Preparation method of F-doped Co3O4 electrode with high efficiency of activating production of chlorine free radicals

Abstract

The application belongs to the technical field of electrode activation of chlorine free radicals of electrocatalytic anode materials, and discloses a preparation method of an F-doped Co3O4 electrode for efficiently activating chlorine free radicals, wherein the synthesis method is mainly a liquid phase method, a volatilization method and a titration method; oxygen vacancies are generated on the surface of Co3O4 particles through the liquid phase method; fluorine ions replace the oxygen vacancies through the volatilization method; the surface of the Co3O4 particles is rich in fluorine ions; and the prepared ink solution is dropped on a carbon cloth through the titration method to prepare a Co3O 4‑ X F y electrode. The electrode material prepared by the method improves the activation rate of chlorine free radicals by doping fluorine ions, effectively improves the degradation rate of chlorinated organic matter systems and the mineralization rate of pollutant systems, and the material synthesis method is simple, which can reduce the material synthesis cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic materials and material preparation, and relates to a method for preparing a F-doped Co3O4 electrode for efficiently activating and generating chlorine free radicals, and in particular to a Co3O4 electrode with an oxygen vacancy structure. 4-X F y Preparation method. Background Art

[0002] Electrocatalytic indirect oxidation technology is widely used in pollutant treatment. The core of this technology is to generate reactive oxygen species (ROS) on the surface of the anode material. Studies have shown that the generation of ROS is directly related to the performance of the anode material.

[0003] The original anode electrode material was graphite, but it was consumed and eliminated during use; subsequently, researchers began to use metal oxides such as IrO2, RuO2, PbO2, and SnO2, but these oxides have the disadvantages of low activity and high cost; at the same time, studies have found that transition metal oxides have the characteristics of high performance and high cost, so they are widely used in anode materials, such as Co3O4 and Fe2O3.

[0004] However, in actual reactions, single metal oxide catalysts have two major disadvantages: lack of surface unit active area and low reuse rate, which are the biggest problems affecting electrochemical activity. In response to the above two problems, researchers have mainly proposed two modification methods, namely modifying the surface structure of metal catalysts and metal co-doping. Existing literature has shown that changing the in-situ growth position of Co3O4 nanomaterials and doping Gd metal can improve electrochemical activity and degradation efficiency. For details, see "Water decontamination via nonradical process by nanoconfined Fenton-like catalysts" and "Strong Structural Modification ofGd to Co3O4for Catalyzing N2ODecompositionunder Simulated Real Tail Gases". However, the materials synthesized by the above two methods are not very stable; Kang Xiao et al. showed in the paper "Activating Lattice Oxygen in Spinel ZnCo2O4 through Filling Oxygen Vacancies with Fluorine for Electrocatalytic Oxygen Evolution" that the lattice oxygen on the surface of the material can reduce the reaction energy barrier. At the same time, due to F - With high electronegativity, use F -Substituting the oxygen vacancies on the surface of the material can activate the lattice oxygen mentioned above, change the oxygen evolution reaction (OER) mechanism to reduce the reaction energy barrier, produce a lower overpotential, and the increase of lattice oxygen can also increase the stability of the catalyst material. Based on the above ideas, the present invention uses F - By replacing oxygen vacancies on the surface of materials, it can produce lower overpotential and higher stability, and is used in the degradation of volatile organic compounds to improve the ROS production rate and pollutant degradation and mineralization performance. Summary of the Invention

[0005] The present invention aims to develop a fluorine-doped Co₃O₄ electrode that efficiently activates and generates chlorine free radicals. The method utilizes a liquid-phase reaction and a high-temperature volatilization reaction, followed by oxidation-reduction, calcination, and titration to produce a fluorine-doped Co₃O₄ electrode that efficiently activates and generates chlorine free radicals. The materials used are readily available and inexpensive, the process is simple, and the cost and equipment requirements are minimal, making it an environmentally friendly and low-cost preparation method.

[0006] The technical solution of the present invention:

[0007] A method for preparing a F-doped Co3O4 electrode for efficiently activating and generating chlorine free radicals, wherein the F-doped Co3O4 electrode comprises a Co3O4 material and a substrate;

[0008] The Co3O4 material has a spherical structure, a particle size of less than 30nm, and a purity of ≥99.5%;

[0009] The substrate is a conductive or non-conductive material with a sheet structure having a supporting function, and is a glass sheet, fluorine-doped SnO2 transparent conductive glass, a metal sheet, or carbon cloth.

[0010] The preparation steps are as follows:

[0011] 1) Substrate pretreatment: Cut the substrate into 2 cm x 3 cm pieces, soak them in pure water and ethanol for 15 minutes, ultrasonically treat, wash, and dry.

