Preparation method and application of nano-nickel embedded cobalt tetroxide nanosheet electrode material
By constructing nano-nickel embedded cobalt tetroxide nanosheet electrode material on the surface of graphite felt, the problem of poor conductivity of traditional transition metal catalysts was solved, efficient persulfate activation and organic pollutant degradation were achieved, and energy consumption was reduced.
Patent Information
- Application Number
- CN202310451467.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-25
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-04-25
AI Technical Summary
In the existing technology, the persulfate activation technology of traditional transition metal catalysts has poor conductivity and low current efficiency, and the material is easily lost and difficult to recycle and regenerate, resulting in high energy consumption of advanced oxidation technology and difficulty in efficiently treating difficult-to-degrade organic pollutants.
Nano-nickel is embedded in cobalt tetroxide nanosheet electrode material. By growing metal nickel nanoparticles (C@Ni) encapsulated by a carbon layer on the surface of graphite felt and combining them with cobalt tetroxide nanosheets, a core-shell structure is constructed to improve the conductivity and specific surface area, thereby achieving efficient activation of persulfate.
The utilization rate of persulfate and the pollutant degradation efficiency are significantly improved, the power consumption is reduced, and the efficient degradation of organic pollutants in a wide pH range is achieved.
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Figure CN116637621B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of electrochemical water treatment, and in particular relates to a preparation method and application of a nano-nickel embedded cobalt tetroxide nanosheet electrode material. Background Art
[0002] In recent years, with the rapid development of industry, water bodies have been increasingly polluted by refractory organic matter. These pollutants are generally difficult to biodegrade and typically require advanced oxidation technologies to improve their biodegradability. Due to the strong oxidizing power of sulfate radicals (E = 2.5–3.1 V), persulfate-based advanced oxidation technologies have attracted widespread attention. However, while these technologies continue to improve their treatment capacity, they are also increasingly moving towards lower chemical and energy consumption. In traditional persulfate activation technologies based on transition metal catalysts, the rate-limiting step in sulfate radical generation is the metal redox pair cycle, particularly the reduction of high-valent metals to low-valent metals. This process often consumes more persulfate than the radical generation process. Furthermore, the efficiency of the reduction process is largely dependent on the stoichiometric ratio of catalyst to persulfate. Both insufficient and excessive persulfate addition are detrimental to efficient radical generation. Furthermore, nanomaterial-based persulfate activation technologies face challenges in practical applications, including material loss, difficulty in recycling, and secondary pollution.
[0003] By immobilizing a transition metal catalyst on the cathode surface, the transition metal-activated persulfate technology is combined with electrocatalysis. Persulfate is not only activated by transition metal sites but can also be directly reduced to sulfate radicals via a single-electron reduction reaction at the cathode. Furthermore, the cathode can directly participate in the reduction of high-valent transition metals, significantly reducing persulfate consumption. However, the bulk conductivity of transition metal compounds is generally poor. Even when supported on a highly conductive carbon matrix, the number of metal sites available for efficient cathodic reduction is limited. Consequently, current electrocatalytic persulfate technology often requires high current densities to drive efficient radical generation, limiting the energy efficiency of the actual treatment process. Chinese invention patent application number CN112794413 discloses a bimetallic-modified graphite felt as a cathode material for electrocatalytic PDS. CuFe2O4, CuO, and elemental Cu nanoparticles on the graphite felt serve as the primary active sites. However, the active sites are unevenly distributed, and the material requires a current density of 50 mA to achieve efficient degradation of diuron in water. Therefore, developing an electro-activated persulfate cathode material with a simple preparation method, high conductivity and high specific surface area through reasonable catalyst structure design is of great significance for realizing the engineering application of this technology.
[0004] Cobalt trioxide is a widely studied semiconductor material with a wide range of sources, rich means of controlling its morphology and structure, and high catalytic activity towards persulfate. However, when used as a cathode material for the electrocatalysis of persulfate, it still faces the problems of poor conductivity and low current efficiency. Nanocarbon layers coated with metal elements (C@M) with a core-shell structure have received widespread attention in recent years. By utilizing the electron penetration effect of the inner metal of C@M, the electronic structure at the interface between the carbon layer of C@M and the material to be modified can be precisely controlled, achieving conductivity, reactivity and morphology of the modified material that is different from its bulk phase. In summary, the use of electron-rich C@M nanoparticles to modify cobalt trioxide nanosheets through appropriate methods can improve the conductivity and current efficiency of cobalt trioxide in the electrocatalysis of persulfate, which has strong feasibility and practical application value. Summary of the Invention
[0005] To solve the above problems, the present invention discloses a preparation method and application of a nano-nickel embedded cobalt tetroxide nanosheet electrode material. Graphite felt is treated using a simple ethanol flame method to grow dense metal nickel nanoparticles (C@Ni) with a carbon layer encapsulation structure on its surface. Subsequently, a complex of Co and melamine is used as a precursor for the cobalt tetroxide nanosheets to construct C@Ni-modified cobalt tetroxide nanosheets on the surface of the graphite felt. This can improve the utilization rate of persulfate and electrical energy in the electrocatalytic persulfate technology, thereby achieving efficient degradation of pollutants in water.
