Electrolyzed water catalyst as well as preparation method and application thereof

Abstract

The invention relates to an electrolyzed water catalyst and a preparation method and application thereof, the electrolyzed water catalyst is a three-dimensional porous material of elemental iridium and / or iridium oxide, the specific surface area of the electrolyzed water catalyst is greater than or equal to 65 m < 2 > / g, the porosity is greater than or equal to 40%, and the electrolyzed water catalyst has a mesoporous and macroporous structure. The electrolyzed water catalyst disclosed by the invention has a large specific surface area, high porosity and a three-dimensional porous structure of mesopores and macropores, so that the electrolyzed water catalyst has better mass transfer performance and apparent catalytic activity. The three-dimensional porous structure of the catalyst can improve the utilization rate of the iridium element, so that the loading amount of iridium in a membrane electrode is reduced, and the catalyst has excellent stability. The preparation method provided by the invention is simple and convenient, and has relatively high economical efficiency.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of electrolysis of water, in particular to an electrolysis of water catalyst and a preparation method and application thereof. BACKGROUND

[0002] The high-quality energy characteristics of hydrogen energy will make it play an important role in the future global energy pattern. The proton exchange membrane water electrolysis hydrogen production technology (PEMWE) has the advantages of small volume, flexible operation, fast start and stop, wide load regulation range, high hydrogen purity, etc., and is more suitable for the volatility of renewable energy. It is the focus of research and development in the field of green hydrogen production.

[0003] In the PEMWE hydrogen production technology, the anode catalyst is the key. The anode undergoes water oxidation reaction to generate oxygen. It is a four-electron coupled proton upshift reaction process, which exhibits higher overpotential and slow oxygen evolution reaction kinetics. At the same time, the strong oxidation conditions and strong acid medium of the anode lead to high requirements for the stability of the catalyst. Therefore, the number of active metal elements available in practice is very limited. Currently, the active metal element of the commercially available anode catalyst is mainly iridium. The price of iridium is very high, and its production and reserves are much lower than that of platinum, which is currently the bottleneck restricting the large-scale commercialization of PEMWE hydrogen production technology.

[0004] Limited by the acidic environment of PEMWE hydrogen production, high anode potential, good electrical conductivity and other factors, the currently commercially available PEMWE anode catalyst is mainly a bulk catalyst composed of iridium single element or its oxide. The iridium content in the membrane electrode is generally higher than 2 mg / cm 2 The current research on reducing the iridium content in the membrane electrode is mainly to improve the catalyst performance and doping and loading. For pure iridium or its oxide catalyst, it is generally a non-porous or low-porous nano-powder, which has the contradiction between increasing the specific surface area and inhibiting the agglomeration of nano-particles. By doping or loading to reduce the iridium content of the catalyst, the problem of how to maintain the electrical conductivity and corrosion resistance of the catalyst layer still needs to be solved.

[0005] The commonly used PEMWE anode catalysts are iridium black and iridium oxide, which are generally non-porous powder catalysts. The conventional synthesis method needs to use surfactants, reducing agents, template agents, organic solvents, nitrate salts, etc., resulting in high preparation cost and the generation of harmful substances such as organic wastewater and NOx.

[0006] The information disclosed in the foregoing BACKGROUND section is only used to strengthen the understanding of the background of the present application, and it can include information that is not known to those skilled in the art. SUMMARY

[0007] The present disclosure aims to provide an electrolytic water catalyst, a preparation method and application thereof, the electrolytic water catalyst being elemental iridium and / or an oxide of iridium, so that the catalyst has higher catalytic activity and excellent stability; and the electrolytic water catalyst has better mass transfer effect and apparent activity, and the dispersibility of the catalyst in slurry is better.

[0008] The first aspect of the present disclosure provides an electrolytic water catalyst, the electrolytic water catalyst being a three-dimensional porous material of elemental iridium and / or an oxide of iridium, having a specific surface area ≥65 m 2 / g, a porosity ≥40%, and mesoporous and macroporous structures.

[0009] Optionally, the specific surface area of the electrolytic water catalyst is 65-150 m 2 / g, preferably 70-135 m 2 / g.

[0010] Optionally, the porosity of the electrolytic water catalyst is 65-90%, preferably 65-85%, and further preferably 67-80%.

[0011] Optionally, the electrolytic water catalyst comprises mesoporous and macroporous structures with a pore size ranging from 2 nm to 1000 nm, wherein the mesoporous structure has a pore size ranging from 2 nm to 50 nm, and the macroporous structure has a pore size greater than 50 nm, preferably greater than 50 nm and less than 1000 nm, and further preferably greater than 50 nm and less than 500 nm.

[0012] Optionally, the total pore volume of the electrolytic water catalyst is 0.15-0.3 cm 3 / g, preferably 0.18-0.26 cm 3 / g.

[0013] Optionally, the oxide of iridium is crystalline iridium oxide and / or amorphous iridium oxide.

[0014] Optionally, the electrolytic water catalyst comprises iridium elements with a mass fraction of 75% or more, and preferably comprises iridium elements with a mass fraction of 77-95%.

[0015] Optionally, the apparent mass-volume ratio of the electrolytic water catalyst is not higher than 0.55 g / cm 3 , preferably 0.15-0.35 g / cm 3 , and preferably 0.18-0.27 g / cm 3 .

[0016] Optionally, the pore structure of the electrolytic water catalyst is connected by nanosheets, and the average thickness of the nanosheets is 1-10 nm, preferably 1.5-8 nm, and further preferably 2-7 nm.

[0017] The second aspect of the present disclosure provides a preparation method of an electrolytic water catalyst, comprising:

[0018] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent with water, and adjusting the pH of the obtained mixture to 5-10 to obtain an iridium source solution;

[0019] (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;

[0020] (3) calcining the aerogel, and obtaining the electrolytic water catalyst after the calcined product is subjected to or not subjected to annealing;

[0021] In the present disclosure, the complexing agent is a polycarboxylic acid salt with a hydroxyl group, and the polysaccharide is selected from one or more of alkali metal salts of alginic acid, alkali metal salts of carboxymethyl cellulose, and alkali metal salts of hyaluronic acid.

[0022] Optionally, in step (1), the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloroiridic acid, acetylacetone iridium, iridium acetate, and alkali metal salts of chloroiridic acid; and / or, the complexing agent is selected from one or more of alkali metal salts of citric acid, tartaric acid, and malic acid; and / or, the molar ratio of the iridium source precursor to the complexing agent is (0.25-20):1, preferably (0.25-10):1, further preferably (0.5-4):1, and more preferably (0.5-2):1.

[0023] Optionally, in step (2), the mass ratio of the polysaccharide to the iridium source precursor in the second sol is (0.1-20):1, and preferably (0.2-10):1; and / or, the first drying comprises supercritical drying and / or freeze drying, and preferably freeze drying; the conditions of the freeze drying include a temperature of -30 to -20℃, and preferably -25 to -20℃; and a time of 24-48h, and preferably 36-48h.

[0024] Optionally, in step (3), the conditions of the calcination include a calcination temperature of 200-550℃, and preferably 320-500℃ or 220-300℃; a time of 0.5-6h, and preferably 1-4h; and a temperature rising rate of 1-10℃ / min, and preferably 2-8℃ / min.

[0025] Optionally, the preparation method further comprises a post-treatment step, the post-treatment comprising washing and a second drying; the washing comprises sequentially subjecting the calcined product to acid washing, water washing and alcohol washing, the acid used in the acid washing being selected from one or more of dilute hydrochloric acid, sulfuric acid, nitric acid and acetic acid, the alcohol used in the alcohol washing being selected from one or more of methanol, ethanol and isopropanol; and / or the conditions of the second drying comprise a temperature of 40-60°C, preferably 45-55°C; and a time of 2-24h, preferably 10-20h.

[0026] The third aspect of the present disclosure provides an electrolytic water catalyst prepared by the preparation method of the second aspect of the present disclosure.

[0027] The fourth aspect of the present disclosure provides an application of the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure as an anode catalyst in proton exchange membrane electrolytic water.

[0028] The fifth aspect of the present disclosure provides a membrane electrode, comprising a proton exchange membrane and a catalyst coated on the proton exchange membrane, the catalyst being the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure.

[0029] The sixth aspect of the present disclosure provides a water electrolyzer, comprising a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, the catalyst being the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure.

[0030] In order to reduce the use cost of the catalyst, it is not only necessary to further improve the electrochemical activity and stability of the electrocatalyst, but also necessary to consider how to adapt to the manufacturing process of the membrane electrode to fully exert the performance of the electrocatalyst, and the dispersibility of the existing electrocatalyst in the catalyst membrane preparation slurry is not ideal; in addition, the microstructure of the electrocatalyst needs to be considered, and how to make the electrocatalyst better exert the electrochemical performance when facing large current, and the field is not deep and comprehensive enough. In addition, there are many shortcomings in the synthesis of catalysts with novel microstructure at present, such as the need to use surfactants, reducing agents, nitrate salts, template agents and organic solvents, which will cause high production cost and generate a large amount of harmful three-waste byproducts; for example, the products obtained by the molten salt method and the soft / hard template method have thick pore walls, some of which have pores and some of which do not have pores, and the pore structure is not ideal; and the porosity is not high enough, the specific surface area is not large enough, and the bulkiness is not high enough.

