A Ca2IrO4 catalyst with dual-site co-doping of anions and cations, its preparation method and application

Abstract

The application discloses a Ca2IrO4 catalyst co-doped with cations and anions at double sites, and a preparation method and application thereof, and relates to the field of energy materials. 2+ , Ir 4+ , Ga 3+ and SO4 2‑ ions are uniformly mixed at a molecular level; then, through a multi-stage heat treatment process, in-situ sulfuration is realized by using the thermal decomposition reaction of thiourea at high temperature, S atoms are induced to be doped into the Ca2IrO4 crystal lattice, and the Ca2IrO4 catalyst co-doped with Ir sites and O sites is obtained. The catalyst has the characteristics of high purity, flexible and changeable doped elements, and adjustable doping ratio, and can reduce the amount of noble iridium, significantly improve the activity and stability of the catalyst for acid electrolysis water oxygen evolution, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of energy materials technology, specifically to a Ca2IrO4 catalyst with dual-site co-doping of anions and cations, its preparation method, and its application. Background Technology

[0002] Hydrogen production via water electrolysis can fully utilize renewable energy to produce high-purity hydrogen, which has significant value in promoting energy transition and reducing dependence on scarce fossil fuels. Compared with alkaline water electrolysis (ALK), proton exchange membrane water electrolysis (PEMWE) has lower ohmic resistance due to its superior proton conductivity and can operate at current densities much higher than ALK, typically reaching 2 A / cm². 2 It can operate at or above the required power, and boasts a wider operating power range and rapid start-stop response. Furthermore, PEMWE's low gas permeability effectively prevents hydrogen-oxygen cross-permeability, ensuring the generation of 99.99% high-purity hydrogen and enhancing operational safety.

[0003] However, the widespread industrial application of PEMWE is limited by anodic oxygen evolution reaction (OER) catalysts. Under strongly acidic and highly oxidizing operating environments, only noble metal iridium (Ir)-based catalysts exhibit excellent activity and corrosion resistance; however, iridium resources are extremely scarce and expensive, with an annual production of less than 10 tons, making it difficult to support large-scale hydrogen production. Therefore, developing novel iridium-based catalysts that combine high intrinsic activity and long-term stability while significantly reducing iridium loading has become the core of current research.

[0004] Currently, the development of iridium salts (A x Ir y O z This is an effective way to reduce the content of precious metals. By diluting iridium in a non-precious metal framework, not only can the use of iridium be reduced, but catalytic performance can also be adjusted by precisely controlling its local environment; among them, it belongs to Ca₂IrO₄ with space group 62m has attracted widespread attention. Its [IrO₆] octahedra are connected by shared edges to form a one-dimensional chain structure. This robust connection allows it to maintain high structural integrity and catalytic activity even after A-site cation leaching. Although previous studies have modified Ca₂IrO₄ by doping the cation sites, such as with Ca₂Y, this approach has not been successful. 0.2 Ir 0.8 O4, Ca 1.6 K 0.4 IrO 4-x Excellent OER activity was obtained, but such studies are mainly limited to cations, i.e., metal site substitution.

[0005] It is noteworthy that existing modification efforts have almost entirely focused on cation sites, i.e., A-sites or B-sites, with very few studies targeting anion sites, i.e., oxygen sites, for doping substitution. In the acidic OER reaction mechanism, the chemical environment of the oxygen site plays a regulatory role in charge transfer efficiency and the reaction mechanism. However, due to the stringent requirements for lattice stability and the complexity of the synthesis process for anion doping, simultaneous co-doping at both Ir cation and O anion sites is currently lacking. This single-level modification strategy limits the possibility of multi-dimensional control over the electronic structure of the catalyst, making it difficult to achieve optimal synergy between activity and stability.

[0006] Therefore, developing a dual-site doped Ca2IrO4 catalyst that introduces a heterometallic element at the Ir site and an anionic element at the O site is of scientific significance and application value for breaking the limitations of existing single-site modification and constructing an efficient and stable low-iridium electrocatalytic system. Summary of the Invention

[0007] 1. The technical problem that the invention aims to solve

[0008] Existing Ca2IrO4 catalysts, when applied to proton exchange membrane water electrolysis, not only suffer from high costs due to high iridium loading but also face the technical bottleneck of balancing catalyst stability and catalytic activity. While existing methods of modifying Ca2IrO4 by doping cation sites can improve catalyst activity, catalyst stability decreases, and research on the modification of Ca2IrO4 by doping anion sites is extremely limited. Therefore, this invention addresses the gap in existing research regarding the simultaneous regulation of Ca2IrO4 cation and anion sites by introducing metallic Ga into the Ir sites of Ca2IrO4 and partially replacing the O sites in the crystal structure with S atoms. This achieves synergistic modification of Ca2IrO4 at both cation and anion sites, resulting in optimized synergy between the stability and catalytic activity of the Ca2IrO4 catalyst.

