Hollow nanoscale transition metal oxide electrocatalyst as well as preparation method and application thereof
By constructing oxygen vacancies on the surface of hollow nanoscale transition metal oxides, the preparation problem of existing catalysts has been solved, achieving efficient and stable OER catalytic performance, suitable for clean energy conversion technologies, and possessing the advantages of low cost and scalable preparation.
Patent Information
- Application Number
- CN202511690063.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-03-06
AI Technical Summary
Existing precious metal and transition metal OER catalysts suffer from problems such as resource scarcity, high cost, poor stability, and uneven particle size distribution, difficulty in morphology control, limited specific surface area, and insufficient exposure of active crystal faces during preparation, which limit their application in clean energy conversion technologies.
Using metal-organic frameworks (MOFs) as self-sacrificing templates, high-concentration oxygen vacancies were constructed on the surface of hollow nanoscale transition metal oxides through low-temperature reduction treatment, optimizing the specific surface area and exposure of active crystal faces of the material. Combined with the morphology inheritance of MOF templates and reduction treatment, a highly efficient hollow nanoscale transition metal oxide electrocatalyst was prepared.
It significantly reduces the overpotential of the oxygen evolution reaction, improves catalytic activity and stability, reduces energy consumption, and has the potential for large-scale preparation. It is suitable for applications such as water electrolysis for hydrogen production, metal-air batteries, and electrochemical synthesis.
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Figure CN121609299A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to a hollow nanoscale transition metal oxide electrocatalyst, its preparation method, and its application. Background Technology
[0002] The oxygen evolution reaction (OER), as the core anode half-reaction in clean energy conversion technologies such as water splitting for hydrogen production, metal-air battery charging, and renewable fuel cells, suffers from slow kinetics and a high reaction energy barrier, which are key bottlenecks restricting overall energy conversion efficiency. In an alkaline environment, the OER involves a complex four-electron transfer process, requiring passage through multiple high-energy intermediate states such as *OH, *O, and *OOH, resulting in a high theoretical minimum overpotential. In metal-air batteries, the high OER overpotential leads to a large charge-discharge voltage difference, shortening cycle life. Therefore, developing efficient, stable, and low-cost OER catalysts is crucial for promoting the commercialization of these technologies.
[0003] Current mainstream OER catalyst systems have significant limitations. Noble metal-based catalysts, such as IrO2 and RuO2, while exhibiting excellent activity, face fundamental problems such as resource scarcity, high cost, poor stability in acidic environments, and susceptibility to deactivation under cyclic conditions, limiting their large-scale application in terms of resource sustainability and cost. Transition metal-based catalysts, as alternatives, also face challenges: layered double hydroxides have poor conductivity and are prone to phase separation; perovskite oxides have high synthesis temperatures, low specific surface areas, and poor stability; and transition metal sulfides / phosphides are easily oxidized and passivated at high potentials. These shortcomings urgently necessitate the search for novel catalyst materials with higher intrinsic activity, better stability, lower cost, and ease of large-scale preparation.
[0004] Transition metal oxides are the most promising alternatives to precious metal catalysts, with their core advantage lying in achieving an excellent balance between performance, cost, and stability. Compared to commercially available IrO2 or RuO2, which boast top-performing but expensive and scarce materials, they are made from inexpensive metals such as iron, cobalt, and nickel, making them extremely low-cost and abundant. Compared to other non-precious metal candidates, transition metal oxides exhibit more reliable activity and stability under alkaline conditions, with a more clearly defined mechanism.
[0005] Currently, the main methods for preparing transition metal oxides include hydrothermal methods, coprecipitation methods, and solid-state methods. However, the materials prepared often suffer from problems such as uneven particle size distribution, difficulty in morphology control, limited specific surface area, insufficient exposure of active crystal faces, and low surface oxygen vacancy concentration, which limit the full realization of their performance.
