Chromium-iridium solid solution oxide electrocatalyst with three-dimensional ordered macroporous structure as well as preparation and application of chromium-iridium solid solution oxide electrocatalyst

Abstract

The invention relates to a chromium-iridium solid solution oxide electrocatalyst with a three-dimensional ordered macroporous structure as well as preparation and application of the chromium-iridium solid solution oxide electrocatalyst. The preparation method comprises the following steps: (1) preparing a highly-monodispersed polymethyl methacrylate (PMMA) colloidal crystal template by adopting an emulsion polymerization method; (2) introducing a chromium precursor and an iridium precursor into the PMMA suspension, and carrying out mixing and heat treatment to obtain a three-dimensional ordered macroporous skeleton; the three-dimensional ordered macroporous skeleton is composed of highly dispersed nanoscale (1-2nm) chromium-iridium solid solution oxide particles; and (3) the obtained catalyst is subjected to pre-acid leaching treatment, soluble heteroatoms are removed, and the structural stability and the metal leaching resistance are enhanced. The obtained catalyst 3DOM H-Cr0. 75Ir0. 25Ox (3DOM represents a three-dimensional ordered macroporous structure, and H-represents an acid treatment step) shows higher electrocatalytic activity and durability than a traditional iridium-based catalyst under an acidic condition, and the use amount of noble metal is remarkably reduced, so that the cost of a membrane electrode is effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a chromium-iridium solid solution oxide electrocatalyst with a three-dimensional ordered macroporous structure, its preparation and application. Background Technology

[0002] Hydrogen energy, as a secondary energy source, produces only water as a byproduct of combustion, unlike traditional fossil fuels. It generates no greenhouse gases and boasts advantages such as high energy density, environmental friendliness, and wide availability, making it widely considered a crucial component of the future energy system. In achieving dual-carbon goals and promoting a green transformation of the energy structure, hydrogen energy plays a dual role as both an energy carrier and a storage medium. Especially against the backdrop of a gradually increasing proportion of renewable energy, utilizing water electrolysis technology to convert intermittent electricity from wind and solar power into a stable hydrogen supply is considered an effective way to achieve green and sustainable hydrogen production.

[0003] Among various water electrolysis technologies, proton exchange membrane water electrolysis (PEMWE) exhibits significant technological advantages and industrialization potential due to its high current density, wide current regulation range, rapid start-up and shutdown response, high hydrogen purity, and suitability for direct coupling with fluctuating renewable energy sources. It is considered one of the core technological pathways for large-scale green hydrogen production in the future. In the PEMWE system, the membrane electrode assembly (MEA) is the key unit for achieving efficient conversion of electrical energy into chemical energy. The MEA consists of a proton exchange membrane, an anode catalyst layer, and a cathode catalyst layer. The oxygen evolution reaction (OER) at the anode is a slow kinetic process and is the main factor determining the overpotential of the entire system. The OER reaction involves multiple electron transfers and the breaking and formation of chemical bonds, exhibiting a high reaction energy barrier, which limits the overall reaction efficiency and stability of PEMWE. Therefore, developing OER catalysts with high catalytic performance and excellent stability is of great significance for promoting the development of PEMWE technology.

[0004] Currently, iridium (Ir)-based catalysts are considered the most promising PEMWE anode catalyst systems due to their excellent stability and high intrinsic activity under acidic environments. However, Ir is a rare and precious metal with extremely low abundance in the Earth's crust, making it expensive and subject to supply chain uncertainties. In practical membrane electrode fabrication, a high Ir loading (~2 mg / cm³) is often required to ensure the performance and durability of the electrolyzer. 2This results in high costs for membrane electrode assemblies (PEMWEs), severely hindering their large-scale commercial application. Furthermore, Ir-based catalysts still suffer from partial metal dissolution and deactivation during long-term operation, further exacerbating challenges to their economic viability and stability.

[0005] To address these issues, industry has proposed various improvement strategies, including introducing a second metal to form composite oxides to optimize electronic structure and constructing structures with large specific surface areas to enhance the exposure of active sites and mass transport efficiency. While these methods have improved catalytic performance to some extent, they still suffer from limitations such as complex synthesis processes, insufficient scalability, and difficulty in significantly reducing the amount of precious metals used. Therefore, how to further reduce the amount of Ir used and improve the simplicity and scalability of preparation methods while maintaining the catalyst's high efficiency and stability remains a key scientific and technological challenge that urgently needs to be overcome in this field.

[0006] The present invention is based on the above discussion. Summary of the Invention

[0007] The purpose of this invention is to provide a chromium-iridium solid solution oxide electrocatalyst with a three-dimensional ordered macroporous structure, its preparation and application, so as to reduce the amount of noble metal Ir used, while maintaining excellent OER catalytic activity and long-term stability.