[0009] 2. Technical Solution To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a Ca2IrO4 catalyst with dual-site co-doping of cations and anions, having the following general chemical formula: Ca2Ir 1-x Ga x O 4-y S y Where x is 0.01~0.15 and y is 0.01~0.4.

[0010] Optionally, the value of x is selected from 0.01, 0.02, 0.05, 0.1, and 0.15, and the value of y is selected from 0.01, 0.02, 0.03, 0.04, 0.1, 0.2, 0.25, 0.3, and 0.4. By reasonably setting the value range of x and y, the ion ratio of the electrocatalyst can be satisfied, thereby improving the performance of the Ca2Ir electrocatalyst. 1-x Ga x O 4-y S y The structure stability and catalytic activity are optimized to achieve comprehensive optimization of catalytic activity, stability, cost and adaptability.

[0011] Furthermore, the catalyst is a single-phase catalyst with a microstructure of nanobulbs and a crystal structure belonging to [missing information]. The catalyst has a space group of 62m, and the elements of the catalyst are diffusely distributed within a single nanobulb.

[0012] Furthermore, the catalyst has an average particle size of 10–80 nm and an electrochemical active area of ​​8–25 cm². 2 The specific capacitance is 0.035 μF / cm. 2 Preferably, the average particle size of the catalyst is 30-80 nm. Reducing the particle size of the catalyst can increase the density of its surface active sites, thereby improving catalytic efficiency; the smaller the particle size, the larger the surface area per unit mass of catalyst, and the more active sites.

[0013] In a second aspect, the present invention provides a method for preparing a Ca2IrO4 catalyst with co-doped anion and cation sites, comprising the following steps: The step of obtaining an aqueous solution, wherein the aqueous solution comprises a calcium source, an organic polyacid, and a sulfur source in a molar ratio of 1:1:0.01 to 0.4; The step of obtaining an alcohol phase solution, wherein the alcohol phase solution includes an iridium source and a gallium source, and the molar number of gallium ions accounts for 0.01~15% of the total molar number of metal ions in the alcohol phase solution; The step of mixing an aqueous phase solution and an alcohol phase solution to obtain a mixed solution under stirring conditions; The steps include drying the mixed solution and grinding it to obtain a solid precursor powder; A multi-stage heat treatment was performed on the solid precursor powder to obtain the heat-treated product. The heat-treated product was subjected to acid treatment to obtain a Ca2IrO4 catalyst with co-doped anion and cation sites; wherein the catalyst has the following general chemical formula: Ca2Ir 1-x Ga x O 4-y S y Where x is 0.01~0.15 and y is 0.01~0.4.

[0014] Furthermore, the catalyst is a single-phase catalyst with a microstructure of nanobulbs and a crystal structure belonging to... The catalyst has a space group of 62m, and the elements of the catalyst are diffusely distributed within a single nanobulb.

[0015] Furthermore, the catalyst has an average particle size of 10-80 nm and an electrochemical active area of ​​8-25 cm². 2 The specific capacitance is 0.035 μF / cm. 2 .

[0016] Furthermore, the process of obtaining a mixed solution by mixing an aqueous phase solution and an alcohol phase solution under stirring conditions is as follows: Under stirring conditions, the aqueous phase solution is added dropwise to the alcohol phase solution and mixed thoroughly to obtain a mixed solution. Optionally, the stirring time is 60-180 minutes; optionally, the stirring conditions are achieved by mechanical stirring or ultrasonic treatment.

[0017] Furthermore, the process of drying the mixed solution and grinding it to obtain solid precursor powder is as follows: The mixed solution was dried at 120~150℃ for 12h to obtain a solid precursor, which was then ground into powder to obtain solid precursor powder.

