A method for preparing a gradient embedded rod-shaped TiO2 supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis and application thereof

Abstract

The application relates to a method for preparing a gradient embedded rod-shaped TiO2 loaded IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis and application, wherein a selected titanium precursor is used as raw material, ammonia water is used for precisely controlling a hydrolysis rate to realize controllable in-situ hydrolysis of the titanium precursor, and a mercapto group and an amino group are used for guiding crystal growth into a rod-shaped TiO2 carrier with regular crystal phase; in the TiO2 growth process, an Ir precursor is reduced into superfine Ir black by using a reducing alcohol, the addition interval of titanium and the Ir precursor is controlled, in-situ gradient embedding of the Ir black in a surface layer and a subsurface layer of the TiO2 is realized; then, unstable titanium species on the surface of the carrier is removed through acid pickling, active sites are fully exposed, finally, the Ir black is oxidized into regular IrO2 through heat treatment, a continuous ultra-thin coating layer is formed, Ti-O-Ir interface covalent interaction is strengthened, finally, an oxygen evolution electrocatalyst with low iridium loading, high catalytic activity and long-term stability is obtained, and the oxygen evolution electrocatalyst can adapt to harsh working conditions of PEM electrolytic water acid OER.

Description

Technical Field

[0001] This invention belongs to the technical field of key materials for proton exchange membrane (PEM) water electrolysis, specifically relating to a method and application for preparing gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis. Background Technology

[0002] High-efficiency hydrogen production via water electrolysis using renewable energy is an ideal way to achieve zero carbon emissions and high-purity green hydrogen, and a strategic high-tech solution to the critical needs of carbon neutrality nations. Compared to alkaline water electrolysis, proton exchange membrane electrolysis (PEMWE) technology offers numerous advantages, including smaller tank volume, lower energy consumption, higher efficiency, better hydrogen quality, and more reliable operation, making it the best foreseeable method for obtaining "green hydrogen." The PEMWE anode oxygen evolution catalyst is primarily iridium-based materials (iridium oxide, iridium black, supported iridium, etc.). Given that the current annual iridium ore mining volume is 4-9 tons, to achieve terawatt-scale application of PEMWE, the total iridium (Ir) loading at the anode (approximately 2 mg·cm³) is required. -2 The cost needs to be reduced by about an order of magnitude. Furthermore, the limited intrinsic activity of iridium-based materials, their susceptibility to oxidation and dissolution under high current and fluctuating power conditions, and structural instability severely limit their large-scale application in PEMWEs. To reduce the cost of PEMWE electrolyzers, increasing current density and adapting to the fluctuating power conditions of wind and solar power are the most efficient, convenient, and feasible solutions. Therefore, developing a high-conductivity, high-interfacial-bonding material with low iridium content and adaptability under high current conditions (>3A·cm) is crucial. -2 Maintaining high activity and durability of PEMWE anode OER catalysts is an important research direction.

[0003] TiO2, as a typical oxide support, is an ideal support for loading Ir-based active components due to its excellent structural stability, resistance to high-potential oxidation, and low cost. Rutile TiO2, in particular, is more suitable for the harsh anodic environment driven by fluctuating power supplies due to its more stable crystal structure and superior oxidation resistance. However, traditional processes often use commercial TiO2 as a support, which suffers from problems such as uneven particle size and poor controllability of surface defects. At the same time, traditional loading methods can only achieve physical adsorption of Ir-based active components, resulting in weak interfacial bonding and an inability to suppress the aggregation, shedding, and oxidative dissolution of active particles. The electron transfer efficiency between the support and the active component is extremely low, which is a common problem faced by TiO2-supported noble metal catalysts.

[0004] Existing supported Ir-based catalyst preparation technologies mostly employ simple impregnation and hydrothermal loading methods, which only achieve the attachment of active components to the support surface. They cannot achieve directional gradient embedding and strong anchoring of IrO2 through the in-situ growth process of TiO2, and they do not effectively remove unstable titanium species on the support surface. This makes it difficult to solve the core problems of weak interfacial bonding between TiO2 support and active phase, low Ir atom utilization, and insufficient stability of the catalytic system. Even with post-modification and support optimization, gradient embedding and continuous coating of active components cannot be achieved. Under harsh conditions of acidity, high potential, and high current, the catalyst is prone to structural collapse, loss of active components, and rapid performance degradation, failing to meet the industrial requirements for long-term stable operation of PEMWE. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a method and application for the in-situ hydrolysis preparation of a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst. The method achieves a gradient-intercalated IrO2-supported catalyst by controlling the slow hydrolysis of the Ti precursor. A thiamine salt containing thiol groups (-SH) and amino groups (-NH2) is introduced, utilizing its growth inhibition effect on the rutile phase TiO2 110 crystal facets to guide the directional growth of TiO2 crystals into a rod-shaped structure. Simultaneously, gradient intercalation and strong interfacial bonding of IrO2 are achieved on the rod-shaped TiO2 support. Through crystal facet orientation control, directional reduction with reducing alcohols, lattice growth confinement, precise impurity removal via acid washing, and the synergistic electronic effect at the Ir-O-Ti interface, the activity, conductivity, and structural stability of the TiO2-supported Ir-based oxygen evolution electrocatalyst are comprehensively enhanced.