[0031] By the technical scheme, the present disclosure provides an electrolytic water catalyst, a preparation method and application thereof. The catalyst of the present disclosure has a three-dimensional porous structure with large specific surface area, high porosity and continuous distribution of mesopores and macropores, thus having better mass transfer performance, apparent catalytic activity and conductivity. Further, the present disclosure can make the apparent mass-volume ratio of the catalyst very low, the bulkiness very high, and the dispersibility in the catalyst slurry better. Due to the continuous mesopore-macropore structure, the catalyst can fully expose the active sites inside the material, improve the utilization rate of iridium element, thereby reducing the loading of iridium in the membrane electrode and reducing the use cost of the catalyst. Further, the catalyst can be a three-dimensional porous material connected by very thin nanosheets, which has high catalytic activity of nanomaterials and can inhibit the agglomeration and deactivation of catalyst nanoparticles, so that the catalyst maintains high catalytic activity while having excellent stability, and to a large extent, solves the activity and stability problems of nanomaterials. Further, by controlling the oxidation state of the catalyst surface, the stability of the catalyst can be further improved based on the aforementioned nanosheet connection structure. When the catalyst of the present disclosure is applied to electrolytic water hydrogen production, it has more excellent oxygen evolution activity, smaller initial overpotential and lower Tafel slope. In particular, the catalyst of the present disclosure has very high stability, and the increase of the final overpotential after stability test is very small compared to the initial overpotential, which has good industrial application prospect. In addition, the preparation method provided by the present disclosure is simple and convenient, and has high economy.

[0032] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the specific embodiments below, serve to explain the present disclosure but do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 is an SEM image of the catalyst C1 prepared in Example 1 of the present disclosure;

[0035] Figure 2 is an XRD image of the catalyst C1 prepared in Example 1 of the present disclosure;

[0036] Figure 3 is a TEM image of the catalyst C1 prepared in Example 1 of the present disclosure;

[0037] Figure 4 is a BET image of the catalyst C1 prepared in Example 1 of the present disclosure;

[0038] Figure 5 is an XPS spectrum of Ir 4f of the catalyst C1 prepared in Example 1 of the present disclosure;

[0039] Figure 6 is a cyclic voltammogram of the catalyst C1 prepared in Example 1 of the present disclosure;

[0040] Figure 7 is a gas bubble discharge graph when an electrode prepared by coating the catalyst C1 prepared in Example 1 of the present disclosure on carbon paper is used for an electrolysis water reaction;

[0041] Figure 8 is an SEM graph of the commercialized iridium oxide D2 used in Comparative Example 2 of the present disclosure;

[0042] Figure 9 is a cyclic voltammogram of the commercialized iridium oxide D2 used in Comparative Example 2 of the present disclosure;

[0043] Figure 10 is a gas bubble discharge graph when an electrode prepared by coating the commercialized iridium oxide D2 used in Comparative Example 2 of the present disclosure on carbon paper is used for an electrolysis water reaction;

[0044] Figure 11 is an XRD graph of a rutile-type iridium dioxide catalyst prepared in one embodiment of the present disclosure;

[0045] Figure 12 is an XRD graph of an elemental iridium catalyst prepared in one embodiment of the present disclosure;

[0046] Figure 13 is an XRD graph of a composite catalyst of elemental iridium and iridium dioxide prepared in one embodiment of the present disclosure.

[0047] Figure 14 is an isothermal adsorption-desorption curve of the catalyst C1 prepared in Example 1 of the present disclosure;

[0048] Figure 15 is a low-magnification STEM graph at different angles of the catalyst C1 prepared in Example 1 of the present disclosure;

[0049] Figure 16 is a high-magnification STEM graph at different angles of the catalyst C1 prepared in Example 1 of the present disclosure;

[0050] Figure 17 is a high-magnification STEM graph at different angles of the commercialized iridium oxide D2 used in Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION

[0051] The specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0052] Explanation of terms:

[0053] The term "mesopore" is defined as a pore having a pore size in the range of 2 nm to 50 nm, and the term "macropore" is defined as a pore having a pore size greater than 50 nm; a pore having a pore size less than 2 nm is defined as a "micropore".

[0054] The term "three-dimensional porous material" is defined as a material having a porosity greater than 15%, and the shape, form of existence or distribution state of the pores in the material is not limited, for example, the material can be composed of mesopores having a pore size in the range of 2 nm to 50 nm and macropores having a pore size greater than 50 nm, wherein the form of existence of the pores can include crosslinked pores, through pores or blind pores, and the distribution state can include uniform or irregular distribution on the surface or inside of the material.

[0055] In the XRD spectrum, the position of each peak is represented by 2θ, and due to instrument bias, differences in measurement environment, etc., the results are biased, and in the XRD spectrum, "around" each 2θ value means a range of ±0.2° of the 2θ value.

[0056] In the present disclosure, the term "amorphous" refers to a state other than crystalline, including amorphous morphology, quasi-crystalline morphology. In the present disclosure, the amorphous iridium oxide exists in amorphous and / or quasi-crystalline morphology.

[0057] In the present disclosure, the content of iridium element and oxygen element is obtained by XRF test.

[0058] The first aspect of the present disclosure provides an electrolytic water catalyst, which is a three-dimensional porous material of elemental iridium and / or an oxide of iridium, having a specific surface area of ≥65 m 2 / g, a porosity of ≥40%, and a continuous distribution of mesopores and macropores.

[0059] The apparent mass-volume ratio of the electrolytic water catalyst of the first aspect of the present disclosure is not higher than 0.55 g / cm 3 , preferably not higher than 0.45 g / cm 3 , further preferably not higher than 0.4 g / cm 3 , and more preferably not higher than 0.35 g / cm 3 .

[0060] The electrolytic water catalyst of the present disclosure has a three-dimensional porous structure with large specific surface area, high porosity, and continuously distributed mesopores and macropores, thus having better mass transfer performance, apparent catalytic activity, and conductivity. Further, the present disclosure can make the apparent mass-to-volume ratio of the catalyst very low, has high bulkiness, and has better dispersibility in catalyst slurry. Due to the continuous mesopore-macropore structure, the catalyst can fully expose the active sites inside the material, improve the utilization rate of iridium elements, thus reducing the loading of iridium in the membrane electrode and reducing the use cost of the catalyst. When the catalyst of the present disclosure is applied to the electrolytic water hydrogen production, it has more excellent oxygen evolution activity, smaller initial overpotential, and lower Tafel slope. In particular, the catalyst of the present disclosure has very high stability, and the increase of the final overpotential after stability test compared with the initial overpotential is very small, thus having good industrial application prospect. In addition, the preparation method provided by the present disclosure is simple and convenient, and has high economy.

[0061] The shape, existence form, or distribution state of the pores in the three-dimensional porous material are not limited, for example, the three-dimensional porous material can be composed of mesopores with a pore size in the range of 2 nm to 50 nm and macropores with a pore size greater than 50 nm, and contains no or a small amount of micropores. The existence form of the pores can include cross-linked pores, through pores, or blind pores, and the distribution state can include uniform or irregular distribution on the surface or inside of the material.

[0062] In an embodiment, the three-dimensional porous structure of the electrolytic water catalyst of the present disclosure comprises multi-level pores of continuously distributed mesopores and macropores with a pore size in the range of 2 nm to 1000 nm, preferably 2 nm to 500 nm, which overall constitute a continuous mesopore-macropore multi-level pore structure. The three-dimensional pore structure of the catalyst comprises a certain number of macropores with a pore size > 200 nm. The "multi-level pores of continuously distributed mesopores and macropores" refer to the multi-level pores composed of continuous macropores (pore size 50-200 nm)-mesopores (pore size 2-50 nm) around the macropores (pore size > 200 nm), wherein "continuous" means that various pore sizes exist, for example, various pore sizes in the range of 2 nm to 200 nm exist. It is believed that the mesopores provide a large specific surface area, expose more reaction sites, and participate in gas transmission; and the macropores, especially the supermacropores with a size of hundreds of nanometers, are very beneficial to water transmission and significantly reduce the apparent mass-to-volume ratio of the catalyst.

[0063] In a further embodiment, the three-dimensional porous structure of the electrolytic water catalyst of the present disclosure can further comprise micropores, wherein the proportion of the micropores is small. In a specific embodiment, the specific surface area of the micropores of the iridium-based catalyst is not more than 35% of the specific surface area of the whole catalyst, preferably not more than 20%, more preferably not more than 15%, and more preferably not more than 10%.

[0064] Iridium is one of the elements with the highest density, and the density of metallic iridium is as high as 22.65 g / cm3 The electrolytic water catalyst provided in the present disclosure has the loose porous microstructure described above, in particular, the bulk of the porous structure of the electrolytic water catalyst comprises mesoporous and macroporous structures, thus the apparent mass volume ratio of the electrolytic water catalyst is far lower than the density of the metal iridium described above, and the electrolytic water catalyst has the higher surface area described above, which further indicates that the electrolytic water catalyst of the present disclosure has the loose porous structure.

[0065] The electrolytic water catalyst of the present disclosure mainly comprises elemental iridium, an oxide of iridium or a composite of elemental iridium and an oxide of iridium. The oxide of iridium can be crystalline or amorphous iridium oxide, and can or can not contain crystal water.

[0066] In a first embodiment of the present disclosure, the electrolytic water catalyst is an amorphous iridium oxide catalyst.

[0067] In the XRD spectrum of the amorphous iridium oxide catalyst, there is a clear broadening characteristic peak between 30-40° of 2θ, but there is no characteristic peak of crystalline iridium oxide, such as the characteristic peak of rutile-type iridium dioxide. The content of iridium element is obtained by XRF test. The amorphous iridium oxide catalyst of the present disclosure is rich in high-activity Ir 4+ and Ir 3+ , which is conducive to improving the intrinsic OER activity of the catalyst. The amorphous iridium oxide catalyst of the present disclosure 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 synthesis raw materials, but these factors have no obvious effect on the structure and catalytic performance of the final catalyst, and the present disclosure does not necessarily limit the types and contents of these impurities.

[0068] In an embodiment of the present disclosure, the mass fraction of iridium element in the amorphous iridium oxide catalyst can be 72%, 74%, 76%, 78%, 80% or 83%, or the mass fraction of iridium element is within the numerical range between any two of them, preferably, the amorphous iridium oxide catalyst contains iridium element with a mass fraction of 75-82%. In the above embodiment, by selecting the preferred content of iridium element, it is conducive to further optimizing the composition and structure of the catalyst, improving the electrical conductivity of the catalyst, and further improving its electrocatalytic activity.

