Precious metal doped transition metal oxide electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a noble metal doped transition metal oxide electrocatalyst and a preparation method and application thereof, and belongs to the field of electrocatalysts.The noble metal doped transition metal oxide electrocatalyst is obtained by taking a metal organic framework (MOF) as a self-sacrifice template through step-by-step doping and a controllable pyrolysis process. Noble metal atoms are uniformly dispersed in transition metal oxide crystal lattices, the electronic structure of the material is effectively regulated and controlled, and the conductivity and the number of active sites of the material are improved. According to the method, the catalytic performance of the transition metal oxide serving as the electrocatalyst is effectively improved, the preparation process is simple, the designed reaction condition is mild, the dosage of precious metal is remarkably reduced, and remarkable technical advancement and industrial application value are embodied.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to a noble metal-doped transition metal oxide electrocatalyst, its preparation method, and its application. Background Technology

[0002] Against the backdrop of an accelerated global energy transition towards a low-carbon model, hydrogen energy, with its high energy density and zero carbon emissions, has become a core carrier for achieving carbon neutrality. Hydrogen production through water electrolysis driven by renewable energy sources is widely recognized as an ideal approach for large-scale green hydrogen production. However, the oxygen evolution reaction (OER) at the anolyte involves a complex process of four-electron proton coupling, exhibiting extremely slow kinetics. This necessitates overcoming excessively high overpotentials at industrial-grade current densities, resulting in significant system energy losses. This bottleneck severely restricts the hydrogen production efficiency and economic feasibility of electrolyzers; therefore, developing high-performance OER catalysts is crucial to overcoming this technological barrier.

[0003] Currently, the catalysts used in commercial electrolyzers are mainly iridium and ruthenium-based noble metal catalysts, such as IrO2 and RuO2. Although they exhibit excellent catalytic activity, these materials face cost pressures due to resource scarcity and are also subject to structural degradation risks during long-term operation. More importantly, the high noble metal loading required to achieve industrial-grade current densities further exacerbates the cost barrier for large-scale applications. Therefore, there is an urgent need to develop novel catalytic systems that combine high activity, high stability, and low resource dependence.

[0004] Transition metal oxides, as representatives of non-noble metal catalysts, have attracted widespread attention due to their elemental abundance and theoretical activity. However, in practical electrochemical environments, these materials are limited by insufficient intrinsic conductivity and inadequate exposure of active sites, resulting in persistently high reaction barriers and performance that falls significantly short of industrial requirements. Although morphology control or composite support strategies can partially improve these issues, the improvement in activity still falls short of the dual standards of overpotential and durability required by commercial electrolyzers.

[0005] Noble metals, with their unique electronic orbital properties and oxidation stability, exhibit multiple synergistic mechanisms when modifying transition metal oxide lattices. On one hand, they can induce charge redistribution at the host metal centers, optimizing the adsorption free energy of oxygen intermediates. On the other hand, they can promote lattice oxygen activation pathways, circumventing the thermodynamic limitations of traditional surface adsorption mechanisms. Furthermore, they can increase the density of active defects through lattice strain effects. However, existing doping techniques generally suffer from fundamental defects such as low noble metal dispersion and inaccurate active interface construction, resulting in atom utilization rates far below theoretical expectations. A more prominent contradiction lies in the difficulty of achieving uniform construction and stable anchoring of active sites with ultra-low noble metal loadings using traditional methods. Atom migration and aggregation during high-temperature processing further weaken the interfacial synergistic effect. This scientific bottleneck at the material preparation level means that while noble metal-doped transition metal oxide systems possess theoretical advantages, they have consistently failed to translate into practically feasible technical solutions. Summary of the Invention

[0006] This invention provides a noble metal-doped transition metal oxide electrocatalyst, its preparation method, and its application. By using a metal-organic framework precursor pyrolysis pathway, the noble metal is uniformly doped in the transition metal oxide, significantly improving the electrocatalytic performance of the material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a noble metal-doped transition metal oxide electrocatalyst includes the following steps: Step 1: Preparation of MOF precursor: Dissolve the metal salt and organic ligand in solvents at a molar ratio of 1:2 to 1:12 respectively. After complete dissolution, pour the solution containing the organic ligand into the solution containing the metal salt under stirring. Continue stirring at room temperature for 12-24 hours. After the reaction is complete, centrifuge the resulting mixture, collect the precipitate, and dry it at 60-80℃ for 10-12 hours to obtain MOF. Step 2: Preparation of composite material: Disperse 100 mg of the above MOF in 30 mL of solvent, and slowly add 30 mL of noble metal salt solution with a concentration of 1-5 g / L at a rate of 0.3 mL / min using a micro-injection pump. Then stir the reaction at 25-50 °C for 10-12 hours. After the reaction is completed, centrifuge and wash at least 3 times with the solvent used in the reaction to obtain noble metal doped MOF composite material (denoted as element symbol @MOF).

