Preparation method and application of oxygen-rich vacancy CoMoO4 micrometer flower ball electrocatalyst

Abstract

The application discloses a preparation method and application of oxygen vacancy-rich CoMoO4 micrometer flower ball electrocatalyst, and belongs to the technical field of electrocatalytic energy materials. The application takes cobalt nitrate hexahydrate and sodium molybdate dihydrate as raw materials, and deionized water-glycol as a mixed solvent, and prepares CoMoO4 micrometer flower ball precursors self-assembled by two-dimensional nanosheets through a simple hydrothermal method, and then, through an inert atmosphere low-temperature annealing process, rich oxygen vacancies are precisely constructed, and finally, the oxygen vacancy-rich CoMoO4 micrometer flower ball electrocatalyst is obtained. The preparation process is simple, mild, green and controllable, and is suitable for large-scale production. The obtained catalyst has a regular hierarchical porous micrometer flower ball structure, rich oxygen vacancy defects, a large specific surface area, a large number of active sites and a fast charge transport rate. The catalyst can be used as a dual-functional electrocatalyst, and is efficiently applied to alkaline system water electrolysis, hydrogen evolution, oxygen evolution and overall water splitting reaction, effectively reduces the water electrolysis reaction overpotential, improves the catalytic efficiency and cycle stability, solves the technical problems of low activity, poor stability and complex preparation process of traditional CoMoO4 catalysts, and has high application value and popularization prospect in the field of green hydrogen energy preparation.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic nanomaterial preparation and energy catalysis technology, specifically relating to a simple hydrothermal preparation method of an oxygen-rich vacancy CoMoO4 micron-sized flower-shaped electrocatalyst, and the application of this catalyst in the fields of hydrogen evolution, oxygen evolution and total water electrolysis. Background Technology

[0002] With the increasing scarcity of fossil fuels and the growing environmental pollution, the development of clean, efficient, and sustainable new energy technologies has become a research hotspot in the global energy sector. Water electrolysis for hydrogen production is one of the most promising green hydrogen production technologies, offering advantages such as pure products, no pollution, and renewable raw materials. The water electrolysis reaction includes the cathode hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Both reactions have high energy barriers and slow kinetic reaction rates, requiring highly efficient electrocatalysts to reduce the reaction overpotential and improve catalytic efficiency.

[0003] Currently, commercially available noble metal catalysts (Pt-based, IrO2-based, RuO2-based) possess excellent electrocatalytic performance, but their scarcity, high cost, and poor stability severely limit their large-scale industrial application. Transition metal oxides, due to their abundant reserves, low cost, and highly tunable electrochemical activity, have become the core research focus for replacing noble metal electrocatalysts. Among them, cobalt-molybdenum bimetallic oxide (CoMoO4) shows promising application prospects in the field of electrocatalysis due to its bimetallic synergistic effect, unique electronic structure, and good electrochemical conductivity.

[0004] In existing technologies, CoMoO4 materials prepared by conventional methods suffer from problems such as fewer defects, insufficient number of active sites, slow charge transport rate, and weak interfacial adsorption capacity, resulting in high electrocatalytic overpotential, low current density, and poor cycling stability. Studies have shown that oxygen vacancies, as typical anionic defects in metal oxides, can effectively regulate the electronic structure of materials, improve surface conductivity, increase electrochemical active sites, and optimize the adsorption-desorption energy barriers of reaction intermediates, significantly improving the kinetic performance of electrocatalytic reactions. However, there is currently a lack of a simple, controllable, and low-cost method to prepare oxygen-vacancy-rich, morphologically regular CoMoO4 micron-sized flower-shaped electrocatalysts. Existing preparation techniques generally suffer from low oxygen vacancy concentration, inhomogeneous morphology, complex preparation processes, high energy consumption, and poor reproducibility, severely restricting the industrial-scale application of CoMoO4-based electrocatalysts.

