0362] Scheme 8. The iridium dioxide catalyst according to Scheme 1, characterized in that in the XRD spectrum of the iridium dioxide catalyst, the half-maximum width of the main diffraction peak of rutile iridium dioxide is 1.5 to 3°, preferably 1.6 to 2.4°;

[0363] Scheme 9. A method for preparing an iridium dioxide catalyst, characterized in that the preparation method comprises:

[0364] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water, and adjusting the pH of the resulting mixture to 5 to 10 to obtain an iridium source solution;

[0365] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0366] (3) calcining the aerogel at a temperature of 200° C. or higher without generating elemental iridium;

[0367] (4) subjecting the obtained calcined product to post-treatment or not, and then subjecting the obtained calcined product to annealing treatment, wherein the annealing treatment temperature is 330° C. or higher;

[0368] Wherein, the complexing agent is a polycarboxylate having a hydroxyl group, and the polysaccharide is selected from one or more of alginic acid, carboxymethyl cellulose and alkali metal salts of hyaluronic acid;

[0369] Scheme 10. The preparation method according to Scheme 9, characterized in that in step (1), the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salts of chloroiridic acid;

[0370] The complexing agent is selected from one or more alkali metal salts of citric acid, tartaric acid and malic acid;

[0371] The molar ratio of the iridium source precursor to the complexing agent is (0.25-4):1, preferably (0.5-2):1;

[0372] Scheme 11. The preparation method according to Scheme 9, characterized in that in step (2), the mass ratio of the polysaccharide to the iridium source precursor in the second sol is (0.1-20):1, preferably (0.2-10):1;

[0373] The first drying includes supercritical drying and / or freeze drying, preferably freeze drying; the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours;

[0374] Scheme 12. The preparation method according to Scheme 9, characterized in that in step (3), the calcination conditions include: a temperature of 220-300°C, preferably 250-280°C; a time of 0.5-6 hours, preferably 2-3 hours; a heating rate of 2-10°C / min, preferably 2-5°C / min;

[0375] Scheme 13. The preparation method according to Scheme 9, characterized in that the post-treatment comprises washing the calcined product and performing a second drying;

[0376] The washing comprises: sequentially performing acid washing, water washing and alcohol washing on the calcined product, wherein the acid used in the acid washing is selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the alcohol used in the alcohol washing is selected from one or more of methanol, ethanol and isopropanol;

[0377] The second drying conditions include: a temperature of 40 to 60°C, preferably 45 to 55°C; a time of 2 to 24 hours, preferably 10 to 20 hours;

[0378] Solution 14. The preparation method according to Solution 9, characterized in that in step (4), the annealing treatment conditions include: heating the calcined product in an air atmosphere to an annealing temperature; the annealing temperature is 350° C. or higher, preferably 360° C. to 550° C., and the annealing holding time is 0.5 to 2 hours, preferably 1 to 2 hours;

[0379] Scheme 15. An iridium dioxide catalyst prepared by the preparation method described in any one of Schemes 9 to 14;

[0380] Scheme 16. Use of the iridium dioxide catalyst described in any one of Schemes 1 to 8 and 15 in PEM water electrolysis for hydrogen production;

[0381] Scheme 17. The use according to Scheme 16, characterized in that the iridium dioxide catalyst is used as an oxygen evolution catalyst for PEM water electrolysis to produce hydrogen;

[0382] Scheme 18. A membrane electrode, characterized in that the membrane electrode comprises a proton exchange membrane and an oxygen evolution catalyst layer coated on the proton exchange membrane, wherein the oxygen evolution catalyst layer comprises the iridium dioxide catalyst according to any one of Schemes 1 to 8 and 15;

[0383] Scheme 19. A water electrolyzer, characterized in that the water electrolyzer comprises an anode catalyst, and the anode catalyst is the iridium dioxide catalyst described in any one of Schemes 1 to 8 and 15.

[0384] Another aspect of the present disclosure discloses the following solution:

[0385] Solution 1. An iridium-based catalyst, characterized in that the iridium-based catalyst is a material having a three-dimensional porous structure, the iridium-based catalyst contains iridium element with a mass fraction of 80% or more; and the iridium-based catalyst has a characteristic peak of elemental iridium in its XRD spectrum;

[0386] Option 2. The iridium-based catalyst according to Option 1, wherein the iridium-based catalyst contains 80 to 95% by mass of iridium element;

[0387] Option 3. The iridium-based catalyst according to Option 1 or 2, wherein the iridium-based catalyst contains 2 to 16% by mass of oxygen.

[0388] Scheme 4. The iridium-based catalyst according to Scheme 1, characterized in that the three-dimensional porous structure comprises mesoporous and macroporous structures; and / or,

[0389] The porosity of the iridium-based catalyst is greater than 40%, preferably 70 to 90%;

[0390] Scheme 5. The iridium-based catalyst according to Scheme 1, characterized in that the specific surface area of ​​the iridium-based catalyst is greater than 65m 2 / g, preferably 70 to 95m 2 / g;

[0391] Scheme 6. The iridium-based catalyst according to Scheme 1, characterized in that the apparent mass volume ratio of the iridium-based catalyst is 0.15 to 0.35 g / cm 3 , preferably 0.20 to 0.30 g / cm 3 ;

[0392] Solution 7. The iridium-based catalyst according to Solution 1, characterized in that the three-dimensional porous structure of the iridium-based catalyst is formed by connecting nanosheets; the average thickness of the nanosheets constituting the pore walls of the three-dimensional porous structure is 2 to 8 nm, preferably 3.5 to 6.5 nm;

[0393] Scheme 8. The iridium-based catalyst according to Scheme 1, characterized in that in the XRD spectrum of the iridium-based catalyst, the half-maximum width of the (111) crystal plane diffraction peak of elemental iridium is 0.8 to 1.0°, preferably 0.85 to 1.0°, and there is no diffraction peak of crystalline iridium oxide in the XRD spectrum of the iridium-based catalyst;

[0394] Scheme 9. The iridium-based catalyst according to Scheme 1, characterized in that the XRD spectrum of the iridium-based catalyst also contains characteristic peaks of amorphous iridium oxide;

[0395] Scheme 10. The iridium-based catalyst according to Scheme 1 is characterized in that the XPS spectrum of the iridium-based catalyst contains a characteristic peak of elemental Ir and an optional characteristic peak of Ir-O, wherein the Ir of elemental iridium is 0 4f 7 / 2 The binding energy of the peak is 61.0–61.4 eV;

[0396] Scheme 11. A method for preparing an iridium-based catalyst, characterized in that the preparation method comprises:

[0397] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water, and adjusting the pH of the resulting mixture to 5 to 10 to obtain an iridium source solution;

[0398] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0399] (3) calcining the aerogel, and subjecting the obtained calcined product to a post-treatment process or not, to obtain the iridium-based catalyst; the calcination temperature is above 320° C.;

[0400] Wherein, the complexing agent in (1) is a polycarboxylate having a hydroxyl group, and the polysaccharide is selected from one or more of alginic acid, carboxymethyl cellulose and alkali metal salts of hyaluronic acid;

[0401] Scheme 12. The preparation method according to Scheme 11, characterized in that in step (1), the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salts of chloroiridic acid;

[0402] The complexing agent is selected from one or more alkali metal salts of citric acid, tartaric acid and malic acid;

[0403] The molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.5-10):1;

[0404] Scheme 13. The preparation method according to Scheme 11, characterized in that in step (2), the mass ratio of the polysaccharide to the iridium source precursor in the second sol is (0.1-20):1, preferably (0.2-10):1;

[0405] The first drying includes supercritical drying and / or freeze drying, preferably freeze drying; the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours;

[0406] Scheme 14. The preparation method according to Scheme 11, characterized in that in step (3), the calcination conditions include: a calcination temperature of 320-550°C, preferably 325-420°C; a calcination time of 0.5-6 hours, preferably 2-3 hours; a heating rate of 1-10°C / min, preferably 2-8°C / min;

[0407] Scheme 15. The preparation method according to Scheme 11, characterized in that in step (3), the post-treatment process includes washing the calcined product and performing a second drying;

[0408] The washing comprises: sequentially performing acid washing, water washing and alcohol washing on the calcined product, wherein the acid used in the acid washing is selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the alcohol used in the alcohol washing is selected from one or more of methanol, ethanol and isopropanol;

[0409] The second drying conditions include: a temperature of 40 to 60°C, preferably 45 to 55°C; a time of 2 to 24 hours, preferably 10 to 20 hours;

[0410] Scheme 16. An iridium-based catalyst prepared by the preparation method described in any one of Schemes 11 to 15;

[0411] Scheme 17. Use of the iridium-based catalyst according to any one of Schemes 1 to 10 and 16 in hydrogen production by proton exchange membrane water electrolysis;

[0412] Solution 18. A membrane electrode, characterized in that the membrane electrode comprises a proton exchange membrane and an anode catalyst layer coated on the proton exchange membrane, wherein the anode catalyst layer comprises the iridium-based catalyst according to any one of Solutions 1 to 10 and 16;

[0413] Option 19. A water electrolyzer, characterized in that the water electrolyzer includes the membrane electrode described in Option 18.

[0414] Another aspect of the present disclosure discloses the following solution:

[0415] Solution 1. A composite catalyst of iridium and iridium dioxide, characterized in that the composite catalyst of iridium and iridium dioxide is a material having a three-dimensional porous structure, and the XRD spectrum of the composite catalyst of iridium and iridium dioxide contains characteristic peaks of rutile iridium dioxide and characteristic peaks of elemental iridium;

[0416] Solution 2. The composite catalyst of iridium and iridium dioxide according to Solution 1, characterized in that the composite catalyst of iridium and iridium dioxide contains iridium element in an amount of 78% by mass or more, preferably 80% to 90% by mass.