[0006] The technical solution adopted in this invention is as follows: A method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis includes the following steps: (1) Weigh out the titanium precursor and dissolve it in isopropanol. Stir magnetically to obtain a uniform and transparent Ti precursor isopropanol solution. In this way, isopropanol is used as a dispersion medium to avoid the rapid hydrolysis of the titanium precursor when it comes into contact with water, thus laying the foundation for a homogeneous system for subsequent controllable hydrolysis and crystal surface regulation. (2) Add a complexing agent and a thiamine salt to the isopropanol solution of the Ti precursor, stir at room temperature until completely dissolved, then add the iridium precursor dropwise, and continue stirring to obtain a Ti-Ir blended precursor isopropanol suspension; thus, the thiamine salt is adsorbed onto the potential growth surface of the TiO2 crystal nucleus through the synergistic effect of the thiol group and the amino group, thereby inhibiting the growth of the rutile phase 110 crystal face and guiding the TiO2 to grow into a rod-shaped structure, while the complexing agent interacts with Ir 4+ To form stable chelates, optimize the intermolecular interaction between Ti and Ir precursors, avoid spontaneous aggregation of Ir ions, and achieve molecular-level uniform mixing of Ti-Ir precursors; (3) The isopropanol suspension of the blended precursor is placed in an ice-water bath, and a pH adjuster is slowly added dropwise while continuously stirring to adjust the pH of the system, so that the titanium precursor is slowly hydrolyzed and preferentially nucleated to form TiO2 crystal nuclei and grow. The thiamine salt continues to play a crystal face regulation role as the TiO2 crystal nuclei grow, avoiding the aggregation of TiO2 grains and random crystal face growth caused by rapid hydrolysis, and obtaining a TiO2 crystal nucleus growth suspension; (4) Keep stirring and place in an ice-water bath, then continue the reaction under ultrasonic conditions to allow the chelated Ir in the system to remain in the system. 4+ Under the reducing action of isopropanol, it is reduced to ultrafine Ir black nanoparticles (abbreviated as "Ir black"). The Ir black nanoparticles are in situ gradient embedded into the surface and subsurface of TiO2 during the growth process, resulting in a TiO2 suspension with gradient embedding of Ir black nanoparticles. Due to their extremely small particle size and strong diffusion and migration ability, the Ir black nanoparticles can efficiently penetrate into and be in situ gradient embedded into the lattice defect sites of the carrier during the growth process of rod-shaped TiO2 crystals. At the same time, relying on the synergistic effect of ultrasound and low temperature, the rod-shaped TiO2 crystals are further refined, ensuring that Ir black is uniformly dispersed in TiO2, inhibiting the secondary agglomeration of active components, and without destroying the rod-shaped crystal structure regulated by thiamine salt. (5) The reaction product of step (4) is subjected to solid-liquid separation. The solid phase is washed alternately with isopropanol and ultrapure water until neutral to remove residual impurity ions and mercaptoamine salts that have not participated in crystal face regulation. The washed solid phase product is dried under vacuum and then ground into powder to obtain TiO2@Ir catalyst precursor. (6) The TiO2@Ir catalyst precursor was placed in an acid solution for acid washing to precisely remove the surface unstable titanium species formed during the in-situ hydrolysis of TiO2, and to break up the titanium species coated on the surface of Ir black nanoparticles to fully expose the active sites, while not destroying the rod-shaped TiO2 crystal structure and the gradient intercalation state of Ir black; after solid-liquid separation, it was washed to neutral and dried to obtain the acid-washed catalyst precursor; (7) The precursor after step (6) is heat-treated to oxidize the Ir black nanoparticles into the IrO2 active phase with regular crystal phase. At the same time, the gradient-embedded Ir black is used as seed crystal to induce the IrO2 to grow in a directional manner along the defect sites of the rod-shaped TiO2 support, which greatly strengthens the Ir-O-Ti covalent interface bonding between the TiO2 support and the IrO2 active phase. The thiamine salt is gradually decomposed during the heat treatment process, leaving no residue and not affecting the catalytic performance. The heat-treated product is naturally cooled, washed, and dried to obtain the gradient-embedded rod-shaped TiO2 supported IrO2 oxygen evolution electrocatalyst.

[0007] In step (1), the titanium precursor is one or more of triethanolamine isopropoxide titanium (TTEAIP), tetrabutyl titanate, titanium isopropoxide, and titanium tetrachloride; In step (2), the complexing agent is one or more of anhydrous citric acid, sodium citrate, and disodium ethylenediaminetetraacetate; The thiamine salt is one or more of the following: mercaptoethylamine methacrylate, N-(2-mercaptoethyl)acrylamide, 3-mercapto-1-propane hydrochloride, and cysteine ​​hydrochloride; The molar ratio of the titanium precursor to the thiamine salt is (1-3):1; preferably 2:1. The iridium precursor is an aqueous solution of Ir salt; the Ir salt is one or more of chloroiridium acid, iridium chloride, and iridium nitrate, and the molar ratio of the complexing agent to the Ir salt is (0.5-2):1, preferably 1:1.

[0008] In step (1), the magnetic stirring time is 20-40 min and the stirring speed is 300-600 rpm; In step (2), the interval between the addition of the titanium precursor and the iridium precursor is 10-60 min, preferably 30 min; In step (2), the time for stirring at room temperature until the complexing agent dissolves is 20-40 min, and the time for stirring at room temperature after adding the Ir salt solution is 0.5-2 h, with a stirring speed of 300-600 rpm throughout the process; In step (3), the pH adjuster is ammonia water; the pH of the ammonia water system is 8-10; the dropping rate of ammonia water is 0.5-2 mL / min, the total dropping time is 30-60 min; the ice water bath temperature is 0-5℃, and the ice water bath stirring speed is 300-600 rpm.

[0009] In step (4), the reaction continues for 2-4 hours, the stirring rate is 300-600 rpm, the ice-water bath temperature is 0-5℃, the ultrasonic power is 300-500W, and the ultrasonic time is 30-60 min.

[0010] In step (5), solid-liquid separation is carried out by vacuum filtration or centrifugation. The centrifugation speed is 8000-12000 rpm. The washing liquid is washed until the conductivity is <1μS / cm. The vacuum drying temperature is 50-80℃ and the drying time is 8-12h.

[0011] In step (6), the acid solution is one or more of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, and the molar concentration of the acid solution is 0.05-0.5 mol / L, preferably 0.1 mol / L; the acid washing temperature is 25-40℃, the acid washing time is 10-60 min, preferably 30 min; after acid washing, solid-liquid separation is carried out by vacuum filtration or centrifugation, and after washing to neutrality, the drying temperature is 40-60℃, and the drying time is 4-8 h.

[0012] In step (7), the precursor is placed in a tube furnace and subjected to programmed temperature rise heat treatment in an air atmosphere; The temperature rise rate of the programmed temperature rise is 2-5℃ / min, the temperature of the heat treatment is 400-500℃, the holding time is 2-6h, and the air flow rate is 30-60mL / min; the heat treatment product is washed with ultrapure water 2-3 times, the drying temperature is 50-70℃, and the drying time is 6-12h.

[0013] The gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst prepared by the method is described.

[0014] The application of the gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst in the oxygen evolution reaction at the anode of proton exchange membrane water electrolysis.

[0015] This invention utilizes complexing agents such as anhydrous citric acid to achieve the reaction of carboxylic acid groups with hydroxyl groups and Ir. 4+ By forming stable coordination bonds and combining them with the TiO2 lattice defects naturally formed during the in-situ hydrolysis of the titanium precursor, strong chemical anchoring of Ir ions can be achieved. This results in a TiO2@Ir precursor with uniform defect distribution and orderly coordination, thus ensuring precise control of Ir atom arrangement and interface structure during subsequent reduction, acid washing, and oxidative heat treatment. The TiO2 lattice defects, acting as natural anchor points, can firmly fix the IrO2 component to the surface and subsurface of the support. Combined with the gradient embedding structure, this effectively prevents the migration, aggregation, and detachment of active components, thereby inhibiting catalyst structure degradation from the root.

[0016] Based on the interfacial chemical bonding and crystal confinement growth mechanism, this invention utilizes the TiO2 lattice gradient defects constructed through the controlled hydrolysis of the titanium precursor to provide preferential nucleation sites for the Ir component. During reduction and oxidation thermal treatment, gradient embedding growth of IrO2 is achieved. Some IrO2 is completely embedded in the TiO2 subsurface, some is partially embedded and exposed on the support surface, and a small amount is uniformly attached to the outer surface, forming a three-dimensional interfacial anchoring structure. This embedding structure significantly enhances the bonding strength between the support and the active phase by strengthening the Ir-O-Ti covalent interfacial bonds, while simultaneously optimizing the interfacial electron transport path, achieving a simultaneous improvement in catalytic activity and structural stability.