[0069] In an embodiment of the present disclosure, the amorphous iridium oxide catalyst contains oxygen with a mass fraction of 15%, 17%, 19%, 21% or 23%, or the mass fraction of oxygen element is within the numerical range between any two of them; preferably contains oxygen with a mass fraction of 14-20%.

[0070] In one embodiment of the present disclosure, the amorphous iridium oxide catalyst has a porosity of greater than 50%, preferably 70-90%, more preferably 74-85%, and even more preferably 74-80%. In the above embodiment, the amorphous iridium oxide catalyst has a hierarchical pore structure consisting essentially of mesopores and macropores, and the pore size distribution of the mesopores and macropores is continuous and average, so that the catalyst has a large specific surface area, porosity and bulkiness.

[0071] In one embodiment, the amorphous iridium oxide catalyst has a specific surface area of 120-150 m 2 / g, preferably 125-140 m 2 / g. In the above embodiment, the amorphous iridium oxide catalyst has a large specific surface area, which is beneficial to improve the mass specific activity and promote the mass transfer process.

[0072] In one embodiment, the apparent mass-volume ratio of the amorphous iridium oxide catalyst is preferably 0.15-0.3 g / cm 3 , more preferably 0.18-0.25 g / cm 3 . In one embodiment, the total pore volume of the amorphous iridium oxide catalyst is 0.15-0.3 cm 3 / g, preferably 0.18-0.26 cm 3 / g. In the above embodiment, the amorphous iridium oxide catalyst has a loose and porous microstructure, and has a high bulkiness, which is not only beneficial to improve the mass transfer effect of the catalyst, thereby improving the electrocatalytic activity of the catalyst, but also can significantly improve the dispersibility of the catalyst slurry during the preparation of the membrane electrode, and reduce the loading of the catalyst.

[0073] In one embodiment of the present disclosure, the three-dimensional porous structure of the amorphous iridium oxide catalyst is connected by nanosheets; in a preferred embodiment, the solid part of the microstructure of the amorphous iridium oxide catalyst of the present disclosure is formed by the mutual connection of a plurality of sheet-shaped nanosheets, specifically, the three-dimensional porous structure formed by the connection of nanosheets in three-dimensional space, the nanosheets extend to form the pore walls ("walls") of a plurality of pores, and the nanosheets also cover the pores to form the "surfaces" of the pores, the nanosheets as "surfaces" and "walls" are connected to each other or overlap with each other, and the pores between the nanosheets are staggered and connected, thereby forming a three-dimensional porous microstructure, as shown in Figure 1 .

[0074] The nanosheet of the present disclosure has a small size and a thin thickness, so that the catalyst has a large porosity and a loose degree, for example, the nanosheet has a size of less than 500 nm. In a preferred embodiment, the entity of the microstructure is substantially free of a portion with a thickness exceeding 10 nm, that is, the thickness of the nanosheet constituting the pore wall of the three-dimensional porous structure is substantially not more than 10 nm, preferably the thickness of the nanosheet is 1-6 nm, and more preferably 2-4 nm. The nanosheet has a very thin thickness, so it can be called a two-dimensional nanosheet. Thus, the amorphous iridium oxide catalyst of the present disclosure has a high catalytic activity of a nanomaterial, and at the same time, because the nanosheet is continuously extended and connected with each other in a three-dimensional space to form a loose and porous three-dimensional structure in a microstructure, the catalyst has a large porosity and a loose degree; the three-dimensional structure of the catalyst has a continuous distribution of mesopores and macropores, especially contains a certain amount of macropores with a size of more than 200 nm, so that the catalyst as a whole is more loose and porous, which is beneficial to improve the mass transfer effect and the apparent activity, and avoid the agglomeration and deactivation of the amorphous iridium oxide catalyst, to a large extent, solve the activity and stability problems of the nanomaterial, and is beneficial to reduce the use amount of the amorphous iridium oxide catalyst and improve the dispersibility thereof. The average thickness of the nanosheet is tested by SEM and statistically analyzed by Nano Measurer 1.2 software.

[0075] In an embodiment of the present disclosure, the continuous nanosheet in the amorphous iridium oxide catalyst is formed by a plurality of nanometer particles of iridium oxide closely arranged and connected with each other, and the average particle size of the nanometer particles of iridium oxide is 1-4 nm, preferably 1.2-2.5 nm. In the above embodiment, the nanometer particles of iridium oxide have a small size, the nanosheet formed thereby has a thin thickness, for example, the thickness is only 1-6 nm, so that the internal structure of the amorphous iridium oxide catalyst composed of the nanosheet is more loose. In a preferred embodiment, the nanosheet formed by the nanometer particles has a wrinkle-like graphene-like morphology, which is beneficial to further improve the apparent activity of the catalyst. The size of the nanometer particles can be obtained by TEM testing.

[0076] In an embodiment, the high-resolution transmission electron microscopy image of the amorphous iridium oxide catalyst has a structure combining long-range disorder and short-range order, which is beneficial to expose more coordination unsaturated active sites and promote the improvement of OER performance.

[0077] In an embodiment of the present disclosure, the XRD spectrum of the amorphous iridium oxide catalyst has only a characteristic peak of the amorphous iridium oxide with a broadened peak width, and does not have a characteristic peak of elemental iridium. Specifically, the XRD spectrum of the amorphous iridium oxide catalyst has an obvious main diffraction peak with a broadened peak width near 2θ = 33.6°, and the half-peak width of the main diffraction peak is 5-6°, preferably 5.2-5.6°.

[0078] In one embodiment of the present disclosure, the amorphous iridium oxide catalyst is rich in high-activity Ir 4+ and Ir 3+ , which is beneficial to improve the intrinsic OER activity of the catalyst. In a specific embodiment, the binding energy of the Ir 4+ 4f 7 / 2 peak in the XPS Ir 4f spectrum of the amorphous iridium oxide catalyst is 61-62 eV; and the binding energy of the Ir 3+ 4f 7 / 2 peak is 62-63 eV. In a preferred embodiment, the mole percentage of Ir 3+ obtained by fitting the XPS Ir 4f spectrum of the amorphous iridium oxide catalyst is 20-50%, preferably 26-40%, i.e., the mole number of Ir 3+ accounts for 20-50%, preferably 26-40%, of the total mole number of Ir species. This indicates that the amorphous iridium oxide catalyst of the present disclosure is rich in high-activity Ir 3+ on the surface, which is beneficial to improve the intrinsic OER activity of the catalyst. In the present disclosure, the "surface layer" refers to a region with a detection depth of less than 10 nm from the outer surface of the catalyst, and specifically refers to the detection depth of XPS.

[0079] In a second embodiment of the present disclosure, the iridium element in the water electrolysis catalyst exists in the form of rutile-type iridium dioxide, i.e., a crystalline iridium dioxide catalyst,

[0080] Specifically, the XRD spectrum contains obvious characteristic peaks of rutile-type iridium dioxide (crystalline iridium oxide), and further, the XRD spectrum contains only the characteristic peaks of the broadened rutile-type iridium dioxide, and no characteristic peaks of elemental iridium. It should be noted that "only" in the present disclosure means that the XRD spectrum mainly contains the characteristic peaks of the broadened rutile-type iridium dioxide, but due to the determination conditions, sample impurities, etc., weak diffraction peaks at other 2θ angles may appear 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.

[0081] The content of the iridium element is 70% or more by mass, preferably 74-88%, relative to the whole catalyst, and specifically, the mass fraction of the iridium element in the iridium dioxide catalyst can be 74%, 76%, 78%, 80%, 81%, 84%, 86%, or 88%, or the mass fraction of the iridium element is within the numerical range between any two of them, and more preferably 76-84%.

[0082] In one embodiment, the mass fraction of oxygen in the iridium dioxide catalyst can be 14-20%, preferably 14-18%.

[0083] Further, in one embodiment, the XRD spectrum of the iridium dioxide catalyst has a relatively broadened main diffraction peak of the rutile-type iridium dioxide at 2θ = 34.8°, and the half-peak width of the main diffraction peak is 1.5-3°, preferably 1.6-2.4°. In the above embodiment, the relatively broadened half-peak width indicates that the grain size of the rutile-type iridium dioxide is relatively small, and a large number of grain boundaries are enriched, which brings more electrochemically active sites, and is conducive to the improvement of the OER performance. Moreover, the rutile-type iridium dioxide itself has high stability, so that the catalyst has high catalytic activity brought by the high specific surface area, high porosity and three-dimensional porous structure, and has higher stability, and the increase of the final overpotential compared with the initial overpotential is small after the stability test, and has good industrial application prospect.

[0084] In one embodiment, the XPS spectrum of the iridium dioxide catalyst has a characteristic peak of iridium dioxide, that is, in the XPS Ir4f spectrum, there is a characteristic peak of Ir 4+ 4f 3+ and a satellite peak, but there is no characteristic peak of Ir 4+ 4f 7 / 2 , and specifically, the binding energy of Ir 4+ 4f 3 peak is 61-62 eV, indicating that the surface layer of the rutile-type iridium dioxide catalyst of the present disclosure is rich in high-valence Ir 3 , which is conducive to improving the stability of the catalyst. The "surface layer" refers to a region with a detection depth of less than 10 nm from the outer surface of the iridium dioxide catalyst. Specifically, the detection depth of XPS is used as a reference.

[0085] In one embodiment, the iridium dioxide catalyst has the above-mentioned three-dimensional porous structure with continuously distributed mesopores and macropores.

[0086] In one embodiment, the porosity of the iridium dioxide catalyst can be 65-90%, preferably 70-85%, and further preferably 70-80%;

[0087] In one embodiment, the apparent mass-volume ratio of the iridium dioxide catalyst can be 0.2-0.34 g / cm 3 , preferably 0.22-0.3 g / cm 3 ;

[0088] In one embodiment, the total pore volume of the iridium dioxide catalyst is 0.1-0.3 cm 3 / g, preferably 0.16-0.26 cm 3 / g.