[0012] 2) Liquid phase reaction: Prepare a sodium borohydride solution with a concentration of 0.025-0.1M, add Co3O4 particles to the sodium borohydride solution and react for 15-60 minutes to reduce the surface of Co3O4 to generate oxygen vacancies. The mixed solution is ultrasonicated and freeze-dried to obtain Co3O4 with a surface rich in oxygen vacancies. 4-X particles;

[0013] 3) High temperature volatilization reaction: First, the Co3O obtained in step 2) 4-X The particles are mixed with ammonium fluoride in a mass ratio of 2:1-1:4, ground until the mixture is uniform, and then the mixed powder is placed in a tube furnace and heated from room temperature to 200°C and calcined for 2-4 hours to make F -High temperature volatilization replaces oxygen vacancies to obtain Co3O 4-X F y granular materials;

[0014] 4) Prepare a mixed solution of isopropyl alcohol, pure water and Nafion membrane solution in a volume ratio of 10:10:1, and 4-X F y The granular material and carbon black are added to the mixed solution in a mass ratio of 2:1, and ultrasonically treated to obtain an electrode liquid material;

[0015] 5) Titration: The electrode liquid material obtained in step 4) is titrated onto the substrate to obtain a F-doped Co3O4 electrode that is highly activated to generate chlorine radicals.

[0016] Beneficial effects of the present invention:

[0017] 1) The present invention uses highly electronegative F - Replace oxygen vacancies, improve ROS production rate and pollutant degradation and mineralization performance, and have high material stability and low synthesis cost;

[0018] 2) The synthesis steps of the electrode material of the present invention are simple, the steps are simple, and the consumption cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the X-ray diffraction pattern (XRD) of the prepared F-doped Co3O4 electrode. The horizontal axis is twice the diffraction angle (2θ), and the vertical axis is the diffraction peak intensity (au)

[0020] Figure 2 This is the scanning electron microscope (SEM) image of the prepared F-doped Co3O4 electrode.

[0021] Figure 3 This is the scanning electron microscope (SEM) image of the prepared Co3O4 electrode

[0022] Figure 4 Co3O 4-X Scanning electron microscope (SEM) image of the electrode

[0023] Figure 5 This is the oxygen vacancy EPR spectrum of the prepared F-doped Co3O4 electrode

[0024] Figure 6 This is the EPR spectrum of activated chlorine radicals of the prepared F-doped Co3O4 electrode

[0025] Figure 7 The prepared Co3O4 electrode, Co3O 4-X Degradation rate of para-chlorophenol within 15 minutes using three electrodes: electrode and F-doped Co3O4 electrode

[0026] Figure 8 The prepared Co3O4 electrode, Co3O 4-X Mineralization rate of para-chlorophenol system in 120 min using three electrodes: electrode and F-doped Co3O4 electrode DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0028] Example 1

[0029] Step 1: First, pre-treat the base carbon cloth, cut it into 2 cm * 3 cm in size, stir it in 50 ml of anhydrous ethanol and pure water for 10 minutes, ultrasonically vibrate it for 2 hours to remove impurities on the surface of the base, and take it out to dry naturally;

[0030] Step 2: Prepare a 0.025M-0.1M sodium borohydride mixed solution; add 1 gram of cobalt trioxide particle powder to the mixed solution and stir for 15-60 minutes. After stirring, the solution is inverted into a centrifuge tube and centrifuged 2-3 times. The supernatant is poured out and the turbid liquid is frozen for 12 hours and then placed in a freeze dryer to obtain Co3O rich in oxygen vacancies. 4-X Granular powder;

[0031] Step 3: Co3O obtained in step 2 4-X The granular powder is mixed with ammonium fluoride in a mass ratio of 2:1-1:4, the mixed drug is ground in a mortar, mixed evenly, and then taken out and placed in a tube furnace and heated from room temperature to 200 degrees Celsius at a rate of 2 degrees Celsius / minute and calcined for 2-4 hours to obtain doped F - Co3O 4-X F y Granular powder;

[0032] Step 4: Take 20 mg of Co3O obtained in step 3 4-X F y The granular powder and 10 mg of carbon black were mixed evenly. The above mixed materials were mixed with 0.5 ml of isopropanol, 0.5 ml of pure water and a Naifon membrane solution with a mass fraction of 0.5%. Ultrasonic treatment was performed for 3 hours and the mixture was fully mixed to form a dispersed suspension ink solution. 1 ml of the ink solution was added dropwise on a 4 square centimeter hydrophilic carbon cloth in 4 times, with 200 microliters added each time. The catalyst loading on each electrode was 1 mg / cm 2 , and obtain F-doped Co3O4 electrode.