[0017] The TiO2-supported IrO2 catalyst prepared in this invention has IrO2 active components coated on the surface of the TiO2 support in a uniform and continuous ultrathin shell, without agglomeration, segregation, or phase separation. The ultrathin shell maximizes the exposure of active sites and shortens the charge transport distance. At the same time, the well-ordered crystalline support formed by the in-situ hydrolysis of TiO2 significantly improves the electron conduction efficiency and significantly accelerates the OER reaction kinetics. The synergistic structure of gradient embedding and ultrathin shell, combined with the full exposure of active sites brought about by acid leaching, ensures both a high active site density and excellent structural stability of the catalyst. Under high current and strong oxidizing acid conditions, it effectively inhibits Ir dissolution, particle agglomeration, and structural collapse, significantly reducing the catalyst deactivation and performance degradation rate.

[0018] The in-situ hydrolysis method for preparing gradient-intercalated TiO2-supported IrO2 provided by this invention has significant advantages compared with traditional impregnation methods, hydrothermal loading methods, and post-modification methods using commercial TiO2: (1) Defects are naturally controllable: The density and distribution of lattice defects on the TiO2 surface are precisely controlled by the hydrolysis rate of the titanium precursor, so as to achieve quantitative control of the loading, distribution state and embedding depth of active components without the need for additional etching process. (2) Strong interfacial anchoring: The combination of complexation coordination and defect anchoring mechanisms forms a stable Ir-O-Ti covalent bond, solving the core pain points of easy detachment of the active phase and weak interfacial bonding in traditional supported catalysts; (3) Highly uniform morphology: Uniform IrO2 ultrathin shell and gradient embedded structure can be prepared in batches. The process has good repeatability and mild conditions, which is convenient for industrial scale-up production. (4) Excellent intrinsic performance of the carrier: In-situ hydrolysis of titanium precursor directly generates rod-shaped TiO2 carrier with regular crystal phase and uniform particle size, avoiding the problems of uneven particle size and poor defect controllability of commercial TiO2, and improving the intrinsic electronic conduction efficiency of the carrier. (5) Gradient loading order: Based on the gradient defect sites formed by TiO2 lattice growth, the IrO2 active components are embedded and loaded in an orderly manner from the surface layer to the subsurface layer of the support. The active phase distribution is free from segregation and agglomeration, and the acid washing process further exposes the active sites and improves the atomic utilization rate.

[0019] Furthermore, the gradient-intercalated TiO2-supported IrO2 oxygen evolution electrocatalyst with optimized preparation conditions exhibited significantly better OER catalytic performance than commercial IrO2 and traditional TiO2-supported IrO2 catalysts: in 0.5 M H2SO4 electrolyte, at 10 mA·cm⁻¹ -2 The overpotential at current density is as low as 253 mV, and the Tafel slope is only 73.07 mV·dec. -1 The double-layer capacitance and electrochemical active area are significantly improved; when applied to PEMWE single cells, the Ir loading is only 0.2 mg Ir·cm⁻¹.-2 ,2A·cm -2 At current density, the cell voltage drops to 1.718V, 3A·cm. -2 The tank voltage is only 1.82V, which fully meets the core requirements of commercial PEM water electrolysis catalysts for activity, stability and low iridium dosage.

[0020] The beneficial effects of this invention are as follows: This invention provides a method and application for the in-situ hydrolysis preparation of a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst, comprising the following steps: Triethanolamine isopropoxide titanium (TTEAIP) is weighed and dissolved in isopropanol, and magnetically stirred to obtain a homogeneous and transparent Ti precursor isopropanol solution; anhydrous citric acid complexing agent and thiamine salt are added to the Ti precursor isopropanol solution, stirred at room temperature until completely dissolved, and then chloroiridium acid solution is added dropwise, with continued stirring to obtain a Ti-Ir blended precursor isopropanol suspension; the above blended precursor suspension is placed in an ice-water bath, and ammonia is slowly added dropwise under continuous stirring to precisely control the pH of the system, allowing TTEAIP to slowly hydrolyze and preferentially nucleate in the isopropanol system, gradually generating and growing TiO2 crystal nuclei; maintaining the ice-water bath and stirring state, and simultaneously placing it in a high-power ultrasonic generator for grain refinement, under the in-situ reduction effect of the reducing alcohol in the system, chelated Ir... 4+ Gradually reduced to ultrafine Ir black nanoparticles, these particles infiltrate in situ and gradient-embed with the surface and subsurface lattice defect sites of TiO2 during its growth, forming an Ir black gradient-embedded TiO2 suspension. The completely reacted suspension is centrifuged to separate the solid and liquid phases, and the solid product is collected and washed alternately with isopropanol and ultrapure water. The washed solid product is dried in a vacuum drying oven and ground into a fine powder to obtain a rod-shaped Ir black gradient-embedded TiO2 catalyst precursor. The TiO2@Ir catalyst precursor is then subjected to acid washing in an acid solution to remove unstable titanium species from the surface. After solid-liquid separation, it is washed until neutral. Drying; the above precursor is placed in a tube furnace and heat-treated in an air atmosphere to completely oxidize the embedded ultrafine Ir black into a well-defined IrO2 active phase, while simultaneously strengthening the Ir-O-Ti covalent interface bond between the TiO2 support and the IrO2 active phase; the heat-treated product is washed with ultrapure water and dried in an oven to finally obtain a gradient-embedded TiO2-supported IrO2 oxygen evolution electrocatalyst; by adjusting the stoichiometric ratio of TTEAIP to chloroiridium acid, the growth rate of rod-shaped TiO2 and the amount of Ir black embedded can be precisely controlled, achieving directional control of catalyst structure and catalytic performance. The in-situ hydrolysis preparation of the gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst of this invention has the characteristics of low iridium loading, high catalytic activity and long-term stability, and can be well adapted to the harsh conditions of acidic OER in PEM water electrolysis. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are TEM images of TiO2@IrO2 with different Ti precursor hydrolysis loads obtained in this invention. Figures a, b, and c correspond to TEM images of the material samples obtained in Comparative Example 3, Example 2, and Comparative Example 2, respectively. Figure 2 These are TEM and SEM images of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of this invention. Figures a and b correspond to the SEM images of the sample obtained in Example 1, Figure c corresponds to the TEM image of the sample obtained in Example 1, and Figure d corresponds to the EDS-TEM image of the sample obtained in Example 1. Figure 3 This is an aberration-corrected electron microscope image of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of the present invention. Figures a and b correspond to images with 10 nm and 5 nm scales, respectively. Figure 4 These are the Ir L-edge XAS and EXAFS characterization diagrams of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Examples 1-5 of this invention; wherein, a is the Ir L-edge XAS spectrum and b is the EXAFS characterization diagram. Figure 5 Figure a is an elemental distribution diagram of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of this invention. Figures a, b, and c correspond to the distribution diagrams of Ir, Ti, and O elements at the catalyst-support interface, respectively. Figure 6 The PEMWE single-cell polarization curves of TiO2@IrO2 oxygen evolution electrocatalysts with different Ti precursor hydrolysis loadings and different Ti-Ir precursor drop intervals obtained in Examples 1-3 and Comparative Examples 1-2 of this invention, as well as the comparative samples, are shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Traditional TiO2-supported IrO2 oxygen evolution electrocatalysts have significant limitations in PEM water electrolysis anode applications: using commercial TiO2 supports easily leads to uneven particle size and poor defect controllability; direct hydrolysis of titanium precursors easily causes rapid nucleation leading to grain agglomeration, and unstable titanium species easily form on the support surface to coat active sites; TiO2 crystal face growth is random, and the preferential growth of the rutile 110 crystal face makes it difficult to form a rod-like structure; in traditional loading processes, uneven mixing of Ti and Ir precursors easily causes Ir active phase agglomeration; the active components are mostly physically adsorbed, and the interfacial bonding is weak. Under acidic, high-potential, and large-current fluctuation conditions, the Ir active phase is easily detached and oxidized and dissolved, while the active sites are not sufficiently exposed, ultimately leading to rapid decay of catalyst activity and a significant reduction in service life. How to achieve the directional control of the crystal phase and crystal plane of TiO2 support through the controlled hydrolysis of titanium precursor, while realizing the in-situ gradient embedding of the Ir active phase, the full exposure of active sites, and the strong interfacial bonding between the support and the active phase, has become a key challenge for the industrial application of TiO2-supported Ir-based OER catalysts.