[0089] In one embodiment, the specific surface area of the iridium dioxide catalyst can be 100-150 m 2 / g, preferably 110-130 m 2 / g. In this embodiment, the iridium dioxide catalyst has a large specific surface area and porosity, and a high degree of fluffiness, which is conducive to promoting the mass transfer process, increasing the mass specific activity, and facilitating dispersion in the slurry preparation.

[0090] In one embodiment, the three-dimensional porous structure of the catalyst is continuously connected by very thin nanosheets, thereby inhibiting the agglomeration of catalyst nanoparticles and deactivation, and enabling the catalyst to maintain a high catalytic activity while having excellent stability. The thickness of the nanosheets can be 1.5-6.5 nm, and preferably 2-4.5 nm. The continuous nanosheets are formed by a plurality of iridium dioxide nanocrystals being closely arranged and connected to each other, and the average particle size of the iridium dioxide nanocrystals can be 2-6 nm, and preferably 2-4 nm.

[0091] In a third embodiment of the present disclosure, the iridium element in the water electrolysis catalyst exists substantially in the form of elemental iridium, i.e., an iridium-based catalyst. The XRD spectrum of the iridium-based catalyst has a characteristic peak of elemental iridium, and does not have a characteristic diffraction peak of rutile-type iridium dioxide.

[0092] In one embodiment, the mass fraction of the iridium element in the iridium-based catalyst can be 80% or more, for example, 80%-97%, and specifically can be 80%, 82%, 84%, 86%, 88%, 91%, 94%, or 97%, or a value within a range between any two of them, and more preferably 80-95%.

[0093] In one embodiment, the mass fraction of oxygen in the iridium-based catalyst can be 2-16%, and preferably 3-14%.

[0094] Further, the XRD spectrum of the iridium-based catalyst has a main diffraction peak of elemental iridium at 2θ = 40.7°, which is a (111) crystal face diffraction peak of elemental iridium. The (111) crystal face diffraction peak is sharp, and further, the half-peak width of the (111) crystal face diffraction peak is 0.8-1.0°, and preferably 0.85-1.0°. In the above embodiment, the presence of elemental iridium is conducive to enhancing the electrical conductivity of the catalyst and improving the OER performance.

[0095] In a specific embodiment, the XRD spectrum of the iridium-based catalyst has only characteristic peaks of elemental iridium, and does not have characteristic peaks of oxides, such as characteristic peaks of rutile-type iridium dioxide and characteristic peaks of amorphous iridium oxide. In this case, the iridium-based catalyst of the third aspect described above is an iridium metal catalyst.

[0096] In one embodiment, the XPS spectrum of the iridium-based catalyst has a characteristic peak of elemental iridium, in which the Ir 4f of the elemental iridium is at 62.5-63.5 eV, and preferably 62.8-63.2 eV. 0 4f 7 / 2The binding energy of the peak is 61.0-61.4 eV. The Ir 0 4f 7 / 2 The peak is shifted to a high electron binding energy direction relative to the standard position (60.9 eV), for example, by 0.1-0.5 eV, indicating that the elemental iridium on the surface layer of the catalyst is in a relatively electron-deficient state, which is conducive to the combination of the adsorbed oxygen intermediate. Alternatively, the XPS spectrum of the catalyst also has an Ir-O sub-peak, indicating that the iridium on the surface layer of the catalyst is oxidized, that is, the surface layer of the catalyst contains iridium oxide, for example, an iridium oxide layer. The "surface layer" refers to a region with a detection depth of less than 10 nm from the outer surface of the catalyst, and specifically, the detection depth of XPS is used as a reference.

[0097] In another specific embodiment, the iridium-based catalyst further contains a small amount of amorphous iridium oxide on the basis of metallic iridium, and at this time, the iridium-based catalyst forms a composite catalyst of metallic iridium and amorphous iridium oxide. In this embodiment, the XRD spectrum of the iridium-based catalyst contains characteristic peaks of amorphous iridium oxide in addition to the characteristic peaks of elemental iridium.

[0098] Specifically, the XRD spectrum of the composite catalyst of elemental iridium and amorphous iridium oxide has a characteristic peak of amorphous iridium oxide with obvious peak broadening near 2θ = 33.6°, and the half-peak width of the characteristic peak is 5-6°, preferably 5.2-5.6°; a characteristic peak of elemental iridium appears near 2θ = 40.8°, and the half-peak width of the characteristic peak of elemental iridium is preferably 0.6-2.0°, preferably 0.8-1.2°.

[0099] In the above embodiment, the amorphous iridium oxide catalyst is rich in high-activity Ir 4+ and Ir 3+ , which is conducive to improving the intrinsic OER activity of the catalyst. In a further specific embodiment, the XPS Ir 4f spectrum of the iridium-based catalyst has a peak of Ir 4+ 4f 7 / 2 with a binding energy of 61-62 eV; and a peak of Ir 3+ 4f 7 / 2 with a binding energy of 62-63 eV. In a preferred embodiment, the XPS Ir 4f spectrum of the amorphous iridium oxide catalyst is fitted to obtain a molar percentage of Ir 3+ of 20-50%, preferably 25-40%, i.e., the number of moles of Ir 3+ accounts for 20-50%, preferably 25-40%, of the total number of moles of Ir species. This indicates that the surface layer of the amorphous iridium oxide catalyst of the present disclosure is rich in high-activity Ir 3+ , which is conducive to improving the intrinsic OER activity of the catalyst. The "surface layer" in the present disclosure refers to a region with a detection depth of less than 10 nm from the outer surface of the catalyst, and specifically, the detection depth of XPS is used as a reference.

[0100] The iridium-based catalyst has the above-mentioned three-dimensional porous structure with continuous distribution of mesopores and macropores; in a further embodiment, the porosity of the iridium-based catalyst can be 70-90%, preferably 70-80% or 75-80%. In a further embodiment, the apparent mass volume ratio of the iridium-based catalyst is not more than 0.55 g / cm 3 , for example, 0.15-0.35 g / cm 3 , preferably 0.20-0.30 g / cm 3 ; in a further embodiment, the total pore volume of the iridium-based catalyst is 0.08-0.18 cm 3 / g, preferably 0.1-0.16 cm 3 / g. In a further embodiment, the specific surface area of the iridium-based catalyst can be 70-95 m 2 / g, preferably 70-90 m 2 / g or 70-80 m 2 / g. In the above-mentioned embodiments, the iridium-based catalyst has a large specific surface area and porosity, and a high bulkiness, which is conducive to promoting the mass transfer process, improving the mass specific activity, and facilitating dispersion in slurry preparation.

[0101] Further, the three-dimensional porous structure of the iridium-based catalyst is continuously connected by very thin nanosheets, thereby inhibiting the agglomeration of catalyst nanoparticles and deactivation, and enabling the catalyst to maintain a high catalytic activity while having excellent stability. In a further embodiment, the thickness of the nanosheets can be 2-8 nm, preferably 3.5-6.5 nm. The continuous nanosheets are formed by closely arranging and connecting multiple iridium nanocrystals, and in a further embodiment, the average particle size of the iridium nanocrystals can be 1-8 nm, preferably 2-5 nm.

[0102] In a fourth embodiment of the present disclosure, the iridium element in the water electrolysis catalyst exists substantially in the form of a composite of elemental iridium and rutile-type iridium dioxide, i.e., a composite catalyst of iridium and iridium dioxide, and the XRD spectrum simultaneously shows obvious characteristic peaks of rutile-type iridium dioxide and elemental iridium.

[0103] In an embodiment, the rutile-type iridium dioxide coats or embeds the elemental iridium, for example, the iridium dioxide coats the surface of the elemental iridium to form a coated composite catalyst, thereby maintaining the high activity and good electrical conductivity of the elemental iridium while further improving the stability of the catalyst.

[0104] Further, in one embodiment, the mass fraction of iridium in the composite catalyst can be 78% or more, preferably the mass fraction of iridium in the composite catalyst is 80%-90%, and more specifically, the mass fraction of iridium can be 78%, 79%, 80%, 81%, 82%, 83%, 85%, 88%, or 90%, or a value within any two of them, and more preferably 80%-84%.

[0105] Further, in one embodiment, the mass fraction of oxygen in the composite catalyst can be 6%-18%, and in one preferred embodiment, the mass fraction of oxygen can be 6%, 7%, 9%, 11%, 14%, or 18%, or a value within any two of them, and preferably 6%-16%.

[0106] Further, in one embodiment, the XRD spectrum of the composite catalyst of iridium and iridium dioxide has a relatively wide main diffraction peak of rutile iridium dioxide ((101) crystal surface) near 2θ = 34.8°, with a half-peak width of 1.5-2.0°, and a sharp main diffraction peak of elemental iridium ((111) crystal surface) near 2θ = 40.8°, with a half-peak width of 0.6-1.2°.

[0107] Further, in one embodiment, the mass percentage of rutile iridium dioxide obtained by fitting the peak areas of the characteristic peaks of rutile iridium dioxide and elemental iridium in the XRD spectrum is 20%-80%, preferably 30%-70%, and more preferably 40%-65%, i.e., the mass percentage of rutile iridium dioxide in the total mass of elemental iridium and rutile iridium dioxide is 20%-80%, preferably 30%-70%, and more preferably 40%-65%. The composite structure of rutile iridium dioxide and elemental iridium can bring more electrochemically active sites, which is conducive to the improvement of OER performance.

