A vacancy-defective Co3O4, its preparation method and application
By rapidly cooling after high-temperature calcination, Co3O4 materials with vacancy defects were prepared, which solved the problems of insufficient performance and preparation complexity of Co3O4 materials in water electrolysis reaction, and realized efficient and low-cost large-scale production and application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN AUTOMOTIVE RES INST BEIJING INST OF TECH (SHENZHEN RES INST OF NAT ENG LAB FOR ELECTRIC VEHICLES)
- Filing Date
- 2023-11-08
- Publication Date
- 2026-05-12
AI Technical Summary
Existing Co3O4 materials suffer from poor conductivity and insufficient activity in water electrolysis, making it difficult to meet practical needs. Furthermore, traditional preparation methods are costly and require complex equipment, making them unsuitable for large-scale production of Co3O4 materials with vacancy defects.
Co3O4 with vacancy defects was prepared by calcining cobalt oxalate at 400–1000℃ for 0.5–4 hours and then rapidly cooling it in a cooling environment. The vacancy defects of the Co3O4 material generated by the decomposition of oxalic acid at high temperature were retained by cooling with room temperature air, water or liquid nitrogen.
制备的空位缺陷Co3O4材料作为析氧电催化剂，提高了电解水效率，降低了成本，简化了制备过程，便于大规模生产和应用。
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Figure CN117623402B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of cobalt tetroxide preparation technology, and in particular to a vacancy-defect Co3O4, its preparation method and application. Background Technology
[0002] In recent years, with the development of the global low-carbon economy, the development and use of renewable energy to replace traditional fossil fuels has significant strategic importance for the sustainable development of human society. Among these methods, the electrolysis of water to produce "green hydrogen" is the most promising approach for developing renewable and clean hydrogen energy.
[0003] However, a significant factor limiting the industrialization of water electrolysis technology is the high energy consumption required to drive the oxygen evolution reaction (OER) at the anode. Developing efficient and inexpensive OER catalysts to replace commercial precious metal catalysts and lowering the OER reaction energy barrier to improve water electrolysis efficiency is crucial for the industrialization of water electrolysis technology.
[0004] Due to the stringent requirements of industrial production regarding the activity, stability, and cost of electrocatalysts, transition metal oxide Co3O4 materials have attracted widespread attention from researchers. However, pure Co3O4 materials suffer from poor conductivity and insufficient activity, making direct application in water electrolysis reactions difficult to meet practical requirements. Defect engineering, often used as an effective modification method, can effectively adjust the surface composition, electronic structure, charge distribution, and local environment around active sites of electrocatalysts, and is widely applied to improve the electrocatalytic oxygen evolution performance of non-noble metal catalysts.
[0005] The introduction of oxygen and metal vacancies has been proven to optimize the adsorption behavior of intermediates, accelerate surface charge transfer, and promote the construction of surface active phases, thereby improving the OER performance of electrocatalysts. Currently, researchers can achieve the formation of oxygen vacancies in Co3O4 materials through methods such as ion implantation, laser or plasma etching, chemical etching, and gas reduction. However, these methods often have drawbacks such as high requirements for equipment, complex subsequent processing, and high costs, which are not conducive to the large-scale preparation of defective Co3O4 materials in practical applications.
[0006] Therefore, how to easily and conveniently produce vacancy-defect Co3O4 materials on a large scale remains a key research focus and challenge in this field. Summary of the Invention
[0007] The purpose of this application is to provide an improved method for preparing vacancy-defect Co3O4, and the vacancy-defect Co3O4 prepared therefrom and its applications.
[0008] The following technical solution is adopted in this application:
[0009] The first aspect of this application discloses a method for preparing vacancy-defect Co3O4, which includes calcining cobalt oxalate at a high temperature of 400-1000°C for 0.5-4 hours, and immediately placing it in a cooling environment for rapid cooling after the high-temperature calcination is completed to obtain Co3O4 with vacancy defects.
[0010] It should be noted that the key point of this application is that the research found that oxalic acid decomposes to produce Co3O4 under high-temperature calcination. Rapidly cooling the Co3O4 material at high temperature preserves defects in its crystal lattice structure, thus producing Co3O4 with vacancy defects. When this vacancy-defect Co3O4 is used as an oxygen evolution catalyst, it can improve water electrolysis efficiency and enhance the OER performance of the electrocatalyst.
[0011] In one implementation of this application, the cooling environment is room temperature air, water, or liquid nitrogen.