[0025] This invention utilizes isopropanol as a dispersion medium, combined with ammonia for pH control, to achieve slow and controllable hydrolysis of the titanium precursor. Simultaneously, a thiamine salt containing thiol (-SH) and amino groups (-NH2) is introduced. Through its growth inhibition effect on the rutile TiO2 110 crystal facets, it guides the directional growth of TiO2 into a rod-like structure, generating a rod-shaped TiO2 support with regular crystal phase and uniform particle size. At the same time, it constructs natural lattice defects to provide anchoring points for the Ir active phase. The Ti / Ir precursor is chelated and anchored with a complexing agent to prevent local aggregation of the Ir precursor. The reducing properties of isopropanol are used to... 4+ The TiO2 catalyst is reduced to ultrafine Ir black, which is then in-situ gradient-embedded into the surface and subsurface layers along with the TiO2 lattice growth, forming a strong Ti-O-Ir interface. Acid washing precisely removes unstable titanium species from the support surface, fully exposing active sites and solving the problem of low active site utilization caused by coating. A novel method combining in-situ hydrolysis with crystal facet control and gradient embedding is employed to synthesize a TiO2-supported IrO2 catalyst with a well-defined crystal phase and crystal facet, gradient IrO2 embedding, and fully exposed active sites, meeting the practical application requirements of PEM water electrolysis.

[0026] Based on the above analysis, this invention uses triethanolamine isopropoxide titanium (TTEAIP) and tetrabutyl titanate as titanium precursors, and isopropanol as a dispersion medium to avoid rapid hydrolysis of the titanium precursors; it introduces a thiamine salt crystal plane control reagent to achieve directional control of TiO2 crystal planes, guiding its growth into a rod-like structure; and it uses a Ti / Ir precursor combined with anhydrous citric acid and other complexing agents to interact with Ir. 4+ Stable coordination bonds are formed to achieve chelation and anchoring of Ir ions; the pH of the system is precisely controlled using ammonia to achieve controllable in-situ hydrolysis of the titanium precursor, generating rod-shaped TiO2 supports with regular crystal phases and faces. Simultaneously, during the TiO2 lattice growth process, the reducing properties of isopropanol are used to chelate and anchor Ir ions. 4+ The process involves reducing the Ir black to ultrafine Ir, allowing it to be in-situ gradient-embedded into the lattice defect sites of the TiO2 surface and subsurface. Acid washing removes the unstable titanium species formed during the in-situ hydrolysis of TiO2, fully exposing the active sites. Finally, heat treatment in air oxidizes the Ir black to a crystalline-regular IrO2, strengthening the covalent bonds at the Ti-O-Ir interface. Through carrier crystal phase and crystal plane regulation, uniform precursor blending, gradient embedding of the active phase, precise exposure of active sites, and synergistic interfacial electronic effects, the activity, conductivity, and structural stability of the TiO2-supported IrO2 oxygen evolution electrocatalyst are comprehensively enhanced.

[0027] This invention provides a method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis, comprising the following steps: Step 1: Weigh a certain mass of titanium precursor and add it to a certain volume of isopropanol. Stir magnetically to obtain a homogeneous and transparent isopropanol solution of Ti precursor. Using isopropanol as a dispersion medium avoids the rapid hydrolysis of titanium precursor upon contact with water, laying the foundation for a homogeneous system for subsequent controllable hydrolysis and crystal surface regulation.

[0028] The titanium precursor is at least one of triethanolamine isopropoxide titanium (TTEAIP), tetrabutyl titanate, titanium isopropoxide, and titanium tetrachloride, preferably triethanolamine isopropoxide titanium (TTEAIP), whose hydrolysis rate is easier to control and can generate rod-shaped TiO2 supports with more regular crystal phases; the magnetic stirring time is 20-40 min and the stirring speed is 300-600 rpm to ensure that the titanium precursor is completely dissolved and a homogeneous system is formed.

[0029] Step 2: Add a complexing agent and a thiamine salt crystal facet control reagent containing thiol (-SH) + amino (-NH2) to the isopropanol solution of the Ti precursor in Step 1. Stir at room temperature until completely dissolved, let stand for a set interval, and then add Ir salt solution dropwise and continue stirring at room temperature to obtain the Ti-Ir blended precursor isopropanol suspension.