[0018] Furthermore, the process of subjecting the solid precursor powder to multi-stage heat treatment to obtain the heat-treated product is as follows: The solid precursor powder was heated at a rate of 0.5–5 °C / min, and then held at 150–250 °C, 300–400 °C, 450–550 °C, and 650–750 °C for 5–7 h, 5–7 h, 2–4 h, and 5–7 h, respectively. After natural cooling to room temperature, a black solid heat-treated product was obtained. The holding temperature at 150–250 °C was mainly used to remove residual solvent and moisture; the holding temperature at 300–400 °C mainly induced the decomposition of the sulfur source and the preliminary carbonization of the organic components, achieving in-situ sulfidation; the holding temperature at 450–550 °C promoted the formation of the mesophase; and finally, the main calcination stage at 650–750 °C promoted crystal growth, effectively achieving high crystallinity and component uniformity of the product, thus obtaining the black powder with the target structure.

[0019] Furthermore, the process of acid treatment of the heat-treated product to obtain a Ca2IrO4 catalyst with co-doped anions and cations is as follows: The heat-treated product was immersed in hydrochloric acid, glacial acetic acid, or perchloric acid at a concentration of 0.5–1 mol / L for 0.5–1 h to fully leach the calcium element from the sample surface. It was then washed 3–5 times with deionized water and anhydrous ethanol, respectively, and vacuum dried to obtain a Ca₂IrO₄ catalyst co-doped with Ir and O sites. The acid treatment aims to selectively and fully leach the calcium element from the sample surface, forming a nanobulb morphology with an average particle size of 10–80 nm and exposing more catalytic active sites.

[0020] Furthermore, the molar number of gallium ions is taken as 5%, 10%, or 15% of the total molar number of metal ions in the alcohol phase solution; by reasonably setting the doping ratio, the electronic structure of Ir sites can be effectively controlled and the generation of surface active sites can be promoted.

[0021] Furthermore, the calcium source is selected from one or more of calcium nitrate, calcium chloride, and calcium carbonate; The organic polyacids are selected from one or more of citric acid, tartaric acid, and oxalic acid. The organic polyacids, combined with the drying and gelation process, can promote the densification and homogenization of the obtained solid precursor, thereby forming a uniform intermediate, which provides a good morphological and structural basis for subsequent multi-stage high-temperature heat treatment.

[0022] The sulfur source is selected from one or more of thiourea, sodium sulfate, and potassium sulfate.

[0023] To address the issue of iridium-based oxides being easily soluble at high acidic potentials, this invention introduces sulfur (S) through an in-situ sulfidation process to reduce some lattice oxygen and increase the number of active sites. This enhancement of active sites, combined with particle size control, creates a synergistic effect, avoiding the risk of element dissolution in the catalyst at high potentials and also mitigating the reduction of active sites and decreased catalytic efficiency caused by excessively large particle sizes.

[0024] Optionally, the molar concentration of the calcium source in the aqueous solution is 0.5~2 mol / L; preferably 0.8~1.5 mol / L; more preferably 1.0 mol / L.

[0025] Furthermore, the iridium source is selected from one or more of the following: potassium hexachloroiridate with tetravalent iridium, sodium hexachloroiridate with tetravalent iridium, potassium hexachloroiridate with trivalent iridium, sodium hexachloroiridate with trivalent iridium, iridium chloride, and chloroiridic acid. The gallium source is selected from one or more of gallium perchlorate, sulfate, and chlorate; The alcohol phase solution is prepared using an organic polyol, which is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

[0026] In a third aspect, the present invention provides the application of the Ca2IrO4 catalyst with dual-site co-doping of anions and cations proposed in the first aspect of the present invention or the catalyst prepared in the second aspect of the present invention in the field of oxygen evolution by water electrolysis.

[0027] Furthermore, when the catalyst was applied in the oxygen evolution reaction of water electrolysis in a three-electrode system, the Tafel slope of the catalyst was tested in a 1 mol / L HClO4 solution environment and found to be 50~95 mV dec. -1 ; The catalyst achieves 10 mA / cm² in an acidic environment with pH=1. 2 The overpotential required for the current density is 200~240mV.

[0028] Furthermore, the catalyst is placed at the positive electrode of the water electrolysis oxygen evolution reaction system.