[0012] Understandably, the key to this application lies in the discovery that rapid cooling of high-temperature Co3O4 produces Co3O4 with vacancy defects. The specific cooling environment can be room temperature air, room temperature water, or liquid nitrogen; it can also be other organic liquids with cooling properties. Of course, to achieve even faster cooling, cooling air or cooling water at 4–20°C can also be used. However, in one implementation of this application, the vacancy-defect Co3O4 obtained by cooling with room temperature water already meets the requirements.
[0013] In one implementation of this application, room temperature water is preferably used as the cooling environment.
[0014] In one implementation of this application, when using water for rapid cooling, at least 100 mL of water is used for cooling for every 0.1 g of Co3O4, or flowing water is used for rapid cooling.
[0015] It should be noted that the requirement of at least 100 mL of water for every 0.1 g of Co3O4 is mainly to ensure that it can be rapidly cooled in water. Understandably, too little water may affect the rapid cooling effect. Of course, to ensure rapid cooling, running water can also be used for cooling.
[0016] It should also be noted that water is preferred for cooling in this application because water molecules react with the sample surface during rapid cooling, causing some Co to dissolve into the water, which will increase the defect concentration in the Co3O4 material.
[0017] In one implementation of this application, cobalt oxalate is cobalt oxalate powder obtained by recycling waste lithium cobalt oxide cathode powder through oxalic acid treatment.
[0018] It should be noted that this application can directly use cobalt oxalate powder obtained from the recycling of waste lithium cobalt oxide cathode powder to prepare vacancy defect Co3O4, which greatly improves the recycling efficiency of cobalt oxalate powder obtained from the recycling of waste lithium cobalt oxide cathode powder and has important value for the recycling of waste lithium cobalt oxide cathode powder.
[0019] It should also be noted that the waste lithium cobalt oxide cathode powder of this application is recycled into cobalt oxalate powder through oxalic acid treatment. This can be referred to in patent application CN114702084A. The organic acid treatment step in this patent application involves mixing lithium cobalt oxide powder with organic acid. After the reaction is completed, solid and liquid are separated to obtain cobalt-containing solid powder. When oxalic acid is used as the organic acid, the cobalt-containing solid powder obtained is cobalt oxalate powder.
[0020] In one implementation of this application, waste lithium cobalt oxide cathode powder is recycled by oxalic acid treatment to obtain cobalt oxalate powder. Specifically, the oxalic acid treatment includes mixing waste lithium cobalt oxide cathode powder with oxalic acid, and after the reaction is completed, separating the solid and liquid to obtain cobalt oxalate powder.
[0021] In one implementation of this application, the reaction conditions between waste lithium cobalt oxide cathode powder and oxalic acid are 60-80°C and 2-4 hours.
[0022] In one implementation of this application, the concentration of oxalic acid is 1 mol / L.
[0023] In one implementation of this application, the solid-liquid ratio of waste lithium cobalt oxide cathode powder to oxalic acid is 1 g / L to 4 g / L.
[0024] The second aspect of this application discloses Co3O4 with vacancy defects prepared by the preparation method of this application.
[0025] It should be noted that the vacancy-defect Co3O4 prepared by the method of this application has the advantages of low cost, simple and convenient preparation method, and large-scale production. On the other hand, the rapid cooling of this application can produce Co3O4 with a large number of vacancy defects. In particular, when water cooling is performed, the reaction of water molecules on the sample surface causes some Co to dissolve into the water, thereby increasing the defect concentration in the Co3O4 material. This gives it a greater advantage when used as an oxygen evolution electrocatalyst.
[0026] The third aspect of this application discloses the application of Co3O4 with vacancy defects in the preparation of oxygen evolution electrocatalysts.
[0027] It should be noted that the Co3O4 with vacancy defects in this application was specifically developed for the oxygen evolution reaction (OER), and therefore can certainly be used as an OER electrocatalyst, or in combination with other OER electrocatalysts with similar functions. It is understood that the Co3O4 with vacancy defects in this application is not limited to use as an OER electrocatalyst; other applications requiring materials with vacancy defects can also utilize the Co3O4 with vacancy defects in this application.
[0028] The fourth aspect of this application discloses an oxygen evolution electrocatalyst containing Co3O4 with vacancy defects as described in this application.
[0029] It should be noted that the oxygen evolution electrocatalyst of this application, due to the use of Co3O4 with vacancy defects, has the advantages of low cost, simple and convenient preparation method, and large-scale production, which facilitates the production and application of the oxygen evolution electrocatalyst of this application. On the other hand, the Co3O4 of this application has a large number of vacancy defects, which can better meet the application requirements of oxygen evolution electrocatalysis.