[0008] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a chromium-iridium solid solution oxide electrocatalyst with a three-dimensional ordered macroporous structure, comprising the following steps: S1. Add the chromium and iridium precursors to the PMMA colloidal crystal template solution, mix them evenly by ultrasonication, evaporate the solution to dryness, and then perform heat treatment. S2. The heat-treated product obtained in S1 is subjected to pre-acid leaching, then washed and dried to obtain a solid product, which is the target catalyst.

[0009] The chromium-iridium solid solution oxide catalyst prepared in this invention possesses significant structural and performance advantages. Its three-dimensional ordered macroporous structure and macroporous framework, composed of highly dispersed nanoscale (1-2 nm) chromium-iridium solid solution oxide particles, significantly increase the specific surface area, thereby exposing more active sites and enabling them to participate in the reaction, thus improving electrochemical activity. The chromium (Cr) element introduced into the material, as a Lewis acid, exhibits strong hydrophilicity, effectively improving the adsorption and activation process of water molecules on the catalyst surface and promoting water dissociation reactions. Simultaneously, the introduction of Cr can reduce the Ir loading while maintaining high catalyst activity, effectively alleviating the problems of dependence on precious metals and excessive cost. Furthermore, the chromium-iridium solid solution oxide exhibits excellent stability in acidic electrolyte environments, avoiding the rapid deactivation phenomenon of traditional high-Ir content catalysts during long-term operation. The catalyst preparation method is simple and controllable, with good scalability and large-scale potential. The catalyst described in this invention exhibits efficient and stable reaction performance in the PEMWE system, thus possessing significant application value in the fields of green hydrogen production and energy conversion.

[0010] Furthermore, in S1, the precursor of chromium used is chromium nitrate or its hydrate, and the precursor of iridium used is iridium acetate or its hydrate.

[0011] Furthermore, in S1, the amounts of chromium and iridium precursors added satisfy the following: the molar ratio of Cr to Ir is 7:3 to 8:2. Additionally, it should be noted that the concentrations of both chromium and iridium precursors in the mixed solution are independently 0.1 to 10 mmol / L.

[0012] Furthermore, in S1, the concentration of the PMMA colloidal crystal template solution is 0.1~1.0 g / mL.

[0013] Furthermore, in S1, the temperature at which the solution is evaporated to dryness is 50~90℃.

[0014] Furthermore, in S1, the heat treatment temperature is 350~550℃, the heating rate is 2~10℃ / min, and the holding time is 0.5~5 hours.

[0015] Furthermore, the PMMA colloidal crystal template solution is prepared by the following method: Under heating conditions, nitrogen gas is passed through deionized water for 0.5 to 1 hour, then an initiator is added and stirred thoroughly. Then, a methyl methacrylate solution is added, and the polymerization reaction is carried out under a nitrogen atmosphere. After centrifugation and washing, PMMA colloidal spheres are obtained, which are then ultrasonically dispersed in deionized water to obtain a PMMA colloidal crystal template solution.

[0016] Furthermore, the initiator is potassium persulfate or ammonium persulfate; The concentration of the initiator in the reaction system is 0.1~10 mmol / L, and the concentration of methyl methacrylate in the reaction system is 0.1~5 mol / L; The polymerization reaction is carried out at a temperature of 70℃~80℃ for a time of 0.5~2h.

[0017] Furthermore, the pre-acid leaching treatment uses a 0.1~1.0 mol / L H2SO4 or HCl solution, and the leaching time is 0.5~24h.

[0018] In a second aspect, the present invention provides a chromium-iridium solid solution oxide electrocatalyst with a three-dimensional ordered macroporous structure, which is prepared by the preparation method described in the first aspect above.

[0019] In a third aspect, the present invention provides the application of a chromium-iridium solid solution oxide electrocatalyst with a three-dimensionally ordered macroporous structure in water oxidation reactions or proton exchange membrane electrolysis of water. In application, this catalyst can efficiently perform oxygen evolution catalysis.

[0020] Compared with the prior art, the present invention has the following advantages: (1) Large specific surface area and fully exposed active sites. By introducing a three-dimensional ordered macroporous structure, and the macroporous framework is composed of highly dispersed nanoscale (1~2nm) chromium-iridium solid solution oxide particles, the specific surface area of ​​the material is effectively increased. The catalyst surface can provide more active sites, which is conducive to accelerating the reaction process at the electrode / electrolyte interface, thereby improving the intrinsic activity of the oxygen evolution reaction.

