A nanoscale low-valence iridium ruthenium oxide catalyst, a preparation method and application thereof

Abstract

This invention relates to a nanoscale low-valence iridium-ruthenium oxide catalyst, its preparation method, and its applications, belonging to the field of nanomaterial preparation technology. The catalyst has a monoclinic crystal structure with nanoscale particle size, wherein Ru and Ir are stable in a mixed low-valence state of +3 to +4. Unlike traditional +4 valence rutile phases, the catalyst of this invention maintains its low valence state even after prolonged catalysis, avoiding irreversible peroxidation, while the oxide framework retains structural rigidity. This invention also provides a preparation method for this catalyst, achieving phase transformation and valence state control through a combination of co-precipitation, calcination, mixed solvothermal reduction, and inert atmosphere heat treatment. This method is controllable and reproducible, and the resulting catalyst exhibits both high activity and high stability at 10 mA cm⁻¹. −2 It can operate stably for more than 100 hours continuously at current density, and can be used as a highly efficient anode electrocatalyst in the field of acidic water splitting for hydrogen production, with broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a nanoscale low-valence iridium-ruthenium oxide catalyst, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane water electrolyzers (PEMWEs) are a key technology for achieving sustainable green hydrogen production, with the oxygen evolution reaction (OER) at the anolyte being the core electrochemical process that determines overall efficiency. However, this reaction faces severe kinetic bottlenecks in acidic media, and the materials also encounter harsh corrosive environments, placing extremely high demands on the catalytic materials.

[0003] Currently, research on oxygen evolution reaction (OER) catalysts mainly focuses on ruthenium-based (Ru) and iridium-based (Ir) oxide systems. While Ru-based oxides (such as RuO2) exhibit high intrinsic activity, they are prone to peroxidation at the OER potential, forming soluble RuO4. 2 Ru's high activity leads to rapid dissolution and failure; while Ir-based oxides (such as IrO2) have good corrosion resistance, their catalytic activity is relatively low. This inherent contradiction between activity and stability has prompted researchers to focus on developing iridium-ruthenium composite oxides, hoping to achieve a synergistic effect of high Ru activity and high Ir stability in a single material.

[0004] However, traditional bimetallic catalysts often struggle to achieve sustained synergistic effects under practical operating conditions. At harsh OER potentials, elemental segregation, irreversible peroxidation, and selective dissolution of unstable components (typically Ru) readily occur on the catalyst surface. This problem persists at high current densities (1~2 A cm⁻¹). 2 The effects are particularly pronounced in industrial environments (or higher), where extreme oxidation can trigger rapid degradation, leading to severe performance decline. Therefore, developing an iridium-ruthenium catalyst that maintains structural integrity and catalytic function under harsh operating conditions is a core technological challenge with significant research and application value. Summary of the Invention

[0005] To address the problem that existing iridium-ruthenium-based catalysts struggle to balance high intrinsic activity and long-term structural stability in acidic oxygen evolution reactions, especially the technical bottleneck of irreversible peroxidation and metal dissolution under high current density conditions, the present invention aims to provide a nanoscale low-valence iridium-ruthenium oxide catalyst, its preparation method, and its applications.

[0006] This invention provides a method for preparing nanoscale low-valence iridium-ruthenium oxide catalysts. By combining co-precipitation, high-temperature calcination, solvothermal reduction, and inert atmosphere heat treatment, the controllable preparation of nanoscale low-valence iridium-ruthenium oxide catalysts can be achieved.

[0007] The nanoscale low-valence iridium-ruthenium oxide provided by this invention has a monoclinic crystal system with space group P21 / c and a particle size of approximately 2 nm, exhibiting a uniform distribution. X-ray photoelectron spectroscopy (XPS) analysis shows that, compared to the characteristic peaks of +4 valence Ir and Ru in rutile iridium-ruthenium solid solution, the binding energies of the characteristic peaks of Ir 4f and Ru 3p orbitals in the nanoscale low-valence iridium-ruthenium oxide are shifted towards higher energies, confirming that Ir and Ru are both in a mixed low-valence state between +3 and +4, consistent with the design expectation of this invention.