[0029] 3. Beneficial effects Compared with the prior art, the technical solution provided by this invention has the following advantages: 1. The Ca2IrO4 catalyst with dual-site co-doping of anions and cations disclosed in this invention, through having In a Ca2IrO4 matrix material with space group 62m, simultaneous Ga doping at Ir sites and S doping at O ​​sites achieves synergistic regulation of both cation and anion sites. The introduction of Ga effectively regulates the electronic structure of Ir sites and promotes the generation of surface active sites, modulates the geometry of surrounding Ir sites, and promotes the generation of surface oxygen species, accelerating the kinetics of the oxygen evolution reaction (OER). Furthermore, in-situ sulfidation achieved by introducing a sulfur source during synthesis allows S to successfully replace some lattice oxygen, reducing the valence states of iridium and gallium at high voltages, preventing the dissolution and loss of active sites at high potentials, and optimizing charge transfer performance. This invention, without disrupting the unique edge-connected [IrO6] octahedral one-dimensional chain framework of Ca2IrO4, introduces metallic Ga and utilizes S atoms to partially replace O sites in the crystal structure, resulting in a catalyst with optimized electron cloud distribution, lower OER overpotential, and better stability. This achieves highly efficient catalysis of the OER under acidic conditions while reducing the amount of noble metal Ir used. The catalyst disclosed in this invention has superior structural stability and intrinsic catalytic activity under strong acid electrolysis conditions, effectively solving the problems of imbalance between catalytic activity and stability and high preparation cost of existing oxygen evolution catalysts.

[0030] 2. The Ca2IrO4 catalyst with dual-site co-doping of anions and cations disclosed in this invention is a single-phase catalyst. Its microstructure consists of nanobulbs with an average particle size of 10-80 nm, and its crystal structure belongs to... The catalyst has a space group of 62m, and its elements are dispersed within a single nanobulb. Experimental results show that the electrocatalyst operates at a current density of 10 mA / cm². 2 The overpotential is only 200~240mV, which is of great practical significance and wide application value for improving the energy conversion efficiency of the PEMWE system, extending the life of the electrolyzer, and reducing the system cost.

[0031] 3. The Ca2IrO4 catalyst of the present invention, which is co-doped at both cation and anion sites, has the following general chemical formula: Ca2Ir 1- x Ga x O 4-y S y Where x ranges from 0 to 0.15 and y ranges from 0 to 0.4; that is, the catalyst has tunable chemical adaptability. Specifically, by adjusting the values ​​of x and y, Ca2Ir can be achieved. 1-x Ga x O 4-y S y The comprehensive optimization of the activity, stability, cost and adaptability of oxygen evolution catalysts provides high-performance and economical catalytic materials for oxygen evolution reaction processes such as water electrolysis to produce hydrogen.

[0032] 4. The preparation method of the Ca2IrO4 catalyst with dual-site co-doped anions and cations disclosed in this invention employs an improved sol-gel method. Thiourea is added as a sulfur source during the sol formation stage, and an organic polybasic acid is used as a multidentate chelating agent to enable Ca... 2+ Ir 4+ Ga 3+ and SO4 2- Ions are uniformly mixed at the molecular level; then, through a subsequent multi-stage heat treatment process, in-situ sulfidation is achieved using the thermal decomposition reaction of thiourea at high temperatures, inducing S atoms to be incorporated into the Ca2IrO4 lattice. The preparation method of this invention is simple, has a uniform elemental distribution, and good reproducibility. The resulting electrocatalyst exhibits excellent acid corrosion resistance and OER catalytic activity in a proton exchange membrane water electrolysis system. Simultaneously, by substituting inexpensive Ga, the amount of precious metal Ir used is significantly reduced, resulting in a significant cost advantage. The overall preparation process parameters of this invention are highly controllable, and the product possesses good morphology and highly exposed active sites, showing broad application prospects in the field of energy catalytic materials. Attached Figure Description

[0033] Figure 1 (a) shows the XRD patterns of the catalysts in Example 1 and Comparative Examples 1-3 of this invention, and (b) shows the Ca2Ir catalyst disclosed in this invention. 1-x Ga x O 4-y S yA schematic diagram of an ideal crystal structure; Figure 2 This is a SEM image of catalyst A in Example 1 of the present invention; Figure 3 This is an EDS surface scan distribution map of catalyst A in Example 1 of the present invention; Figure 4 These are the oxygen evolution LSV polarization curves of the catalysts in Example 1, Comparative Examples 1-3, and commercially available IrO2 of the present invention. Detailed Implementation

[0034] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] As used in this invention, the term "about" is used to provide flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0038] As used in this invention, "adjacent" means two structures or elements that are close to each other. Specifically, elements identified as "adjacent" may be adjacent or connected. Such elements may also be close to or near each other without necessarily touching. In some cases, the precision of proximity may depend on the specific context.