[0030] The thiamine salt is at least one of mercaptoethylamine methacrylate, N-(2-mercaptoethyl)acrylamide, 3-mercapto-1-propylamine hydrochloride, and cysteine ​​hydrochloride. The molar ratio of the titanium precursor to the thiamine salt is (1-3):1, preferably 2:1. The thiamine salt is adsorbed onto the potential growth surface of TiO2 crystal nuclei through the synergistic effect of thiol and amino groups, thereby inhibiting the growth of the rutile phase 110 crystal face and guiding the directional growth of TiO2 into a rod-like structure. The complexing agent is at least one of anhydrous citric acid, sodium citrate, and disodium ethylenediaminetetraacetate, preferably anhydrous citric acid. The Ir salt is chloroiridium acid. At least one of iridium chloride and iridium nitrate, preferably chloroiridium acid; the molar ratio of the complexing agent to the Ir salt is (0.5-2):1, preferably 1:1; the interval between the addition of Ti and the Ir precursor is 10-60 min, preferably 30 min, to optimize the intermolecular interaction between the two through interval compounding and avoid Ir precursor aggregation; the time for stirring at room temperature until the complexing agent and thiamine salt are completely dissolved is 20-40 min; the time for stirring at room temperature after adding the Ir salt solution is 0.5-2 h; the stirring speed throughout is 300-600 rpm to ensure the complexing agent and Ir... 4+ Stable chelates are formed, while achieving molecular-level homogeneous mixing of Ti-Ir precursors.

[0031] Chelation anchoring refers to the ability of molecules containing carboxylic acid and hydroxyl groups, such as anhydrous citric acid, to bind with Ir. 4+ Metal ions form stable complexes, achieving chelation and anchoring of Ir metal ions, preventing their spontaneous aggregation in subsequent reactions, and laying a precursor foundation for the uniform reduction and gradient intercalation of Ir black.

[0032] Step 3: Place the Ti-Ir blend precursor isopropanol suspension from Step 2 in an ice-water bath, and slowly add ammonia water while continuously stirring. Precisely control the pH of the system to allow the titanium precursor to slowly hydrolyze and preferentially nucleate to form TiO2 crystal nuclei, thus obtaining a rod-shaped TiO2 crystal nucleus growth suspension.

[0033] The ice-water bath temperature is 0-5℃, the ammonia dripping rate is 0.5-2mL / min, the total dripping time is 30-60min, the pH of the ammonia-controlled system is 8-10, and the constant temperature water bath stirring rate is 300-600rpm. By precisely controlling the pH, hydrolysis temperature, and ammonia dripping rate, the slow and controllable hydrolysis of the titanium precursor is achieved. The thiamine salt continues to play a crystal face control role as the TiO2 crystal nuclei grow, avoiding the aggregation of TiO2 grains and random crystal face growth caused by rapid hydrolysis. This ensures that the generated TiO2 crystal nuclei have uniform particle size and regular crystal phase and crystal face. At the same time, high-density lattice defects will naturally form during the TiO2 lattice growth process, providing natural anchoring points for the gradient embedding of Ir black.

[0034] Step 4: Continue the reaction while maintaining an ice-water bath and continuous stirring to allow the chelated Ir in the system to remain.4+ Under the reducing action of isopropanol, it is gradually reduced to ultrafine Ir black nanoparticles. The Ir black nanoparticles are then in situ gradient embedded into the lattice defect sites of the TiO2 surface and subsurface during the growth process of the rod-shaped TiO2 lattice, resulting in a rod-shaped TiO2 suspension with Ir black gradient embedding.

[0035] The reaction continues for 2-4 hours, with a stirring rate of 300-600 rpm, to ensure Ir 4+ It is fully reduced to ultrafine Ir black nanocrystals; isopropanol, as a reducing alcohol, realizes Ir during the reaction. 4+ The in-situ reduction produces ultrafine Ir black particles with extremely small particle size and strong diffusion and migration ability. They can efficiently penetrate and embed into the lattice defect sites of the TiO2 surface and subsurface during the growth process of the rod-shaped TiO2 lattice, complete the in-situ gradient embedding and loading of active components, form a preliminary strong interface bond, and the thiamine salt continuously inhibits the growth of the rutile phase 110 crystal plane during this process, ensuring the directional growth of the rod-shaped structure.

[0036] Step 5: The rod-shaped TiO2 suspension with Ir black gradient embedded in step 4 is subjected to high-power ultrasonic treatment in an ice bath environment to obtain a uniform catalyst precursor suspension.

[0037] The ice bath temperature is 0-5℃, the ultrasonic power is 300-500W, and the ultrasonic time is 30-60min. By relying on the synergistic effect of low temperature and ultrasound, the rod-shaped TiO2 grains are further refined, the Ir black is evenly dispersed in TiO2, the secondary agglomeration of active components is inhibited, and the rod-shaped crystal structure regulated by thiamine salt is not destroyed.

[0038] Step 6: The reaction product from Step 5 is subjected to solid-liquid separation. The solid phase is washed alternately with isopropanol and ultrapure water until neutral, then vacuum dried and ground into fine particles to obtain rod-shaped TiO2@Ir catalyst precursor.

[0039] The solid-liquid separation is performed by vacuum filtration or centrifugation at a speed of 8000-12000 rpm. The washing solution is washed until its conductivity is below 1 μS / cm, and isopropanol and ultrapure water are used alternately to thoroughly remove residual unhydrolyzed precursors, impurity ions, and thiamine salts that have not participated in crystal facet regulation, thus avoiding the generation of byproducts in subsequent reactions. The vacuum drying temperature is 50-80℃, and the drying time is 8-12 hours to ensure that the precursor is fully dried. The dried solid is then thoroughly ground in a mortar to obtain a precursor powder with uniform particle size.

[0040] Step 7: Place the rod-shaped TiO2@Ir catalyst precursor from Step 6 into an acid solution for acid washing. After solid-liquid separation, wash the solid phase until neutral and dry it to obtain the acid-washed catalyst precursor.

[0041] The acid solution is at least one of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, with a molar concentration of 0.05-0.5 mol / L, preferably 0.1 mol / L. The acid washing temperature is 25-40℃, and the acid washing time is 10-60 min, preferably 30 min. This process precisely removes the unstable titanium species formed during the in-situ hydrolysis of TiO2 while avoiding etching the rod-shaped TiO2 crystal structure and the embedded Ir black. After acid washing, solid-liquid separation is performed by vacuum filtration or centrifugation. The solid phase is washed with ultrapure water until neutral, and the drying temperature is 40-60℃ for 4-8 h. Acid washing removes the titanium species coated on the surface of Ir black, fully exposing the active sites and improving the utilization rate of Ir atoms.

[0042] Step 8: The acid-washed catalyst precursor is subjected to programmed temperature heat treatment in an air atmosphere, and after natural cooling, it is washed with water and dried to obtain a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst with IrO2 gradient embedding.

[0043] Specifically, the heat treatment under an air atmosphere employs a programmed temperature rise strategy to achieve complete oxidation of Ir black and strengthening of covalent bonds at the Ti-O-Ir interface: oxygen in the air is used to fully oxidize the embedded ultrafine Ir black into a regularly crystalline IrO2 active component, while the gradient-embedded Ir black serves as a seed crystal to induce IrO2 to grow directionally along the defect sites of the rod-shaped TiO2 support, significantly enhancing the covalent bonding at the Ti-O-Ir interface and stabilizing the gradient embedding structure; the thiamine salt gradually decomposes during the heat treatment process, leaving no residue and not affecting the catalytic performance.