[0008] The first objective of this invention is to provide a method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst, the steps of which are as follows:

[0009] (1) Dissolve 1 mmol of iridium salt and ruthenium salt in 20-50 mL of deionized water at a predetermined molar ratio, and stir until completely dissolved to form a homogeneous mixture; add 0.5-2.0 g of polyvinylpyrrolidone (PVP, molecular weight 10,000-40,000) as a dispersant to the above mixture and sonicate at room temperature for 15-30 min; then, under vigorous stirring, add dropwise a concentration of 1-3 mol L. −1 The system was prepared with an alkaline solution, and the pH was adjusted to 5-11. The reaction system was heated to 60-100 °C and stirred for 0.5-4 h to form a homogeneous hydroxide coprecipitate. After the reaction was completed, the system was naturally cooled to room temperature, and the precipitate was separated by centrifugation. It was washed 3-5 times alternately with deionized water and anhydrous ethanol, and then dried under vacuum at 60-80 °C for 12-24 h to obtain the iridium-ruthenium hydroxide precursor.

[0010] Among them, the metallic iridium salt is selected from one of iridium trichloride, potassium hexachloroiridate, or iridium acetylacetonate;

[0011] The ruthenium salt is selected from one of ruthenium trichloride, potassium pentachlororuthenate, or ruthenium acetylacetonate;

[0012] The molar ratio of the metallic iridium salt to the metallic ruthenium salt is x:(1−x), where 0 < x < 1. Hydroxide precursors with different iridium-ruthenium ratios can be obtained by adjusting the value of x.

[0013] The alkaline solution is selected from one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution;

[0014] (2) Place the iridium-ruthenium hydroxide precursor obtained in step (1) in a muffle furnace and heat it at 2-5 °C for 1 minute in an air atmosphere. −1 The temperature was increased to 400~700 ℃ at a rate of 100%, and calcined at a constant temperature for 2~5 h. After natural cooling to room temperature, iridium-ruthenium solid solution powder with rutile phase was obtained.

[0015] (3) Take 50~150 mg of the solid solution powder obtained in step (2) and disperse it in 40~80 mL of mixed reducing solvent to obtain a dispersion system; the mixed reducing solvent is a mixture of two alcohol solvents in a volume ratio of 1:1, and 0.1~0.5 g of cetyltrimethylammonium bromide (CTAB) is added as a structure directing agent; transfer the dispersion system to a high-pressure reactor with a polytetrafluoroethylene liner, seal it and react it at 160~220 ℃ for 6~24 h; after the reaction is completed, cool it naturally to room temperature, centrifuge the product, wash the centrifuged product with anhydrous ethanol and deionized water 3~5 times each, and then vacuum dry it at 50~70 ℃ for 8~12 h;

[0016] Among them, the two alcohol solvents are any combination of ethylene glycol and 1,2-propanediol, ethylene glycol and triethylene glycol, glycerol and diethylene glycol, glycerol and 1,3-butanediol, 1,2-propanediol and furfuryl alcohol, and 1,3-butanediol and furfuryl alcohol.

[0017] (4) The product obtained in step (3) is heat-treated at 200~300 °C for 1~3 h in an inert atmosphere (nitrogen or argon) to remove residual organic matter on the surface, and finally the nano-scale low-valence iridium ruthenium oxide powder of the present invention is obtained.

[0018] The second objective of this invention is to provide a nanoscale low-valence iridium-ruthenium oxide prepared by the above method.

[0019] A third objective of this invention is to provide the application of the above-mentioned nanoscale low-valence iridium-ruthenium oxide as an electrocatalyst for the oxygen evolution reaction in acidic media.

[0020] Beneficial effects

[0021] This invention achieves the controllable preparation of nanoscale low-valence iridium-ruthenium oxide, with the obtained product having a particle size of approximately 2 nm and a uniform distribution. The preparation method employs a multi-step process combining co-precipitation, high-temperature calcination, and mixed solvothermal reduction, enabling multi-scale synergistic control of the product's crystal phase structure, metal valence state, and microstructure. Because Ir and Ru are stabilized in a mixed low-valence state of +3 to +4, this catalyst effectively maintains its low-valence structure during the acidic oxygen evolution reaction, inhibiting irreversible peroxidation and metal dissolution. At 10 mA cm⁻¹, the catalyst exhibits excellent performance. −2 It can operate stably continuously for over 100 hours at the specified current density. Simultaneously, its intrinsic catalytic activity is significantly enhanced, with an overpotential of only 230 mV (@10 mA cm⁻¹) under three-electrode conditions. −2 In a proton exchange membrane electrolysis water bath, a voltage of 1.8V@2.4A can be achieved. −2 With a current density of [value missing], it exhibits excellent oxygen evolution catalytic performance and can be used as a highly efficient and stable anolyte electrocatalyst in the field of acidic water splitting for hydrogen production. Attached Figure Description

[0022] Figure 1 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention;

[0023] Figure 2 X-ray photoelectron spectroscopy (XPS) of nanoscale low-valence iridium ruthenium oxides Ir 4f and Ru 3p prepared in Example 1 of this invention.