[0008] Step 3: Pyrolysis treatment: The obtained noble metal-doped MOF composite material is heated to 350-450℃ in air at a heating rate of 2-5℃ / min, and calcined for 2 hours. After natural cooling, the noble metal-doped transition metal oxide electrocatalyst is obtained.

[0009] In the steps described above, the MOF in step 1 is ZIF-67, UiO-66, NiCo-BTC, etc.

[0010] The metal salt cations in step 1 are transition metal ions such as cobalt ions, nickel ions, zirconium ions, etc., and the anions can be nitrate ions, sulfate ions, chloride ions, etc.

[0011] The organic ligands in step 1 are 2-methylimidazole, terephthalic acid, pyromellitic acid, etc.

[0012] The solvents used in steps 1 and 2 are common solvents such as deionized water, methanol, and ethanol.

[0013] The precious metal salts include, but are not limited to, soluble precious metal salts such as iridium chloride, ruthenium chloride, and chloroiridium acid.

[0014] The solvents used in step 2 are common solvents such as deionized water, ethanol, and DMF.

[0015] The noble metal-doped transition metal oxide electrocatalyst prepared above exhibits a rough, protruding sheet-like structure under microscopic conditions. The noble metal atoms are uniformly dispersed in the transition metal oxide lattice, and a cobalt-ruthenium synergistic active center is constructed in the transition metal oxide lattice.

[0016] The noble metal-doped transition metal oxide electrocatalyst prepared above can be used for the oxygen evolution reaction at the anode.

[0017] Beneficial Effects: This invention provides a noble metal-doped transition metal oxide electrocatalyst, its preparation method, and its application. Using MOF as a precursor, a stepwise doping and controllable pyrolysis process is employed to achieve uniform dispersion of noble metal atoms in the transition metal oxide lattice, effectively regulating the electronic structure of the material and improving its conductivity and the number of active sites. The resulting catalyst has a higher specific surface area and more catalytic active sites. When the catalyst undergoes the oxygen evolution reaction in an alkaline electrolyte, it exhibits significantly better catalytic performance than pure transition metal oxides and is close to that of commercial ruthenium dioxide. This effect is attributed to the transition metal-noble metal synergistic active centers constructed in the transition metal oxide lattice through ion exchange. During the reaction, the noble metal sites, as the main active centers, adsorb hydroxide ions and undergo deprotonation to form key intermediates. Adjacent transition metal sites not only regulate the electron cloud density of the noble metal sites through electronic effects, optimizing the adsorption free energy of the reaction intermediates, but also directly participate in the formation of oxygen-oxygen bonds. The hydroxyl groups adsorbed at the transition metal sites nucleophilically attack oxygen species on the noble metal sites, synergistically completing the rate-determining step of the reaction. This atomic-scale synergistic mechanism significantly reduces the reaction energy barrier. Simultaneously, the stable transition metal oxide support structure effectively inhibits the over-oxidation and loss of the noble metal active centers, enabling the catalyst to maintain high activity while possessing excellent stability. This unique mechanism allows this invention to achieve near-ruthenium dioxide catalytic efficiency while significantly reducing the amount of noble metal used, demonstrating significant technological advancement and industrial application value. Attached Figure Description

[0018] Figure 1 The image shows the XRD pattern of the Ir@Co3O4 catalyst prepared in the embodiments of the present invention. Figure 2 Here is a SEM image of the Ir@Co3O4 catalyst prepared in the embodiments of the present invention; Figure 3 The image shows the EDS diagram of the Ir@Co3O4 catalyst prepared in the embodiments of the present invention. Figure 4 The LSV diagrams of Ir@Co3O4, Ru@Co3O4 catalysts and RuO2 prepared in the embodiments of the present invention are compared. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: Example 1

[0020] A method for preparing a noble metal-doped transition metal oxide electrocatalyst includes the following steps: 0.8185 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) was weighed and dissolved in 40 mL of methanol. 1.85 g of 2-methylimidazole was weighed and dissolved in 40 mL of methanol. Under magnetic stirring, the 2-methylimidazole solution was quickly poured into the cobalt nitrate hexahydrate solution. After mixing, the mixture was stirred continuously at room temperature for 12 hours. The resulting purple precipitate was collected by centrifugation, washed three times with methanol, and then dried in a vacuum drying oven at 80 °C for 10 hours to obtain the ZIF-67 precursor.