[0108] Further, in one embodiment, the XPS spectrum of the composite catalyst has characteristic peaks of rutile iridium dioxide and elemental iridium, i.e., in the XPS Ir 4f spectrum, there are characteristic peaks of Ir 0 , Ir 4+ , and satellite peaks, the binding energy of Ir 0 4f 7 / 2 peaks is 61.0-61.4 eV, and the binding energy of Ir 4+ 4f 7 / 2 peaks is 61.4-62.0 eV. In one embodiment, according to the XPS Ir 4f spectrum, the mass percentage of rutile iridium dioxide is 20%-80%, preferably 30%-70%, and more preferably 40%-65%, i.e., the mass percentage of rutile iridium dioxide in the total mass of elemental iridium and rutile iridium dioxide is 20%-80%, preferably 30%-70%, and more preferably 40%-65%. 4+ 7 / 2 0 4f​​7 / 2 Peak area fitting analysis of the peaks, with the total number of moles of Ir 0 and Ir 4+ as the reference, the mole percentage of surface layer Ir 4+ is 20-90%, preferably 35-75%, i.e. the number of moles of surface layer Ir 4+ is 20-90% of the total number of moles of surface layer Ir 0 and Ir 4+ , preferably 35-75%. In the above embodiments, the surface layer of the composite catalyst is rich in high-valence iridium species, which is conducive to balancing the activity and stability of the catalyst. The "surface layer" refers to a region with a detection depth of less than 10 nm from the outer surface of the composite catalyst. Specifically, the detection depth is based on XPS.

[0109] The composite catalyst of iridium and iridium dioxide has the above-mentioned three-dimensional porous structure with continuously distributed mesopores and macropores. In a further embodiment, the porosity of the composite catalyst can be 60-85%, preferably 65-75%. In a further embodiment, the apparent mass-volume ratio of the composite catalyst can be 0.18-0.35 g / cm 3 , preferably 0.2-0.3 g / cm 3 . In a further embodiment, the total pore volume is 0.1-0.2 cm 3 / g, preferably 0.1-0.15 cm 3 / g. In a further embodiment, the specific surface area of the composite catalyst can be 70-90 m 2 / g, preferably 75-85 m 2 / g. In the above embodiments, the composite catalyst has a large specific surface area and porosity, and a high bulkiness, which is conducive to promoting the mass transfer process, increasing the mass-specific activity, and facilitating the dispersion of the catalyst in the slurry preparation.

[0110] Further, the three-dimensional porous structure of the composite catalyst is continuously connected by very thin nanosheets, thereby inhibiting the agglomeration of catalyst nanoparticles and deactivation, allowing the catalyst to maintain a high catalytic activity while having excellent stability. In a further embodiment, the thickness of the nanosheet can be 2-10 nm, preferably 4-7 nm. The continuous nanosheet is formed by the close arrangement and mutual connection of multiple iridium-based nanocrystals, and the grain size of the above-mentioned nanocrystals is small, for example, the average particle size of the nanocrystals is 2-10 nm, preferably 2.5-6 nm.

[0111] The second aspect of the present disclosure provides a preparation method of an electrolytic water catalyst, the preparation method comprising:

[0112] (1) mixing a polysaccharide with water to form a first sol; mixing an iridium source precursor, a complexing agent with water, and adjusting the pH of the obtained mixture to 5-10 to obtain an iridium source solution;

[0113] (2) mixing the first sol with the iridium source solution to form a second sol; subjecting the second sol to a first drying to obtain an aerogel;

[0114] (3) calcining the aerogel, and obtaining the water electrolysis catalyst from the calcined product with or without annealing;

[0115] In the formula, the complexing agent is a polycarboxylic acid salt with a hydroxyl group, and the polysaccharide is selected from one or more of alkali metal salts of alginic acid, alkali metal salts of carboxymethyl cellulose and alkali metal salts of hyaluronic acid.

[0116] The method of the present disclosure uses specific polysaccharides and complexing agents to form an iridium source-containing hydrosol, and uses the three-dimensional sheet-shaped structure aerogel obtained by drying the hydrosol as a precursor to obtain a three-dimensional porous water electrolysis catalyst containing elemental iridium and / or iridium oxide by calcination at a specific temperature. The aerogel preparation method of the present disclosure is different from the existing aerogel preparation method. The aerogel of the present disclosure is directly formed by drying the flowable hydrosol, and does not form a hydrogel before the aerogel is prepared.

[0117] The preparation method provided by the present disclosure is simple and convenient, the synthesis route is green and economical, the obtained water electrolysis catalyst has a novel three-dimensional multi-level porous loose structure, the microstructure shows that the structure is connected by very thin nanosheets, has a large specific surface area, and therefore has high catalytic activity and high stability, and has excellent electrochemical catalytic performance, and can be used in the electrolysis of water to produce hydrogen.

[0118] The term "sol" in the present disclosure is defined as a dispersion system with flowability and viscosity greater than water.

[0119] In an embodiment of the present disclosure, in step (1), the polysaccharide is selected from one or more of alkali metal salts of alginic acid, alkali metal salts of carboxymethyl cellulose and alkali metal salts of hyaluronic acid. Preferably, in an embodiment, the alkali metal salt of each polysaccharide can be independently a sodium salt or a potassium salt. Specifically, when the polysaccharide is selected from an alkali metal salt of alginic acid, it can be sodium alginate or potassium alginate; when the polysaccharide is selected from an alkali metal salt of carboxymethyl cellulose, it can be sodium carboxymethyl cellulose or potassium carboxymethyl cellulose; and when the polysaccharide is selected from an alkali metal salt of hyaluronic acid, it can be sodium hyaluronate or potassium hyaluronate.

[0120] In one embodiment of the present disclosure, the iridium source precursor can use various types of iridium source precursors known to those skilled in the art, preferably, the iridium source precursor is selected from one or more of anhydrous iridium chloride, iridium chloride hydrate, chloro iridic acid, acetylacetone iridium, iridium acetate, and alkali metal salts of chloro iridic acid, wherein the alkali metal salts of chloro iridic acid include sodium chloro iridic acid and potassium chloro iridic acid.

[0121] In the present disclosure, as the polybasic carboxylic acid having a hydroxyl group, it can be a carboxylic acid having 1 to 4 hydroxyl groups, 2 to 4 carboxyl groups, and a total carbon atom number of 3 to 10.

[0122] In one embodiment, the polybasic carboxylic acid having a hydroxyl group has 1 to 2 hydroxyl groups. In one embodiment of the present disclosure, the polybasic carboxylic acid having a hydroxyl group has 2 to 3 carboxyl groups. In one embodiment of the present disclosure, the polybasic carboxylic acid having a hydroxyl group has a total carbon atom number of 4 to 8.

[0123] In one embodiment of the present disclosure, the polybasic carboxylic acid having a hydroxyl group is at least one selected from malic acid, citric acid, isocitric acid, tartronic acid, tartaric acid, 3-hydroxy-3-methylglutaric acid, and mevalonic acid. In one embodiment of the present disclosure, the salt of the polybasic carboxylic acid having a hydroxyl group can each independently be an alkali metal salt, an alkaline earth metal salt. More preferably, the salt of the polybasic carboxylic acid having a hydroxyl group can each independently be an alkali metal salt.

[0124] In one embodiment of the present disclosure, the salt of the polybasic carboxylic acid having a hydroxyl group can each independently be a sodium salt, a potassium salt, a calcium salt, and an ammonium salt.

[0125] In a preferred embodiment, the complexing agent is selected from one or more of alkali metal salts of citric acid, tartaric acid, and malic acid, and the alkali metal salt is preferably a sodium salt or a potassium salt; in a further preferred embodiment, the complexing agent can be sodium citrate, potassium citrate, sodium tartrate, potassium tartrate, sodium malate, or potassium malate.

[0126] In one embodiment of the present disclosure, the molar ratio of the iridium source precursor to the complexing agent is (0.25 to 20): 1, preferably (0.25 to 10): 1, further preferably (0.5 to 4): 1, and more preferably (0.5 to 2): 1.

[0127] In the above embodiment, by selecting the preferred components and contents, it is advantageous to synthesize an electrolytic water catalyst with more loose pores, and to improve the specific surface area and stability of the catalyst.

[0128] In an embodiment of the present disclosure, the pH of the obtained mixed solution in step (1) is adjusted to 5-10, preferably 6-10, which is beneficial to the formation of a uniform and stable state of the iridium source solution and the uniform distribution of iridium elements in the iridium source solution. The pH adjustment can be performed by using conventional methods and reagents in the art, such as ammonia, alkali hydroxides or basic salts, etc. For example, one or more of the following can be used: sodium carbonate solution, sodium hydroxide solution, sodium bicarbonate solution and ammonia.

[0129] In an embodiment of the present disclosure, 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.

[0130] In an embodiment of the present disclosure, the first drying includes supercritical drying and / or freeze drying. In a preferred embodiment, the drying is freeze drying, and the conditions of the freeze drying include a temperature of -30 to -20℃, preferably -25 to -20℃, and a time of 24-48h, preferably 36-48h. In the above embodiment, by selecting the preferred mass ratio, a three-dimensional aerogel intermediate with a suitable structure is formed, and the pyrolysis process is precisely controlled; by selecting the preferred freeze drying, a more stable aerogel with a porous structure can be obtained. In an embodiment of the present disclosure, after the freeze drying, the temperature is further increased to 10-40℃ for drying.

[0131] In an embodiment of the present disclosure, in step (3), the aerogel is calcined to prepare a calcined product. In an embodiment of the present disclosure, the calcined product is an iridium-based catalyst of the present disclosure. In the embodiment in which the calcined product is further subjected to a post-treatment step, the product obtained after the post-treatment of the calcined product is the iridium-based catalyst of the present disclosure.

[0132] In an embodiment of the present disclosure, in step (3), the calcination is performed under the following conditions: a calcination temperature of 200℃ or higher without destroying the three-dimensional porous structure, for example, the calcination temperature can be 200-550℃, preferably 320-500℃ or 220-300℃; a time of 0.5-6h, preferably 1-4h, more preferably 2-3h; and a temperature increasing rate of 1-10℃ / min, preferably 2-8℃ / min. In the above embodiment, by selecting the preferred calcination conditions, the porous aerogel is converted into an electrolytic water catalyst with a three-dimensional porous structure.