[0006] The strategy of using metal-organic frameworks (MOFs) as self-sacrificing templates offers a promising approach for preparing high-performance hollow nanoscale transition metal oxides. This method can precisely replicate the precursor morphology of MOFs, and by accurately controlling the pyrolysis atmosphere and temperature, hollow nanomaterials with high specific surface areas and specific geometries can be obtained, optimizing mass transport pathways. However, conventional MOF derivatization techniques still have limitations: the obtained transition metal oxides often lack sufficient intrinsic active sites, restricting further improvements in their catalytic performance.
[0007] In summary, given the urgent need for efficient OER catalysts in the energy transition and the inherent limitations of existing noble metal and transition metal catalyst systems, the preparation of hollow nanoscale transition metal oxides based on the MOF self-sacrificial template method offers a better solution. Through the synergistic effect of intrinsic material activity optimization and nanostructure engineering, this material not only holds the promise of significantly reducing OER overpotential and energy consumption, improving energy efficiency and extending device lifespan in applications such as water electrolysis for hydrogen production, metal-air batteries, and electrochemical synthesis, but also offers a highly promising solution for overcoming key bottlenecks in current clean energy conversion technologies due to its relatively low cost and scalable preparation potential. Summary of the Invention
[0008] This invention provides a hollow nanoscale transition metal oxide electrocatalyst, its preparation method, and its application. By performing a controllable low-temperature reduction post-treatment on MOF-derived oxides, a high concentration of stable oxygen vacancies is successfully constructed on their surface, solving the problems of uneven particle size distribution, difficulty in morphology control, limited specific surface area, insufficient exposure of active crystal faces, and low surface oxygen vacancy concentration in existing transition metal oxide OER electrocatalysts.
[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a hollow nanoscale transition metal oxide electrocatalyst includes the following steps: Step 1: Prepare the solution: Weigh a certain proportion of transition metal salt and organic ligand, dissolve the organic ligand in a solvent, and prepare an organic ligand solution with a molar concentration of 0.01 mol / L to 1 mol / L; dissolve the transition metal salt in a solvent of the same volume as the organic ligand solution and stir until completely dissolved to prepare a transition metal salt solution. Step 2, Mixing reaction: Under stirring conditions, the organic ligand solution obtained in step 1 is poured into the transition metal salt solution, and the reaction is carried out by stirring at room temperature for 12 to 20 hours. Step 3, Separation and washing: Centrifuge the mixture obtained in Step 2, collect the precipitate, and wash the precipitate with solvent at least 3 times to obtain MOF; Step 4, Drying: Place the MOF obtained in step 3 in a vacuum drying oven and dry it at 60°C to 80°C until the residual solvent is completely removed; Step 5, pyrolysis: The dried MOF powder obtained in step 4 is heated to 350°C to 500°C in air at a heating rate of no more than 5°C per minute, and held at that temperature for 1.5 hours to 3 hours to obtain transition metal oxides. Step 6, Reduction treatment: The transition metal oxide obtained in step 5 is heated to 150°C to 250°C at a heating rate of 5°C / min under a mixed atmosphere of hydrogen and nitrogen, and then held at that temperature for 0 to 2 hours. After that, the heating is stopped and the oxide is allowed to cool naturally to room temperature in the furnace to obtain a hollow transition metal oxide with abundant oxygen vacancies on its surface.
[0010] In the steps described above, the cation of the transition metal salt in step 1 can be cobalt ion, nickel ion, zirconium ion, etc.; the anion can be nitrate ion, sulfate ion, chloride ion, etc.; the molar ratio of the transition metal salt to the organic ligand is 1:4-16. The organic ligands are 2-methylimidazolium, terephthalic acid, pyromellitic acid, 2,5-dihydroxyterephthalic acid, etc. The solvent in step 1 can be a common solvent such as deionized water, methanol, or ethanol.
[0011] The hollow nanoscale transition metal oxide electrocatalyst prepared by the above method inherits the morphology of the MOF template and has abundant oxygen vacancies on its surface. The catalyst has a large specific surface area, which is conducive to exposing more active sites. The increase in oxygen vacancies will increase the local electron density on the material surface, and the transition metal ions will perform charge compensation through valence state adjustment, thereby optimizing the adsorption strength of oxygen-containing intermediates during the reaction.