[0033] Comparative Example 1

[0034] Untreated Co3O4 nanoparticles were used to prepare a Co3O4 electrode according to step 4 of the present invention in Example 1, and the electrochemical properties of the material of the present invention were compared.

[0035] Comparative Example 2

[0036] According to the steps 1 and 2 of the present invention in Example 1, Co3O3 rich in oxygen vacancies was obtained. 4-X Granular powder, and according to step 4 of the present invention in Example 1, Co3O 4-X Electrode, compare the electrochemical performance of the materials of the present invention.

[0037] Example 2

[0038] The F-doped Co3O4 electrode obtained in Example 1 was used as the anode, a 1 square cm*1 square cm foil was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode to construct a three-electrode system. The electrolyte was a 0.1 M NaCl solution. A voltage of 1.8 volts was applied to the system, and the EPR spectrum of chlorine radicals generated by the system was detected for 15 minutes.

[0039] Example 3

[0040] The three electrodes obtained in Example 1, Comparative Example 1 and Comparative Example 2 were respectively used as anodes, a 1 cm²*1 cm² foil was used as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode to construct a three-electrode system. The electrolyte was a 0.1 M NaCl solution. A voltage of 1.8 volts was applied to the system. 100 mg / L p-chlorophenol was added to the system. After high performance liquid chromatography analysis, the Co3O4 electrode, Co3O 4-X The degradation rates of para-chlorophenol over the three electrodes, namely, F-doped Co3O4 electrode and F-doped Co3O4 electrode, were 38.3%, 59.5% and 92.1% in 15 minutes, respectively. This proves that at the same voltage, the F-doped Co3O4 electrode has a lower overpotential, a higher current density, the highest electrocatalytic reaction efficiency and the best pollutant degradation efficiency.

[0041] Example 4

[0042] The three electrodes obtained in Example 1, Comparative Example 1 and Comparative Example 2 were respectively used as anodes, a 1 cm²*1 cm² foil was used as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode to construct a three-electrode system. The electrolyte was a 0.1 M NaCl solution. A voltage of 1.8 volts was applied to the system. 100 mg / L p-chlorophenol was added to the system. After TOC analysis, the Co3O4 electrode, Co3O 4-X The mineralization rates of the three electrodes, namely, F-doped Co3O4 electrode and F-doped Co3O4 electrode, can reach 33%, 50% and 65% respectively within 120 minutes, which proves that in the same system, F-doped Co3O4 electrode can continuously mineralize the system, with the best material stability and the highest mineralization rate.

Claims

1. A method for preparing a F-doped Co3O4 electrode for efficient activation and generation of chlorine free radicals, characterized in that: The F-doped Co3O4 electrode includes a Co3O4 material and a substrate; The preparation steps are as follows: 1) Substrate pretreatment: Cut the substrate to a fixed size, soak it in pure water and ethanol for 15 minutes, ultrasonically treat it, wash it, and dry it; 2) Liquid phase reaction: Prepare a sodium borohydride solution with a concentration of 0.025-0.1M, add Co3O4 particles to the sodium borohydride solution and react for 15-60 minutes to reduce the surface of Co3O4 to generate oxygen vacancies. The mixed solution is ultrasonicated and freeze-dried to obtain Co3O4 with a surface rich in oxygen vacancies. 4-X particles; 3) High temperature volatilization reaction: First, the Co3O obtained in step 2) 4-X The particles are mixed with ammonium fluoride in a mass ratio of 2:1-1:4 and ground until the mixture is uniform; The mixed powder was then placed in a tube furnace and heated from room temperature to 200°C for 2-4 hours to make F - High temperature volatilization replaces oxygen vacancies to obtain Co3O 4-X F y granular materials; 4) Prepare a mixed solution of isopropyl alcohol, pure water and Nafion membrane solution in a volume ratio of 10:10:1, and 4-X F y The granular material and carbon black are added to the mixed solution in a mass ratio of 2:1, and ultrasonically treated to obtain an electrode liquid material; 5) Titration: The electrode liquid material obtained in step 4) is titrated onto the substrate to obtain a F-doped Co3O4 electrode that is highly activated to generate chlorine radicals.

2. The preparation method according to claim 1, characterized in that The Co3O4 material has a spherical structure and a particle size of less than 30nm.

3. The preparation method according to claim 1, characterized in that The substrate is a conductive or non-conductive material with a sheet structure having a supporting function, and is a glass sheet, fluorine-doped SnO2 transparent conductive glass, a metal sheet, or carbon cloth.

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