[0133] In an embodiment of the present disclosure, the above calcination is performed in an air atmosphere.

[0134] In a first further embodiment, the calcination conditions include: a calcination temperature of 200°C or higher and not resulting in elemental iridium, preferably 220°C or higher or 250°C or higher and not resulting in elemental iridium; further preferably a calcination temperature of 220-300°C, more preferably 250-280°C; optionally, the calcination product can be further subjected to an annealing treatment, the annealing treatment being at a temperature of less than 330°C, preferably 200-300°C; the annealing treatment being for a time period of 0.5-2h, preferably 1-2h; the micro-3D porous structure of the material before and after the annealing treatment does not change significantly. In this embodiment, the electrolysis water catalyst prepared is an amorphous iridium oxide catalyst.

[0135] In a second further embodiment, the calcination conditions include: a calcination temperature of 200°C or higher and not resulting in elemental iridium, preferably 220°C or higher or 250°C or higher and not resulting in elemental iridium, further preferably 220-300°C, more preferably 250-280°C; and the calcination product is subjected to or not subjected to a post-treatment, and then subjected to an annealing treatment, the annealing treatment being at a temperature of 330°C or higher and not destroying the 3D porous structure, preferably 350°C or higher and not destroying the 3D porous structure, more preferably 360-550°C, the annealing treatment being for a time period of 0.5-2h, preferably 1-2h; the micro-3D porous structure of the material before and after the annealing treatment does not change significantly. In this embodiment, the electrolysis water catalyst prepared is a rutile iridium dioxide catalyst.

[0136] In a third further embodiment, the calcination conditions include: a calcination temperature of 320°C or higher and not destroying the 3D porous structure, preferably 320-550°C, more preferably 325-420°C; the calcination product is not subjected to an annealing treatment; in this embodiment, the electrolysis water catalyst prepared mainly comprises elemental iridium, and optionally further comprises a small amount of amorphous iridium oxide.

[0137] In a fourth further embodiment, the calcination conditions include: a calcination temperature of 320°C or higher and not destroying the 3D porous structure, preferably 320-500°C, further preferably 320-450°C, more preferably 330-450°C; and the calcination product is subjected to or not subjected to a post-treatment, and then subjected to an annealing treatment, the annealing treatment being at a temperature of 300°C or higher and not destroying the 3D porous structure, preferably 300-550°C, further preferably 300-500°C, 350-500°C or 400-500°C, for a time period of 0.5-2h, preferably 1-2h; the micro-3D porous structure of the material before and after the annealing treatment does not change significantly. In this embodiment, the electrolysis water catalyst prepared is a composite of elemental iridium and rutile iridium dioxide.

[0138] Through the above specific embodiments, the preparation method of the present disclosure can prepare electrolytic water catalysts with different crystal forms and control the surface oxidation state thereof by controlling the process conditions of calcination and annealing treatment, and can further regulate the activity and stability of the catalyst while maintaining the three-dimensional porous structure of the catalyst.

[0139] In an embodiment of the present disclosure, the method further comprises a post-treatment step. The post-treatment comprises washing and / or a second drying, such as washing and second drying of the calcined product in step (3).

[0140] In an embodiment, the washing in step (3) comprises: acid washing, water washing and alcohol washing of the calcined product. The sequence of acid washing, water washing and alcohol washing in the 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; and can also be water washing, acid washing and alcohol washing in sequence. In a preferred embodiment of the present disclosure, the washing in step (3) comprises: acid washing, water washing and alcohol washing of the calcined product in sequence.

[0141] In an embodiment, the acid used in the acid washing in the washing in step (3) 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, wherein the alcohol washing can use alcohol or an alcohol-water mixed solution.

[0142] In an embodiment, the number of times of washing using each washing liquid is not particularly limited, and can be appropriately selected by those skilled in the art as needed, such as 1 time, 2 times, 3 times, 4 times or 5 times.

[0143] In an embodiment, the conditions of the second drying comprise: a temperature of 40-60°C, preferably 45-55°C; and a time of 2-24h, preferably 10-20h. In the above embodiment, by selecting the preferred washing and second drying, the catalyst surface can be removed from the surface of the catalyst. Residual inorganic salts, carbon and metal elements and other impurities.

[0144] The third aspect of the present disclosure provides an electrolytic water catalyst prepared by the method of the second aspect of the present disclosure.

[0145] The fourth aspect of the present disclosure provides a use of the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure as an anode catalyst in a proton exchange membrane electrolytic water.

[0146] The fifth aspect of the present disclosure provides a membrane electrode, which comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, and the catalyst is the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure.

[0147] The sixth aspect of the present disclosure provides a water electrolyzer, which comprises a proton exchange membrane and a catalyst coated on the anode side of the proton exchange membrane, and the catalyst is the electrolytic water catalyst of the first aspect and / or the third aspect of the present disclosure.

[0148] The electrolytic water catalyst provided by the present disclosure has excellent electrochemical catalytic performance when used for electrolysis of water to produce hydrogen, has a small initial overpotential, a low Tafel slope, and a small increase in the final overpotential after stability test compared with the initial overpotential, and has a good industrial application prospect. In the specific embodiments of the present disclosure, the electrolytic water catalyst is used as an oxygen evolution catalyst for electrolysis of water to produce hydrogen, and the use amount of iridium in the membrane electrode can be reduced.

[0149] In the present disclosure, the directly stated content is given priority, and any matters or issues not mentioned are directly applicable to the existing knowledge in the art without any change.

[0150] The present disclosure will be further illustrated by examples, but the present disclosure is not limited in any way by the examples. Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure are purchased through commercial channels, and are pure reagents; among them, the related reagents can be prepared into a certain concentration of water or alcohol solution for subsequent use.

[0151] Instrument method for BET analysis: the model of the fully automatic BET specific surface area tester is JW-BK200C of Jingmiao Gaobo, and the test conditions include: the test principle is static capacity method, the adsorption gas is N2, and the adsorption temperature is 77K. The N2 adsorption and desorption curve of the catalyst is obtained by testing, the multi-point BET specific surface area is obtained by analysis and calculation, the pore volume and pore size distribution obtained by BJH method analysis, and the slit type pore HK method is used for micropore analysis.

[0152] Pore rate calculation: pore rate = 100% x pore volume / (pore volume + solid volume), wherein the pore volume is obtained by BET test, the test pore size range is 2-200 nm, that is, the pore volume of all pores with a pore size in the range of 2-200 nm is measured, and the solid volume is calculated according to the mass and density of the catalyst. The solid volume of the catalyst is determined by XRF analysis of the content of iridium oxide and calculation of the density. It can be understood in the art that, since the catalyst also contains macropores with a pore size > 200 nm, and the BET test pore size range is 2-200 nm, the pore volume measured in this way is the pore volume of the relatively small pores with a pore size of 2-200 nm of the catalyst, and the calculated pore rate is also the minimum pore rate of the catalyst. The density of iridium oxide is calculated as iridium dioxide.

[0153] In the present disclosure, the apparent mass volume ratio, also known as apparent density, refers to the ratio of the physical mass of the catalyst to the apparent volume, and the apparent volume refers to the sum of the physical volume and the closed pore volume of the catalyst. The specific method for measuring the apparent mass volume is as follows: the catalyst is sieved, and the catalyst with a particle size of 15 μm or less is selected as the 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 into a precision graduated cylinder with a scale to 1-2 ml, the graduated cylinder is vertically placed and slightly shaken, the upper surface is parallel to the scale line, and the volume value is read as the apparent volume. Specifically, the method for measuring the bulk density in GB / T 13566.1-2008 can be referred to. Thus, the apparent mass volume ratio can be calculated. The apparent mass volume ratio is measured three times, and the average value is taken.

[0154] Instrument method for mass transfer performance test: a typical three-electrode system is used, CHI760E electrochemical workstation is used for constant current test, CV activation and stabilization are performed first, and the un-wetted bubbles on the surface of the electrode are removed, and subsequent constant current test is performed; a high-speed industrial camera is used to shoot the bubbles generated on the surface of the electrode during the test.

[0155] Instrument method for testing the content of iridium element: the model of X-ray fluorescence spectrometer (XRF) is Japanese Rigaku Priums IV, the catalyst is tabletized, and the element is analyzed; for light elements such as C, H and O, a more accurate C, H and O element analyzer is used for analysis, and the catalyst is not pretreated by vacuum water removal, oxygen and other adsorption media before testing.

[0156] In the present disclosure, the apparent mass volume ratio, also known as apparent density, refers to the ratio of the physical mass of the catalyst to the apparent volume, and the apparent volume refers to the sum of the physical volume and the closed pore volume of the catalyst. The specific method for measuring the apparent mass volume is as follows: the catalyst is sieved, and the catalyst with a particle size of 15 μm or less is selected as the 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 into a precision graduated cylinder with a scale to 1-2 ml, the graduated cylinder is vertically placed and slightly shaken, the upper surface is parallel to the scale line, and the volume value is read as the apparent volume. Specifically, the method for measuring the bulk density in GB / T 13566.1-2008 can be referred to. Thus, the apparent mass volume ratio can be calculated. The apparent mass volume ratio is measured three times, and the average value is taken.

[0157] SEM is used to analyze the morphology characteristics, thickness of nanosheets and size of nanoparticles of the catalyst, and NanoMeasurer 1.2 software is used for statistical analysis. The instrument, method and conditions for SEM analysis are as follows: the model of scanning electron microscope (SEM) is Hitachi S-4800 scanning electron microscope, the working voltage is 5 kV-20 kV, and energy dispersive X-ray spectroscopy (EDS) is equipped.