[0021] (2) The introduction of chromium improves hydrophilicity and reaction kinetics. As a Lewis acid, chromium has strong hydrophilicity, which can significantly improve the adsorption and activation behavior of water molecules on the catalyst surface, reduce the reaction energy barrier of OER, accelerate the conversion rate of key intermediates, and thus improve catalytic efficiency.

[0022] (3) Reduce the loading of precious metal Ir, significantly reducing costs. The introduction of the chromium-iridium solid solution structure can reduce the amount of Ir used while maintaining catalytic activity, effectively alleviating the problem of Ir scarcity and high price, and significantly reducing the overall cost of the catalyst in PEMWE membrane electrode applications.

[0023] (4) Enhanced structural stability and resistance to metal leaching. After pre-acid leaching treatment, the structural stability of the chromium-iridium solid solution oxide is significantly improved. It can maintain its activity for a long time in an acidic electrolysis environment, inhibiting the dissolution and loss of Ir during the electrolysis process, and exhibiting excellent cycle life and durability.

[0024] (5) The preparation method is easy to scale up. The template-assisted synthesis and post-processing process used in this invention is simple, highly controllable, suitable for mass production and industrial application, and has good prospects for promotion. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope (SEM) image of the PMMA colloidal crystal template prepared in Example 1 of the present invention.

[0026] Figure 2 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the catalyst (a, b).

[0027] Figure 3 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x Selected area electron diffraction (SAED) pattern of the catalyst.

[0028] Figure 4 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x Comparison of X-ray diffraction (XRD) of the catalyst with commercial Cr2O3 and IrO2 (a, b).

[0029] Figure 5 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x High-resolution X-ray photoelectron spectroscopy (XPS) of the catalyst (a, b).

[0030] Figure 6 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x Comparison of OER linear voltammetric scan curves of the catalyst with those of commercial Cr2O3 and IrO2.

[0031] Figure 7 The three-dimensional ordered macroporous structures 3DOM H-Cr with different Cr / Ir ratios prepared in Comparative Example 1 of this invention are examples of such structures. δ Ir 1-δ O x XRD patterns of the catalysts (δ = 1.0, 0.9, 0.75, 0.5, 0).

[0032] Figure 8 The three-dimensional ordered macroporous structures 3DOM H-Cr with different Cr / Ir ratios prepared in Comparative Example 1 of this invention are examples of such structures. δ Ir 1-δ O x Comparison of OER linear voltammetric scan curves of catalysts (δ = 1.0, 0.9, 0.75, 0.5, 0).

[0033] Figure 9 The 3DOM H-Cr prepared at different heat treatment temperatures in Comparative Example 2 of this invention 0.75 Ir 0.25 O x XRD pattern of the catalyst.

[0034] Figure 10 The 3DOM H-Cr prepared at different heat treatment temperatures in Comparative Example 2 of this invention 0.75 Ir 0.25 O x Comparison of OER linear voltammetric scan curves of the catalysts.

[0035] Figure 11 The H-Cr prepared in Comparative Example 4 of this invention 0.75 Ir 0.25 O x SEM image of the catalyst (without PMMA template).

[0036] Figure 12 The three-dimensional ordered macroporous structure 3DOM H-Cr prepared in Example 2 of this invention 0.75 Ir 0.25 O x Comparison of electrochemical polarization curves of the catalyst and the traditional IrO2 catalyst.

[0037] Figure 13 The diagram shows the structure of the electrolytic cell used in this invention and the 3DOM H-Cr prepared in Example 2. 0.75 Ir 0.25 O x and the 3DOM Cr prepared in Comparative Example 3 0.75 Ir 0.25 O x Performance diagrams (a, b) of the membrane electrode prepared without pre-acid leaching in proton exchange membrane water electrolysis (PEMWE). Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0041] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0042] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0043] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0044] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0045] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0046] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0047] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0048] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0049] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0050] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0053] In the following embodiments, chromium nitrate, iridium acetate, methyl methacrylate, potassium persulfate, and sulfuric acid solution were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Unless otherwise specified, the other raw materials or processing technologies are all commercially available products or conventional processing technologies in the art.

[0054] Preparation method of working electrode: Weigh 4 mg of the prepared catalyst material using an analytical balance, disperse it in 1 mL of a mixed solution of deionized water and ethanol (volume ratio of 4:1), add 20 μL of 5% Nafion solution, and sonicate for 30 min to obtain catalyst slurry. Take 5 μL and drop it onto a glassy carbon electrode with a diameter of 3 mm. After air drying, use it as the working electrode.

[0055] OER linear voltammetric scan curve and polarization curve test method: using a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and a glassy carbon electrode with a catalyst drop-coated as the working electrode, the OER linear voltammetric scan curve was obtained in a 0.5 mol / L sulfuric acid aqueous solution at a scan rate of 100 mV / s.