[0006] To achieve the above object, the technical solution of the present invention is as follows:
[0007] A method for preparing a nano-nickel embedded cobalt tetroxide nanosheet electrode material, comprising the following steps:
[0008] (1) Flame treatment of graphite felt: The graphite felt is placed above an ethanol flame to obtain a graphite felt with metal nano-nickel particles encapsulated by an in-situ carbon layer grown on the surface;
[0009] (2) Precursor loading: Melamine and CoCl2 are added to ethanol, heated and ultrasonically mixed to obtain a cobalt tetroxide precursor suspension, and the suspension is dropped onto the surface of the graphite felt after the flame treatment in step (1), and quickly placed in an oven for drying. The above steps are repeated several times until the surface of the graphite felt is densely covered with the precursor;
[0010] (3) Preparation of nano-nickel embedded cobalt oxide nanosheet electrode material: The graphite felt loaded with the precursor obtained in step (2) is placed in a tube furnace for calcination, cooled, washed and dried, and cobalt oxide nanosheets (Co@FCF) modified with C@Ni nanoparticles are loaded on the surface of the graphite felt.
[0011] As an improvement of the present invention, the flame-treated graphite felt preparation step in step (1) is as follows:
[0012] S1. Wash and dry a graphite felt with a diameter of 5-50 mm and a thickness of 0.5-6 mm in acetone. Immerse it in a 0.05-0.5 M NiCl₂ ethanol solution for 1-10 min, then quickly remove it and dry it in an oven again.
[0013] S2. The NiCl2-loaded graphite felt dried in S1 was placed 5–20 mm above the wick of an ethanol lamp and heat-treated for 2–10 min. Both sides of the graphite felt were subjected to the above-mentioned treatment and then washed in 0.01 M HCl solution to obtain C@Ni-loaded graphite felt (FCF).
[0014] As an improvement of the present invention, in step (2), the mass ratio of CoCl2 to melamine is 1-20 wt%, the concentration of the cobalt trioxide precursor suspension is 0.05-0.5 g / mL, and the final loading amount of the precursor on the graphite felt is 0.1-10 wt%.
[0015] As an improvement of the present invention, in step (2), the ultrasonic time is 10-120 min and the heating temperature is 10-40°C.
[0016] As an improvement of the present invention, in step (3), the calcination temperature is 350-650°C, the heating rate during calcination is 2-10°C / min, the calcination time is 0.5-2 h, and the calcination atmosphere is an air flow with a flow rate of 50-500 mL / min.
[0017] The present invention also provides an application of nano-nickel embedded in cobalt tetroxide nano-sheet electrode material in removing organic pollutants in wastewater.
[0018] As an improvement of the present invention, the nano-nickel embedded in cobalt tetroxide nanosheet electrode material is used as a cathode material for electro-activating persulfate, and is used to remove organic pollutants in wastewater with a pH of 2-11.
[0019] As an improvement of the present invention, when the Co@FCF prepared by the method of the present invention is used as a cathode material for electroactivated persulfate to remove sulfamethoxazole in water, carbon cloth is used as a counter electrode and degradation is carried out in a constant voltage mode of -0.2 V vs SCE, with an applicable pH range of 2-9.
[0020] The beneficial effects of the present invention are:
[0021] Compared with traditional transition metal materials used as cathode materials for electrocatalytic persulfate, the present invention uses carbon-layer-encapsulated nano-nickel particles to modify cobalt oxide nanosheets. Through the shuttling effect of electrons in the metallic nickel, the conductive properties of the bulk cobalt oxide nanosheets are greatly improved, and the electron exchange rate during the electroactivation of persulfate by cobalt oxide is accelerated. This can improve the effective utilization of persulfate and reduce the energy consumption of pollutant degradation. Its specific advantages are as follows:
[0022] 1. The present invention uses cobalt tetroxide nanosheets as the main active site for activating persulfate. Cobalt tetroxide nanosheets are uniformly grown on the carbon fiber surface of the graphite felt. Cobalt tetroxide nanosheets have strong adsorption capacity for persulfate and high intrinsic catalytic activity, which can ensure the stable generation of sulfate radicals.