[0012] The aforementioned hollow nanoscale transition metal oxide electrocatalysts can be used for oxygen evolution reactions.
[0013] Beneficial Effects: This invention provides a hollow nanoscale transition metal oxide electrocatalyst, its preparation method, and its applications. Compared with existing technologies, it has the following advantages: By combining the morphological inheritance of the MOF template with the construction of oxygen vacancies generated by subsequent reduction, this invention successfully achieves the synergy of a high specific surface area hollow structure and a highly intrinsically active surface in the same material. The abundant oxygen vacancies on the surface can optimize the electronic configuration of transition metal atoms, acting as highly efficient active centers and significantly reducing the adsorption energy barrier of key oxygen-containing intermediates in the oxygen evolution reaction, thereby greatly improving the intrinsic catalytic activity of the material. This strategy effectively overcomes the technical bottleneck of traditional catalysts, which struggle to balance macroscopic structure and microscopic activity. Furthermore, the preparation process of this invention is simple, the conditions are mild, and the cost is low, demonstrating significant advantages in sustainability and commercial application compared to noble metal catalysts. Attached Figure Description
[0014] Figure 1 The Co3O prepared in the embodiments of the present invention 4-x XRD pattern of the catalyst; Figure 2 The Co3O prepared in the embodiments of the present invention 4-x SEM image of the catalyst; Figure 3 The Co3O prepared in the embodiments of the present invention 4-x XPS comparison of the O1s orbitals of the catalyst and Co3O4; Figure 4 The Co3O prepared in the embodiments of the present invention 4-x XPS comparison of the Co2p orbitals of the catalyst and Co3O4; Figure 5 The Co3O prepared in the embodiments of the present invention 4-x EPR diagram of the catalyst; Figure 6 The Co3O prepared in the embodiments of the present invention 4-x LSV curve of the catalyst. Specific implementation methods
[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0016] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased. Example 1
[0017] A transition metal oxide electrocatalyst with the chemical composition NiCo2O 4-x Its preparation method includes the following steps: Step 1, prepare the solution: Weigh 1.164g nickel nitrate hexahydrate, 2.910g cobalt nitrate hexahydrate and 1.260g trimellitic acid. Dissolve cobalt nitrate hexahydrate and nickel nitrate hexahydrate in a mixed solvent of 60mL N,N-dimethylformamide and 20mL anhydrous ethanol. Dissolve trimellitic acid in another portion of the same mixed solvent and stir until completely dissolved. Step 2, Mixing reaction: Under stirring conditions, the pyromellitic acid solution obtained in Step 1 is poured into a solution of cobalt nitrate hexahydrate and nickel nitrate hexahydrate, and the reaction is continuously stirred at room temperature for 12 hours. Step 3, separation and washing: The reaction mixture obtained in Step 2 is centrifuged at a speed of 9000 rpm for 5 minutes. The precipitate is collected and washed three times alternately with DMF and anhydrous ethanol to obtain a green precipitate, denoted as NiCo-BTC. Step 4, Drying: Place the NiCo-BTC precipitate obtained in Step 3 in a vacuum drying oven and dry it under vacuum at 60°C for 10 hours; Step 5, pyrolysis: The dried NiCo-BTC powder obtained in step 4 is placed in a muffle furnace and heated to 350°C in air at a heating rate of 5°C / min, and held at that temperature for 2 hours to obtain a black powder, denoted as NiCo2O4.