[0039] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0040] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as "less than about 4.5," which should be interpreted to include all the values ​​and ranges described above. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0041] Any step described in any method or process claim (e.g., steps S1, S2, S3... or steps (1), (2), (3)... or steps 1), 2), 3)...) may be performed in any order and is not limited to the order set forth in the claims.

[0042] The method + function or step + function limitation is used only if all of the following conditions are met in a particular claim: a) it expressly states "a method for..." or "a step for..."; b) it expressly states the corresponding function. The structures, materials, or actions supporting the method + function are expressly described in the description herein. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and embodiments given herein.

[0043] Currently, iridium (Ir)-based catalysts used in proton exchange membrane (PEM) water electrolysis, such as Ca2IrO4 catalysts, suffer from challenges in balancing catalytic activity and stability, as well as high iridium loading and high cost. While cation-doped Ca2IrO4 catalysts reduce iridium loading, an imbalance between catalytic activity and stability still exists. To address these issues, this invention provides a dual-site co-doped Ca2IrO4 catalyst, its preparation method, and its applications. Addressing the gap in existing research regarding the simultaneous regulation of both cation and anion sites in Ca2IrO4, this invention achieves synergistic modification of both sites by introducing Ga metal into the Ir sites of Ca2IrO4 and partially replacing O sites in the crystal structure with S atoms. This results in a synergistic improvement in both catalytic activity and stability. Furthermore, the synergistically modified Ca2IrO4 catalyst is particularly suitable for PEM water electrolysis systems, offering significant practical implications and broad application prospects for improving the performance and controlling the cost of PEMWE technology.

[0044] Specifically, this invention provides a method for preparing a Ca2IrO4 catalyst with dual-site co-doping of anions and cations, comprising the following steps: The step of obtaining an aqueous solution, wherein the aqueous solution comprises a calcium source, an organic polyacid, and a sulfur source in a molar ratio of 1:1:0.01 to 0.4; The step of obtaining an alcohol phase solution, wherein the alcohol phase solution includes an iridium source and a gallium source, and the molar number of gallium ions accounts for 0.01~15% of the total molar number of metal ions in the alcohol phase solution; The step of mixing an aqueous phase solution and an alcohol phase solution to obtain a mixed solution under stirring conditions; The steps include drying the mixed solution and grinding it to obtain a solid precursor powder; A multi-stage heat treatment was performed on the solid precursor powder to obtain the heat-treated product. The process was as follows: the solid precursor powder was heated at a heating rate of 0.5~5℃ / min, and then held at 150~250℃, 300~400℃, 450~550℃ and 650~750℃ for 5~7h, 5~7h, 2~4h and 5~7h respectively. After natural cooling to room temperature, a black solid heat-treated product was obtained.

[0045] The heat-treated product was subjected to acid treatment to obtain a Ca2IrO4 catalyst with co-doped anion and cation sites. The process was as follows: the heat-treated product was soaked in hydrochloric acid, glacial acetic acid or perchloric acid with a concentration of 0.5~1mol / L for 0.5~1h to fully leach out the calcium element on the surface of the sample. Then it was washed with deionized water and anhydrous ethanol 3~5 times. After vacuum drying, the Ca2IrO4 catalyst with co-doped Ir site and O site was obtained.

[0046] The catalyst obtained has the following general chemical formula: Ca2Ir 1-x Ga x O 4-y S y Where x is 0.01~0.15 and y is 0.01~0.4; the catalyst is a single-phase catalyst, and its microstructure is a nanobulb, and its crystal structure belongs to... The catalyst has a space group of 62m, and the elements of the catalyst are dispersedly distributed within a single nanobulb; furthermore, the average particle size of the catalyst is 10~80nm, and the electrochemical active area is 8~25cm². 2 The specific capacitance is 0.035 μF / cm. 2 .