[0024] Figure 3 Transmission electron microscope (TEM) image of nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of the present invention;

[0025] Figure 4 A high-resolution transmission electron microscope (HRTEM) image of nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention;

[0026] Figure 5 The oxygen evolution polarization curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention in a three-electrode system;

[0027] Figure 6 The curves showing the change in metal dissolution (iridium and ruthenium) over time during 10 h of catalysis of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention.

[0028] Figure 7 The constant current stability test curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of the present invention;

[0029] Figure 8 The image shows the XRD pattern of nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention after 100 h of catalysis.

[0030] Figure 9 X-ray photoelectron spectroscopy (XPS) of Ir 4f and Ru 3p after 100 h of catalysis by nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of this invention.

[0031] Figure 10 The oxygen evolution polarization curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 1 of the present invention in a proton exchange membrane water electrolysis cell;

[0032] Figure 11 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 2 of this invention;

[0033] Figure 12 The oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide prepared in Example 2 of this invention in a three-electrode system;

[0034] Figure 13The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 3 of this invention;

[0035] Figure 14 The oxygen evolution polarization curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 3 of this invention in a three-electrode system;

[0036] Figure 15 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 4 of this invention;

[0037] Figure 16 The oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide prepared in Example 4 of this invention in a three-electrode system;

[0038] Figure 17 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 5 of this invention;

[0039] Figure 18 The oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide prepared in Example 5 of this invention in a three-electrode system;

[0040] Figure 19 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 6 of this invention;

[0041] Figure 20 The oxygen evolution polarization curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 6 of this invention in a three-electrode system;

[0042] Figure 21 The XRD pattern of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 7 of this invention;

[0043] Figure 22 The oxygen evolution polarization curve of the nanoscale low-valence iridium-ruthenium oxide prepared in Example 7 of this invention in a three-electrode system. Detailed Implementation

[0044] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples, so as to facilitate a fuller understanding of the technical content and advantages of the present invention. However, the scope of protection of the present invention is not limited to the specific embodiments. Any equivalent modifications or adjustments made within the framework of the technical concept of the present invention should be considered to fall within the scope of protection of the present invention.

[0045] The process conditions listed in the following embodiments are merely examples, and their actual allowable range has been defined in the foregoing invention content section. Other unspecified process parameters can be determined according to conventional methods in the field.

[0046] Example 1

[0047] (1) Preparation of the iridium-ruthenium hydroxide precursor: 176 mg (0.5 mmol) of iridium trichloride (IrCl3·3H2O) and 131 mg (0.5 mmol) of ruthenium trichloride (RuCl3·3H2O) were dissolved in 30 mL of deionized water and stirred until completely dissolved to form a homogeneous mixture. 1.0 g of polyvinylpyrrolidone (PVP, molecular weight 20,000) was added to the above mixture as a dispersant and ultrasonically dispersed at room temperature for 20 min. Subsequently, under vigorous stirring, the mixture was dispersed at approximately 1 mL / min. −1 The rate of addition was 2 mol L. −1 The pH of the system was adjusted to 8 using an aqueous sodium hydroxide solution. The reaction system was heated to 80 °C and stirred for 2 h to form a homogeneous hydroxide coprecipitate. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The precipitate was then centrifuged, washed three times alternately with deionized water and anhydrous ethanol, and dried under vacuum at 80 °C for 18 h to obtain 150 mg of iridium-ruthenium hydroxide precursor.

[0048] (2) Preparation of rutile phase iridium-ruthenium solid solution: 70 mg of iridium-ruthenium hydroxide precursor was placed in a muffle furnace and heated at 3 °C for 3 min in an air atmosphere. −1 The temperature was increased to 600 °C at a rate of 100 °C, calcined at a constant temperature for 3 h, and then naturally cooled to room temperature to obtain rutile phase iridium-ruthenium solid solution powder.