[0056] Polarization curve testing method: The polarization curve was obtained using the chronopotential method, with the current set to 10 mA / cm. 2 The experimental test temperature was 25 °C.

[0057] Preparation method of membrane electrode: using the 3DOM H-Cr prepared in Example 2 0.75 Ir 0.25 O x As the anolyte water oxidation catalyst, commercially available 20 wt% Pt / C was used as the cathode water reduction catalyst, and Nafion 115 was used as the proton exchange membrane solid electrolyte. Membrane electrodes were prepared using an ultrasonic spraying method. The specific steps are as follows: First, anode and cathode spraying slurries were prepared. A certain mass of catalyst material was weighed and dispersed in an isopropanol aqueous solution (the volume ratio of isopropanol to deionized water was 1:1). After ultrasonic dispersion, a certain volume of 20 wt% Nafion solution was added, and the mixture was ultrasonically mixed again until homogeneous. The mass ratio of catalyst to 20 wt% Nafion solution in the slurry was maintained at 4:5, and the mass ratio of catalyst to isopropanol aqueous solution was 1:100. The anode and cathode catalyst slurries were then sprayed onto both sides of the Nafion membrane using an ultrasonic spraying method. The cathode catalyst loading was 0.15 mg. Pt / cm 2 The anode catalyst loading was 0.25 mg. Ir / cm 2 The catalysts prepared in other comparative examples were used to prepare membrane electrodes using the same method.

[0058] Electrolytic cell electrolysis test method: Electrolysis current density set to 1 A / cm 2The temperature is 60 °C.

[0059] Electrochemical data were collected using a CHI 760E (Shanghai Chenhua) and Xinwei testing system.

[0060] Example 1: Preparation of PMMA colloidal crystal templates: PMMA colloidal crystal templates were prepared using emulsion polymerization. Deionized water was added to a three-necked flask, and the mixture was heated to 70°C. Nitrogen gas was bubbled through the flask for 30 minutes with magnetic stirring to remove dissolved oxygen. Potassium persulfate, the initiator, was then added to the deionized water, and the mixture was stirred thoroughly until a homogeneous mixture was obtained. Finally, methyl methacrylate (MMA) solution was rapidly added, and the polymerization reaction was carried out under continuous heating and magnetic stirring. After polymerization, the resulting PMMA emulsion was centrifuged and washed three times with deionized water to remove unreacted organic molecules and impurities. The resulting PMMA colloidal spheres were then ultrasonically dispersed again in deionized water to form a PMMA suspension (0.35 g / mL). The final concentration of potassium persulfate in the system was 2 mmol / L, and the final concentration of MMA was 1 mol / L. The polymerization reaction was carried out at 75°C for 1 hour after the addition of MMA.

[0061] Example 2: Three-dimensional ordered macroporous 3DOM H-Cr 0.75 Ir 0.25 O x Catalyst preparation: Cr(NO3)3·9H2O and Ir(OAC)3·3H2O were added to the PMMA suspension prepared in Example 1 above, with the concentrations of Cr(NO3)3·9H2O controlled at 7.5 mM and Ir(OAC)3·3H2O at 2.5 mM. The mixture was ultrasonically treated to ensure homogeneous mixing. The solution was then evaporated to dryness at 80°C, and the product was transferred to a muffle furnace for heat treatment. The temperature was increased from room temperature to 450°C at a rate of 5°C / min, and held at 450°C for 30 min to obtain the pre-catalyst. To enhance structural stability and suppress metal leaching during electrocatalysis, the heat-treated catalyst was subsequently subjected to a pre-acid leaching process. Specifically, the catalyst was soaked in a 0.5 M H2SO4 acidic solution for 24 h, washed with deionized water, and thoroughly dried to obtain the catalyst 3DOM H-Cr. 0.75 Ir 0.25 O x (Where, 3DOM represents a three-dimensional ordered macroporous structure, and H- represents the acid treatment step.) Comparative Example 1: Compared with Example 2, Comparative Example 1 changed the feed ratio of Cr and Ir elements to explore the effect of different Cr / Ir ratios on the oxygen evolution performance of the catalyst.

[0062] 3DOM H-Cr with different Cr / Ir ratios δ Ir 1-δ O x Preparation of catalysts (δ = 1.0, 0.9, 0.75, 0.5, 0): Cr(NO3)3·9H2O and Ir(OAC)3·3H2O were added to the PMMA suspension prepared in Example 1 above at molar ratios of Cr / (Cr+Ir) = 1.0, 0.9, 0.75, 0.5, and 0 (maintaining a total precursor molar concentration of 10 mM). The mixture was ultrasonically treated to ensure homogeneous mixing. The solution was then evaporated to dryness at 80°C, and the product was transferred to a muffle furnace for heat treatment. The temperature was increased from room temperature to 450°C at a rate of 5°C / min and held at 450°C for 30 min. Subsequently, the catalyst was soaked in a 0.5 M H2SO4 acidic solution for 24 h, washed with deionized water, and thoroughly dried to obtain the catalyst 3DOMH-CrO. x 3DOM H-Cr 0.9 Ir 0.1 O x 3DOM H-Cr 0.75 Ir 0.25 O x 3DOM H-Cr 0.5 Ir 0.5 O x 3DOM H-IrO x .