[0018] Step 6, Reduction Treatment: The NiCo2O4 black powder obtained in Step 5 is placed in a tube furnace and heated to 150°C at a heating rate of 5°C / min under a mixed atmosphere of hydrogen and nitrogen (10% hydrogen, 90% nitrogen). After holding at this temperature for 0.5 hours, heating is stopped, and the furnace is allowed to cool naturally to room temperature to obtain a porous cubic electrocatalyst, denoted as NiCo2O4. 4-x . Example 2
[0019] A transition metal oxide electrocatalyst with the chemical composition Co3O 4-x The microstructure is a hollow dodecahedron, and its preparation method includes the following steps: Step 1, prepare the solution: Weigh 1.637g of cobalt nitrate hexahydrate and 3.7g of dimethylimidazole, dissolve cobalt nitrate hexahydrate and dimethylimidazole separately in 80ml of methanol, and stir until completely dissolved; Step 2, Mixing reaction: Under stirring conditions, the dimethylimidazolium methanol solution obtained in Step 1 is poured into the cobalt nitrate methanol hexahydrate solution, and the reaction is continuously stirred at room temperature for 18 hours. Step 3, Separation and Washing: The reaction mixture obtained in Step 2 was centrifuged at 9000 rpm for 5 minutes, and the precipitate was collected. The precipitate was washed three times with methanol to obtain a purple precipitate, denoted as ZIF-67. Step 4, Drying: Place the ZIF-67 purple precipitate obtained in Step 3 in a vacuum drying oven and dry it under vacuum at 80°C for 10 hours; Step 5, pyrolysis: The dried ZIF-67 purple powder obtained in step 4 is placed in a muffle furnace and heated to 400°C in air at a heating rate of 5°C / min, and held at that temperature for 2 hours to obtain a black powder, denoted as Co3O4. Step 6, Reduction Treatment: The black Co3O4 powder obtained in Step 5 is placed in a tube furnace and heated to 200°C at a heating rate of 5°C / min under a mixed atmosphere of hydrogen and nitrogen (10% hydrogen, 90% nitrogen). After holding at this temperature for 1 hour, heating is stopped, and the furnace is allowed to cool naturally to room temperature, yielding a non-noble metal electrocatalyst with a hollow dodecahedral structure, denoted as Co3O4. 4-x . Example 3
[0020] A transition metal oxide electrocatalyst with the chemical composition NiO 1-x The microstructure is a porous rod-like structure, and its preparation method includes the following steps: Step 1, Solution preparation: Weigh 2.908g of nickel nitrate hexahydrate and 2.342g of 2,5-dihydroxyterephthalic acid. Dissolve the nickel nitrate hexahydrate and 2,5-dihydroxyterephthalic acid separately in a mixed solvent of 60 mL of N,N-dimethylformamide and 20 mL of anhydrous ethanol, and stir until completely dissolved. Step 2, Mixing and Reaction: Under stirring conditions, the 2,5-dihydroxyterephthalic acid solution obtained in Step 1 was poured into the nickel nitrate hexahydrate solution, and the reaction was carried out with stirring at room temperature for 20 hours. Step 3, separation and washing: The reaction mixture obtained in Step 2 is centrifuged at 9000 rpm for 5 minutes. The precipitate is collected and washed with DMF and anhydrous ethanol alternately at least 3 times to obtain a yellow precipitate, which is denoted as Ni-MOF-74. Step 4, Drying: Place the yellow Ni-MOF-74 precipitate obtained in Step 3 in a vacuum drying oven and dry it under vacuum at 80°C for 10 hours.
[0021] Step 5, pyrolysis: The dried Ni-MOF-74 yellow powder obtained in step 4 is placed in a muffle furnace and heated to 450°C in air at a heating rate of 5°C / min, and held at that temperature for 2 hours to obtain a black powder, denoted as NiO. Step 6, Reduction Treatment: The NiO black powder obtained in Step 5 is placed in a tube furnace and heated to 250°C at a heating rate of 5°C / min under a mixed atmosphere of hydrogen and nitrogen (10% hydrogen, 90% nitrogen). After holding at this temperature for 1.5 hours, heating is stopped, and the furnace is allowed to cool naturally to room temperature, yielding a non-noble metal electrocatalyst with a porous rod-like structure, denoted as NiO. 1-x .
[0022] Figure 1 It is a catalyst, Co3O 4-x The X-ray diffraction pattern is consistent with the standard PDF card, indicating that the method successfully synthesized spinel Co3O4 without other impurities.
[0023] Figure 2 Co3O catalyst 4-x The microstructure under a scanning electron microscope shows that it perfectly inherits the morphology of the MOF precursor dodecahedron. At the same time, the hollow structure inside can be seen from the broken part. This special microstructure and the rough surface with tiny particles provide more active sites for the catalytic process.