[0049] (3) Preparation of crude iridium-ruthenium oxide in low valence state: 50 mg of rutile-phase iridium-ruthenium solid solution powder was dispersed in 60 mL of mixed reducing solvent to obtain a dispersion system. The mixed reducing solvent consisted of ethylene glycol and 1,2-propanediol in a volume ratio of 1:1, with 0.2 g of hexadecyltrimethylammonium bromide (CTAB) added as a structure directing agent. The above dispersion system was transferred to a high-pressure reactor with a polytetrafluoroethylene liner, sealed, and reacted at 200 °C for 12 h. After the reaction was completed, the mixture was naturally cooled to room temperature, and the product was centrifuged. The centrifuged product was then washed three times each with anhydrous ethanol and deionized water, and then dried under vacuum at 60 °C for 10 h to obtain crude iridium-ruthenium oxide powder in low valence state.

[0050] (4) Removal of organic matter by inert atmosphere treatment: The crude product powder of low-valence iridium ruthenium oxide was heat-treated at 200 °C for 1 h under nitrogen atmosphere to remove residual organic matter on the surface, and 50 mg of nano-sized low-valence iridium ruthenium oxide powder was obtained.

[0051] Characterization of oxygen evolution catalytic performance of nanoscale low-valence iridium-ruthenium oxide: A standard three-electrode system was used at 0.1 mol / L... −1Oxygen evolution reaction (OER) tests were conducted in HClO4 solution. The working electrode was a glassy carbon electrode (3 mm in diameter) with a catalyst layer supported on its surface; the reference electrode was a saturated calomel electrode, and the counter electrode was a platinum wire. The catalyst slurry was prepared as follows: 4 mg of the nano-sized low-valence iridium-ruthenium oxide powder prepared in this example was mixed with 200 μL of isopropanol and 200 μL of Nafion solution (0.5 wt%), and ultrasonically treated to obtain a uniformly dispersed catalyst slurry; 2.0 μL of the catalyst slurry was pipetted onto the surface of the glassy carbon electrode and dried at room temperature to form a film. Electrochemical tests were then performed on a Chenhua workstation, and 85% iR compensation was used when recording the polarization curves.

[0052] Characterization of the catalytic performance of nanoscale low-valence iridium-ruthenium oxide in water electrolysis using a proton exchange membrane: 35 mg of nanoscale low-valence iridium-ruthenium oxide was dispersed as the anolyte catalyst in a mixed solvent of 20 mL isopropanol and deionized water (volume ratio 1:1). A 5% (w / w) Nafion solution was added (making the Nafion to catalyst mass ratio 3:20), and the mixture was ultrasonically dispersed to form a uniform anolyte catalyst slurry. A commercial Pt / C catalyst (40% Pt mass fraction) was used as the cathode catalyst, and a cathode catalyst slurry was prepared using the same solvent composition and Nafion / catalyst mass ratio. The anolyte and cathode catalyst slurries were uniformly deposited on both sides of a proton exchange membrane (Nafion 115) using ultrasonic spraying, with an effective spraying area of ​​5 cm². 2 The noble metal loading of the anode catalyst is 0.6 mg. cm −2 The cathode catalyst Pt loading is 0.2 mg. cm⁻². The sprayed membrane electrode was placed in a hot press and hot-pressed at 130 ℃ and 10 MPa for 3 min to complete the preparation of the membrane electrode assembly. The prepared membrane electrode was assembled in a single-cell test fixture, with deionized water as the feed at a flow rate of 60 mL·min⁻¹ on the anode side and no water supply on the cathode side. The electrolyzer temperature was maintained at 60 ℃ during the test. The oxygen evolution catalytic performance was evaluated using a Xinwei electrochemical workstation to characterize the catalyst activity at industrial-grade current densities.

[0053] The nanoscale low-valence iridium-ruthenium oxide catalyst prepared by the above method was characterized as follows.

[0054] Figure 1 The XRD pattern of the prepared nanoscale low-valence iridium-ruthenium oxide shows that the diffraction peak positions are significantly different from those of the rutile phase iridium-ruthenium solid solution, indicating that a significant phase transformation occurred in the material during the solvothermal reduction process.