[0417] Option 3. The composite catalyst of iridium and iridium dioxide according to Option 1 or 2, characterized in that the composite catalyst of iridium and iridium dioxide contains 6 to 16% by mass of oxygen;

[0418] Solution 4. The composite catalyst of iridium and iridium dioxide according to Solution 1, characterized in that the three-dimensional porous structure comprises mesopores and macropores; and / or the porosity of the composite catalyst of iridium and iridium dioxide is greater than 40%, preferably 60-85%, and more preferably 65-75%.

[0419] Scheme 5. The composite catalyst of iridium and iridium dioxide according to Scheme 1, characterized in that the specific surface area of ​​the composite catalyst of iridium and iridium dioxide is 70m 2 / g or more, preferably 70 to 90m 2 / g, more preferably 75 to 85m 2 / g;

[0420] Scheme 6. The composite catalyst of iridium and iridium dioxide according to Scheme 1, characterized in that the apparent mass volume ratio of the composite catalyst of iridium and iridium dioxide is 0.18 to 0.35 g / cm 3 , preferably 0.20 to 0.30 g / cm 3 ;

[0421] Solution 7. The composite catalyst of iridium and iridium dioxide according to Solution 1, characterized in that the three-dimensional porous structure of the composite catalyst of iridium and iridium dioxide is formed by connecting nanosheets; the average thickness of the nanosheets constituting the pore walls of the three-dimensional porous structure is 2 to 10 nm, preferably 4 to 7 nm;

[0422] Scheme 8. The composite catalyst of iridium and iridium dioxide according to Scheme 1 is characterized in that, in the XRD spectrum of the composite catalyst of iridium and iridium dioxide, the half-peak width of the (101) crystal plane diffraction peak of rutile iridium dioxide is 1.5 to 2.0°, and the half-peak width of the (111) crystal plane diffraction peak of elemental iridium is 0.6 to 1.2°; and / or

[0423] The mass percentage of rutile iridium dioxide is 20 to 80%, preferably 30 to 70%, relative to the total mass of elemental iridium and rutile iridium dioxide;

[0424] Scheme 9. The composite catalyst of iridium and iridium dioxide according to Scheme 1, characterized in that the XPS Ir4f spectrum of the composite catalyst of iridium and iridium dioxide contains typical Ir 0 and Ir 4+ The peaks of Ir 0 and Ir 4+ Based on the total molar number of Ir 4+ The molar percentage is 20 to 90%, preferably 35 to 75%;

[0425] Scheme 10. A method for preparing a composite catalyst of iridium and iridium dioxide, characterized in that the preparation method comprises:

[0426] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water, and adjusting the pH of the resulting mixture to 5 to 10 to obtain an iridium source solution;

[0427] (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel;

[0428] (3) calcining and post-treating the aerogel, wherein the calcination temperature is 320 to 500° C.;

[0429] (4) annealing the product obtained by the post-treatment, wherein the annealing temperature is above 300° C.;

[0430] Wherein, the complexing agent is a polycarboxylate having a hydroxyl group, and the polysaccharide is selected from one or more of alginic acid, carboxymethyl cellulose and alkali metal salts of hyaluronic acid;

[0431] Scheme 11. The preparation method according to Scheme 10, characterized in that in step (1), the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salts of chloroiridic acid;

[0432] The complexing agent is selected from one or more alkali metal salts of citric acid, tartaric acid and malic acid;

[0433] The molar ratio of the iridium source precursor to the complexing agent is (0.25-4):1, preferably (0.5-2):1;

[0434] Scheme 12. The preparation method according to Scheme 10, characterized in that in step (2), the mass ratio of the polysaccharide to the iridium source precursor in the second sol is (0.1-20):1, preferably (0.2-10):1;

[0435] The first drying includes supercritical drying and / or freeze drying, preferably freeze drying; the freeze drying conditions include: temperature of -30 to -20°C, preferably -25 to -20°C; time of 24 to 48 hours, preferably 36 to 48 hours;

[0436] Scheme 13. The preparation method according to Scheme 10, characterized in that in step (3), the calcination conditions include: a temperature of 320-450°C, preferably 330-450°C; a time of 0.5-6 hours, preferably 2-3 hours; a heating rate of 2-10°C / min, preferably 2-5°C / min;

[0437] Solution 14. The preparation method according to Solution 10, characterized in that the post-treatment includes washing the calcined product and a second drying; the washing includes: sequentially performing acid washing, water washing, and alcohol washing on the calcined product, the acid used in the acid washing being selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid, and acetic acid, and the alcohol used in the alcohol washing being selected from one or more of methanol, ethanol, and isopropanol;

[0438] The second drying conditions include: a temperature of 40 to 60°C, preferably 45 to 55°C; a time of 2 to 24 hours, preferably 10 to 20 hours;

[0439] Scheme 15. The preparation method according to Scheme 10, characterized in that in step (4), the annealing conditions include: heating the product obtained by post-treatment in an air atmosphere to an annealing temperature; the annealing temperature is 300-550°C, preferably 350-500°C, and the time is 0.5-2 hours, preferably 1-2 hours;

[0440] Scheme 16. A composite catalyst of iridium and iridium dioxide prepared by the preparation method described in any one of Schemes 10 to 15;

[0441] Scheme 17. Use of the composite catalyst of iridium and iridium dioxide according to any one of Schemes 1 to 9 and 16 in hydrogen production by PEM water electrolysis;

[0442] Scheme 18. The use according to Scheme 17, characterized in that the composite catalyst of iridium and iridium dioxide is used as an oxygen evolution catalyst for PEM water electrolysis to produce hydrogen;

[0443] Scheme 19. A membrane electrode, characterized in that the membrane electrode comprises a proton exchange membrane and an oxygen evolution catalyst layer coated on the proton exchange membrane, wherein the oxygen evolution catalyst layer comprises the composite catalyst of iridium and iridium dioxide according to any one of Schemes 1 to 9 and 16;

[0444] Scheme 20. A water electrolyzer, characterized in that the water electrolyzer comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is a composite catalyst of iridium and iridium dioxide as described in any one of Schemes 1 to 9 and 16.

[0445] Example

[0446] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby. Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure were purchased from commercial sources and are pure reagents; the relevant reagents can be prepared into water or alcohol solutions of a certain concentration for subsequent use.

[0447] Instrumental method for BET analysis: The model of the fully automatic BET specific surface area tester is JW-BK200C produced by Jingwei Gaobo. The test conditions include: the test principle is the static capacity method, the adsorption gas is N2, the adsorption temperature is 77K, the N2 adsorption and desorption curve of the catalyst is obtained by test, the multi-point BET specific surface area is obtained by analysis and calculation, the pore volume and pore size distribution are obtained by BJH method analysis, and the micropore analysis adopts the slit pore HK method.

[0448] Porosity calculation: Porosity = 100% × Pore Volume / (Pore Volume + Solid Volume), where the pore volume is determined based on the BET test, with a pore size range of 2 to 200 nm. This means the measured pore volume is the pore volume of all pores with a pore size between 2 and 200 nm. The solid volume is calculated based on the mass and density of the catalyst. The solid volume of the catalyst is determined by dividing the iridium content analyzed by XRF by the density. It is understood in the art that since the catalyst also contains macropores with a pore size greater than 200 nm, and the BET test pore size range is 2 to 200 nm, the pore volume measured here is the pore volume of the relatively smaller pores with a pore size between 2 and 200 nm. The calculated porosity is also the minimum porosity of the catalyst.

[0449] In the present disclosure, the apparent mass volume ratio is also called the apparent density, which refers to the ratio of the actual mass of the catalyst to the apparent volume. The apparent volume refers to the sum of the actual volume of the catalyst and the closed pore volume. The specific method for determining the apparent mass volume is as follows: the catalyst is sieved, and a catalyst with a particle size of 15 μm or less is selected as a sample. The sample is naturally placed in a precision graduated cylinder with a scale to 1-2 ml, and the volume value is read as the apparent volume. More specifically, the sample is poured freely into a precision graduated cylinder with a scale to 1-2 ml, the graduated cylinder is vertically tilted and slightly shaken so that its upper surface is parallel to the scale line, and the volume value is read as the apparent volume. For details, reference can be made to the determination method of loose bulk density in GB / T 13566.1-2008. Thus, the apparent mass volume ratio can be calculated, and the apparent mass volume ratio is measured three times and the average value is taken.

[0450] Instrumental method for mass transfer performance testing: A typical three-electrode system was used, and the constant current test was performed using a CHI760E electrochemical workstation. CV activation and stabilization were first performed, and non-wetted bubbles on the electrode surface were removed. Then, a constant current test was performed. A high-speed industrial camera was used to capture the bubbles generated on the electrode surface during the test.

[0451] Instrumental method for testing iridium content: A Rigaku Priums IV X-ray fluorescence spectrometer (XRF) was used. The catalyst was pressed into pellets for full elemental analysis. Light elements such as C, H, and O were analyzed using more precise C, H, and O elemental analyzers. Prior to testing, the catalyst was not pretreated to remove water, oxygen, or other adsorption media in a vacuum.