[0158] TEM was used to analyze the micro-morphology and nanoparticle size of the catalyst. The instrument, method and conditions for TEM analysis were as follows: the model of high-resolution transmission electron microscope (HRTEM) was JEM-2100 (Japan Electron Corporation), the acceleration voltage for testing was 200 kV; the model of spherical aberration-corrected scanning transmission electron microscope (CS-STEM) was JEOL ARM 200F, the acceleration voltage for testing was 200 kV, and it was equipped with energy dispersive X-ray spectroscopy (EDS). The related analysis was performed by using the matching DigitalMicrograph 3.9.1 software.

[0159] XPS was used to analyze the element types and contents in the surface layer of the catalyst. The instrument, method and conditions for XPS analysis were as follows: the X-ray photoelectron spectroscopy analyzer was ESCALab220i-XL type produced by VG Scientifc Corporation and equipped with Avantage V5.926 software, the X-ray photoelectron spectroscopy analysis test conditions were as follows: the excitation source was monochromatic Al Kα X-ray, the power was 330 W, and the base vacuum during analysis and testing was 3×10 -9 mbar. In addition, the electron binding energy was corrected by using the C1s peak (284.8 eV) of elemental carbon, and the correction software was CasaXPS2.3.25PR1.0 version.

[0160] Example 1

[0161] (1) 0.8 g of sodium alginate was dissolved in ultrapure water to prepare a first sol of 0.8 wt%; an appropriate amount of IrCl3 and sodium citrate was dissolved in ultrapure water to obtain a mixture, and the molar ratio of IrCl3 to sodium citrate in the mixture was 0.8:1, then the pH of the mixture was adjusted to 7.5 to obtain a uniform and stable iridium source solution;

[0162] (2) The iridium source solution was added to the first sol and stirred to disperse uniformly to obtain a second sol, and the mass ratio of polysaccharide sodium alginate to iridium source precursor IrCl3 in the second sol was 4:1; the second sol was placed in a freeze-drying box for freeze-drying, the freeze-drying temperature was -20℃, and the time was 40 h, until it became an aerogel with a porous structure;

[0163] (3) The aerogel was placed in a muffle furnace in an air atmosphere at a certain flow rate, and calcined at 280℃ for 2.5 h with a heating rate of 5℃ / min to obtain a calcined product; the calcined product was naturally cooled to room temperature, and then centrifuged in dilute acid, ultrapure water and alcohol-water mixed solution for several times, respectively, until the pH of the supernatant was neutral, and then placed in a vacuum drying box for second drying, the second drying temperature was 50℃, and the time was 12 h, to collect a catalyst 1, which was labeled as C1, and its composition was shown in Table 1.

[0164] The total pore volume of the catalyst C1 prepared in this example is 0.227 cm 3 / g, the specific surface area is 134.1 m 2 / g, the apparent mass / volume ratio is 0.187 g / cm 3 , and the specific surface area of the micropores accounts for 20.1% of the specific surface area of the whole catalyst.

[0165] The SEM image of the catalyst 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 image is shown in Figure 4 , the XPS spectrum of Ir 4f is shown in Figure 5 , the cyclic voltammogram is shown in Figure 6 , and the bubble discharge diagram of the catalyst C1 coated on carbon paper to prepare an electrode for electrolysis of water is shown in Figure 7 .

[0166] As shown in Table 1 and Figure 1 , the catalyst C1 has a three-dimensional porous structure composed of continuous nanosheets of wrinkle-like graphene, which is rich in continuous meso-macro-pore hierarchical structures, including macro-pores of >200 nm and meso-pores of 2-50 nm and macro-pores of 50-200 nm distributed continuously around the macro-pores; the "surface" of the semi-transparent thin layer covering the pores and the pore wall of the internal pores are both formed by the mutual connection of a plurality of sheet-shaped entities of wrinkle-like graphene nanosheets, i.e., by the connection of the nanosheets in three-dimensional space, and the nanosheets are composed of a plurality of nanoparticles connected to each other, with an average particle size of 2.1 nm and a thickness of the nanosheets of only 2.5 nm, indicating that the catalyst C1 has a loose porous microstructure and a large porosity and specific surface area, which is conducive to improving the mass transfer effect and apparent electrochemical activity of the catalyst and reducing the amount of catalyst used.

[0167] Figure 2 The XRD spectrum of the catalyst C1 shows an obvious characteristic diffraction peak of amorphous iridium oxide at 2θ = 33.6°, and no characteristic diffraction peak of elemental iridium appears, and the half-peak width of the main peak is 5.48°.

[0168] Figure 3 The catalyst C1 has a composite structure of long-range disorder and short-range order, which is conducive to providing a large number of coordination unsaturated active sites and improving the catalytic activity and stability.

[0169] Figure 4 The three-dimensional porous structure of the catalyst C1 is rich in macro-pores and meso-pores, and the pore size distribution is uniform and continuous, and the pore size distribution curve has no obvious sharp peak.

[0170] Figure 5 The catalyst C1 shows obvious Ir 4+ and Ir 3+ characteristic peaks in the high-resolution XPS spectrum of Ir 4f, wherein the binding energy of Ir 4+ 4f 7 / 2 peak is 61-62 eV, and the binding energy of Ir 3+ 4f 7 / 2 peak is 62-63 eV. The percentage of Ir 3+ in the catalyst C1 is 25-35%, indicating that the surface layer of the catalyst is rich in high-activity Ir 3+ , which is beneficial to improve the intrinsic OER activity of the catalyst.

[0171] Figure 6 The catalyst C1 shows obvious redox peaks (Ir 3+ / Ir 4+ ) in the potential range of 0.8 V-1.0 V vs. RHE in the cyclic voltammetry curve, indicating that the catalyst C1 has rich Ir 3+ active components, and obvious redox peaks (Ir 4+ / Ir 5+ ) in the potential range of 1.2 V-1.4 V vs. RHE; meanwhile, the peak current and area are larger, indicating that the catalyst C1 has more active sites, which is beneficial to improve the electrochemical activity.

[0172] Figure 7 The catalyst C1 shows very small bubbles on the electrode surface during the reaction process, and the bubbles are easy to desorb from the electrode surface, indicating that the catalyst C1 has good mass transfer effect, which is beneficial to maintain high oxygen evolution performance under high current density.

[0173] Figure 14 The isothermal adsorption / desorption curve of the catalyst C1 is shown, and the proportion of the specific surface area of the micropore to the specific surface area of the whole catalyst can be calculated through the curve.

[0174] Figure 15 The low-magnification STEM images of the catalyst C1 at different angles are shown, and it can be seen that the catalyst has rich macropores of >50 nm, especially rich macropores of different sizes of >200 nm, which reflects very small mass volume ratio and large porosity.

[0175] Figure 16 The high-magnification STEM images of the catalyst C1 at different angles are shown, and it can be seen that the catalyst has rich 1-100 nm pore structures of different sizes, which reflects large porosity and specific surface area.

[0176] Example 2

[0177] The same as example 1, the difference is that the catalyst C1 prepared in example 1 is continued to be heated to 280℃ in a muffle furnace in an air atmosphere at a certain flow rate to perform annealing treatment, the holding time of the annealing is 2h, and the heating rate is 3℃ / min, and finally catalyst 2 is collected, which is marked as C2, and the composition is shown in Table 1.

[0178] Example 3

[0179] (1) 0.8g of carboxymethyl cellulose sodium was dissolved in ultrapure water to prepare a first sol of 0.8wt%; an appropriate amount of chloroiridic acid solution was dispersed in a solution containing sodium tartrate to obtain a mixture with a molar ratio of chloroiridic acid to sodium tartrate of 1:1, and then the pH of the mixture was adjusted to 6.5 to obtain an iridium source solution;

[0180] (2) The iridium source solution was added to the first sol and stirred to disperse uniformly to obtain a second sol, and the mass ratio of polysaccharide to iridium source precursor in the second sol was 0.5:1; the second sol was placed in a freeze-drying box for freeze-drying, the freeze-drying temperature was -25℃, and the time was 45h until it became a porous aerogel;

[0181] (3) The aerogel was placed in a muffle furnace and calcined at 300℃ for 2h in an air atmosphere at a certain flow rate, and the heating rate was 3℃ / min to obtain a calcined product. The calcined product was naturally cooled to room temperature, and the cooled calcined product was washed several times by centrifugation in dilute acid, ultrapure water and alcohol-water mixed solution respectively until the pH of the supernatant was neutral, and then placed in a vacuum drying box for second drying, the second drying temperature was 50℃, and the time was 14h. Catalyst 3 was collected, which was marked as C3, and the composition is shown in Table 1.

[0182] Comparative Example 1

[0183] The same as example 1, the difference is that the first sol is not used, and the IrCl3 complex solution prepared in step (1) is directly subjected to oven drying treatment, and then the prepared iridium precursor powder is placed in a muffle furnace and calcined at 280℃ for 2.5h in an air atmosphere at a certain flow rate, and the heating rate is 5℃ / min, and finally comparative catalyst 1 is collected, which is marked as D1, and the composition is shown in Table 1. The SEM result of D1 shows that it does not have a loose three-dimensional porous structure.

[0184] Comparative Example 2

[0185] Commercial iridium oxide (purchased from TANAKA company, amorphous, product number TEC77100) was used as comparative catalyst 2, which was marked as D2, and the composition is shown in Table 1.

[0186] The SEM image of comparative catalyst D2 is shown in Figure 8 , and the cyclic voltammogram is shown inFigure 9 , the bubble discharge diagram when the electrode is coated on carbon paper and electrolyzed water is shown in Figure 10 .

[0187] Figure 8 It shows that commercial iridium oxide catalysts are relatively large nanoparticles that aggregate with each other. The interior of the material is relatively compact, without a loose porous structure and no significant mesoporous-macroporous structure.

[0188] Figure 9 It shows that the peak current and peak area of ​​the comparative catalyst 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.