[0047] The Ca2IrO4 catalyst prepared in this invention, with dual-site co-doped anions and cations, achieves synergistic modification of the Ca2IrO4 by introducing metallic Ga into the Ir sites and partially replacing the O sites in the crystal structure with S atoms. The in-situ substitution of some Ir elements by Ga forms an asymmetric combination of active sites, effectively improving the charge transfer performance of the material, regulating the geometry and electronic structure of the surrounding Ir sites, and promoting the generation of surface oxygen species, further accelerating the oxygen evolution reaction (OER). The introduction of sulfur effectively modulates the electronic structure of iridium ions by adjusting the specific coordination environment around them, enabling iridium ions to exhibit suitable adsorption and activation capabilities for oxygen species generated during the catalytic reaction, thereby significantly accelerating the OER process. Furthermore, due to the different electronegativity of S and O, the introduction of S reduces the valence states of iridium and gallium elements at high voltages, preventing the dissolution and loss of active sites at high potentials and significantly improving the stability of this catalyst.

[0048] Through the synergistic effect of the above two aspects, the Ca2IrO4 catalyst co-doped with both cation and anion sites in this application exhibits optimized electron cloud distribution, lower oxygen evolution reaction overpotential, and better stability. This allows for highly efficient catalysis of the oxygen evolution reaction (OER) under acidic conditions while reducing the amount of noble metal Ir used, demonstrating excellent OER performance. Specifically, when the catalyst is applied in the oxygen evolution reaction of water electrolysis in a three-electrode system, in a 1 mol / L HClO4 solution environment, the Tafel slope of the catalyst is tested to be 50~95 mVdec. -1 The catalyst achieves 10 mA / cm² in an acidic environment with pH=1. 2 The overpotential at the current density is only 200~240mV. The low Tafel slope indicates that the activation energy of each intermediate step in the oxygen evolution reaction is reduced by the modulation of the electronic structure of the Ir site by Ga, thereby significantly improving the energy conversion efficiency of hydrogen production by water electrolysis and reducing energy consumption. The low overpotential directly reflects that the dual-site doped catalyst structure has extremely high intrinsic catalytic activity, enabling the electrolyzer to achieve high current density output at a lower operating voltage, effectively reducing the power cost in the hydrogen production process.

[0049] In summary, this application achieves a significant improvement in the catalytic efficiency and stability of water electrolysis under acidic conditions through the synergistic control of the Tafel slope and overpotential, thereby reducing the energy consumption for hydrogen production throughout the entire life cycle and improving the reliability and consistency of the catalytic reaction under complex acidic environments.

[0050] The following detailed description, with reference to specific embodiments, further illustrates the Ca2IrO4 catalyst with dual-site co-doped anions and cations disclosed in this invention, its preparation method, and its applications, to more clearly demonstrate the technical problems solved, technical solutions, and beneficial effects of this application. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Room temperature refers to the range of 20~35°C, and all chemical reagents are commercially available.

[0051] Example 1 The chemical formula of the anion-cation co-doped Ca2IrO4 catalyst prepared in this embodiment is: Ca2Ir 0.9 Ga 0.1 O 3.75 S 0.25 Let this be catalyst A. The synthetic route for this material is as follows: 1) Preparation of aqueous solution: 1 mmol calcium nitrate tetrahydrate, 1 mmol citric acid monohydrate and 0.15 mmol thiourea are completely placed in 5 mL of deionized water and stirred at a constant temperature until the solute molecules are uniformly distributed. 2) Prepare an alcohol phase solution by introducing 0.135 mmol of potassium hexachloroiridate with tetravalent iridium and 0.015 mmol of gallium perchlorate (Ga atoms account for 10% of the total (Ir+Ga)) into 4 mL of ethylene glycol solvent and then performing high-frequency magnetic dispersion. 3) Under the mechanical flow field of continuous stirring, the alcohol phase solution is slowly injected into the aqueous phase solution by dropping using a dropper to assemble a highly stable sol-like mixed solution. The stirring time is 120 min. 4) The above mixed solution is transferred into a blower drying device and subjected to a deep desolvation treatment at 150°C for 12 hours. The resulting solid precursor is mechanically ground into solid precursor powder. 5) Place the solid precursor powder into a programmable temperature controlled furnace and set the heating slope to 2℃ / min. The heat treatment program is strictly limited to four temperature gradients: first, stay at 200℃ for 6 hours to evaporate excess solvent; then raise the temperature to 350℃ to trigger the in-situ sulfidation reaction and hold for 6 hours; then hold at 500℃ for 3 hours; finally, set the final temperature to 700℃ and maintain for 6 hours of crystal growth; after the system cools to room temperature, obtain the black solid heat-treated product.