[0452] X-ray diffraction (XRD) was used to analyze the phase and ratio of elemental iridium and iridium oxide in the catalyst bulk phase in the disclosed Examples and Comparative Examples. X-ray diffraction (XRD) analysis was performed using a Shimadzu XRD-6000 X-ray diffractometer. Test conditions included: tube voltage of 40 kV, tube current of 40 mA, Cu target Kα radiation, a 2θ scan range of 5°-80°, and a scan rate of 5° / min. The main peak was analyzed using the analyze half-width function in Jade 6.5 software.

[0453] SEM was used to analyze the morphological characteristics of the catalyst, the thickness of the nanosheets and the size of the nanoparticles, and Nano Measurer 1.2 software was used for statistical analysis. The instrument, method and conditions for the SEM analysis were as follows: the scanning electron microscope (SEM) was a Hitachi S-4800 scanning electron microscope with an operating voltage of 5 kV-20 kV and equipped with energy dispersive X-ray spectroscopy (EDS).

[0454] TEM was used to analyze the catalyst's micromorphology and nanoparticle size. The following instruments, methods, and conditions were used: a JEM-2100 high-resolution transmission electron microscope (HRTEM) (JEOL Ltd.) at an accelerating voltage of 200 kV; and a JEOL ARM 200F spherical aberration-corrected scanning transmission electron microscope (CS-STEM) at an accelerating voltage of 200 kV, equipped with energy-dispersive X-ray spectroscopy (EDS). Analyses were performed using the accompanying DigitalMicrograph 3.9.1 software.

[0455] XPS was used to analyze the element types and contents of the catalyst surface layer. The instrument, method, and conditions for XPS analysis were as follows: an ESCALab220i-XL X-ray electron spectrometer equipped with Avantage V5.926 software produced by VG Scientific was used as the X-ray photoelectron spectrometer. The X-ray photoelectron spectrometer test conditions were as follows: the excitation source was monochromatic A1Kα X-ray with a power of 330 W, and the basic vacuum during the analysis was 3×10 -9 In addition, the electron binding energy was calibrated using the C1s peak of elemental carbon (284.8 eV) using CasaXPS 2.3.25PR 1.0.

[0456] Example 1-1

[0457] (1) Weighing 0.8 g of sodium alginate and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; weighing appropriate amounts of IrCl3 and sodium citrate and dissolving them in ultrapure water to obtain a mixture having a molar ratio of IrCl3 to sodium citrate of 0.8:1, and then adjusting the pH of the mixture to 7.5 to obtain a uniform and stable iridium source solution;

[0458] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 4:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -20°C for 40 hours until the sol becomes an aerogel with a porous structure;

[0459] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 280°C for 2.5 hours with a heating rate of 5°C / min to obtain a calcined product; the calcined product was naturally cooled to room temperature, and the cooled calcined product was centrifuged and washed several times in a mixed solution of dilute hydrochloric acid, ultrapure water and ethanol water until the pH of the supernatant was neutral, and then placed in a vacuum drying oven for a second drying at a temperature of 50°C and a time of 12 hours. Catalyst I-1 was collected and labeled as I-C1. Its composition is shown in Table I-1.

[0460] The total pore volume of catalyst I-C1 prepared in this example is 0.227 cm 3 / g, and a specific surface area of ​​134.1m 2 / g, and the apparent mass volume ratio is 0.187g / cm 3 The specific surface area of ​​the micropores accounts for 20.1% of the specific surface area of ​​the entire catalyst.

[0461] The SEM image of catalyst I-C1 prepared in this example is shown in Figure 1, the XRD spectrum is shown in Figure 2, the TEM image is shown in Figure 3, the BET diagram is shown in Figure 4, the XPS spectrum of Ir 4f is shown in Figure 5, and the cyclic voltammetry spectrum is shown in Figure 6; the bubble discharge diagram when catalyst I-C1 is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 7.

[0462] According to Table I-1 and Figure 1, catalyst I-C1 has a three-dimensional porous structure composed of continuous wrinkled graphene-like nanosheets, and the three-dimensional porous structure is rich in a continuous mesopore-macroporous hierarchical pore structure, wherein the hierarchical pore structure includes macropores greater than 200 nm and continuously distributed 2-50 nm mesopores and 50-200 nm macropores surrounding the macropores; wherein the "surface" of the translucent thin layer with pores covering the pores and the pore walls of the internal pores are both formed by interconnecting a plurality of sheet-like entities of wrinkled graphene-like nanosheets, that is, the nanosheets with pores are connected, and the nanosheets are composed of a plurality of interconnected nanoparticles, the average particle size of the nanoparticles is 2.1 nm, and the thickness of the nanosheets is only 2.5 nm, indicating that catalyst I-C1 has a loose and porous microstructure and a large porosity and specific surface area, which is beneficial to improving the mass transfer effect and apparent electrochemical activity of the catalyst, while reducing the amount of catalyst used.

[0463] FIG2 shows that the XRD spectrum of catalyst I-C1 exhibits a characteristic peak of amorphous iridium oxide with obvious peak broadening at 2θ=33.6°, but no characteristic peak of elemental iridium appears, and the half-width of the main peak is 5.48°.

[0464] Figure 3 shows that catalyst I-C1 has a composite structure of long-range disorder and short-range order, which is beneficial for providing a large number of coordinatively unsaturated active sites and improving catalytic activity and stability.

[0465] Figure 4 shows that the three-dimensional porous structure of catalyst I-C1 is rich in macropores and mesopores, and the pore size distribution is uniform and continuous, and the pore size distribution curve has no obvious peaks.

[0466] Figure 5 shows that catalyst I-C1 has obvious Ir4f in the high-resolution XPS spectrum. 4+ and Ir 3+ The characteristic peaks of Ir 4+ 4f 7 / 2 The peak binding energy is 61~62eV, Ir 3+ 4f 7 / 2 The peak binding energy is between 62 and 63 eV, and the Ir 4f spectrum obtained by XPS fitting is 3+ The molar percentage is 25-35%, indicating that the catalyst surface is rich in highly active Ir 3+ , which is beneficial to improving the intrinsic OER activity of the catalyst.

[0467] Figure 6 shows that in the cyclic voltammetry curve, catalyst I-C1 has an obvious redox peak in the potential range of 0.8V~1.0Vvs.RHE (Ir 3+ / Ir 4+ ), rich in Ir 3+ Active components, a clear redox peak appears in the potential range of 1.2V~1.4V vs.RHE (Ir 4+ / Ir 5+ ); meanwhile, the peak current and area are larger, indicating that catalyst I-C1 has more active sites, which is beneficial to improving its electrochemical activity.

[0468] Figure 7 shows that the bubbles on the electrode surface of catalyst I-C1 during the reaction are very small and easily desorbed from the electrode surface, indicating that catalyst I-C1 has a good mass transfer effect, which is conducive to maintaining a high oxygen evolution performance at a high current density.

[0469] FIG37 shows the isothermal adsorption-desorption curve of catalyst I-C1. From this curve, the ratio of the specific surface area of ​​the micropores to the specific surface area of ​​the entire catalyst can be calculated.

[0470] Figure 38 shows low-magnification STEM images of catalyst I-C1 at different angles. It can be seen that the catalyst has abundant macropores >50 nm, especially macropores of different sizes >200 nm, reflecting a very small mass-to-volume ratio and a large porosity.

[0471] Figure 39 shows high-magnification STEM images of catalyst I-C1 at different angles. It can be seen that the catalyst has a rich pore structure of different sizes ranging from 1 to 100 nm, reflecting a large porosity and specific surface area.

[0472] Example I-2

[0473] The same as Example I-1, except that the catalyst I-C1 prepared in Example I-1 was further heated to 280°C in a muffle furnace in an air atmosphere with a certain flow rate for annealing. The annealing time was 2 hours and the heating rate was 3°C / min. Catalyst 2 was finally collected and labeled as I-C2. Its composition is shown in Table I-1.

[0474] Example I-3

[0475] (1) Weighing 0.8 g of sodium carboxymethyl cellulose and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; taking an appropriate amount of chloroiridic acid solution and dispersing it in a solution containing sodium tartrate, wherein the molar ratio of chloroiridic acid to sodium tartrate in the obtained mixture is 1:1, and then adjusting the pH of the mixture to 6.5 to obtain an iridium source solution;

[0476] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 0.5:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -25°C for 45 hours until the sol becomes an aerogel with a porous structure;

[0477] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate and calcined at 300°C for 2 hours at a heating rate of 3°C / min to obtain a calcined product. The calcined product was naturally cooled to room temperature and centrifuged and washed several times in dilute hydrochloric acid, deionized water, and a mixed solution of ethanol and water until the pH of the supernatant was neutral. The product was then placed in a vacuum drying oven for a second drying at a temperature of 50°C for 14 hours. Catalyst I-3 was collected and labeled as I-C3. The composition of the catalyst is shown in Table I-1.

[0478] Comparative Example I-1

[0479] The same method as Example I-1 was used, except that the first sol was not used. The IrCl3 complex solution prepared in step (1) was directly oven-dried. The iridium precursor powder was then placed in a muffle furnace in an air atmosphere with a constant flow rate and calcined at 280°C for 2.5 hours at a heating rate of 5°C / min. Comparative catalyst 1 was finally collected and labeled I-D1. The composition of the catalyst is shown in Table I-1. SEM results of I-D1 showed that the catalyst did not have a loose three-dimensional porous structure.

[0480] Comparative Example I-2

[0481] Commercial iridium oxide (product number TEC77100, purchased from TANAKA, amorphous) was used as comparative catalyst I-2, labeled I-D2, and its composition is shown in Table I-1.

[0482] The SEM image of comparative catalyst I-D2 is shown in Figure 8, the cyclic voltammetry curve is shown in Figure 9, and the bubble discharge diagram when coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 10.