[0044] The temperature rise rate of the programmed heating is 2-5℃ / min, the heat treatment temperature range is 400-500℃, the holding time is 2-6h, and the air flow rate is 30-60mL / min. These process conditions can ensure that Ir black is completely oxidized to IrO2, while avoiding the TiO2 crystal transformation and IrO2 particle agglomeration caused by high temperature.

[0045] Further, the heat-treated product is washed 2-3 times with ultrapure water to remove residual heat-treated byproducts on the surface, and then placed in an oven to dry at a temperature of 50-70℃ for 6-12 hours. The dried sample is then taken out and thoroughly ground to finally obtain a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst with IrO2 gradient embedding.

[0046] Unless otherwise specified, all raw materials used in the following examples are commercially available and are acceptable as long as they meet the specified requirements.

[0047] Example 1 This embodiment provides a method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis, comprising the following steps: (1) Dissolve 10 mL of triethanolamine isopropoxide titanium (TTEAIP) in 100 mL of isopropanol and stir magnetically at 300 rpm for 30 min to obtain a uniform and transparent Ti precursor isopropanol solution. (2) Add 50 mL of 0.05 mol / L anhydrous citric acid solution and 1.66 g of cysteine ​​hydrochloride (TTEAIP to cysteine ​​hydrochloride molar ratio 2:1) to the above solution, stir at 300 rpm at room temperature for 30 min until completely dissolved, let stand for 30 min, then add 50 mL of 0.05 mol / L chloroiridium acid solution dropwise, and continue stirring at 450 rpm at room temperature for 2 h to obtain the Ti-Ir blend precursor isopropanol suspension; (3) Place the blended precursor suspension in an ice-water bath, add ammonia water dropwise at a rate of 1 mL / min while stirring continuously at 300 rpm for a total dropwise time of 45 min, adjust the pH of the system to 9, and obtain a rod-shaped TiO2 crystal nucleus growth suspension; (4) Continue the reaction for 3 hours while maintaining an ice-water bath and a stirring rate of 450 rpm to obtain a rod-shaped TiO2 suspension with Ir black gradient embedded. (5) Place the above suspension in a 2°C ice-water bath and sonicate at 400W for 45 minutes to obtain a uniform catalyst precursor suspension. (6) The precursor suspension was centrifuged at 10,000 rpm to separate solid and liquid phases. The solid phase was washed alternately with isopropanol and ultrapure water until the conductivity was <1 μS / cm. After vacuum drying at 60℃ for 10 h, it was ground into powder to obtain rod-shaped TiO2@Ir catalyst precursor. (7) The TiO2@Ir precursor was placed in 0.1 mol / L dilute hydrochloric acid, acid washed at 30℃ for 30 min, filtered, washed with ultrapure water until neutral, and dried at 50℃ for 6 h to obtain the acid-washed catalyst precursor. (8) The acid-washed precursor was placed in a tube furnace and heated to 450°C at 3°C / min under an air atmosphere, and kept at the temperature for 4 hours with an air flow rate of 45 mL / min. After natural cooling, it was washed twice with ultrapure water and dried at 60°C for 8 hours to obtain a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst with IrO2 gradient embedding.

[0048] Example 2 This embodiment provides a method for preparing a gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis. The difference from Embodiment 1 is that the operations of steps (1) and (2) are different, specifically: (1) Dissolve 10 mL of tetrabutyl titanate in 100 mL of isopropanol and stir magnetically at 300 rpm for 30 min to obtain a homogeneous and transparent Ti precursor isopropanol solution. (2) Add 50 mL of 0.05 mol / L anhydrous citric acid solution and 1.66 g of cysteine ​​hydrochloride (TTEAIP to cysteine ​​hydrochloride molar ratio 2:1) to the above solution, stir at 300 rpm at room temperature for 30 min until completely dissolved, let stand for 30 min, then add 50 mL of 0.05 mol / L chloroiridium acid solution dropwise, and continue stirring at 450 rpm at room temperature for 2 h to obtain the Ti-Ir blend precursor isopropanol suspension; Steps (3)-(8) are completely consistent with Example 1, and rod-shaped TiO2 supported IrO2 oxygen evolution electrocatalyst with IrO2 gradient embedding is obtained.

[0049] Example 3 This embodiment provides a method for preparing a gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis. The difference from Example 1 is that step (7) is different, specifically: The TiO2@Ir precursor was placed in 0.1 mol / L dilute hydrochloric acid and acid-washed at 30℃ for 10 min. After filtration, it was washed with ultrapure water until neutral and dried at 50℃ for 6 h to obtain the acid-washed catalyst precursor. Steps (1)-(6) and (8) are completely consistent with those in Example 1, and rod-shaped TiO2 supported IrO2 oxygen evolution electrocatalyst with IrO2 gradient embedding is obtained.

[0050] Comparative Example 1 This comparative example provides a method for preparing a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst. The difference from Example 1 is that the acid washing step (7) is omitted. The TiO2@Ir precursor is directly placed in a tube furnace, and then heat-treated, washed with water and dried in the same process as step (8) of Example 1 to obtain the rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst.

[0051] Comparative Example 2 This comparative example provides a method for preparing a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst. The difference between this method and Example 1 is that step (2) is different, specifically: Add 50 mL of 0.05 mol / L anhydrous citric acid solution, 1.66 g of cysteine ​​hydrochloride and 50 mL of 0.05 mol / L chloroiridium acid solution to the isopropanol solution of Ti precursor obtained in step (1), let stand without interval, stir at room temperature for 2.5 h at 450 rpm to obtain Ti-Ir blended precursor isopropanol suspension; The remaining steps are exactly the same as in Example 1, resulting in a rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst.

[0052] Comparative Example 3 This comparative example provides a method for preparing an IrO2-supported oxygen evolution electrocatalyst on a commercial TiO2 support. The difference between this method and Example 1 is that the operation of step (1) is different, specifically: 1.0 g of commercial rutile TiO2 was dispersed in 100 mL of isopropanol and ultrasonically dispersed at 300 W for 30 min to obtain TiO2 isopropanol dispersion. The remaining steps are exactly the same as in Example 1, resulting in an IrO2-supported oxygen evolution electrocatalyst on a commercial TiO2 support.

[0053] Comparative Example 4 This comparative example provides a method for preparing a TiO2-supported IrO2 oxygen evolution electrocatalyst. The difference between this method and Example 1 is that step (2) is different, specifically: Add 50 mL of 0.05 mol / L anhydrous citric acid solution to the Ti precursor isopropanol solution obtained in step (1), without adding cysteine ​​hydrochloride, stir at 300 rpm at room temperature for 30 min until completely dissolved, let stand for 30 min, then add 50 mL of 0.05 mol / L chloroiridium acid solution dropwise, and continue stirring at 450 rpm at room temperature for 2 h to obtain the Ti-Ir blended precursor isopropanol suspension.