[0030] The beneficial effects of this application are as follows:
[0031] The method for preparing vacancy-defect Co3O4 disclosed in this application is simple and convenient, enabling large-scale production of vacancy-defect Co3O4 and meeting the requirements for use in water electrolysis reactions. It solves the problems of high requirements for instruments and equipment, complex subsequent processing, and high cost in existing methods for preparing defective Co3O4. Attached Figure Description
[0032] Figure 1 These are the Raman curves of vacancy defects Co3O4 obtained by three cooling methods in the embodiments of this application;
[0033] Figure 2 These are the EPR spectra of vacancy defect Co3O4 obtained by three cooling methods in the embodiments of this application;
[0034] Figure 3 This is a linear sweep voltammetric curve of vacancy defect Co3O4 obtained by three cooling methods in the embodiments of this application;
[0035] Figure 4 The vacancy defects Co3O4 obtained by the three cooling methods in the embodiments of this application are at current densities of 10, 20, and 50 mA / cm². -2 The corresponding overpotential result diagram;
[0036] Figure 5 It is the Tafel slope of the vacancy defect Co3O4 obtained by the three cooling methods in the embodiments of this application. Detailed Implementation
[0037] Existing methods for preparing defective Co3O4 require specialized instruments and equipment, or involve complex and costly subsequent processing, which hinders the large-scale production and use of defective Co3O4 materials.
[0038] This study found that when preparing Co3O4 material by calcining cobalt oxalate powder obtained from the oxalic acid treatment of waste lithium cobalt oxide cathode powder, directly placing the high-temperature Co3O4 material in a cooling environment for cooling can preserve the defects in the Co3O4 crystal lattice structure, thus obtaining Co3O4 with vacancy defects. This precisely meets the requirement of using defective Co3O4 in oxygen evolution electrocatalysis.
[0039] Based on the above research and findings, this application creatively provides a method for preparing Co3O4 with vacancy defects, which includes calcining cobalt oxalate at a high temperature of 400-1000℃ for 0.5-4h, and immediately placing it in a cooling environment for rapid cooling after the high temperature calcination is completed to obtain Co3O4 with vacancy defects.
[0040] When the vacancy-defective Co3O4 prepared by the method of this application is used as an oxygen evolution electrocatalyst, it can improve the water electrolysis efficiency and enhance the OER performance of the electrocatalyst.
[0041] The present application will be further described in detail below with reference to specific embodiments and accompanying drawings. The following embodiments are only for further illustration of the present application and should not be construed as limiting the present application.
[0042] Example
[0043] The preparation method of the vacancy-defect Co3O4 material in this example specifically includes the following steps:
[0044] (1) After treating the waste lithium cobalt oxide cathode powder with oxalic acid, cobalt oxalate powder is obtained. This step is referred to patent application CN114702084A. Specifically, lithium cobalt oxide powder is mixed with oxalic acid with a concentration of 1M. The mixed solution is heated to 80°C and reacted for 2 hours. The solid-liquid ratio of lithium cobalt oxide powder to oxalic acid is 4g / L. After the reaction is completed, the solid and liquid are separated to obtain cobalt oxalate powder.
[0045] (2) Calcine cobalt oxalate powder in air for 2 hours at a temperature of 400°C.
[0046] (3) After calcination, immediately remove the product from the annealing furnace and perform rapid cooling as follows:
[0047] Room temperature air cooling, that is, placing the product of step (2) in room temperature air to cool it rapidly, to obtain Co3O4 with vacancy defects, labeled as air-cooled-Co3O4;
[0048] The product from step (2) was placed in room temperature water and cooled rapidly. Each 0.1 g of Co3O4 corresponds to 100 mL of water. Co3O4 with vacancy defects was obtained and labeled as water-cooled Co3O4.
[0049] Liquid nitrogen cooling: The product of step (2) is placed in liquid nitrogen, which submerges Co3O4 and rapidly cools it to obtain Co3O4 with vacancy defects, which is labeled as liquid nitrogen-cooled Co3O4.
[0050] Raman and EPR tests were performed on Co3O4 with vacancy defects obtained by the three cooling methods mentioned above: air-cooled Co3O4, water-cooled Co3O4, and liquid nitrogen-cooled Co3O4. The Raman test was performed on a Renishaw 2000 Raman instrument using a 785nm wavelength laser. The test results are as follows: Figure 1 As shown. The EPR test was performed using a Bruker-EMXPlus-10, with the powder tested at room temperature and pressure. The test results are as follows. Figure 2 As shown.