[0483] FIG8 shows that the commercial iridium oxide catalyst is composed of relatively large nanoparticles aggregated with each other. The interior of the material is relatively compact, without a loose porous structure and without a significant mesoporous-macroporous structure.

[0484] Figure 9 shows that the peak current and peak area of ​​comparative catalyst I-D2 are significantly smaller than those of I-C1 prepared in Example I-1 under the same loading, scan rate and potential range, indicating that I-D2 has fewer electrochemical active sites.

[0485] Figure 10 shows that the bubbles on the electrode surface of I-D2 during the reaction are large and the bubbles are not easy to desorb from the electrode surface, indicating that I-D2 has poor mass transfer effect, which is not conducive to maintaining high oxygen evolution performance at high current density.

[0486] Figure 40 shows high-magnification STEM images of catalyst I-D2 at different angles. It can be seen that the catalyst is composed of small-particle nanocrystal stacking, has no obvious three-dimensional macroporous-mesoporous structure, and does not have the porous characteristics of catalyst I-C1 disclosed in the present invention.

[0487] Table I-1 Structural characteristics of catalysts prepared in different embodiments and comparative examples

[0488] From the data in Table I-1 above, it can be seen that the electrolytic water catalysts prepared in Examples I-1 to I-3 have a three-dimensional multi-level pore structure, a large specific surface area and porosity, a small apparent mass-to-volume ratio and a high fluffiness, and are rich in Ir 3+Active species. This water electrolysis catalyst has high mass transfer efficiency and conductivity, maintaining high catalytic activity while also having excellent stability. When used for hydrogen production from water electrolysis, it can reduce the amount of catalyst used. The comparative catalysts provided in Comparative Examples I-1 and I-2 lack a three-dimensional porous structure and high fluffiness, requiring a relatively high catalyst loading to achieve similar performance.

[0489] Test Examples I-1-1 to I-1-5

[0490] Test Examples I-1 to I-5 are used to compare and illustrate the electrochemical performance of the catalysts prepared according to the first embodiment of the present disclosure.

[0491] The catalysts prepared in Examples I-1 to I-3 of the present disclosure and the comparative catalysts prepared in Comparative Examples I-1 to I-2 were used as oxygen evolution catalysts, and the electrochemical catalytic oxygen evolution performance was evaluated using the following test method. The electrochemical workstation model is PARSTAT3000A-DX, and the rotating disk electrode model is 636A. A three-electrode system was adopted, with a saturated calomel electrode (SCE) protected by a double salt bridge as the reference electrode, a high-purity graphite rod as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H2SO4 solution. The catalyst to be tested was ultrasonically uniformly dispersed in a mixed solution of isopropanol, water, and Nafion, and dropped onto the surface of the glassy carbon electrode. After natural drying, the working electrode was obtained, and the catalyst loading was 0.38 mg / cm 2 The test temperature was 22-25°C. Oxygen was introduced for at least 30 minutes before the test to saturate the solution with oxygen. The rotation speed was 2500 rpm. The scan range of the cyclic voltammetry curve was 0 V to 1.20 V vs. SCE at a scan rate of 100 mV / s. The scan range of the linear polarization curve was 0.80 V to 1.4 V vs. SCE at a scan rate of 5 mV / s. The stability test scan range was 1.29 V to 1.54 V vs. RHE at a scan rate of 100 mV / s, and the number of scan cycles was 10,000. The test results are shown in Table 2.

[0492] Table I-2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0493] It can be seen from the data in Table I-2 above that compared with the comparative catalysts I-D1 to I-D2, the iridium element in the catalysts I-C1 to I-C3 is basically in the form of amorphous iridium oxide. When the catalysts I-C1 to I-C3 are used for electrolysis of water to produce hydrogen, the battery 2 and 50mA / cm 2The catalysts I-C1 to I-C3 prepared in the present embodiment have excellent acidic electrochemical oxygen evolution activity and high stability. Furthermore, the catalysts have a continuously distributed mesoporous and macroporous structure composed of connected nanosheets, which can prevent catalyst aggregation and deactivation. The catalysts have a high degree of fluffiness, which greatly reduces the amount of catalyst used while achieving higher catalytic activity, providing important reference for achieving high-performance low-iridium loading applications.

[0494] Example II-1

[0495] (1) Weighing 0.8 g of sodium alginate and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; weighing appropriate amounts of IrCl3 and sodium citrate and dissolving them in ultrapure water to obtain a mixture having a molar ratio of IrCl3 to sodium citrate of 0.8:1, and then adjusting the pH of the mixture to 7.5 to obtain a uniform and stable iridium source solution;

[0496] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 4:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -20°C for 40 hours until the sol becomes an aerogel with a porous structure;

[0497] (3) The aerogel is placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 280°C for 2.5 hours with a heating rate of 5°C / min to obtain a calcined product; the calcined product is naturally cooled to room temperature, and the cooled calcined product is centrifuged and washed several times in a mixed solution of dilute hydrochloric acid, ultrapure water and ethanol water until the pH of the supernatant is neutral, and then placed in a vacuum drying oven for a second drying at a temperature of 50°C and a time of 12 hours, and the second dried product is collected.

[0498] (4) The second dried product was placed in a muffle furnace and heated to an annealing temperature in an air atmosphere at a certain flow rate for annealing treatment. The annealing temperature was 360°C, the annealing holding time was 1.5 h, and the heating rate was 3°C / min. Catalyst II-1 was collected and labeled as II-C1. Its composition is shown in Table II-1.

[0499] The total pore volume of catalyst II-C1 prepared in this example is 0.212 cm 3 / g, and a specific surface area of ​​118.2m 2 / g, and the apparent mass volume ratio is 0.235g / cm 3 .

[0500] An SEM image of catalyst II-C1 prepared in this example is shown in Figure 11, where the right image is an enlarged view of the white box area in the left image; an XRD spectrum is shown in Figure 12, an XPS spectrum of Ir 4f is shown in Figure 13, and a cyclic voltammogram is shown in Figure 14. A diagram of bubble discharge when catalyst II-C1 is coated on carbon paper to prepare an electrode for water electrolysis is shown in Figure 15.

[0501] Table II-1 and Figure 11 show that Catalyst II-C1 has a three-dimensional porous structure composed of continuous, wrinkled graphene-like nanosheets. This three-dimensional porous structure is rich in a continuous, mesopore-macropore hierarchical pore structure with minimal micropore content. The pore-bearing, translucent "surface" covering the pores and the pore walls within the pores are both formed by interconnecting multiple, sheet-like, wrinkled graphene-like nanosheets. In other words, the nanosheets are composed of interconnected, porous nanosheets. The nanosheets are composed of interconnected, small-sized iridium dioxide nanocrystals with an average grain size of 3.4 nm, resulting in a nanosheet thickness of only 3.8 nm. This indicates that Catalyst II-C1 has a loose, porous microstructure with a high porosity and specific surface area, which improves the catalyst's mass transfer efficiency and apparent electrochemical activity while reducing catalyst usage. Comparison with the SEM image of the unannealed material shows that the pore structure characteristics of the unannealed SEM image of Catalyst II-C1 are retained after annealing.

[0502] Figure 12 shows that the XRD spectrum of catalyst II-C1 shows a characteristic peak of rutile iridium dioxide with a broadened peak at 2θ = 34.8°, but no characteristic peak of elemental iridium appears. The half-width of the main peak is 2.18°, which is relatively wide, indicating that the grain size is small, which can bring more electrochemical active sites and is beneficial to the improvement of OER performance.

[0503] Figure 13 shows that catalyst II-C1 has obvious Ir 4f in the high-resolution XPS spectrum. 4+ and satellite peaks, but no Ir 3+ The characteristic peaks of Ir 4+ 4f 7 / 2 The peak binding energy is 61-62 eV, indicating that the surface of catalyst II-C1 is rich in high-valent Ir 4+ , which is beneficial to improving the stability of the catalyst. The "surface layer" refers to the area with a detection depth of less than 10nm from the outer surface of the catalyst. Specifically, it is based on the detection depth of XPS.

[0504] Figure 14 shows that in the cyclic voltammetry curve, catalyst II-C1 has an obvious redox peak in the potential range of 0.8V~1.0Vvs.RHE (Ir 3+ / Ir 4+), a clear redox peak appears in the potential range of 1.2V~1.4V vs.RHE (Ir 4+ / Ir 5+ ); At the same time, the peak current and area are larger, indicating that catalyst II-C1 has more active sites, which is beneficial to improving its electrochemical activity.

[0505] Figure 15 shows that the bubbles on the electrode surface of catalyst II-C1 during the reaction are very small and easily desorbed from the electrode surface, indicating that catalyst II-C1 has a good mass transfer effect, which is conducive to maintaining a high oxygen evolution performance at a high current density.

[0506] Example II-2

[0507] The same as Example II-1, the only difference is that in step (4), the annealing temperature is 480°C, the holding time is 2h, and finally the catalyst II-2 is collected and marked as II-C2. Its composition is shown in Table II-1.

[0508] Example II-3

[0509] (1) Weighing 0.8 g of sodium carboxymethyl cellulose and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; taking an appropriate amount of chloroiridic acid solution and dispersing it in a solution containing sodium tartrate, wherein the molar ratio of chloroiridic acid to sodium tartrate in the obtained mixture is 1:1, and then adjusting the pH of the mixture to 6.5 to obtain an iridium source solution;

[0510] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 0.5:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -25°C for 45 hours until the sol becomes an aerogel with a porous structure;

[0511] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 300°C for 2 hours with a heating rate of 3°C / min to obtain a calcined product. The calcined product was naturally cooled to room temperature, and the cooled calcined product was centrifuged and washed several times in dilute hydrochloric acid, ultrapure water, and ethanol-water mixed solutions until the pH of the supernatant was neutral. The product was then placed in a vacuum drying oven for a second drying at a temperature of 50°C for 14 hours, and the product after the second drying was collected.