[0005] To address the shortcomings of existing technologies, this invention proposes a method for preparing oxygen-vacancy-rich CoMoO4 micron-sized flower-shaped electrocatalysts. By employing a simple hydrothermal combined with low-temperature annealing process, the oxygen vacancy concentration and microstructure of the material can be precisely controlled, thus solving the technical problems of poor activity, weak stability, and complex preparation processes of traditional CoMoO4 catalysts. Summary of the Invention

[0006] Purpose of this invention

[0007] This invention aims to overcome the shortcomings of existing CoMoO4 electrocatalysts, such as low oxygen vacancy content, disordered microstructure, poor electrocatalytic activity and stability, and complex preparation process. It provides a simple, mild, controllable, and environmentally friendly method for preparing oxygen-rich CoMoO4 micron-sized flower-shaped electrocatalysts. At the same time, it provides the efficient application of this catalyst in water electrolysis, realizing low-cost and high-performance water electrolysis catalysis.

[0008] Technical solution

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst includes the following steps:

[0011] (1) Preparation of precursor solution: Weigh out cobalt nitrate hexahydrate and sodium molybdate dihydrate according to the molar ratio of cobalt source to molybdenum source of 1:1 to 1.2:1, add them to a mixed solvent of deionized water and ethylene glycol, and stir magnetically at room temperature for 30 to 60 minutes until the solute is completely dissolved to form a uniform and transparent precursor mixed solution; wherein, the volume ratio of deionized water to ethylene glycol is 3:1 to 5:1, and the total metal ion concentration in the precursor mixed solution is 0.05 to 0.15 mol / L.

[0012] (2) Preparation of precursor by hydrothermal reaction: The precursor solution prepared in step (1) is transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed and placed in an oven, and hydrothermally reacted at a constant temperature of 120~160℃ for 6~12h. After the reaction is completed, it is naturally cooled to room temperature to obtain a brown suspension.

[0013] (3) Washing and drying treatment: The suspension obtained in step (2) is centrifuged and washed 3 to 5 times with deionized water and anhydrous ethanol respectively to remove surface impurities and unreacted raw materials. The washed solid product is placed in a vacuum drying oven at 60 to 80°C and dried for 10 to 14 hours to obtain CoMoO4 micron flower ball precursor powder.

[0014] (4) Low-temperature annealing to construct oxygen vacancies: The precursor powder prepared in step (3) is placed in a tube furnace and heated to 300-450°C at a heating rate of 3-5°C / min under an inert nitrogen atmosphere. It is then annealed at a constant temperature for 2-4 hours and naturally cooled to room temperature to finally obtain oxygen-rich CoMoO4 micron flower-shaped electrocatalyst.

[0015] Preferably, in step (1), the optimal molar ratio of cobalt source to molybdenum source is 1.1:1, the volume ratio of deionized water to ethylene glycol is 4:1, and the total metal ion concentration is 0.1 mol / L.

[0016] Preferably, the hydrothermal reaction temperature in step (2) is 140°C and the reaction time is 8 hours.

[0017] Preferably, in step (4), the annealing temperature is 380℃, the annealing time is 3h, and the heating rate is 4℃ / min.

[0018] The application of the oxygen-enriched vacancy CoMoO4 micron-sized flower-shaped electrocatalyst of the present invention is as follows: the catalyst is used for the catalytic reactions of hydrogen evolution, oxygen evolution and total water electrolysis in water electrolysis. The specific application method is as follows: the oxygen-enriched vacancy CoMoO4 micron-sized flower-shaped electrocatalyst is uniformly mixed with a conductive agent and a binder at a mass ratio of 8:1:1, dispersed in an ethanol aqueous solution and ultrasonically dispersed to form a uniform slurry. The slurry is uniformly coated on a carbon cloth substrate and dried at room temperature to obtain a working electrode for the catalytic reaction of water electrolysis under alkaline conditions.

[0019] Beneficial effects

[0020] Compared with the prior art, the present invention has the following significant advantages:

[0021] 1. This invention employs a simple process combining hydrothermal treatment and low-temperature inert annealing to prepare for the first time a CoMoO4 micron-sized flower-shaped structure with regular morphology and uniform dispersion rich in oxygen vacancies. The micron-sized flower-shaped structure is self-assembled from two-dimensional nanosheets. The hierarchical porous structure can greatly increase the specific surface area of ​​the material, expose more electrochemical active sites, and provide sufficient channels for electrolyte penetration, ion transport and gas diffusion, effectively improving the kinetic rate of electrocatalytic reaction.