[0021] 100 mg of the ZIF-67 prepared above was dispersed in 30 mL of methanol. 10 mL of a 10 g / L ruthenium chloride (RuCl3·3H2O) methanol solution was diluted with methanol to 30 mL, yielding a ruthenium chloride methanol solution of approximately 3.3 g / L. The ruthenium chloride methanol solution was slowly added dropwise to the ZIF-67 suspension at a rate of 0.3 mL / min using a micro-injection pump. After the addition was complete, the mixture was stirred at 25 °C for 10 hours. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed three times with methanol to obtain the Ru@ZIF-67 composite material.

[0022] The obtained Ru@ZIF-67 was transferred to a corundum crucible, placed in a muffle furnace, heated to 350°C at a rate of 2°C / min in air atmosphere, and calcined at this temperature for 2 hours. After cooling to room temperature with the furnace, it was removed to obtain black Ru@Co3O4 electrocatalyst powder. Example 2

[0023] A method for preparing a noble metal-doped transition metal oxide electrocatalyst includes the following steps: 1.637 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) was dissolved in 80 mL of methanol, and 3.7 g of 2-methylimidazole was dissolved in 80 mL of methanol. Under magnetic stirring, the 2-methylimidazole solution was rapidly poured into the cobalt nitrate hexahydrate solution, and the mixture was stirred continuously at room temperature for 15 hours. The resulting purple precipitate was collected by centrifugation, washed three times with methanol, and then dried in a vacuum drying oven at 80 °C for 10 hours to obtain the ZIF-67 precursor.

[0024] 100 mg of the ZIF-67 prepared above was dispersed in 30 mL of methanol. 10 mL of a 10 g / L chloroiridic acid (H₂IrCl₆·6H₂O) methanol solution was diluted with methanol to 30 mL, yielding a chloroiridic acid methanol solution of approximately 3.3 g / L. This chloroiridic acid solution was slowly added dropwise to the ZIF-67 suspension at a rate of 0.3 mL / min using a micro-injection pump. After the addition was complete, the mixture was stirred at 40 °C for 11 hours. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed three times with methanol to obtain the Ir@ZIF-67 composite material.

[0025] The obtained Ir@ZIF-67 was transferred to a corundum crucible, placed in a muffle furnace, heated to 400°C at a rate of 3°C / min in air atmosphere, and calcined at this temperature for 2 hours. After cooling to room temperature with the furnace, it was removed to obtain black Ir@Co3O4 electrocatalyst powder. Example 3

[0026] A method for preparing a noble metal-doped transition metal oxide electrocatalyst includes the following steps: 3.274 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) was weighed and dissolved in 160 mL of methanol, and 7.4 g of 2-methylimidazole was weighed and dissolved in 160 mL of methanol. Under magnetic stirring, the 2-methylimidazole solution was rapidly poured into the cobalt nitrate hexahydrate solution, and the mixture was stirred continuously at room temperature for 18 hours. The resulting purple precipitate was collected by centrifugation, washed three times with methanol, and then dried in a vacuum drying oven at 80 °C for 10 hours to obtain the ZIF-67 precursor.

[0027] 100 mg of the ZIF-67 prepared above was dispersed in 30 mL of methanol. 10 mL of a 10 g / L iridium chloride (IrCl3) methanol solution was diluted with methanol to 30 mL, yielding an approximately 3.3 g / L iridium chloride methanol solution. This iridium chloride methanol solution was slowly added dropwise to the ZIF-67 suspension at a rate of 0.3 mL / min using a micro-injection pump. After the addition was complete, the mixture was stirred at 50 °C for 12 hours. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed three times with methanol to obtain the Ir@ZIF-67 composite material.

[0028] The obtained Ir@ZIF-67 was transferred to a corundum crucible, placed in a muffle furnace, and heated to 450°C at a rate of 5°C / min under air atmosphere, and held at this temperature for 2 hours. After cooling to room temperature in the furnace, it was removed to obtain black Ir@Co3O4 electrocatalyst powder.