[0512] (4) The second dried product was placed in a muffle furnace and heated to an annealing temperature in an air atmosphere with a certain flow rate for annealing treatment. The annealing temperature was 420°C, the holding time was 1 hour, and the heating rate was 6°C / min. Catalyst II-3 was collected and labeled as II-C3. Its composition is shown in Table II-1.

[0513] Comparative Example II-1

[0514] The same as Example II-1, except that: the first sol is not used, and the IrCl3 complex solution prepared in step (1) is directly oven-dried; the prepared iridium precursor powder is then placed in a muffle furnace in an air atmosphere with a certain flow rate and calcined at 280°C for 2.5 hours at a heating rate of 5°C / min, and then washed and dried to obtain a second dried product; in step (4), the second dried product is annealed in an air atmosphere at 360°C for 1.5 hours at a heating rate of 3°C / min, and collected to obtain a comparative catalyst II-1, labeled II-D1, whose composition is shown in Table II-1. The SEM results of catalyst II-D1 show that it does not have a loose three-dimensional porous structure.

[0515] Comparative Example II-2

[0516] Commercial rubidium dioxide (purchased from Alfa, product number A17849) was used as comparative catalyst II-2, labeled as II-D2, and its composition is shown in Table II-1.

[0517] The SEM image of comparative catalyst II-D2 is shown in Figure 16, the cyclic voltammogram is shown in Figure 17, and the bubble discharge diagram when coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 18.

[0518] Figure 16 shows that the commercial rutile iridium dioxide catalyst is a polyhedral block. The interior of the material is relatively compact, does not have a loose porous structure, and does not have a significant mesoporous-macroporous structure.

[0519] Figure 17 shows that the peak current and peak area of ​​II-D2 are significantly smaller than those of C1 prepared in Example 1 under the same loading, scan rate and potential range, indicating that D2 has fewer electrochemical active sites.

[0520] Figure 18 shows that the bubbles on the electrode surface of II-D2 during the reaction are large and not easy to desorb from the electrode surface, indicating that II-D2 has poor mass transfer effect, which is not conducive to maintaining high oxygen evolution performance at high current density.

[0521] Table II-1 Structural characteristics of catalysts prepared in different examples and comparative examples

[0522] As can be seen from the data in Table II-1 above, the iridium dioxide catalysts prepared in Examples II-1 to II-3 have a three-dimensional porous structure, and the three-dimensional porous structure contains mesopores and macropores, which gives the catalyst a large specific surface area and porosity while also having a small apparent mass volume ratio and a very high fluffiness. When the iridium dioxide catalyst is used for electrolysis of water to produce hydrogen, it has a high mass transfer effect and conductivity, maintains high catalytic activity while having excellent stability, and the porous structure can reduce the amount of catalyst used. The comparative catalysts provided in Comparative Examples II-1 to II-2 do not have a three-dimensional porous structure and high fluffiness, and a relatively large catalyst loading is required to achieve similar performance.

[0523] Test Examples II-1 to II-5

[0524] The catalysts prepared in Examples II-1 to II-3 of the present disclosure and the comparative catalysts prepared in Comparative Examples II-1 to II-2 were used as oxygen evolution catalysts, and the electrochemical catalytic oxygen evolution performance was evaluated using the following test method. The electrochemical workstation model is PARSTAT3000A-DX, and the rotating disk electrode model is 636A. A three-electrode system was adopted, with a saturated calomel electrode (SCE) protected by a double salt bridge as the reference electrode, a high-purity graphite rod as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H2SO4 solution. The catalyst to be tested was ultrasonically uniformly dispersed in a mixed solution of isopropanol, water, and Nafion, and dropped onto the surface of the glassy carbon electrode. After natural drying, the working electrode was obtained, and the catalyst loading was 0.38 mg / cm 2 The test temperature was 22-25°C. Oxygen was introduced for at least 30 minutes before testing to saturate the solution with oxygen. The rotation speed was 1600 rpm. The cyclic voltammetry curve was scanned from 0 V to 1.20 V vs. SCE at a scan rate of 100 mV / s. The linear polarization curve was scanned from 0.80 V to 1.4 V vs. SCE at a scan rate of 5 mV / s. The stability test scanned from 1.29 V to 1.54 V vs. RHE at a scan rate of 100 mV / s for 10,000 cycles. The test results are shown in Table II-2.

[0525] Table II-2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0526] From the data in Table II-2 above, it can be seen that compared with the comparative catalysts II-D1 to II-D2, when catalysts II-C1 to II-C3 are used for electrolysis of water to produce hydrogen, the battery is 2 and 50mA / cm 2The catalysts II-C1 to II-C3 prepared in the present embodiments exhibited excellent acidic electrochemical oxygen evolution activity and high stability, with a lower initial overpotential and Tafel slope. Furthermore, the catalysts exhibited excellent acidic electrochemical oxygen evolution activity and high stability. Importantly, the catalysts possessed high fluffiness, which prevented catalyst aggregation and deactivation. This significantly reduced catalyst usage while achieving higher catalytic activity, providing valuable insights for achieving high-performance low-iridium-loading applications.

[0527] Example III-1

[0528] (1) Weighing 0.8 g of sodium alginate and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; weighing appropriate amounts of IrCl3 and sodium citrate and dissolving them in ultrapure water to obtain a mixture having a molar ratio of IrCl3 to sodium citrate of 0.8:1, and then adjusting the pH of the mixture to 7.5 to obtain a uniform and stable iridium source solution;

[0529] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 4:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -20°C for 40 hours until the sol becomes an aerogel with a porous structure;

[0530] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 330°C for 2.5 hours with a heating rate of 8°C / min to obtain a calcined product; the calcined product was naturally cooled to room temperature, and the cooled calcined product was centrifuged and washed several times in a mixed solution of dilute hydrochloric acid, ultrapure water and ethanol water until the pH of the supernatant was neutral, and then placed in a vacuum drying oven for a second drying at a temperature of 50°C and a time of 12 hours. Catalyst III-1 was collected and labeled as III-C1. Its composition is shown in Table III-1.

[0531] The total pore volume of catalyst III-C1 prepared in this example is 0.117 cm 3 / g, with a specific surface area of ​​72.7m 2 / g, and the apparent mass volume ratio is 0.26g / cm 3 The specific surface area of ​​the micropores accounts for 15.2% of the specific surface area of ​​the entire catalyst.

[0532] The SEM image of catalyst III-C1 prepared in this example is shown in Figure 19, the XRD spectrum is shown in Figure 20, the TEM image is shown in Figure 21, the BET diagram is shown in Figure 22, the XPS spectrum of Ir4f is shown in Figure 23, and the bubble discharge diagram when catalyst III-C1 is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 24.

[0533] According to Table III-1 and Figure 19, catalyst III-C1 has a three-dimensional porous microstructure composed of continuous nanosheets, which is rich in mesopores and macropores and has very little micropores. The "surface" of the translucent thin layer with pores covering the pores and the pore walls of the internal pores are both formed by interconnected nanosheets of multiple sheet-like entities, that is, they are composed of interconnected nanosheets with pores, and the nanosheets are composed of interconnected nanocrystals of multiple elemental iridium. The average grain size of the elemental iridium nanocrystals is 3.5 nm, and the average thickness of the nanosheets is only 4 nm, indicating that catalyst III-C1 has a loose three-dimensional porous microstructure and a large porosity and specific surface area, which is beneficial to improving the mass transfer effect and apparent electrochemical activity of the catalyst, while reducing the amount of catalyst used.

[0534] Figure 20 shows that the XRD spectrum of catalyst III-C1 has an obvious characteristic peak of elemental iridium at 2θ = 40.7°, and no characteristic peak of crystalline iridium oxide appears. The half-peak width of the characteristic peak of elemental iridium is 0.979°, indicating that the grain size of elemental iridium is small, which is beneficial to enhancing the conductivity of the catalyst and improving the OER performance.

[0535] Figure 21 is a transmission electron microscope image of the iridium-based catalyst III-C1. It can be clearly seen that the interior of the catalyst also has a continuous mesoporous-macroporous three-dimensional structure. At the same time, the nanosheets that constitute the pore walls are composed of small-sized elemental iridium nanocrystals that are interconnected, which corresponds well to the SEM image. This is conducive to increasing the electrochemical active area and promoting mass transfer effects, thereby improving catalytic activity.

[0536] Figure 22 shows that the three-dimensional porous structure of catalyst III-C1 is rich in macropores and mesopores, and the pore size distribution is uniform and continuous, and the pore size distribution curve has no obvious peaks.

[0537] Figure 23 shows that the Ir 4f characteristic peaks of catalyst III-C1 show obvious characteristic peaks of elemental iridium and Ir-O peaks of slight surface oxidation. 0 4f 7 / 2 Peak, the Ir 0 4f 7 / 2 The peak shifted by 0.3 eV relative to the standard position (60.9 eV) toward higher electron binding energies, indicating that the surface iridium of catalyst C1 is relatively electron-deficient, which is beneficial for promoting oxygen evolution in acidic water electrolysis. The "surface" refers to the region less than 10 nm deep from the catalyst's outer surface, specifically based on the XPS detection depth.