[0051] Figure 1 The results show that the main locations of Raman Peak are at 194.1, 483.7, 525.5, and 689.4 cm. -1 F corresponding to Co3O4 material 2g E g F 2g and A 1g Vibration modes, in addition, different cooled samples at A 1g The position shift indirectly confirms the presence of oxygen vacancies. Furthermore, Figure 2 The EPR spectra show that the g-factor value (g = 2.004) directly confirms the presence of oxygen vacancies in the air-cooled, water-cooled, and liquid nitrogen-cooled samples. Furthermore, the peak intensities of the EPR curves indicate the following order of oxygen vacancy concentrations: water-cooled - Co3O4 > liquid nitrogen-cooled - Co3O4 > air-cooled - Co3O4. The reason for this is believed to be that during rapid cooling with water, water molecules react with the sample surface, causing some Co to dissolve into the water, thus increasing the defect concentration in the Co3O4 material.
[0052] Three different Co3O4 materials were prepared into electrocatalytic electrodes, and their electrocatalytic OER performance was characterized on the Metrohm Autolab electrochemical workstation. Specifically, 5 mg of the catalyst material to be tested was mixed with 1 ml of isopropanol / water (volume ratio 4:1), 100 μL of 5 wt% Nafion solution was added, and the mixture was ultrasonically dispersed to form a slurry. This slurry was then drop-coated onto the surface of carbon paper and dried for later use. OER performance was mainly measured by LSV. A three-electrode testing system was used, with Ag / AgCl as the reference electrode, a graphite rod as the counter electrode, and the material as the working electrode. The electrolyte was 1.0 M KOH. Linear voltammetry was performed with a voltage range of 0–0.8 V (vs. Ag / AgCl) and a scan rate of 5 mV / s. -1 The test results are as follows: Figures 3 to 5 As shown. Among them, Figure 3 These are linear sweep voltammetry (LSV) plots of three Co3O4 materials. Figure 4 Three Co3O4 materials were tested at current densities of 10, 20, and 50 mA cm⁻¹. -2 The corresponding overpotential result diagram; Figure 5 These are the Tafel slopes of the three Co3O4 materials.
[0053] Figures 3 to 5 The results showed that the water-cooled Co3O4 electrocatalyst exhibited the lowest overpotential (η). 10 =306mV) and Tafel slope (55.3mV dec) -1 It has the best electrochemical OER performance.
[0054] Based on the above experiments, this example further investigated the high-temperature calcination temperature of cobalt oxalate. Specifically, calcination temperatures of 350℃, 500℃, 600℃, 700℃, 800℃, 900℃, and 1000℃ were tested, followed by water cooling after 2 hours of calcination. The results showed that the Co3O4 material obtained at 350℃ had fewer vacancy defects and poorer electrochemical OER performance; the other calcination temperatures all yielded Co3O4 materials with vacancy defects and better electrochemical OER performance. As for the high-temperature calcination temperature, calcination for 0.5–4 hours generally yielded the desired Co3O4 material with vacancy defects.
[0055] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. Those skilled in the art to which this application pertains can make several simple deductions or substitutions without departing from the concept of this application.
Claims
1. A method for preparing vacancy-defect Co3O4, characterized in that: This includes calcining cobalt oxalate at 400~1000℃ for 0.5~4h, and immediately placing it in a cooling environment for rapid cooling after the high-temperature calcination to obtain Co3O4 with vacancy defects; The cooling environment is room temperature water; Cooling can be performed using at least 100 mL of water for every 0.1 g of Co3O4, or by using flowing water for rapid cooling.
2. The preparation method according to claim 1, characterized in that: The cobalt oxalate is cobalt oxalate powder obtained by recycling waste lithium cobalt oxide cathode powder through oxalic acid treatment.
3. The preparation method according to claim 2, characterized in that: The waste lithium cobalt oxide cathode powder is recycled by oxalic acid treatment to obtain cobalt oxalate powder. The specific oxalic acid treatment includes mixing the waste lithium cobalt oxide cathode powder with oxalic acid, and after the reaction is completed, separating the solid and liquid to obtain cobalt oxalate powder.
4. The preparation method according to claim 3, characterized in that: The specific conditions for the reaction are 60~80℃ and 2~4h.
5. The preparation method according to claim 3, characterized in that: The concentration of oxalic acid is 1 mol / L.
6. The preparation method according to claim 5, characterized in that: The solid-liquid ratio of the waste lithium cobalt oxide cathode powder to oxalic acid is 1 g / L to 4 g / L.
7. Co3O4 with vacancy defects prepared by the preparation method according to any one of claims 1-6.
8. The application of the Co3O4 with vacancy defects as described in claim 7 in the preparation of oxygen evolution electrocatalysts.
9. An oxygen evolution electrocatalyst comprising Co3O4 with vacancy defects as described in claim 7.