[0055] Figure 2This is a comparison of X-ray photoelectron spectroscopy (XPS) spectra of nanoscale low-valence iridium-ruthenium oxide and rutile-phase iridium-ruthenium solid solution. Compared to the rutile-phase iridium-ruthenium solid solution (where all metals are in the +4 valence state), the characteristic peaks of Ir 4f and Ru 3p in the nanoscale low-valence iridium-ruthenium oxide shift towards higher binding energies, indicating that the oxidation states of Ir and Ru are in a mixed low-valence range from +3 to +4.

[0056] Figure 3 The image is a TEM image of nanoscale low-valence iridium-ruthenium oxide, which shows that the sample is composed of uniform particles of about 2 nm.

[0057] Figure 4 HRTEM image of the prepared nanoscale low-valence iridium-ruthenium oxide; clear lattice fringes on the nanoscale low-valence iridium-ruthenium oxide particles prove that the material can still maintain a good degree of crystallization after reduction.

[0058] Figure 5 The nanoscale low-valence iridium-ruthenium oxide and ruthenium-ruthenium solid solution in 0.1 mol L −1 Anodic oxygen evolution polarization curve in HClO4 electrolyte. At 10 mA cm⁻¹ −2 At the specified current density, the overpotential of nanoscale low-valence iridium-ruthenium oxide is 230 mV, while that of rutile-phase iridium-ruthenium solid solution is 310 mV. This indicates that, compared to the traditional +4 valence rutile structure, nanoscale low-valence iridium-ruthenium oxide significantly enhances the intrinsic oxygen evolution activity of the catalyst.

[0059] Figure 6 The curves show the metal dissolution amounts (iridium and ruthenium) of nanoscale low-valence iridium-ruthenium oxides as a function of catalytic time. Within the first 4 hours of the reaction, the dissolution amounts of iridium and ruthenium rapidly stabilized. Afterward, up to 10 hours, there was no significant further dissolution of either metal, with the cumulative dissolution ratio remaining below 0.2%. This indicates that the catalyst maintains high stability of the metal components during catalysis and exhibits excellent structural stability.

[0060] Figure 7 For nanoscale low-valence iridium-ruthenium oxide at 10 mA cm⁻¹ −2 The constant current stability test curves at the current density show that the catalyst can continuously and stably catalyze for more than 100 h.

[0061] Figure 8 The image shows the XRD pattern of nanoscale low-valence iridium-ruthenium oxide after 100 h of catalysis. The diffraction peak positions are compared with those of the nanoscale low-valence iridium-ruthenium oxide before catalysis. Figure 1 The fact that it hardly changed indicates that it can still maintain good structural stability after long-term catalysis.

[0062] Figure 9The image shows a comparison of the X-ray photoelectron spectroscopy (XPS) spectra of nanoscale low-valence iridium-ruthenium oxide after 100 h of catalysis and before catalysis. Compared with the material before catalysis, the positions of the characteristic peaks of Ir 4f and Ru 3p in the catalyzed material are not significantly different, indicating that the oxidation states of Ir and Ru are still maintained in the mixed low-valence range of +3 to +4 after catalysis.

[0063] Figure 10 The figure shows the polarization curves of nanoscale low-valence iridium-ruthenium oxide in a proton exchange membrane water electrolysis cell. At 1.8 V, a polarization of 2.4 A / cm² can be achieved. 2 It exhibits good catalytic activity at a current density of [value missing].

[0064] Table 1 shows the cell parameter information of the prepared nanoscale low-valence iridium-ruthenium oxide after X-ray diffraction Rietveld refinement. Its crystal system and cell parameters have changed significantly compared with the rutile phase iridium-ruthenium solid solution, proving that the rutile phase iridium-ruthenium solid solution underwent a phase transformation after solvothermal reduction, generating a new crystal phase.

[0065] Table 1. Cell parameters of low-valence iridium-ruthenium oxide and rutile-phase iridium-ruthenium solid solution

[0066] a(Å) 4.49 5.37 b(Å) 4.49 4.75 c(Å) 3.12 5.37 α(°) 90.00 90.00 β(°) 90.00 108.59 γ(°) 90.00 90.00 <![CDATA[Unit cell volume (Å 3 )]]> 63.09 129.88 Crystal system Tetragonal crystal system Monoclinic crystal system Space Group <![CDATA[P42 / mnm]]> <![CDATA[P21 / c]]> Unweighted profile factor / 5.20% Weighted profile factor / 7.44%