[0063] Comparative Example 2: Compared with Example 2, Comparative Example 2 changed the carbonization temperature of the material to investigate the effect of different heat treatment temperatures and the relative oxygen evolution performance of the catalyst.

[0064] 3DOM H-Cr at different calcination temperatures 0.75 Ir 0.25 O x Preparation of -T (T = 350℃, 400℃, 450℃, 500℃, 550℃) catalysts: 7.5 mM Cr(NO3)3·9H2O and 2.5 mM Ir(OAC)3·3H2O were added to the PMMA suspension prepared in Example 1 above, and the mixture was ultrasonically treated to ensure homogeneous mixing. The solution was then evaporated to dryness at 80°C, and the product was transferred to a muffle furnace for heat treatment. The temperature was increased from room temperature to 350°C, 400°C, 450°C, 500°C, and 550°C at a rate of 5°C / min, and held for 30 min. Subsequently, the catalyst was immersed in 0.5 M H2SO4 acidic solution for 24 h, washed with deionized water, and thoroughly dried to obtain the catalyst 3DOM H-Cr. 0.75 Ir 0.25 O x -350℃, 3DOM H-Cr 0.75 Ir 0.25 O x -400℃, 3DOM H-Cr 0.75 Ir 0.25 O x -450℃, 3DOM H-Cr 0.75 Ir 0.25 O x -500℃, 3DOM H-Cr 0.75 Ir 0.25 O x -550℃.

[0065] Comparative Example 3: Compared with Example 2, Comparative Example 3 omitted the pre-acid leaching step to investigate the effect of pre-acid leaching on catalyst stability.

[0066] No pre-acid leaching step 3DOM Cr 0.75 Ir 0.25 O x Catalyst preparation: 7.5 mM Cr(NO3)3·9H2O and 2.5 mM Ir(OAC)3·3H2O were added to the PMMA suspension prepared in Example 1 above, and the mixture was ultrasonicated to ensure homogeneous mixing. The solution was then evaporated to dryness at 80°C, and the product was transferred to a muffle furnace for heat treatment. The temperature was increased from room temperature to 450°C at a rate of 5°C / min, and held at 450°C for 30 min to obtain the catalyst 3DOM Cr. 0.75 Ir 0.25 O x .

[0067] Comparative Example 4: Compared with Example 2, Comparative Example 4 removed the PMMA template agent to investigate the effect of three-dimensional ordered macroporous structure on catalyst structure.

[0068] template-free H-Cr0.75 Ir 0.25 O x Catalyst preparation: 7.5 mM Cr(NO3)3·9H2O and 2.5 mM Ir(OAC)3·3H2O were added to 30 mL of aqueous solution, and the mixture was sonicated to ensure homogeneous mixing. The solution was then evaporated to dryness at 80 °C, and the product was transferred to a muffle furnace for heat treatment. The temperature was increased from room temperature to 450 °C at a rate of 5 °C / min and held for 30 min. Subsequently, the catalyst was immersed in 0.5 M H2SO4 acidic solution for 24 h, washed with deionized water, and thoroughly dried to obtain the catalyst H-Cr. 0.75 Ir 0.25 O x .

[0069] Figure 1 Scanning electron microscope (SEM) images of the PMMA colloidal crystal template prepared in Example 1 are shown. The images reveal that the obtained PMMA colloidal spheres are regularly arranged, exhibiting a typical hexagonal close-packed structure, indicating that this method can successfully prepare highly ordered three-dimensional colloidal crystals. The images show that the PMMA colloidal spheres are uniform in size, approximately 120 nm in diameter, and are concentrated in distribution, with close packing and few defects. This ordered colloidal template provides an ideal structural basis for the subsequent construction of three-dimensional ordered macroporous inorganic oxide catalysts.