[0189] Figure 10 It shows that the bubbles on the electrode surface of D2 during the reaction are large and the bubbles are not easy to desorb from the electrode surface, indicating that D2 has poor mass transfer effect, which is not conducive to maintaining high oxygen evolution performance at high current density.

[0190] Figure 17 The low-magnification STEM images of catalyst D2 at different angles show 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 the catalyst C1 disclosed in the present invention.

[0191] Table 1 Structural characteristics of catalysts prepared in different embodiments and comparative examples

[0192]

[0193] From the data in Table 1 above, it can be seen that the electrolytic water catalysts prepared in Examples 1 to 3 have a three-dimensional multi-level pore structure, a large specific surface area and porosity, a small apparent mass 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 1 and 2 lack a three-dimensional porous structure and high fluffiness, requiring a relatively high catalyst loading to achieve similar performance.

[0194] Test cases 1 to 5

[0195] Test Examples 1 to 5 are used to compare and illustrate the electrochemical performance of the catalysts prepared according to the first embodiment of the present disclosure.

[0196] The catalysts prepared in Examples 1 to 3 of the present disclosure and the comparative catalysts prepared in Comparative Examples 1 to 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.

[0197] Table 2 Electrochemical catalytic properties of catalysts prepared in different examples and comparative examples

[0198]

[0199] It can be seen from the data in Table 2 above that compared with the comparative catalysts D1 to D2, the iridium element in the catalysts C1 to C3 is basically in the form of amorphous iridium oxide. When the catalysts C1 to C3 are used for electrolysis of water to produce hydrogen, the battery 2 and 50mA / cm 2 The catalysts C1 to 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.

[0200] Test Example 6

[0201] This test example is used to compare and illustrate the electrochemical performance of the catalyst prepared in the second embodiment of the present disclosure.

[0202] The XRD spectrum of the catalyst is shown in Figure 1. Figure 11 It can be seen that the catalyst is a rutile-type iridium dioxide. The pore distribution and SEM image of the catalyst are basically the same as those of the catalyst C1, and the catalyst also shows a three-dimensional porous material with a continuous distribution of mesopores and macropores, with a porosity of 70-80% and an apparent mass-volume ratio of 0.22-0.3 g / cm 3 The specific surface area is 110-130 m 2 / g. The commercial rutile-type iridium dioxide has a porosity of less than 10%, a specific surface area of less than 20 m 2 / g, and an apparent mass-volume ratio of greater than 1.2 g / cm 3 , and does not have a three-dimensional porous structure and high bulkiness.

[0203] The electrochemical performance of the catalyst and the commercial rutile-type iridium dioxide was tested by the method of Test Examples 1-5 (the rotation speed of the solution oxygenation step was changed to 1600 rpm), and the results showed that the oxygen evolution activity and stability of the catalyst were much higher than those of the commercial rutile-type iridium dioxide. The initial overpotential at 10 mA / cm 2 was about 170 mV lower than that of the commercial rutile-type iridium dioxide, and the overpotential increase value in the 10,000-cycle stability test was about 50% lower than that of the commercial rutile-type iridium dioxide. The bubble discharge graph of the catalyst was basically the same as that of the catalyst C1 and the comparative catalyst D2.

[0204] Test Example 7

[0205] This test example is used to compare and illustrate the electrochemical performance of the catalyst prepared by the third embodiment of the present disclosure.

[0206] The XRD spectrum of the catalyst is shown in Figure 1. Figure 12 It can be seen that the catalyst is a single iridium catalyst. The pore distribution and SEM image of the catalyst are basically the same as those of the catalyst C1, and the catalyst also shows a three-dimensional porous material with a continuous distribution of mesopores and macropores, with a porosity of 75-80% and an apparent mass-volume ratio of 0.2-0.3 g / cm 3 The specific surface area is 70-80 m 2 / g. The commercial iridium black has a porosity of only about 5%, a specific surface area of only about 30 m 2 / g, and does not have a three-dimensional porous structure and high bulkiness.

[0207] The electrochemical performance of the catalyst and commercialized iridium black was tested by the same method as in Test Examples 1-5, and the results showed that the catalyst had slightly higher oxygen evolution activity, but the stability of the two was quite different, the overpotential of the commercialized iridium black increased by more than 70 mV in the stability test of 10,000 cycles, while the overpotential of the catalyst increased by only about 15 mV. It is shown that the catalyst prepared according to the present disclosure has a three-dimensional porous structure connected by nanosheets, which significantly improves the stability of the catalyst while improving the catalytic activity. The bubble discharge graph of the catalyst is basically the same as that of catalyst C1 and comparative catalyst D2 compared with the bubble discharge graph of commercialized iridium black.

[0208] Test Example 8

[0209] This test example is used to compare and illustrate the electrochemical performance of the catalyst prepared according to the fourth embodiment of the present disclosure.

[0210] The XRD spectrum of the catalyst is shown in Figure 13 , which shows that the catalyst is a composite catalyst of rutile-type iridium dioxide and elemental iridium. According to the calculation by XRD, the mass percentage of rutile-type iridium dioxide is 40-65%. The pore distribution and SEM graph of the catalyst are basically the same as those of catalyst C1, which shows that the catalyst is a three-dimensional porous material with continuous distribution of mesopores and macropores, the porosity is 65-75%, and the apparent mass volume ratio is 0.2-0.3 g / cm 3 . The specific surface area is 75-85 m 2 / g. The commercialized rutile-type iridium dioxide has a porosity of less than 10%, a specific surface area of less than 20 m 2 / g, and an apparent mass volume ratio of more than 1.2 g / cm 3 , and does not have a three-dimensional porous structure and high bulkiness.

[0211] The electrochemical performance of the catalyst and commercialized rutile-type iridium dioxide was tested by the method of Test Examples 1-5 (the rotation speed of the solution oxygenation step was changed to 1600 rpm), and the results showed that the oxygen evolution activity and stability of the catalyst were much higher than those of commercialized rutile-type iridium dioxide. The initial overpotential at 10 mA / cm 2 was about 150 mV lower than that of commercialized rutile-type iridium dioxide, and the overpotential increase value in the stability test of 10,000 cycles was more than 50% lower than that of commercialized rutile-type iridium dioxide. The bubble discharge graph of the catalyst is basically the same as that of catalyst C1 and comparative catalyst D2 compared with the bubble discharge graph of commercialized rutile-type iridium dioxide.

[0212] The preferred embodiments of the present disclosure are described in detail above with reference to the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and all these simple modifications shall fall within the protection scope of the present disclosure.

[0213] In addition, it should be noted that each specific technical feature described in the above-described specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again by the present disclosure.

[0214] In addition, various different embodiments of the present disclosure can also be combined in any appropriate manner, as long as it does not deviate from the idea of the present disclosure, and it should be considered as disclosed by the present disclosure.

Claims

1. A water electrolysis catalyst, characterized in that The electrolytic water 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 structures.

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

3. The water electrolysis catalyst according to claim 1, characterized in that The porosity of the water electrolysis catalyst is 65-90%, preferably 65-85%, and more preferably 67-80%.

4. The water electrolysis catalyst according to claim 1, characterized in that The water electrolysis catalyst comprises mesoporous and macroporous structures with pore sizes ranging from 2 nm to 1000 nm, wherein the pore size of the mesopores ranges from 2 nm to 50 nm, and the pore size of the macropores is greater than 50 nm, preferably greater than 50 nm and below 1000 nm, and further preferably greater than 50 nm and below 500 nm.

5. The water electrolysis catalyst according to claim 1, characterized in that The total pore volume of the water electrolysis catalyst is 0.15 to 0.3 cm 3 / g, preferably 0.18 to 0.26 cm 3 / g.

6. The water electrolysis catalyst according to claim 1, characterized in that The iridium oxide is crystalline iridium oxide and / or amorphous iridium oxide.

7. The water electrolysis catalyst according to claim 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%.

8. The water electrolysis catalyst according to claim 1, characterized in that The apparent mass volume ratio of the electrolytic water catalyst is not higher than 0.55 g / cm 3 , preferably 0.15 to 0.35 g / cm 3 , preferably 0.18 to 0.27 g / cm 3 .

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

10. A method for preparing a water electrolysis catalyst, characterized in that: The preparation method comprises: (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; (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 to obtain the water electrolysis catalyst with or without annealing the calcined product; Wherein, the complexing agent is a polycarboxylate having a hydroxyl group, and the polysaccharide is one or more selected from the group consisting of an alkali metal salt of alginic acid, an alkali metal salt of carboxymethyl cellulose and an alkali metal salt of hyaluronic acid.

11. The preparation method according to claim 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; and / or, The complexing agent is selected from one or more alkali metal salts of citric acid, tartaric acid and malic acid; 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 (0.5-4):1, and more preferably (0.5-2):

1.

12. The preparation method according to claim 10, characterized in that In step (2), the mass ratio of polysaccharide to iridium source precursor in the second sol is (0.1-20):1, preferably (0.2-10):1; and / or, 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.

13. The preparation method according to claim 10, characterized in that In step (3), the calcination conditions include: calcination temperature of 200-550°C, preferably 320-500°C or 220-300°C; time of 0.5-6h, preferably 1-4h; heating rate of 1-10°C / min, preferably 2-8°C / min.

14. The preparation method according to claim 10, characterized in that The preparation method further comprises a post-processing step, wherein the post-processing comprises washing and a second drying; 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; and / or, 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.

15. A water electrolysis catalyst prepared by the preparation method according to any one of claims 10 to 14.

16. Use of the water electrolysis catalyst according to any one of claims 1 to 9 and 15 as an anode catalyst in proton exchange membrane water electrolysis.

17. A membrane electrode, characterized in that The membrane electrode comprises a proton exchange membrane and a catalyst coated on the proton exchange membrane, and the catalyst is the water electrolysis catalyst according to any one of claims 1 to 9 and 15.

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, wherein the catalyst is the water electrolysis catalyst according to any one of claims 1 to 9 and 15.

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