[0067] Example 2

[0068] In this embodiment, the iridium salt in step (1) was replaced with potassium hexachloroiridate, the ruthenium salt was replaced with potassium pentachlororuthenate, the molar ratio of iridium salt to ruthenium salt was changed from 1:1 to 7:3 (i.e., x=0.7), the pH of the reaction system was adjusted from 8 to 10, and the reaction time was extended from 2 h to 3 h. All other synthesis conditions were the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide with a yield of 50 mg. Figure 11 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 12 The oxygen evolution polarization curves of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system are shown. Electrochemical tests indicate that at 10 mA cm⁻¹... −2 At the specified current density, the oxygen evolution overpotential was 232 mV, which is very close to the 230 mV in Example 1. Characterization results indicate that changing the type of metal salt, the molar ratio of iridium to ruthenium, adjusting the pH, and altering the reaction time do not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide or its excellent oxygen evolution catalytic performance.

[0069] Example 3

[0070] In this embodiment, the amount of dispersant PVP in step (1) was changed from 1.0 g to 0.8 g, and the reaction temperature was increased from 80℃ to 90℃, while the reaction time was shortened from 2 h to 1.5 h. All other synthesis conditions were the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide with a yield of 50 mg. Figure 13 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 14 The figure shows the oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system. Electrochemical tests show that it reaches its maximum oxidation state at 10 mA cm⁻¹. −2 The overpotential was 234 mV, which is very close to 230 mV in Example 1. The characterization results show that appropriately adjusting the amount of PVP, changing the reaction temperature and reaction time will not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide and its excellent oxygen evolution catalytic performance.

[0071] Example 4

[0072] In this embodiment, the molar ratio of iridium salt to ruthenium salt in step (1) is changed from 0.5:0.5 to 0.4:0.6 (i.e., x=0.4), the calcination temperature in step (2) is changed from 600 ℃ to 450 ℃, and the heating rate is changed from 3 ℃ min. −1 Change to 5 ℃min −1 The calcination time was changed from 3 h to 2 h, while other synthesis conditions remained the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide, with a yield of 50 mg. Figure 15 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 16 The figure shows the oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system. Electrochemical tests show that it reaches its maximum oxidation state at 10 mA cm⁻¹. −2 The overpotential was 236 mV, which is very close to 230 mV in Example 1. The characterization results show that changing the molar ratio of iridium salt to ruthenium salt, calcination temperature, heating rate, and calcination time does not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide and its excellent oxygen evolution catalytic performance.

[0073] Example 5

[0074] In this embodiment, the mixed reducing solvent in step (3) was changed from ethylene glycol and 1,2-propanediol to glycerol and diethylene glycol. Simultaneously, the reaction temperature was changed from 200 °C to 220 °C, and the reaction time was shortened from 12 h to 8 h. All other synthesis conditions remained the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide, with a yield of 50 mg. Figure 17 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 18 The figure shows the oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system. Electrochemical tests show that it reaches its maximum oxidation state at 10 mA cm⁻¹. −2 The overpotential was 229 mV, which is very close to 230 mV in Example 1. The characterization results show that changing the type of reducing alcohol, reaction temperature, and reaction time does not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide and its excellent oxygen evolution catalytic performance.

[0075] Example 6

[0076] In this embodiment, the amount of structure-directing agent CTAB in step (3) was changed from 0.2 g to 0.4 g, the reaction temperature was reduced from 200 ℃ to 170 ℃, and the reaction time was extended from 12 h to 18 h. All other synthesis conditions were the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide with a yield of 50 mg. Figure 19 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 20 The figure shows the oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system. Electrochemical tests show that it reaches its maximum oxidation state at 10 mA cm⁻¹. −2 The overpotential was 232 mV, which is very close to the 230 mV in Example 1. The characterization results show that appropriately changing the amount of CTAB, reaction temperature, and time does not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide and its excellent oxygen evolution catalytic performance.