[0070] Figure 2 The 3DOM H-Cr with a three-dimensional ordered macroporous structure prepared in Example 2 of this invention is shown. 0.75 Ir 0.25 O x Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the catalyst (a, b). Among them, Figure 2 The scanning electron microscope image of a clearly shows a uniformly distributed periodic porous array on the material surface, with pore sizes in the range of hundreds of nanometers, indicating that the template method used can effectively replicate the ordered arrangement characteristics of the polymer template. Figure 2 The transmission electron microscopy (TEM) image of b further reveals the internal morphology of the structure, showing a three-dimensional ordered macroporous framework composed of continuous channels and interconnected pore walls. This macroporous framework consists of highly dispersed nanoscale (1-2 nm) chromium-iridium solid solution oxide particles. This macroporous structure and the pore wall features of the highly dispersed nanoscale (1-2 nm) particles not only facilitate sufficient electrolyte wetting and rapid transport of reactants / products, but also expose more active sites, thereby improving the catalyst's utilization efficiency and overall performance in electrochemical reactions.

[0071] Figure 3 The 3DOM H-Cr with a three-dimensional ordered macroporous structure prepared in Example 2 of this invention is shown. 0.75 Ir0.25 O x Selected area electron diffraction (SEED) pattern of the catalyst. Clear ring-shaped diffraction patterns are observed in the image, indicating that the material has a polycrystalline structure. The yellow-marked diffraction rings correspond to the characteristic crystal planes (110) and (200) of IrO2, reflecting the presence of the Ir component in the solid solution. The white-marked diffraction rings correspond to the characteristic crystal planes (110), (113), (116), and (300) of Cr2O3, indicating the contribution of Cr elements in the crystal lattice. These results collectively verify that Cr and Ir form a solid solution structure in the catalyst, and that the characteristic diffraction peaks of different metal oxide phases appear synergistically in this solid solution system, further confirming the three-dimensional ordered structure and solid solution properties of the material.

[0072] Figure 4 The 3DOM H-Cr with a three-dimensional ordered macroporous structure prepared in Example 2 of this invention is shown. 0.75 Ir 0.25 O x Comparison of X-ray diffraction (XRD) images of the catalyst and commercial Cr2O3, IrO2 (a, b). From Figure 4 As can be seen from a, 3DOM H-Cr 0.75 Ir 0.25 O x The diffraction peaks corresponding to the characteristic crystal planes of IrO2 in the sample are generally broadened, indicating that Ir mainly exists in an amorphous state in the material. This amorphous structure is beneficial for exposing more active sites, thereby enhancing the catalytic activity of the oxygen evolution reaction. Meanwhile, several diffraction peaks originating from Cr2O3 can still be observed in the sample, indicating that Ir and Cr achieve a synergistic effect in the solid solution. Further analysis... Figure 4 As can be seen from the magnified image of b, compared with pure Cr2O3, the catalyst of this invention exhibits a significant shift in diffraction peaks at the (116) crystal plane. This result indicates that the introduction of Ir leads to lattice distortion. This lattice regulation, combined with the synergistic effect of amorphous Ir species, endows the material with excellent electrocatalytic performance.

[0073] Figure 5 The 3DOM H-Cr with a three-dimensional ordered macroporous structure prepared in Example 2 of this invention is shown. 0.75 Ir 0.25 O xHigh-resolution X-ray photoelectron spectroscopy (XPS) of the catalyst (a, b). In this invention, by introducing Cr to form a solid solution oxide with Ir, effective control of the electronic structure of the active center is achieved. XPS results show that, compared to the control sample Cr₂O₃, the Cr 2p peak in the solid solution shifts towards higher binding energies, indicating a slight increase in the valence state of some Cr. Conversely, compared to IrO₂, the Ir 4f peak in the solid solution shifts towards lower binding energies, indicating that Ir exists in a relatively lower valence state. This indicates a significant electron transfer between Cr and Ir, with electrons migrating from Cr to Ir. This synergistic valence state control not only improves the catalyst's band structure and d-orbital electron distribution but also optimizes the adsorption energy for key reaction intermediates (such as *OH, *O, and *OOH). Notably, the decrease in Ir's valence state effectively slows its dissolution behavior during the reaction, thereby further enhancing the catalyst's structural stability. In summary, this synergistic effect jointly promotes the high activity and excellent stability of the catalyst under acidic conditions for OER.

[0074] Figure 6 The 3DOM H-Cr with a three-dimensional ordered macroporous structure prepared in Example 2 of this invention is shown. 0.75 Ir 0.25 O x Comparison of OER linear voltammetric scans of the catalyst with those of commercial Cr2O3 and IrO2. The figure shows that 3DOM H-Cr... 0.75 Ir 0.25 O x The catalyst exhibits a higher current density at the same potential, significantly superior to the control samples Cr2O3 and IrO2, indicating faster reaction kinetics and better catalytic activity. Cr2O3 showed almost no significant catalytic current, while IrO2, as a control, exhibited some activity, but it was still significantly lower than that of the catalyst of this invention. These results demonstrate that the solid solution structure not only effectively reduces the amount of Ir used but also significantly improves the oxygen evolution activity of the catalyst, exhibiting performance advantages over existing technologies.