[0538] Figure 24 shows that the bubbles on the electrode surface of catalyst III-C1 during the reaction are very small and easily desorbed from the electrode surface, indicating that catalyst III-C1 has a good mass transfer effect, which is conducive to maintaining a high oxygen evolution performance at a high current density.

[0539] Example III-2

[0540] The same as Example III-1, the only difference is that: in step (3), the aerogel is placed in a muffle furnace and calcined at 400°C for 2.5h with a heating rate of 4°C / min. Finally, catalyst III-2 is collected and labeled as III-C2. Its composition is shown in Table III-1.

[0541] The XRD pattern of catalyst III-C2 prepared in this example is shown in Figure 25, and the cyclic voltammogram is shown in Figure 26.

[0542] Figure 25 shows that the XRD spectrum of catalyst III-C2 has an obvious characteristic peak of elemental iridium at 2θ = 40.7°, and a slight characteristic peak of amorphous iridium oxide at 2θ = 33.8°. The half-peak width of the characteristic peak of elemental iridium is 1.013°.

[0543] Figure 26 shows that in the cyclic voltammetry curve, catalyst III-C2 has a redox peak in the potential range of 0.4V to 0.6V vs. RHE (Ir 0 / Ir 3+ ), a clear redox peak appears in the potential range of 0.8V~1.0Vvs.RHE (Ir 3+ / Ir 4+ ), a clear redox peak appears in the potential range of 1.2V~1.4V vs.RHE (Ir 4+ / Ir 5+ ); At the same time, the peak area is larger, indicating that catalyst III-C2 has more active sites, which is beneficial to improving its electrochemical activity.

[0544] Example III-3

[0545] (1) Weighing 0.8 g of sodium alginate and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; taking an appropriate amount of chloroiridic acid solution and dispersing it in a solution containing sodium tartrate, wherein the molar ratio of chloroiridic acid to sodium tartrate in the obtained mixture is 8:1, and then adjusting the pH of the mixture to 6.5 to obtain an iridium source solution;

[0546] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 0.5:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -25°C for 45 hours until the sol becomes an aerogel with a porous structure;

[0547] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate and calcined at 370°C for 2 hours at a heating rate of 8°C / min to obtain a calcined product. The calcined product was naturally cooled to room temperature and centrifuged and washed several times in a mixed solution of dilute hydrochloric acid, ultrapure water, and ethanol water until the pH of the supernatant was neutral. The product was then placed in a vacuum drying oven for a second drying at a temperature of 50°C for 14 hours. Catalyst III-3 was collected and labeled as III-C3. The composition of the catalyst is shown in Table III-1.

[0548] The XRD pattern of catalyst III-C3 prepared in this example is shown in Figure 27.

[0549] Figure 27 shows that the XRD spectrum of catalyst III-C3 shows an obvious characteristic peak of elemental iridium at 2θ = 40.7°, and an obvious characteristic peak of amorphous iridium oxide at 2θ = 33.8°. The half-peak width of the characteristic peak of elemental iridium is 1.939°, indicating that the size of the nanoparticles is smaller.

[0550] Comparative Example III-1

[0551] The same as Example III-1, except that the first sol was not used, and the IrCl3 complex solution prepared in step (1) was directly oven-dried. The prepared iridium precursor powder was then placed in a muffle furnace in an air atmosphere with a constant flow rate and calcined at 330°C for 2.5 hours at a heating rate of 5°C / min. Comparative catalyst III-1 was finally collected and labeled as III-D1. Its composition is shown in Table III-1. SEM test results show that III-D1 does not have a three-dimensional porous structure.

[0552] Comparative Example III-2

[0553] Commercial iridium black was used as comparative catalyst 2, marked as III-D2, and purchased from Alfa Company, product number 010746.

[0554] Table III-1 Structural characteristics of catalysts prepared in different examples and comparative examples

[0555] As can be seen from the data in Table III-1 above, compared to the prior art, the iridium-based catalysts prepared in Examples III-1 to III-3 have a three-dimensional porous structure, contain iridium elements at a mass fraction of 80% or more, have a porosity greater than 75%, and simultaneously exhibit a significantly lower apparent mass-to-volume ratio, a very high bulkiness, and a large specific surface area. This iridium-based catalyst exhibits high mass transfer efficiency and conductivity, maintaining high catalytic activity while also exhibiting excellent stability. This allows for reduced catalyst usage when used in hydrogen production from water electrolysis. The comparative catalysts provided in Comparative Examples III-1 to III-2, however, lack the three-dimensional porous structure and high bulkiness, requiring a relatively high catalyst dosage to achieve comparable catalytic performance.

[0556] Test Examples III-1 to III-4

[0557] The iridium-based catalysts prepared in Examples III-1 to III-3 of the present disclosure and the comparative catalyst prepared in Comparative Example III-1 were used as oxygen evolution catalysts, and the electrochemical catalytic oxygen evolution performance was evaluated using the following test method. The electrochemical workstation model is PARSTAT3000A-DX, and the rotating disk electrode model is 636A. A three-electrode system was adopted, with a saturated calomel electrode (SCE) protected by a double salt bridge as the reference electrode, a high-purity graphite rod as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H2SO4 solution or a 0.1M HClO4 solution. The catalyst to be tested was ultrasonically uniformly dispersed in a mixed solution of isopropanol, water and Nafion, dropped onto the surface of the glassy carbon electrode, and naturally dried to obtain a working electrode. The catalyst loading was 0.38 mg / cm 2 The test temperature was 20-25°C. Oxygen was introduced for at least 30 minutes before testing to saturate the solution with oxygen. The rotation speed was 2500 rpm. The cyclic voltammetry curve was scanned from 0 V to 1.20 V vs. SCE at a scan rate of 100 mV / s. The linear polarization curve was scanned from 0.80 V to 1.4 V vs. SCE at a scan rate of 5 mV / s. The stability test scanned from 1.29 V to 1.54 V vs. RHE at a scan rate of 100 mV / s for 10,000 cycles. The test results are shown in Table III-2.

[0558] Table III-2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0559] It can be seen from the data in Table III-2 above that, compared with the comparative catalyst III-D1, when catalysts III-C1 to III-C3 are used for electrolysis of water to produce hydrogen, the battery 2 and 50mA / cm 2The catalysts III-C1 to III-C3 prepared in the present embodiments exhibited a smaller initial overpotential and a lower Tafel slope. The final overpotential after stability testing showed a smaller increase than the initial overpotential, demonstrating that they exhibited superior acidic electrochemical oxygen evolution activity and increased stability. Furthermore, the catalysts disclosed herein possess a three-dimensional porous structure composed of interconnected nanosheets and exhibited a high degree of bulkiness, which prevents catalyst aggregation and deactivation. This significantly reduces catalyst usage while achieving higher catalytic activity, enabling high-performance applications with low iridium loadings.

[0560] Test Example III-5

[0561] The catalytic performance of the commercial iridium black of III-D2 was tested under the same conditions as test examples III-1 to III-4. The results showed that the catalysts III-C1 to III-C3 prepared in the embodiments of the present disclosure had lower overpotential and lower Tafel slope than III-D2 overall; and the stability test results showed that the overpotential of the commercial iridium black increased by more than 70 mV compared with before the test, and its stability was far inferior to that of the catalysts III-C1 to III-C3 prepared in the embodiments of the present disclosure. This shows that since the catalyst prepared in the embodiments of the present disclosure has a three-dimensional porous structure formed by connected nanosheets, the stability of the catalyst is significantly improved while improving the catalytic activity.

[0562] Figure 28 shows the bubble discharge during the water electrolysis reaction using commercial iridium black, tested under the same conditions as Example III-1. The figure shows that bubbles on the electrode surface of the commercial iridium black are significantly larger during the reaction, and bubbles do not easily desorb from the electrode surface, indicating that III-D2 has poor mass transfer efficiency, which is not conducive to maintaining high oxygen evolution performance at high current densities.

[0563] Example IV-1

[0564] (1) Weighing 0.8 g of sodium alginate and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; weighing appropriate amounts of IrCl3 and sodium citrate and dissolving them in ultrapure water to obtain a mixture having a molar ratio of IrCl3 to sodium citrate of 0.8:1, and then adjusting the pH of the mixture to 7.5 to obtain a uniform and stable iridium source solution;

[0565] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 4:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -20°C for 40 hours until the sol becomes an aerogel with a porous structure;

[0566] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 360°C for 2.5 hours with a heating rate of 5°C / min to obtain a calcined product; the calcined product was naturally cooled to room temperature, and the cooled calcined product was centrifuged and washed several times in a mixed solution of dilute hydrochloric acid, ultrapure water and ethanol water until the pH of the supernatant was neutral, and then placed in a vacuum drying oven for a second drying at a temperature of 50°C and a time of 12 hours, and the post-processed product was collected.

[0567] (4) The product obtained by post-treatment was placed in a muffle furnace and heated to the annealing temperature in an air atmosphere with a certain flow rate for annealing treatment. The annealing temperature was 360°C, the annealing holding time was 1.5 hours, and the heating rate was 3°C / min. Catalyst IV-1 was collected and labeled as IV-C1. Its composition is shown in Table IV-1.

[0568] The total pore volume of catalyst IV-C1 prepared in this example is 0.135 cm 3 / g, with a specific surface area of ​​80.5m 2 / g, and the apparent mass volume ratio is 0.253g / cm 3 .

[0569] The SEM image of catalyst IV-C1 prepared in this example is shown in Figure 29, the XRD spectrum is shown in Figure 30, the XPS spectrum of Ir 4f is shown in Figure 31, the cyclic voltammogram is shown in Figure 32, and the bubble discharge diagram when catalyst IV-C1 is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 33.