[0052] 6) Immerse the heat-treated product in a 1 mol / L hydrochloric acid solution and maintain the controlled reaction for 0.5 h. This process aims to remove solid impurities such as calcium oxide and induce the leaching of surface Ca elements, thereby generating a highly active surface layer. The reactants are centrifuged and washed 4 times each with deionized water and anhydrous ethanol, and dried in a vacuum environment to finally obtain catalyst A.

[0053] The structure and morphology of catalyst A were characterized and analyzed: Reference Figure 1 The XRD data shown in (a) are compared with the standard Ca2IrO4 spectrum. Catalyst A exhibits typical Ca2IrO4 ( The characteristic peak of the 62m space group indicates that the product is a single pure phase. Furthermore, since the radii of Ga and Ir ions are similar, the position of the main peak does not show a measurable lattice shift compared to the pure phase Ca2IrO4.

[0054] Reference Figure 2 The SEM data shown indicates that catalyst A is mainly composed of nanobulbs with regular geometric contours and an average size between 30 and 80 nm.

[0055] The composition of catalyst A was traced using EDS energy dispersive spectroscopy, and the results are as follows: Figure 3 As shown, the Ca, Ir, Ga, S and O elements are highly dispersed within a single nanoblock, demonstrating the successful doping of Ga and S elements and the high consistency between the abundance of each element and the feed ratio.

[0056] Ideally, Ca2Ir 1-x Ga x O 4-y S y A schematic diagram of the crystal structure is shown below. Figure 1 As shown in (b); according to the above Figure 1 (a) Figure 2 and Figure 3 Analysis of catalyst A, namely Ca2Ir 0.9 Ga 0.1 O 3.75 S 0.25 The crystal structure conforms to the schematic diagram of the ideal crystal structure and belongs to the same category. 62m space group.

[0057] Comparative Example 1 Comparative Example 1 prepared Ca2IrO4 doped with a single cation site, denoted as catalyst B, with the general chemical formula Ca2Ir. 0.9 Ga 0.1 O4; its preparation method differs from that of Example 1 in that thiourea is not added to the aqueous solution in step 1), while the remaining steps and parameters are the same as those in Example 1.

[0058] Comparative Example 2 Comparative Example 2 prepared Ca2IrO4 doped with a single anion site, denoted as catalyst C, with the general chemical formula Ca2IrO. 3.75 S 0.25 The preparation method differs from that in Example 1 in that gallium perchlorate is not added to the alcohol phase solution in step 2), and potassium hexachloroiridate is changed to 0.15 mmol. The remaining steps and parameters are the same as in Example 1.

[0059] Comparative Example 3 In Comparative Example 3, undoped Ca2IrO4 was prepared, which is catalyst D. The preparation method of catalyst D is different from that of Example 1. Gallium perchlorate and thiourea are not added in steps 1) and 2), and potassium hexachloroiridate is changed to 0.15 mmol. The remaining steps and parameters are the same as those in Example 1.

[0060] The catalyst prepared in Example 1 above was subjected to electrochemical performance evaluation: The catalyst A prepared above is used in the electrolysis of water to produce hydrogen through oxygen evolution, and is placed at the positive electrode in the working system. Catalyst A is typically prepared in a catalyst ink with a mass concentration of 5-20 mg / mL, preferably 10 mg / mL. The catalyst ink also includes a conductive agent with a mass concentration of 0.5-5 mg / mL, preferably 3 mg / mL. The specific type of conductive agent is not limited and is determined according to the actual situation, such as carbon black.

[0061] The specific application environment for the positive electrode containing catalyst A is as follows: Oxygen evolution kinetics of catalyst A were evaluated in a strongly acidic electrolyte with a concentration of 1 mol / L HClO4. The electrochemical performance of catalysts B, C, and D prepared in Comparative Examples 1-3 was evaluated using the same procedure, and the results are as follows. Figure 4 As shown.

[0062] like Figure 4 The polarization curves show that catalyst A at 10 mA / cm 2 At the standard current density, the corresponding overpotential is only 200mV, and the derived Tafel slope is locked at 52mVdec. -1 It is significantly superior to catalyst D (undoped Ca2IrO4) and monodoped Ca2IrO4 (including Ca2IrO4 catalyst B with a single cation site doping). 0.9 Ga 0.1 O4, Ca2IrO4 catalyst with single anion site doping C Ca2IrO 3.75 S 0.25 ) and commercial IrO2.