[0075] Figure 7 This invention demonstrates three-dimensional ordered macroporous 3DOM H-Cr with different Cr / Ir ratios prepared in Comparative Example 1. δ Ir 1-δ O x XRD patterns of the catalysts (δ = 1.0, 0.9, 0.75, 0.5, 0). As shown in the figure, each sample exhibits characteristic diffraction peaks corresponding to Cr2O3 and IrO2, indicating the formation of an Ir–Cr solid solution structure in the material; meanwhile, no obvious metallic Ir peaks were detected.

[0076] Figure 8 This invention demonstrates three-dimensional ordered macroporous 3DOM H-Cr with different Cr / Ir ratios prepared in Comparative Example 1. δ Ir 1-δ O x Comparison of OER linear voltammetric scan curves for the catalysts (δ = 1.0, 0.9, 0.75, 0.5, 0). It can be seen that IrO... x Although the sample exhibited some catalytic activity, its overall current density was lower than that of the solid-solution catalyst; while pure CrO x The lack of a noticeable current response indicates limited catalytic activity in the oxygen evolution reaction. Introducing an appropriate amount of Ir significantly improved the catalytic activity, particularly 3DOM H-Cr. 0.75 Ir 0.25 O x The optimal current response indicates that proper control of element content helps achieve a balance between activity and cost.

[0077] Figure 9 This invention demonstrates the 3DOM H-Cr prepared in Comparative Example 2 of the present invention at different heat treatment temperatures. 0.75 Ir 0.25 O x The XRD patterns of the -T (T = 350℃, 400℃, 450℃, 500℃, 550℃) catalysts show that each sample exhibits characteristic diffraction peaks corresponding to Cr₂O₃ and IrO₂, indicating that Ir and Cr can form solid solution structures at different temperatures. With increasing heat treatment temperature, the diffraction peaks gradually become sharper and more intense, indicating a continuous improvement in the crystallinity of the material. Simultaneously, the positions of some characteristic peaks show slight shifts, reflecting an adjustment in the crystal structure due to the heat treatment conditions. These results demonstrate that by controlling the heat treatment temperature, the crystallinity and lattice structure of Cr–Ir solid solution oxides can be effectively adjusted, thus providing a structural basis for optimizing their electrocatalytic performance.

[0078] Figure 10 This invention demonstrates the 3DOM H-Cr prepared in Comparative Example 2 of the present invention at different heat treatment temperatures. 0.75 Ir 0.25 O x Comparison of OER linear voltammetric scan curves for the -T (T = 350℃, 400℃, 450℃, 500℃, 550℃) catalysts. The sample obtained at 450℃ exhibits the best OER performance compared to other carbonization temperatures.

[0079] Figure 11 This invention demonstrates the H-Cr without PMMA template agent prepared in Comparative Example 4. 0.75 Ir 0.25 Ox Scanning electron microscopy (SEM) images of the catalyst. The images clearly show that the sample exhibits a densely aggregated particle morphology with blurred interparticle boundaries, a relatively compact overall structure, and uneven pore distribution. This indicates that without the introduction of the template agent PMMA during synthesis, the system lacks effective spatial confinement, leading to uneven nucleation and growth of the precursor during heat treatment. This results in easy sintering and aggregation of particles, forming a bulky cluster structure. Compared to the three-dimensional ordered macroporous structure and highly dispersed nanoparticle (1-2 nm) pore wall characteristics of catalysts prepared using the PMMA template method, the template-free sample has insufficient exposure of active sites, limiting mass transfer between the electrolyte and reactant molecules, thus reducing catalytic activity. Furthermore, the agglomerated structure may also lead to insufficient electrode surface contact during catalysis, further affecting its stability and electron transport efficiency. Therefore, Figure 11 The key role of the template agent PMMA in the preparation system of this invention was verified. By guiding the formation of an ordered porous network structure, it can effectively inhibit particle aggregation and increase the exposure of active sites, thereby significantly improving the structural uniformity and catalytic performance of the catalyst.

[0080] Figure 12 At a constant current density (10 mA cm⁻¹) -2 Under the specified conditions, the traditional IrO2 catalyst and the 3DOM H-Cr catalyst prepared in this invention were compared and tested. 0.75 Ir 0.25 O x Electrochemical stability of the catalyst. As shown in the figure, the potential of the IrO2 electrode rises rapidly after about 120 hours of reaction, indicating significant deactivation during long-term operation. In contrast, the 3DOM H-Cr of this invention… 0.75 Ir 0.25 O x The catalyst exhibited excellent stability under the same conditions; its potential showed almost no significant increase after 200 hours of continuous testing, remaining around 1.58 V (vs. RHE), indicating that its structure and active sites possess higher durability and resistance to dissolution during the acidic oxygen evolution reaction. Therefore, the 3DOM H-Cr catalyst of this invention... 0.75 Ir 0.25 O x By introducing the Lewis acidic element Cr, the electronic structure of the Ir active site was regulated, effectively inhibiting the excessive oxidation and dissolution of Ir species, thereby significantly improving the long-term stability of the catalyst under acidic conditions.