[0570] According to Table IV-1 and Figure 29, catalyst IV-C1 has a three-dimensional porous microstructure composed of continuous nanosheets, which is rich in continuous mesopores and macropores and has very little micropore content. The "surface" covering the pores and the pore walls of the internal pores are both formed by interconnecting rough nanosheets of multiple sheet-like entities with pores, that is, they are composed of interconnected nanosheets with pores, and the nanosheets are composed of multiple iridium dioxide nanocrystals and elemental iridium nanocrystals interconnected. The average grain size of the iridium dioxide nanocrystals and the elemental iridium nanocrystals is 2.5 to 6 nm, and the thickness of the formed nanosheets is only 4 to 7 nm, indicating that catalyst IV-C1 has a loose three-dimensional porous microstructure and a large porosity and specific surface area, which is beneficial to improving the mass transfer effect and apparent electrochemical activity of the catalyst, while reducing the amount of catalyst used.

[0571] Figure 30 shows that the XRD spectrum of catalyst IV-C1 shows a characteristic peak of rutile iridium dioxide with a broadened peak near 2θ = 34.8°, with a half-peak width of 1.881°. The half-peak width is relatively wide, indicating that the grain size of rutile iridium dioxide is relatively small; at the same time, a sharp characteristic peak of elemental iridium appears near 2θ = 40.8°, with a half-peak width of 0.796°, indicating that elemental iridium has a relatively high crystallinity; the mass percentage of rutile iridium dioxide obtained according to peak fitting is 41.5%, which is beneficial to improving OER activity and stability.

[0572] Figure 31 shows that catalyst IV-C1 has obvious Ir 4f in the high-resolution XPS spectrum. 0 、Ir 4+ and the characteristic peaks of satellite peaks, Ir 0 4f 7 / 2 The binding energy of the peak is 61.0~61.4eV, Ir 4+ 4f 7 / 2 The peak binding energy is 61.4~62.0eV; according to the peak fitting results, the surface Ir 4+ Account for Ir 0 、Ir 4+ The molar percentage of the total amount is 66.2%. The "surface layer" refers to the region with a depth of less than 10 nm from the outer surface of the composite catalyst, specifically, the detection depth of XPS. In the above embodiment, the surface layer of the catalyst is rich in high-valent iridium species, which is conducive to balancing the activity and stability of the catalyst.

[0573] Figure 32 shows that in the cyclic voltammetry curve, catalyst IV-C1 has an obvious redox peak in the potential range of 0.8V~1.0Vvs.RHE (Ir 3+ / Ir 4+ ), a clear redox peak appears in the potential range of 1.2V~1.4V vs.RHE (Ir 4+ / Ir 5+ ); At the same time, the peak current and area are larger, indicating that catalyst IV-C1 has more active sites, which is beneficial to improving its electrochemical activity.

[0574] Figure 33 shows that the bubbles on the electrode surface of catalyst IV-C1 during the reaction are very small and easily desorbed from the electrode surface, indicating that catalyst IV-C1 has a good mass transfer effect, which is conducive to maintaining a high oxygen evolution performance at a high current density.

[0575] Example IV-2

[0576] The same as Example IV-1, the only difference is that in step (4), the annealing temperature is 480°C, the holding time is 2h, and finally the catalyst IV-2 is collected and marked as IV-C2. Its composition is shown in Table IV-1.

[0577] Example IV-3

[0578] (1) Weighing 0.8 g of sodium carboxymethyl cellulose and dissolving it in ultrapure water to prepare a 0.8 wt% first sol; taking an appropriate amount of chloroiridic acid solution and dispersing it in a solution containing sodium tartrate, wherein the molar ratio of chloroiridic acid to sodium tartrate in the obtained mixture is 1:1, and then adjusting the pH of the mixture to 6.5 to obtain an iridium source solution;

[0579] (2) adding the iridium source solution to the first sol, stirring and dispersing the solution uniformly to obtain a second sol, wherein the mass ratio of the polysaccharide to the iridium source precursor in the second sol is 0.5:1; placing the second sol in a freeze drying oven for freeze drying at a temperature of -25°C for 45 hours until the sol becomes an aerogel with a porous structure;

[0580] (3) The aerogel was placed in a muffle furnace in an air atmosphere with a certain flow rate, and calcined at 340°C for 2 hours with a heating rate of 3°C / min to obtain a calcined product. The calcined product was naturally cooled to room temperature, and the cooled calcined product was centrifuged and washed several times in dilute hydrochloric acid, ultrapure water, and ethanol-water mixed solutions until the pH of the supernatant was neutral. The product was then placed in a vacuum drying oven for a second drying at a temperature of 50°C for 14 hours, and the post-treatment product was collected.

[0581] (4) The product obtained by post-treatment was placed in a muffle furnace and heated to the annealing temperature in an air atmosphere with a certain flow rate for annealing treatment. The annealing temperature was 420°C, the holding time was 1 hour, and the heating rate was 6°C / min. Catalyst IV-3 was collected and labeled as IV-C3. Its composition is shown in Table IV-1.

[0582] Comparative Example IV-1

[0583] The same as Example IV-1, except that: the first sol is not used, and the IrCl3 complex solution prepared in step (1) is directly oven-dried; the prepared iridium precursor powder is then placed in a muffle furnace in an air atmosphere with a certain flow rate and calcined at 360°C for 2.5 hours at a heating rate of 5°C / min, and then washed and dried to obtain a second dried product; in step (4), the second dried product is annealed in an air atmosphere at 360°C for 1.5 hours at a heating rate of 3°C / min, and collected to obtain comparative catalyst IV-1, labeled IV-D1, whose composition is shown in Table IV-1. SEM results of catalyst IV-D1 show that it does not have a three-dimensional porous structure.

[0584] Comparative Example IV-2

[0585] Commercial rutile iridium dioxide (purchased from Alfa, product number 043396) was used as comparative catalyst IV-2, labeled as IV-D2, and its composition is shown in Table IV-1.

[0586] The SEM image of the commercial rutile iridium dioxide is shown in Figure 34, the cyclic voltammogram is shown in Figure 35, and the bubble discharge diagram when it is coated on carbon paper to prepare an electrode for water electrolysis reaction is shown in Figure 36.

[0587] FIG34 shows that the commercial rutile iridium dioxide catalyst is a polyhedral block without a significant mesoporous-macroporous structure.

[0588] Figure 35 shows that the peak current and peak area of ​​the commercial rutile iridium dioxide catalyst are significantly smaller than those of IV-C1 prepared in Example 1 under the same loading, scan rate and potential range, indicating that IV-D2 has fewer electrochemical active sites.

[0589] Figure 36 shows that the commercial rutile iridium dioxide catalyst has large bubbles on the electrode surface during the reaction and is not easy to desorb from the electrode surface, indicating that it has poor mass transfer effect and is not conducive to maintaining high oxygen evolution performance at high current density.

[0590] Table IV-1 Structural characteristics of catalysts prepared in different embodiments and comparative examples

[0591] As can be seen from the data in Table IV-1 above, the composite catalysts of iridium and iridium dioxide prepared in Examples IV-1 to IV-3 have a three-dimensional porous structure, with a large specific surface area and porosity while also having a small apparent mass-to-volume ratio and a very high fluffiness. When used for hydrogen production by electrolysis of water, the composite catalysts of iridium and iridium dioxide have a high mass transfer effect and conductivity, maintain high catalytic activity while also having excellent stability. At the same time, the porous structure can reduce the amount of catalyst used. The comparative catalysts provided in Comparative Examples IV-1 to IV-2 do not have a three-dimensional porous structure and high fluffiness, and a relatively large catalyst loading is required to achieve similar performance.

[0592] Test Examples IV-1 to IV-4

[0593] The catalysts prepared in Examples IV-1 to IV-3 of the present disclosure and the comparative catalyst prepared in Comparative Example IV-1 were used as oxygen evolution catalysts, and the electrochemical catalytic oxygen evolution performance was evaluated using the following test method. The electrochemical workstation model is PARSTAT3000A-DX, and the rotating disk electrode model is 636A. A three-electrode system was adopted, with a saturated calomel electrode (SCE) protected by a double salt bridge as the reference electrode, a high-purity graphite rod as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions was a 0.5M H2SO4 solution. The catalyst to be tested was ultrasonically uniformly dispersed in a mixed solution of isopropanol, water and Nafion, dropped onto the surface of the glassy carbon electrode, and naturally dried to obtain a working electrode. The catalyst loading was 0.38 mg / cm 2 The test temperature was 22-25°C. Oxygen was passed through the solution for at least 30 minutes before the test to saturate the solution with oxygen. The rotation speed was 1600 rpm. The scan range of the cyclic voltammetry curve was 0 V to 1.20 V vs. SCE, and the scan rate was 100 mV / s. The scan range of the linear polarization curve was 0.80 V to 1.45 V vs. SCE, and the scan rate was 5 mV / s. The scan range of the stability test was 1.29 V to 1.54 V vs. RHE, the scan rate was 100 mV / s, and the number of scan cycles was 10,000. The test results are shown in Table IV-2.

[0594] Table IV-2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0595] It can be seen from the data in Table IV-2 above that compared with the comparative catalyst IV-D1, when catalysts IV-C1 to IV-C3 are used for electrolysis of water to produce hydrogen, the battery 2 and 50mA / cm 2 The catalysts IV-C1 to IV-C3 prepared in the present embodiments exhibited excellent acidic electrochemical oxygen evolution activity and high stability, with a lower initial overpotential and Tafel slope. The catalysts exhibited excellent acidic electrochemical oxygen evolution activity and high stability. Importantly, the catalysts exhibited high fluffiness, which prevented catalyst aggregation and deactivation. This significantly reduced catalyst usage while achieving higher catalytic activity, providing valuable insights for achieving high-performance low-iridium-loading applications.