[0063] The present invention and its embodiments have been described above illustratively. This description is not restrictive and is merely one embodiment of the present invention, and is not actually limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A Ca2IrO4 catalyst with dual-site co-doping of anions and cations, characterized in that, It has the following general chemical formula: Ca2Ir 1-x Ga x O 4-y S y Where x is 0.01~0.15 and y is 0.01~0.

4.

2. The Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 1, characterized in that, The catalyst is a single-phase catalyst with a microstructure of nanobulbs and a crystal structure belonging to... The catalyst has a space group of 62m, and the elements of the catalyst are diffusely distributed within a single nanobulb.

3. The Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 1, characterized in that, The catalyst has an average particle size of 10-80 nm and an electrochemical active area of ​​8-25 cm². 2 The specific capacitance is 0.035 μF / cm. 2 .

4. A method for preparing a Ca2IrO4 catalyst with dual-site co-doping of anions and cations, characterized in that, Includes the following steps: The step of obtaining an aqueous solution, wherein the aqueous solution comprises a calcium source, an organic polyacid, and a sulfur source in a molar ratio of 1:1:0.01 to 0.4; The step of obtaining an alcohol phase solution, wherein the alcohol phase solution includes an iridium source and a gallium source, and the molar number of gallium ions accounts for 0.01~15% of the total molar number of metal ions in the alcohol phase solution; The step of mixing an aqueous phase solution and an alcohol phase solution to obtain a mixed solution under stirring conditions; The steps include drying the mixed solution and grinding it to obtain a solid precursor powder; A multi-stage heat treatment was performed on the solid precursor powder to obtain the heat-treated product. The heat-treated product was subjected to acid treatment to obtain a Ca2IrO4 catalyst with co-doped anion and cation sites; wherein the catalyst has the following general chemical formula: Ca2Ir 1-x Ga x O 4-y S y Where x is 0.01~0.15 and y is 0.01~0.

4.

5. The method for preparing the Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 4, characterized in that, The process of obtaining the heat-treated product by performing multi-stage heat treatment on solid precursor powder is as follows: The solid precursor powder was heated at a heating rate of 0.5~5℃ / min, and then held at 150~250℃, 300~400℃, 450~550℃ and 650~750℃ for 5~7h, 5~7h, 2~4h and 5~7h respectively. After naturally cooling to room temperature, a black solid heat-treated product was obtained.

6. The method for preparing the Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 4, characterized in that, The process of obtaining a Ca2IrO4 catalyst with both cation and anion co-doped sites by acid treatment of the heat-treated product is as follows: The product was soaked in hydrochloric acid, glacial acetic acid or perchloric acid at a concentration of 0.5~1 mol / L for 0.5~1 h to fully leach out the calcium element on the surface of the sample. Then it was washed with deionized water and anhydrous ethanol 3~5 times respectively. After vacuum drying, the Ca2IrO4 catalyst with Ir site and O site co-doped was obtained.

7. The method for preparing the Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 4, characterized in that, The calcium source is selected from one or more of calcium nitrate, calcium chloride, and calcium carbonate; The organic polyacid is selected from one or more of citric acid, tartaric acid, and oxalic acid; The sulfur source is selected from one or more of thiourea, sodium sulfate, and potassium sulfate.

8. The method for preparing the Ca2IrO4 catalyst with dual-site co-doping of anions and cations according to claim 4, characterized in that, The iridium source is selected from one or more of the following: potassium hexachloroiridate with tetravalent iridium, sodium hexachloroiridate with tetravalent iridium, potassium hexachloroiridate with trivalent iridium, sodium hexachloroiridate with trivalent iridium, iridium chloride, and chloroiridic acid. The gallium source is selected from one or more of gallium perchlorate, sulfate, and chlorate; The alcohol phase solution is prepared using an organic polyol, which is selected from one or more of ethylene glycol, propylene glycol, and glycerol.

9. The application of a catalyst prepared by the method of preparing a Ca2IrO4 catalyst with dual-site co-doped anions and cations as described in any one of claims 1-3 or the Ca2IrO4 catalyst with dual-site co-doped anions and cations as described in any one of claims 4-8 in the field of oxygen evolution by water electrolysis.

10. The application according to claim 9, characterized in that, When the catalyst was applied in the oxygen evolution reaction of water electrolysis in a three-electrode system, the Tafel slope of the catalyst was tested in a 1 mol / L HClO4 solution environment and was found to be 50~95 mV dec. -1 ; The catalyst achieves 10 mA / cm² in an acidic environment with pH=1. 2 The overpotential required for the current density is 200~240mV.

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