[0081] Figure 13 The diagram shows the structure of the electrolytic cell used in this invention and the 3DOM H-Cr prepared in Example 2. 0.75 Ir 0.25 Ox , and the untreated sample 3DOM Cr prepared in Comparative Example 3 0.75 Ir 0.25 O x Polarization performance diagrams (a, b) in proton exchange membrane water electrolysis (PEMWE). From Figure 13 As can be seen from a, the electrolytic cell mainly consists of end plates, titanium felt, membrane electrode assembly (MEA), and polytetrafluoroethylene gaskets. The catalyst prepared in this invention is applied to the anode side of the membrane electrode to achieve a highly efficient oxygen evolution reaction. From Figure 13 b shows that in Comparative Example 3, 3DOM Cr without pre-acid leaching treatment 0.75 Ir 0.25 O x The catalyst exhibited a high voltage during operation, while the 3DOM H-Cr pre-acid-leached catalyst in Example 2... 0.75 Ir 0.25 O x The catalyst exhibits lower voltage and a more stable operating potential. These results demonstrate that pre-acid leaching not only enhances catalyst activity but also effectively improves its stability, thereby significantly improving the overall performance of the proton exchange membrane water electrolysis system.

[0082] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for the preparation of a chromium iridium solid solution oxide electrocatalyst having a three-dimensionally ordered macroporous structure, characterized in that, The method comprises the following steps: S1, adding a chromium precursor and an iridium precursor into a PMMA colloidal crystal template solution, ultrasonic mixing, evaporating the solution, and then performing a heat treatment; S2, performing a pre-acid immersion treatment on the product obtained after the heat treatment in S1, and then cleaning, drying, and obtaining a solid product, i.e., a target catalyst.

2. A process for the preparation of a chromium iridium solid solution oxide electrocatalyst having a three-dimensionally ordered macroporous structure according to claim 1, characterized in that, In S1, the chromium precursor is chromium nitrate or a hydrate thereof, and the iridium precursor is iridium acetate or a hydrate thereof.

3. The method of claim 1, wherein the method is characterized by: In S1, the chromium precursor and the iridium precursor are added in an amount that satisfies a molar ratio of Cr to Ir of 7:3-8:

2.

4. The method of claim 1, wherein the method is characterized by: In S1, the PMMA colloidal crystal template solution has a concentration of 0.1-1.0 g / mL.

5. The method of claim 1, wherein the method is characterized by: In S1, the heat treatment is performed at a temperature of 350-550℃, a heating rate of 2-10℃ / min, and a holding time of 0.5-5 hours.

6. The method of claim 1, wherein the method further comprises the step of: The PMMA colloidal crystal template solution is prepared by the following method: ​ Under a heating condition, nitrogen is introduced into deionized water for 0.5-1 hour, an initiator is then added, and the reaction system is fully stirred and mixed, and then methyl methacrylate solution is added, and a polymerization reaction is performed under the protection of a nitrogen atmosphere, and then centrifugation and washing are performed to obtain PMMA colloidal spheres, which are then ultrasonically dispersed in deionized water to obtain the PMMA colloidal crystal template solution.

7. A process for the preparation of a chromium iridium solid solution oxide electrocatalyst having a three-dimensionally ordered macroporous structure according to claim 6, characterized in that, The initiator is potassium persulfate or ammonium persulfate; The concentration of the initiator in the reaction system is 0.1-10 mmol / L, and the concentration of methyl methacrylate in the reaction system is 0.1-5 mol / L; The polymerization reaction is performed at a temperature of 70-80℃ for 0.5-2 hours.

8. The method of claim 1, wherein the method further comprises the step of: In S2, the pre-acid immersion treatment is performed using a 0.1-1.0 mol / L H2SO4 or HCl solution, and the immersion time is 0.5-24 hours. ​ 9. A chromium-iridium solid solution oxide electrocatalyst having a three-dimensionally ordered macroporous structure, which is prepared by the method according to any one of claims 1-8.

10. Use of the chromium-iridium solid solution oxide electrocatalyst having a three-dimensionally ordered macroporous structure according to claim 9 in a water oxidation reaction or a proton exchange membrane electrolysis water.

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