[0596] The catalytic performance of commercial rutile iridium dioxide of comparative example IV-2 was tested under the same conditions as in test examples IV-1 to IV-4. The results showed that the catalytic performance of commercial rutile iridium dioxide of comparative example IV-2 was 10 mA / cm 2The overpotential is greater than 430 mV, the Tafel slope is about 90 mV / dec, and the stability test results show that the overpotential increases by nearly 30 mV, indicating that its catalytic activity and stability are far inferior to those of catalysts IV-C1 to IV-C3 prepared in the embodiments of the present disclosure.

[0597] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0598] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0599] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. An iridium-based catalyst, characterized in that The catalyst comprises elemental iridium and optionally iridium oxide. The iridium content is 70% or more by mass, preferably 80-95%, more preferably 80-90%, relative to the entire catalyst. The apparent mass-to-volume ratio of the catalyst is not higher than 0.55 g / cm 3 , preferably not higher than 0.45g / cm 3 , further preferably not higher than 0.4g / cm 3 , further preferably not higher than 0.35g / cm 3 .

2. The catalyst according to claim 1, characterized in that The catalyst satisfies at least one of the following conditions: The porosity of the catalyst is 40%, preferably 70-90%, more preferably 70-80%, and even more preferably 75-80%; and / or The specific surface area of ​​the catalyst is greater than 65m 2 / g, preferably 70 to 95m 2 / g, more preferably 70 to 90m 2 / g, more preferably 70 to 80m 2 / g; and / or The apparent mass volume ratio of the catalyst is 0.15 to 0.4 g / cm 3 , preferably 0.15 to 0.35 g / cm 3 , more preferably 0.20 to 0.30 g / cm 3 and / or The total pore volume of the catalyst is 0.08 to 0.18 cm 3 / g, preferably 0.1 to 0.16 cm 3 / g; and / or The catalyst has a three-dimensional porous structure formed by connecting multiple nanosheets in three-dimensional space. Preferably, the average thickness of the nanosheets does not exceed 20 nm, preferably the thickness of the nanosheets is 2 to 8 nm, and more preferably 3.5 to 6.5 nm.

3. The catalyst according to claim 1 or 2, characterized in that The catalyst satisfies at least one of the following conditions: In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.7°; and / or The half-value width of the characteristic peak appearing near 2θ=40.7° is 0.8 to 2.0°, preferably 0.85 to 1.0°.

4. The catalyst according to any one of claims 1 to 3, characterized in that The iridium-based catalyst comprises rutile iridium dioxide, thereby forming a composite catalyst of elemental iridium and rutile iridium dioxide, wherein: In the XRD spectrum of the iridium-based catalyst, a characteristic peak of rutile iridium dioxide appears near 2θ=34.8°, and preferably the half-peak width of the characteristic peak of rutile iridium dioxide is 1.5-2.0°; and / or In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.8°, and preferably the half-peak width of the characteristic peak of elemental iridium is 0.6 to 1.2°; and / or In the iridium-based catalyst, the mass of rutile iridium dioxide accounts for 20 to 80% of the total mass of elemental iridium and rutile iridium dioxide, preferably 30 to 70%, and more preferably 40 to 65%; and / or In the XPS Ir 4f spectrum of the iridium-based catalyst, Ir 0 4f 7 / 2 The binding energy of the peak is 61.0~61.4eV, Ir 4+ 4f 7 / 2 The binding energy of the peak is between 61.4 and 62.0 eV; and / or Ir on the catalyst surface 0 and Ir 4+ The total molar number of the surface Ir is taken as the basis. 4+ The molar percentage is 20 to 90%, preferably 35 to 75%.

5. The catalyst according to any one of claims 1 to 3, characterized in that The iridium-based catalyst comprises amorphous iridium oxide, thereby forming a composite catalyst of elemental iridium and amorphous iridium oxide, wherein: In the XRD spectrum of the iridium-based catalyst, a characteristic peak of amorphous iridium oxide appears near 2θ=33.6°, and preferably the half-peak width of the characteristic peak of the amorphous iridium oxide is 5-6°, preferably 5.2-5.6°; and / or In the XRD spectrum of the iridium-based catalyst, a characteristic peak of elemental iridium appears near 2θ=40.8°, and preferably the half-peak width of the characteristic peak of elemental iridium is 0.6 to 1.2°; and / or In the XPSIr4f spectrum of the iridium-based catalyst, Ir 4+ 4f 7 / 2 The binding energy of the peak is 61-62 eV, Ir 3+ 4f 7 / 2 The binding energy of the peak is 62 to 63 eV; and / or Ir 3+ The ratio of the molar number of iodine to the total molar number of Ir species is 20 to 50%, preferably 25 to 40%.

6. The catalyst according to any one of claims 1 to 5, characterized in that The catalyst satisfies at least one of the following conditions: The content of oxygen in the catalyst as a whole may be 2 to 16% or 3 to 14% by mass, preferably 6 to 16% by mass; and / or The catalyst has a three-dimensional porous structure, which is formed by multiple porous nanosheets connected in three-dimensional space.

7. A method for preparing an iridium-based catalyst, characterized in that: The preparation method comprises the following steps: (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent, and water to obtain an iridium source solution; (2) mixing the first sol with the iridium source solution to form a second sol; and subjecting the second sol to a first drying to obtain an aerogel; (3) calcining the aerogel; and Optional (4), wherein the product of the previous step is annealed; The complexing agent is at least one selected from polycarboxylic acids having hydroxyl groups or their salts, and the polysaccharide is at least one selected from alginic acid and its salts, carboxymethyl cellulose and its salts, and hyaluronic acid and its salts.

8. The method for preparing the catalyst according to claim 7, characterized in that: In step (1), The polysaccharide is at least one selected from sodium alginate, sodium carboxymethyl cellulose, sodium hyaluronate, potassium alginate, potassium carboxymethyl cellulose, and potassium hyaluronate; and / or The iridium source precursor is at least one selected from anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, iridium acetylacetonate, iridium acetate and alkali metal salt of chloroiridic acid, preferably at least one selected from sodium chloroiridate and potassium chloroiridate; and / or The polycarboxylic acid having a hydroxyl group is a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups and a total carbon number of 3 to 10. Preferably, the polycarboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, hydroxymalonic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonic acid; the salt of the polycarboxylic acid having a hydroxyl group is a sodium salt, potassium salt, calcium salt or ammonium salt; and / or The molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, more preferably (0.25-4):1, and more preferably (0.5-2):1; and / or When preparing the iridium source solution, the pH of the solution is adjusted to 5-11, preferably 6-10.

9. The method for preparing the catalyst according to claim 7 or 8, characterized in that: In step (2), In the preparation of the second sol, the mass ratio of the polysaccharide in the first sol to the iridium source precursor in the iridium source solution is (0.1-20):1, preferably (0.2-10):1, and more preferably (0.5-4):1; and / or The first drying method is one or more selected from supercritical drying and freeze drying; preferably, the drying is freeze drying, and the freeze drying conditions include: a temperature of -30 to 10°C, preferably -30 to 0°C, more preferably -30 to -20°C, and even more preferably -25 to -20°C; a time of 24 to 48 hours, preferably 36 to 48 hours, and more preferably heating to 10 to 40°C for drying after freeze drying.

10. The method for preparing a catalyst according to any one of claims 7 to 9, characterized in that: In step (3), The calcination conditions include: a calcination temperature of 200° C. or higher, preferably 320-550° C., more preferably 325-420° C.; a calcination time of 0.5-6 h, preferably 1-4 h, more preferably 2-3 h; and a heating rate of 1-10° C. / min, preferably 2-8° C. / min.

11. The method for preparing a catalyst according to any one of claims 7 to 10, characterized in that: The method further comprises a post-treatment step (3') between step (3) and the optional step (4); the post-treatment comprises washing and / or a second drying, wherein the calcined product of step (3) is washed and / or second dried, and the product of step (3') is annealed in the optional step (4); The washing comprises: performing acid washing, water washing and alcohol washing on the calcined product of step (3); preferably, the acid washing, water washing and alcohol washing are performed in sequence; preferably, the acid used in the acid washing is one or more selected from dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, and the solvent used in the alcohol washing is one or more selected from methanol, ethanol and isopropanol, or a mixed solvent of at least one of them and water; The second drying conditions include: a temperature of 40 to 60° C., preferably 45 to 55° C.; and a time of 2 to 24 hours, preferably 10 to 20 hours.

12. The method for preparing a catalyst according to any one of claims 7 to 11, characterized in that: There is step (4), where The annealing temperature is 300 to 550° C., preferably 300 to 500° C., more preferably 350 to 500° C., and the annealing holding time is 0.5 to 2 hours, preferably 1 to 2 hours.

13. An iridium-based catalyst prepared by the preparation method according to any one of claims 7 to 12.

14. Use of the iridium-based catalyst according to any one of claims 1 to 6 and 13 as an anode catalyst in proton exchange membrane water electrolysis.

15. A membrane electrode, characterized in that: The membrane electrode comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, wherein the catalyst is the iridium-based catalyst according to any one of claims 1 to 6 and 13.

16. A water electrolyzer, characterized in that: The water electrolyzer comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, wherein the catalyst is the iridium-based catalyst according to any one of claims 1 to 6 and 13.

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