[0024] Figure 3 Co3O4 and catalyst Co3O 4-x The change in the peak at 531.4 eV in the X-ray photoelectron spectrum of the O1s orbital indicates that the oxygen vacancy content increased after the mixed gas reduction treatment.
[0025] Figure 4 Co3O4 and catalyst Co3O 4-x X-ray photoelectron spectroscopy of the Co2p orbital, via Co 2+ With Co 3+ The ratio of peak areas indicates the amount of Co in the catalyst after reduction treatment. 2+ The increase in energy level is beneficial for optimizing the adsorption / desorption energy barrier of the material for oxygen intermediates, thereby enhancing its OER catalytic activity.
[0026] Figure 5 Co3O catalyst 4-x The electron paramagnetic resonance (EPR) spectrum, with a signal at g=2.003, confirms the presence of oxygen vacancies in the catalyst. This change increases the local charge density on the material surface, thereby optimizing the adsorption of oxygen-containing intermediates.
[0027] Figure 6 Co3O catalyst 4-x The linear voltammetry curves were measured in 1M KOH electrolyte. The counter electrode was a platinum sheet, the reference electrode was a mercury oxide reference electrode, and the working electrode was carbon paper loaded with the catalyst. The linear voltammetry curves showed that Co3O... 4-x It exhibits excellent OER activity at 10 mA cm⁻¹ -2 The overpotential at the current density is only 364 mV.
[0028] The above are merely preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that for those skilled in the art, any modifications and improvements made without departing from the concept of the present invention are protected by the present invention.
Claims
1. A method for preparing a hollow nanoscale transition metal oxide electrocatalyst, characterized in that, The method comprises the following steps: preparing a transition metal salt solution and an organic ligand solution respectively; pouring the organic ligand solution into the transition metal salt solution for reaction; centrifuging the reaction product of the organic ligand solution and the transition metal salt solution to collect the precipitate, and obtaining MOF after treatment; annealing the MOF in air to obtain a transition metal oxide; reducing the transition metal oxide in a mixed atmosphere of hydrogen and nitrogen to obtain a hollow nanoscale transition metal oxide.
2. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1, characterized in that, The molar concentration of the organic ligand solution is 0.01-1 mol / L.
3. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1 or 2, characterized in that, The molar ratio of the transition metal salt to the organic ligand is 1:4-16.
4. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1 or 2, characterized in that, The cation of the transition metal salt is cobalt ion, nickel ion or zirconium ion, and the anion is nitrate, sulfate or chloride.
5. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1 or 2, characterized in that, The organic ligand is 2-methylimidazole, terephthalic acid, trimesic acid or 2,5-dihydroxyterephthalic acid.
6. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1, characterized in that, The organic ligand solution is poured into the transition metal salt solution and stirred at room temperature for 12-20 hours.
7. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1, characterized in that, The annealing process of the MOF in air is as follows: heating to 350-500℃ at a heating rate of not higher than 5℃ / min in air, and keeping the temperature for 1.5-3 hours to obtain the transition metal oxide.
8. The method for preparing hollow nanoscale transition metal oxide electrocatalysts according to claim 1, characterized in that, The specific process of reducing the transition metal oxide in a mixed atmosphere of hydrogen and nitrogen is as follows: heating the transition metal oxide to 150-250℃ at a heating rate of 5℃ / min in a mixed atmosphere of hydrogen and nitrogen, keeping the temperature for 0-2 hours, stopping heating, and naturally cooling to room temperature to obtain the hollow transition metal oxide with rich oxygen vacancies on the surface.
9. The hollow nanosized transition metal oxide electrocatalyst produced by the method of any one of claims 1 to 8, characterized in that, The electrocatalyst inherits the morphology of the MOF template and has rich oxygen vacancies on the surface; wherein the transition metal ions are charge-compensated by valence adjustment.
10. Use of the hollow nanosized transition metal oxide electrocatalyst according to claim 9, characterized in that The electrocatalyst is used for oxygen evolution reaction.