[0029] Figure 1 The image shows a comparison between the XRD pattern of the Ir@Co3O4 catalyst prepared in Example 2 and the standard PDF card of Co3O4. This illustrates that iridium ions were successfully doped into the Co3O4 lattice without generating new substances. Furthermore, since the amount of iridium doping is very small, it did not cause a shift in the Co3O4 signal peak.

[0030] Figure 2 The image shown is a scanning electron microscope image of Example 2. Under the microscope, the catalyst appears as a plate with a rough surface and protrusions, providing a large number of adsorption sites for oxygen-containing intermediates. Since the noble metal salt exhibits a certain degree of acidity after dissolving in the solvent used for ion exchange, the catalyst structure collapses to some extent compared to the MOF precursor.

[0031] Figure 3 The energy scattering spectrum of Example 2 shows that iridium is uniformly dispersed in Co3O4, proving its successful introduction.

[0032] Figure 4 The graphs are obtained by linear sweep voltammetry for Examples 1, 2, and 3, and RuO2. A comparison is made at a current density of 10 mA / cm². -2 The potential values ​​at the point indicate that, under the same usage, the noble metal-doped transition metal catalyst prepared in this invention outperforms the commercial RuO2 catalyst.

[0033] The above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A noble metal-doped transition metal oxide electrocatalyst, characterized in that, The noble metal atoms in the catalyst are uniformly dispersed in the transition metal oxide lattice, and cobalt-ruthenium synergistic active centers are constructed in the transition metal oxide lattice.

2. The noble metal-doped transition metal oxide electrocatalyst of claim 1, wherein, The catalyst is in the form of a flaky sheet with rough surface and protrusions under a microscope, serving as sites for adsorbing oxygen-containing intermediates.

3. A method for preparing a noble metal-doped transition metal oxide electrocatalyst, characterized by, The method comprises the following steps: Preparation of MOF precursor; Preparation of noble metal doped MOF composite material by ion exchange method; Obtaining noble metal doped transition metal oxide electrocatalyst by controllable annealing treatment of the noble metal doped MOF composite material.

4. The method of claim 3, wherein the noble metal-doped transition metal oxide electrocatalyst is prepared by a method comprising: The preparation of the MOF precursor specifically comprises the following steps: The transition metal salt and the organic ligand are dissolved in solvents respectively, and after complete dissolution, the solution containing the organic ligand is poured into the solution containing the metal salt under stirring, and stirring is continued at room temperature for 12-24 hours; after the reaction is completed, the obtained mixture is centrifuged, the precipitate is collected, and dried at 60-80℃ for 10-12 hours to obtain the MOF precursor.

5. The method for preparing a noble metal-doped transition metal oxide electrocatalyst according to claim 4, characterized in that, The mass ratio of the transition metal salt to the organic ligand is 1:2-1:

12.

6. The method of claim 3, wherein the noble metal-doped transition metal oxide electrocatalyst is prepared by the steps of: The preparation of the noble metal doped MOF composite material comprises the following steps: dispersing the MOF precursor in a solvent, slowly adding a noble metal salt solution, then stirring at 25-50℃ for 10-12 hours, after the reaction is completed, centrifuging and washing with the solvent used in the reaction for at least 3 times to obtain the noble metal doped MOF composite material.

7. The method for preparing a noble metal-doped transition metal oxide electrocatalyst according to claim 6, characterized in that, The mass ratio of the MOF precursor to the noble metal salt is 1:(0.3-1.5).

8. The method for preparing a noble metal-doped transition metal oxide electrocatalyst according to claim 3, characterized in that, The annealing process is as follows: heating to 350-450℃ at a heating rate of 2-5℃ / min in an air atmosphere, and holding for calcination for 2 hours.

9. The method for preparing a noble metal-doped transition metal oxide electrocatalyst according to claim 3, characterized in that, The MOF is ZIF-67, UiO-66 or NiCo-BTC; the transition metal salt cation is cobalt ion, nickel ion or zirconium ion; and the noble metal salt includes but is not limited to iridium chloride, ruthenium chloride, chloroiridic acid.

10. Use of the noble metal-doped transition metal oxide electrocatalyst according to any one of claims 1 to 2, characterized in that The catalyst is used for anodic oxygen evolution reaction.

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