[0023] 2. The present invention further uses carbon-encapsulated nano-nickel particles (C@Ni) to modify the cobalt oxide nanosheets, which can significantly reduce the charge transfer resistance of the cobalt oxide, increase the specific surface area of the composite material, and enhance the mass transfer effect between pollutants and persulfate at the electrode interface;
[0024] 3. After cobalt tetroxide provides electrons to persulfate to generate sulfate radicals, the C@Ni uniformly embedded in the cobalt tetroxide nanosheets can act as an electron shuttle, continuously replenishing electrons from the external circuit to the cobalt tetroxide, maintaining the efficient circulation of metal redox pairs on its surface, thereby improving the utilization rate of persulfate;
[0025] 4. The present invention maintains the aforementioned cyclic reaction at relatively low voltages, avoiding side reactions at high electrode potentials and significantly improving the current efficiency during electroactivation of persulfate. The reaction conditions are mild, the preparation process is simple, and the resulting composite electrode exhibits high catalytic activity at pH values between 3 and 11, effectively degrading organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 This is the microscopic morphology of the graphite felt surface after flame treatment in Example 1 of the present invention.
[0027] Figure 2 This is the microscopic morphology of the graphite felt after direct in-situ growth of cobalt tetroxide on the surface of Example 2 of the present invention.
[0028] Figure 3 The microscopic morphology of the nano-nickel embedded in the cobalt oxide nanosheet of the present invention.
[0029] Figure 4 This is a diagram showing the effect of electro-activated PMS degrading sulfamethoxazole in Example 4-7 of the present invention. DETAILED DESCRIPTION
[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.
[0031] Example 1: Graphite Felt Supported C@Ni (FCF)
[0032] A graphite felt with a diameter of 30 mm and a thickness of 2 mm was washed and dried with acetone, immersed in a 0.1 M NiCl2 ethanol solution for 5 min, quickly taken out, and placed in an oven to dry again.
[0033] The graphite felt loaded with NiCl2 was placed 10 mm above the wick of an ethanol lamp and heat treated for 5 min. After the above operation was performed on both sides of the graphite felt, it was washed in 0.01 M HCl solution to obtain a graphite felt loaded with C@Ni (FCF). Its micromorphology is shown in Figure 2. Figure 1 shown.
[0034] Example 2: Graphite Felt Supported Cobalt Tetroxide Nanosheets (Co / CF)
[0035] CoCl2 and melamine were added to ethanol at a mass ratio of 10 wt% to prepare a precursor solution with a concentration of 0.2 g / mL. The precursor suspension was obtained by ultrasonication at 30 °C for 60 min. The suspension was evenly drop-coated on the surface of graphite felt and quickly dried in an oven at 60 °C. The above operation was repeated until the precursor loading reached 5 wt%.
[0036] The graphite felt loaded with the precursor was calcined in a tube furnace at 450°C for 1 h under air conditions with a heating rate of 5°C / min. After cooling, it was washed with 0.01 M dilute hydrochloric acid and then with an alcohol solution. Finally, it was dried in vacuum to obtain a graphite felt (Co / CF) with cobalt oxide nanosheets grown on it. Its micromorphology is shown in the figure. Figure 2 shown.
[0037] Example 3: Graphite Felt Surface Loading of C@Ni Modified Cobalt Tetroxide Nanosheets (Co@FCF)
[0038] A graphite felt with a diameter of 30 mm and a thickness of 2 mm was washed and dried with acetone, then immersed in a 0.1 M NiCl2 ethanol solution for 5 minutes, quickly removed, and dried in an oven again. The NiCl2-loaded graphite felt was then heat-treated for 5 minutes at a height of 10 mm above the wick of an ethanol lamp. Both sides of the graphite felt were subjected to the above treatment and then washed in a 0.01 M HCl solution to obtain a C@Ni-loaded graphite felt (FCF).
[0039] CoCl2 and melamine were added to ethanol at a mass ratio of 10 wt% to prepare a precursor solution with a concentration of 0.2 g / mL. The precursor suspension was obtained by ultrasonication at 30 °C for 60 min. The suspension was evenly drop-coated on the surface of FCF and then quickly dried in an oven at 60 °C. The above operation was repeated until the precursor loading reached 5 wt%.
[0040] The precursor-loaded FCF was calcined in a tube furnace at 450°C for 1 h in air at a heating rate of 5°C / min. After cooling, it was washed with 0.01 M dilute hydrochloric acid and then an alcohol aqueous solution, and then dried. Co@FCF nanosheets modified with C@Ni were grown on the surface of the graphite felt. After the graphite felt was treated by flame fusion, cobalt tetroxide was in situ grown, and finally, nano-nickel embedded cobalt tetroxide nanosheets were obtained. Its micromorphology is shown in the figure. Figure 3 shown.