[0022] 2. This invention precisely constructs abundant oxygen vacancies through an inert atmosphere low-temperature annealing process, eliminating the need for additional reducing agents and etching agents, making it green, environmentally friendly, and low-cost. The introduction of oxygen vacancies can effectively regulate the electronic structure of CoMoO4, improve the surface conductivity of the material, optimize the adsorption and desorption energy barriers of HER and OER reaction intermediates, significantly reduce the overpotential of the water electrolysis reaction, and significantly enhance catalytic activity.

[0023] 3. The preparation process of this invention is mild, highly controllable, and reproducible. The raw materials are conventional chemical raw materials with low cost. No complex and precision equipment is required, making it suitable for large-scale industrial production. The prepared catalyst has both excellent hydrogen evolution and oxygen evolution dual-function catalytic performance and ultra-long cycle stability. It can be directly used in the whole water splitting system and has extremely strong practicality.

[0024] 4. Compared with traditional defect-free CoMoO4 catalysts, the oxygen-rich vacancy CoMoO4 micron-shaped flower-shaped catalyst of this invention exhibits an oxygen evolution overpotential of only 280~310mV and a hydrogen evolution overpotential of only 120~150mV at a current density of 10mA / cm² in alkaline electrolyte. The total water splitting operating voltage is as low as 1.58~1.65V, and it can be stably cycled for more than 50 hours without significant performance degradation. Its catalytic performance far exceeds that of conventional CoMoO4-based catalysts. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] Example 1

[0027] A method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst includes the following steps:

[0028] (1) Preparation of precursor solution: Weigh 0.11 mmol cobalt nitrate hexahydrate and 0.1 mmol sodium molybdate dihydrate at a molar ratio of 1.1:1, add them to a mixed solvent of 40 mL deionized water and 10 mL ethylene glycol, stir magnetically at room temperature for 40 min to obtain a uniform and transparent precursor solution with a total metal ion concentration of 0.1 mol / L.

[0029] (2) Hydrothermal reaction: The precursor solution was transferred to a 100mL polytetrafluoroethylene hydrothermal reactor, sealed, and subjected to a constant temperature hydrothermal reaction at 140℃ for 8 hours, and then naturally cooled to room temperature.

[0030] (3) Washing and drying: The cooled suspension was centrifuged at 8000 r / min for 5 min, and washed with deionized water and anhydrous ethanol alternately 4 times. The solid product was placed in a vacuum drying oven at 70℃ and dried for 12 h to obtain CoMoO4 micron flower ball precursor.

[0031] (4) Oxygen vacancy construction: The precursor powder was placed in a tube furnace and heated to 380°C at 4°C / min under a nitrogen atmosphere. After constant temperature annealing for 3 hours and natural cooling, oxygen-rich CoMoO4 micron flower-shaped electrocatalyst was obtained.

[0032] Catalyst Application: 80 mg of the catalyst prepared in this example, 10 mg of conductive carbon black, and 10 mg of Nafion binder were dispersed in 10 mL of ethanol-water solution and sonicated for 30 min to form a uniform slurry. This slurry was then coated onto carbon cloth to prepare the working electrode. Electrolysis of water was tested in a 1 mol / L KOH alkaline electrolyte. The test results showed that at a current density of 10 mA / cm², the OER overpotential was 295 mV, the HER overpotential was 130 mV, the total water splitting voltage was 1.60 V, and there was no significant performance degradation after 50 hours of continuous cycling.

[0033] Example 2

[0034] A method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst includes the following steps:

[0035] (1) Preparation of precursor solution: Weigh 0.1 mmol cobalt nitrate hexahydrate and 0.1 mmol sodium molybdate dihydrate in a 1:1 molar ratio, add them to a mixed solvent of 30 mL deionized water and 10 mL ethylene glycol, stir magnetically at room temperature for 30 min to obtain the precursor solution, with a total metal ion concentration of 0.05 mol / L.

[0036] (2) Hydrothermal reaction: The hydrothermal reaction was carried out at a constant temperature of 120℃ for 12 hours. The remaining operations were the same as in Example 1.

[0037] (3) The washing, drying and annealing parameters are the same as those in Example 1.

[0038] Electrolysis test results: At a current density of 10mA / cm², the OER overpotential is 310mV, the HER overpotential is 145mV, the total water electrolysis voltage is 1.64V, and the cycle stability is good.