[0077] Example 7

[0078] In this embodiment, the mixed reducing solvent in step (3) was changed from ethylene glycol and 1,2-propanediol to 1,3-butanediol and furfuryl alcohol. The inert atmosphere heat treatment temperature in step (4) was changed from 200 ℃ to 250 ℃, and the holding time was changed from 1 h to 1.5 h. All other synthesis conditions were the same as in Example 1. The results showed that this method could still successfully prepare nanoscale low-valence iridium-ruthenium oxide with a yield of 50 mg. Figure 21 The XRD pattern of the prepared sample shows that the diffraction peak positions are consistent with those of the sample in Example 1, indicating that low-valence iridium-ruthenium oxide was successfully synthesized. Figure 22 The figure shows the oxygen evolution polarization curve of nanoscale low-valence iridium-ruthenium oxide in a three-electrode system. Electrochemical tests show that it reaches its maximum oxidation state at 10 mA cm⁻¹. −2The overpotential was 231 mV, which is very close to the 230 mV in Example 1. The characterization results show that changing the type of reducing alcohol, appropriately changing the heat treatment temperature and treatment time, does not affect the successful synthesis of nanoscale low-valence iridium-ruthenium oxide and its excellent oxygen evolution catalytic performance.

Claims

1. A method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst, comprising the following steps: (1) Dissolve 1 mmol of iridium and ruthenium salts in 20-50 mL of deionized water and stir until completely dissolved to form a homogeneous mixture; add 0.5-2.0 g of polyvinylpyrrolidone as a dispersant to the mixture and sonicate at room temperature for 15-30 min; then, under vigorous stirring, add dropwise a concentration of 1-3 mol L. −1 The system was prepared with an alkaline solution, and the pH was adjusted to 5-11. The reaction system was heated to 60-100 °C and stirred for 0.5-4 h to form a homogeneous hydroxide coprecipitate. After the reaction was completed, the system was naturally cooled to room temperature, and the precipitate was separated by centrifugation. It was washed 3-5 times alternately with deionized water and anhydrous ethanol, and then dried under vacuum at 60-80 °C for 12-24 h to obtain the iridium-ruthenium hydroxide precursor. (2) Place the iridium-ruthenium hydroxide precursor obtained in step (1) in a muffle furnace and heat it at 2-5 °C for 1 minute in an air atmosphere. −1 The temperature was increased to 400~700 ℃ at a rate of 100%, and calcined at a constant temperature for 2~5 h. After natural cooling to room temperature, iridium-ruthenium solid solution powder with rutile phase was obtained. (3) Take 50~150 mg of the solid solution powder obtained in step (2) and disperse it in 40~80 mL of mixed reducing solvent to obtain a dispersion system; the mixed reducing solvent is a mixture of two alcohol solvents in a volume ratio of 1:1, and 0.1~0.5 g of hexadecyltrimethylammonium bromide is added as a structure directing agent; transfer the dispersion system to a high-pressure reactor with a polytetrafluoroethylene liner, seal it and react it at 160~220 ℃ for 6~24 h; after the reaction is completed, cool it naturally to room temperature, centrifuge the product, wash the centrifuged product with anhydrous ethanol and deionized water 3~5 times each, and then vacuum dry it at 50~70 ℃ for 8~12 h; (4) The product obtained in step (3) is heat-treated at 200~300 °C for 1~3 h in an inert atmosphere to remove residual organic matter on the surface, and finally nano-sized low-valence iridium ruthenium oxide powder is obtained.

2. The method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 1, characterized in that: The iridium salt in step (1) is selected from one of iridium trichloride, potassium hexachloroiridate, and iridium acetylacetonate; the ruthenium salt is selected from one of ruthenium trichloride, potassium pentachlororuthenate, and ruthenium acetylacetonate.

3. The method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 1, characterized in that: In step (1), the molar ratio of iridium salt to ruthenium salt is x:(1−x), where 0 < x < 1.

4. The method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 1, characterized in that: The alkaline solution in step (1) is selected from one of the following: sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution.

5. The method for preparing a nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 1, characterized in that: The two alcohol solvents in step (3) are any combination of ethylene glycol and 1,2-propanediol, ethylene glycol and triethylene glycol, glycerol and diethylene glycol, glycerol and 1,3-butanediol, 1,2-propanediol and furfuryl alcohol, and 1,3-butanediol and furfuryl alcohol.

6. A nanoscale low-valence iridium-ruthenium oxide catalyst, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 5.

7. The nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 6, characterized in that, The catalyst has a monoclinic crystal structure, space group P21 / c, particle size of 1~5 nm, and average oxidation states of Ir and Ru are both between +3 and +4.

8. The application of the nanoscale low-valence iridium-ruthenium oxide catalyst as described in claim 6 or 7 as an electrocatalyst for the oxygen evolution reaction in acidic media.

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