[0054] Figure 1 These are TEM images of TiO2@IrO2 with different Ti precursor hydrolysis loadings obtained in this invention. Figures a, b, and c correspond to Comparative Example 3, Example 2, and Comparative Example 2, respectively. As can be seen from the figures, Comparative Example 3 uses commercial TiO2 as a support, and the IrO2 active component shows obvious aggregation and segregation on the support surface, with loose bonding and uneven morphology at the two-phase interface. Example 2 uses a titanium precursor with a faster hydrolysis rate. Because the titanium precursor is difficult to hydrolyze slowly and controllably, TiO2 preferentially and rapidly nucleates and grows, separating from the Ir component, resulting in decreased rod-like morphology integrity, poor IrO2 dispersion, and inability to form an ideal gradient embedding structure. Comparative Example 2 does not use TiO2. Adding a spacer to the Ir precursor and simultaneously hydrolyzing Ti and the Ir precursor led to distortion of the TiO2 rod-like structure, uneven distribution of IrO2, and local agglomeration, resulting in poor overall structural stability. Comparative results show that using a titanium precursor with a moderate hydrolysis rate, combined with Ti… Only through in-situ hydrolysis with intercalation of Ir precursors can rod-shaped TiO2@IrO2 catalysts with regular morphology, high dispersion of IrO2, and gradient embedding be obtained.

[0055] Figure 2These are TEM and SEM images of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of this invention; Figures a and b correspond to the SEM images of the sample obtained in Example 1, Figure c corresponds to the TEM image of the sample obtained in Example 1, and Figure d corresponds to the EDS-TEM image of the sample obtained in Example 1. As can be seen from the figures, after controlled in-situ hydrolysis and crystal plane regulation by TTEAIP, the sample of Example 1 exhibits a uniform, regular, and consistent rod-shaped morphology with no obvious agglomeration or structural distortion. The rod-shaped TiO2 support has uniform size and excellent dispersibility. The TEM images further confirm that the sample maintains a complete rod-shaped structure, and the IrO2 active component is highly dispersed in the form of ultrafine nanoparticles on the surface and subsurface of the rod-shaped TiO2, without agglomeration or segregation, and is tightly bound to the support with a clear interface. (EDS-TEM) The elemental distribution diagram shows that Ti, O, and Ir are continuously and uniformly distributed on the rod-shaped structure, with no local enrichment or deficiency of elements. This fully demonstrates that IrO2 has achieved uniform loading and in-situ gradient embedding on the rod-shaped TiO2 support. The interface is firmly bonded and the component distribution is uniform, which is highly consistent with the gradient embedding rod-shaped TiO2@IrO2 catalyst structure designed in this invention.

[0056] Figure 3 Figure 1 shows an aberration-corrected electron microscope image of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of this invention. Figures a and b correspond to images on 10 nm and 5 nm scales, respectively. As can be seen from the figures, the IrO2 active component in the sample of Example 1 is not simply attached to the surface of the TiO2 support, but is embedded in situ in the surface and subsurface lattice of the TiO2 support in the form of ultrafine nanocrystals, forming a typical gradient embedding configuration. The IrO2 nanocrystals are small in size, highly uniform in distribution, and have no obvious agglomeration or segregation. The high-resolution image clearly shows that the TiO2 support lattice fringes are continuous and regular, and the embedded IrO2 forms a tightly bonded Ir-O-Ti interface with the support, without obvious interface gaps. This further confirms that the present invention can successfully achieve precise gradient embedding of IrO2 on rod-shaped TiO2 through the controlled in-situ hydrolysis and low-temperature reduction-heat treatment process of TTEAIP, constructing catalytic active sites with strong interfacial bonding and high structural stability.

[0057] Figure 4 The images show the Ir L-edge XAS and EXAFS characterizations of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Examples 1-5 of this invention; from the Ir L-edge XANES spectrum ( Figure 4 a) It can be seen that the absorption edge position of TiO2@IrO2 is between that of IrCl3 (Ir 3+ ) and IrO2 (Ir 4+The distance between the two values ​​indicates that the Ir species exhibits a moderate oxidation state, which stems from the electronic interactions between Ir and the TiO2 support. Fourier transform EXAFS R-space spectrum ( Figure 4 b) Further, it is shown that TiO2@IrO2 at ~1.6 Only a distinct Ir-O coordination peak was observed at this location, with a slight shift in peak position from IrO2. No Ir-Ir metallic bond peak was detected (~2.6). ) and Ir-Cl residual peak (~2.0) The XANES and EXAFS results confirm that Ir species are highly dispersed on the surface of the TiO2 support and form a strong interaction with the support through the Ir-O-Ti interfacial bonding structure. This interfacial bonding not only stabilizes the valence state of Ir, but also provides structural support for the active sites.

[0058] Figure 5 Figure 1 shows the elemental distribution of TiO2@IrO2 supported by triethanolamine isopropoxide titanium (TTEAIP) hydrolysis obtained in Example 1 of this invention. Figures a, b, and c correspond to the distribution of Ir, Ti, and O elements at the catalyst-support interface, respectively. As can be seen from the figures, Ti, O, and Ir all exhibit a continuous, uniform, and highly overlapping distribution on the overall structure of the rod-shaped catalyst, with no obvious elemental segregation, local enrichment, or absence. The distribution profile of Ir element completely matches the distribution profiles of Ti and O elements, confirming that the active component of IrO2 is not locally agglomerated or attached to the surface, but is uniformly dispersed and gradient-embedded in the surface and subsurface layers of the rod-shaped support during the in-situ hydrolysis and crystal growth of TiO2, forming a globally uniform composite structure with the support. This further verifies that the in-situ hydrolysis process of this invention can achieve precise, uniform, and segregation-free loading of the Ir component on the rod-shaped TiO2 support, providing a reliable structural and component guarantee for the high activity and high stability of the catalyst.

[0059] Figure 6 The figures show the PEMWE single-cell polarization curves of TiO2@IrO2 oxygen evolution electrocatalysts with different Ti precursor hydrolysis loadings and different Ti-Ir precursor drop intervals obtained in Examples 1-3 and Comparative Examples 1-2 of this invention, as well as the comparative samples. As can be seen from the figures, Example 1 uses TTEAIP controlled hydrolysis and Ti... With the addition of Ir at intervals and optimized acid washing and heat treatment processes, the OER electrocatalytic performance was optimal under the same Ir loading, exhibiting the lowest cell voltage and highest catalytic activity at the same current density. Example 2 showed phase separation due to excessively rapid hydrolysis of the titanium precursor, and Example 3 showed insufficient exposure of active sites due to insufficient acid washing time; both examples performed slightly worse than Example 1. Comparative Example 1, without acid washing, had unstable titanium species coating the active sites, resulting in a significant decrease in activity and a significant increase in cell voltage. Comparative Example 2 did not include Ti... With the addition of spacers to the Ir precursor, the active components exhibit poor dispersion and weak interfacial bonding, resulting in the worst catalytic performance. These results fully demonstrate the controllability of the titanium precursor hydrolysis rate and the effectiveness of Ti... The Ir precursor intercalation strategy and acid washing post-treatment process play a key role in improving the activity and stability of the catalyst under actual PEM water electrolysis conditions. Only by adopting the optimized in-situ hydrolysis, gradient embedding and interface enhancement process of this invention can the high activity and high stability of acidic OER electrocatalytic performance under low iridium loading be achieved.