[0039] Example 3

[0040] A method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst includes the following steps:

[0041] (1) Preparation of precursor solution: Weigh 0.12 mmol cobalt nitrate hexahydrate and 0.1 mmol sodium molybdate dihydrate at a molar ratio of 1.2:1, add them to a mixed solvent of 50 mL deionized water and 10 mL ethylene glycol, stir magnetically at room temperature for 60 min to obtain the precursor solution, with a total metal ion concentration of 0.15 mol / L.

[0042] (2) Hydrothermal reaction: The hydrothermal reaction was carried out at a constant temperature of 160℃ for 6 hours. The remaining operations were the same as in Example 1.

[0043] (3) The washing, drying and annealing parameters are the same as those in Example 1.

[0044] Electrolysis test results: At a current density of 10 mA / cm², the OER overpotential is 285 mV, the HER overpotential is 125 mV, and the total water electrolysis voltage is 1.59 V, demonstrating excellent catalytic performance.

[0045] Comparative Example 1 (Ordinary CoMoO4 catalyst without vacancies)

[0046] The inert annealing step in Example 1 was omitted, and the hydrothermally dried precursor was used directly as the catalyst, while the other preparation parameters remained the same. Test results showed that at a current density of 10 mA / cm², the OER overpotential was 380 mV, the HER overpotential was 210 mV, and the total water splitting voltage was 1.78 V. Performance significantly declined after 20 hours of cycling, demonstrating that the introduction of oxygen vacancies can significantly improve catalytic performance and stability.

Claims

1. A method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst, characterized in that, Includes the following steps: (1) Preparation of precursor solution: Cobalt nitrate hexahydrate and sodium molybdate dihydrate are added to a mixed solvent of deionized water and ethylene glycol at a molar ratio of cobalt source to molybdenum source of 1:1 to 1.2:

1. The mixture is stirred at room temperature for 30 to 60 min to obtain a homogeneous precursor mixed solution. The volume ratio of deionized water to ethylene glycol is 3:1 to 5:1, and the total metal ion concentration in the precursor mixed solution is 0.05 to 0.15 mol / L. (2) Hydrothermal reaction: The precursor mixture solution is placed in a hydrothermal reactor and subjected to a constant temperature hydrothermal reaction at 120~160℃ for 6~12h. After natural cooling to room temperature, a suspension is obtained. (3) Washing and drying: The suspension is centrifuged and washed with deionized water and anhydrous ethanol alternately 3 to 5 times, and then vacuum dried at 60 to 80°C for 10 to 14 hours to obtain CoMoO4 micron flower head precursor powder. (4) Construction of oxygen vacancy: The precursor powder was placed in a tube furnace and heated to 300-450°C at a heating rate of 3-5°C / min under a nitrogen inert atmosphere. After constant temperature annealing for 2-4 hours, the oxygen-rich CoMoO4 micron flower-shaped electrocatalyst was obtained after natural cooling.

2. The method for preparing an oxygen-rich vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst according to claim 1, characterized in that, In step (1), the molar ratio of cobalt source to molybdenum source is 1.1:1, the volume ratio of deionized water to ethylene glycol is 4:1, and the total metal ion concentration is 0.1 mol / L.

3. The method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 140℃ and the reaction time is 8h.

4. The method for preparing an oxygen-vacancy-enriched CoMoO4 micron-sized flower-shaped electrocatalyst according to claim 1, characterized in that, In step (4), the annealing temperature is 380℃, the annealing time is 3h, and the heating rate is 4℃ / min.

5. The application of an oxygen-rich vacancy CoMoO4 micron-sized flower-shaped electrocatalyst prepared by the method according to any one of claims 1-4, characterized in that, The electrocatalyst is used for hydrogen evolution, oxygen evolution, and total water electrolysis catalytic reactions in an alkaline electrolyte system.

6. The application according to claim 5, characterized in that, The specific application method is as follows: oxygen-rich vacancy CoMoO4 micron flower-shaped electrocatalyst, conductive agent, and binder are mixed in a mass ratio of 8:1:1, dispersed in an ethanol aqueous solution, and ultrasonically prepared into a uniform slurry. This slurry is then coated onto a carbon cloth substrate and dried to serve as the working electrode for water electrolysis.