[0041] Example 4: Degradation of sulfamethoxazole by electro-activation of PMS using graphite felt
[0042] The degradation of sulfamethoxazole by electro-activation of PMS on graphite felt was carried out in a flow-through electrolysis reactor with a volume of 25 mL, with an external 50 mL wastewater storage tank. The reaction was run in a three-electrode system, with graphite felt as the working electrode, saturated calomel electrode as the reference electrode, platinum mesh as the counter electrode, and E = -0.2 (vs SCE). 50 mL of sulfamethoxazole (50 mg / L) aqueous solution was used as simulated wastewater, the wastewater circulation rate was 5 mL / min, the PMS addition concentration was 1 g / L, and no additional supporting electrolyte was required. The wastewater pH = 6.7, the reaction was carried out at room temperature of 22.5°C, and pre-adsorption was performed for 30 min before power was applied. The degradation effect was as follows: Figure 4 shown.
[0043] Example 5: Degradation of sulfamethoxazole by FCF electroactivation of PMS
[0044] The difference between this embodiment and embodiment 4 is that the working electrode used is FCF, and the degradation effect is as follows Figure 4 shown.
[0045] Example 6: Degradation of sulfamethoxazole by Co / CF electroactivation of PMS
[0046] The difference between this embodiment and embodiment 4 is that the working electrode used is Co / CF, and the degradation effect is as follows Figure 4 shown.
[0047] Example 7: Degradation of sulfamethoxazole by electroactivation of PMS using Co@FCF
[0048] The difference between this embodiment and embodiment 4 is that the working electrode used is Co@FCF, and the degradation effect is as follows Figure 4 shown.
[0049] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made on the basis of the above embodiment, and these improvements and modifications all fall within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a nano-nickel embedded cobalt tetroxide nanosheet electrode material, characterized in that: The specific steps are as follows: (1) Flame treatment of graphite felt: The graphite felt is placed above an ethanol flame to obtain a graphite felt with metal nano-nickel particles encapsulated by an in-situ carbon layer grown on the surface: S1. Wash and dry a graphite felt with a diameter of 5–50 mm and a thickness of 0.5–6 mm in acetone. Immerse the felt in a 0.05–0.5 M NiCl₂ ethanol solution for 1–10 min, remove the felt, and dry. S2. Heat the dried NiCl2-loaded graphite felt from S1 at a position 5–20 mm above the wick of an ethanol burner for 2–10 min, then rinse in 0.01–0.1 M hydrochloric acid solution. (2) Precursor loading: Melamine and CoCl2 are added to ethanol, heated and ultrasonically mixed to obtain a cobalt tetroxide precursor suspension, and the suspension is dropped onto the surface of the graphite felt after the flame treatment in step (1), and quickly placed in an oven for drying. The above steps are repeated several times until the surface of the graphite felt is densely covered with the precursor; (3) Preparation of nano-nickel embedded cobalt oxide nanosheet electrode material: The graphite felt loaded with the precursor obtained in step (2) is placed in a tube furnace for calcination, cooled, washed, and dried to obtain a cobalt oxide nanosheet electrode material with nano-nickel particles uniformly embedded in the bulk phase. The calcination temperature is 350-650°C, the heating rate during calcination is 2-10°C / min, the calcination time is 0.5-2h, and the calcination atmosphere is an air flow with a flow rate of 50-500 mL / min.
2. The method for preparing a nano-nickel embedded cobalt oxide nanosheet electrode material according to claim 1, characterized in that: In step S2, both sides of the graphite felt are flame treated and then washed in a 0.01-0.1 M hydrochloric acid solution.
3. The method for preparing a nano-nickel embedded cobalt oxide nanosheet electrode material according to claim 1, characterized in that: In the step (2), the mass ratio of CoCl2 to melamine is 1-20 wt%, the concentration of the cobalt trioxide precursor suspension is 0.05-0.5 g / mL, and the final loading amount of the precursor on the graphite felt is 0.1-10 wt%.
4. The method for preparing a nano-nickel embedded cobalt oxide nanosheet electrode material according to claim 3, characterized in that: In the step (2), the ultrasonic time is 10-120 min, and the heating temperature is 10-40°C.
5. Use of a nano-nickel embedded cobalt tetroxide nanosheet electrode material prepared by the method according to any one of claims 1 to 4 in removing organic pollutants from wastewater.
6. The use according to claim 5, characterized in that: The nano nickel embedded in cobalt tetroxide nano sheet electrode material is used as a cathode material for electrically activated persulfate and is used to remove organic pollutants in wastewater with a pH of 2 to 11.