[0060] This invention provides a method for preparing a gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis and its application. Using selected titanium precursors as raw materials, the in-situ hydrolysis of titanium precursors was achieved by precisely controlling the hydrolysis rate with ammonia water. Simultaneously, mercapto (-SH) and amino (-NH2) groups were used to guide the growth of crystals into rod-shaped TiO2 supports with regular crystal phases. During the TiO2 growth process, the Ir precursor was reduced to ultrafine Ir black using reducing alcohols in the system. By controlling the addition interval of titanium and Ir precursors, their interaction was optimized, achieving in-situ gradient embedding of Ir black in the surface and subsurface layers of TiO2. The unstable titanium species on the support surface were then precisely removed by acid washing to fully expose the active sites. Finally, heat treatment oxidized Ir black to IrO2 with regular crystal phases, forming a continuous ultrathin coating layer, which strengthened the covalent interaction at the Ti-O-Ir interface. Ultimately, a low-iridium-loaded, high-catalytic-activity, and long-term stable oxygen evolution electrocatalyst was obtained, which can be well adapted to the harsh conditions of acidic OER in PEM water electrolysis.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis, characterized in that, Includes the following steps: (1) Weigh out the titanium precursor and dissolve it in isopropanol, and stir to obtain a homogeneous and transparent Ti precursor isopropanol solution; (2) Add complexing agent and thiamine salt to the isopropanol solution of Ti precursor, stir at room temperature until completely dissolved, then add iridium precursor dropwise, and continue stirring to obtain Ti-Ir blended precursor isopropanol suspension; (3) Place the blended precursor isopropanol suspension in an ice-water bath, and slowly add pH adjuster while continuously stirring to adjust the pH of the system, so that the titanium precursor is slowly hydrolyzed and preferentially nucleated to form TiO2 crystal nuclei, and obtain TiO2 crystal nucleus growth suspension. (4) Keep stirring and place in an ice-water bath, then continue the reaction under ultrasonic conditions to allow the chelated Ir in the system to remain in the system. 4+ Under the reducing action of isopropanol, it is reduced to ultrafine Ir black nanoparticles, and the Ir black nanoparticles are in situ gradient embedded into the surface and subsurface of TiO2 during the growth process of TiO2, resulting in a TiO2 suspension with gradient embedding of Ir black nanoparticles. (5) The reaction product of step (4) is subjected to solid-liquid separation. The solid phase is washed alternately with isopropanol and ultrapure water until neutral. After vacuum drying, it is ground into powder to obtain TiO2@Ir catalyst precursor. (6) The TiO2@Ir catalyst precursor was placed in an acid solution for acid washing, and after solid-liquid separation, it was washed until neutral and dried; (7) The precursor after step (6) is heat-treated to oxidize the Ir black nanoparticles into IrO2 with regular crystal phase and strengthen the Ti-O-Ir interface bonding. After natural cooling, it is washed and dried to obtain a gradient-embedded rod-shaped TiO2 supported IrO2 oxygen evolution electrocatalyst.

2. The method for preparing a gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (1), the titanium precursor is one or more of triethanolamine isopropoxide titanium, tetrabutyl titanate, titanium isopropoxide, and titanium tetrachloride.

3. The method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (2), the complexing agent is one or more of anhydrous citric acid, sodium citrate, and disodium ethylenediaminetetraacetate; The thiamine salt is one or more of the following: mercaptoethylamine methacrylate, N-(2-mercaptoethyl)acrylamide, 3-mercapto-1-propane hydrochloride, and cysteine ​​hydrochloride; The molar ratio of the titanium precursor to the thiamine salt is (1-3):1; preferably 2:

1. The iridium precursor is an aqueous solution of Ir salt; the Ir salt is one or more of chloroiridium acid, iridium chloride, and iridium nitrate, and the molar ratio of the complexing agent to the Ir salt is (0.5-2):1, preferably 1:

1.

4. The method for preparing a gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (2), the interval between the addition of the titanium precursor and the iridium precursor is 10-60 min, preferably 30 min; In step (2), the time for stirring at room temperature until the complexing agent dissolves is 20-40 min, and the time for stirring at room temperature after adding the Ir salt solution is 0.5-2 h, with a stirring speed of 300-600 rpm throughout the process; In step (3), the pH adjuster is ammonia water; the pH of the ammonia water system is 8-10; the dropping rate of ammonia water is 0.5-2 mL / min, the total dropping time is 30-60 min; the ice water bath temperature is 0-5℃, and the ice water bath stirring speed is 300-600 rpm.

5. The method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (4), the reaction continues for 2-4 hours, the stirring rate is 300-600 rpm, the ice-water bath temperature is 0-5℃, the ultrasonic power is 300-500W, and the ultrasonic time is 30-60 min.

6. The method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (5), solid-liquid separation is carried out by vacuum filtration or centrifugation. The centrifugation speed is 8000-12000 rpm. The washing liquid is washed until the conductivity is <1μS / cm. The vacuum drying temperature is 50-80℃ and the drying time is 8-12h.

7. The method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (6), the acid solution is one or more of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid, and the molar concentration of the acid solution is 0.05-0.5 mol / L, preferably 0.1 mol / L; the acid washing temperature is 25-40℃, the acid washing time is 10-60 min, preferably 30 min; after acid washing, solid-liquid separation is carried out by vacuum filtration or centrifugation, and after washing to neutrality, the drying temperature is 40-60℃, and the drying time is 4-8 h.

8. The method for preparing a gradient-intercalated rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst by in-situ hydrolysis according to claim 1, characterized in that, In step (7), the precursor is placed in a tube furnace and subjected to programmed temperature rise heat treatment in an air atmosphere; The temperature rise rate of the programmed temperature rise is 2-5℃ / min, the temperature of the heat treatment is 400-500℃, the holding time is 2-6h, and the air flow rate is 30-60mL / min; the heat treatment product is washed with ultrapure water 2-3 times, the drying temperature is 50-70℃, and the drying time is 6-12h.

9. The gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst prepared by the method according to any one of claims 1-8.

10. The application of the gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst prepared by any one of claims 1-8 or the gradient-embedded rod-shaped TiO2-supported IrO2 oxygen evolution electrocatalyst of claim 9 in the anodic oxygen evolution reaction of proton exchange membrane water electrolysis.

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