Preparation method of oxygen functionalized cobalt-nitrogen-carbon catalyst and application of oxygen functionalized cobalt-nitrogen-carbon catalyst in electrosynthesis of hydrogen peroxide

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method of an oxygen functionalized cobalt-nitrogen-carbon catalyst and application of the oxygen functionalized cobalt-nitrogen-carbon catalyst in electrosynthesis of hydrogen peroxide, and the preparation method comprises the following preparation steps: S1, dissolving melamine and glucose in deionized water, adding cobalt acetate and a precursor modifier, and stirring to obtain a uniform mixed solution; s2, heating and stirring the mixed solution until moisture is evaporated, drying, adding into a tubular furnace, heating from room temperature to 850-900 DEG C, keeping the temperature for 1-2 hours, and grinding into powder, so as to obtain a modified precursor material; and S3, adding the oxygen-functionalized modified liquid into the modified precursor material, stirring after ultrasonic dispersion, carrying out centrifugal separation, washing to be neutral, and drying to obtain the oxygen-functionalized cobalt-nitrogen-carbon catalyst. Through the synergistic effect of the precursor modifier and the oxygen functionalization modification liquid, the electrocatalytic oxygen reduction reaction activity and the hydrogen peroxide selectivity are improved, and excellent electrochemical stability and structural durability are shown while the high activity is kept.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst and its application in the electrosynthesis of hydrogen peroxide. Background Technology

[0002] Hydrogen peroxide is an extremely important chemical, widely used in chemical synthesis, wastewater treatment, papermaking, medical, and semiconductor manufacturing industries. Traditional hydrogen peroxide production mainly uses the anthraquinone process, which is energy-intensive, highly polluting, and poses safety risks during storage and transportation. Therefore, in recent years, electrosynthesis of hydrogen peroxide has been developed. Its basic principle is to use electrical energy to selectively electrocatalytically reduce oxygen molecules to hydrogen peroxide under specific pH conditions. Compared to the traditional anthraquinone process, electrosynthesis of hydrogen peroxide is not only environmentally friendly but also enables the online production of high-purity hydrogen peroxide. In electrosynthesis of hydrogen peroxide, the oxygen reduction catalyst at the cathode is the key material determining the hydrogen peroxide production rate and Faradaic efficiency. Developing oxygen reduction electrocatalysts with high activity, high two-electron selectivity, and high stability is crucial for achieving efficient electrosynthesis of hydrogen peroxide.

[0003] Numerous experimental and theoretical calculations have demonstrated that nitrogen-doped carbon-based cobalt single-atom catalysts not only possess excellent electrocatalytic activity for oxygen reduction (OR) but also exhibit considerable two-electron selectivity, making them a promising class of catalysts for the electrosynthesis of hydrogen peroxide. However, the two-electron selectivity of currently developed cobalt-nitrogen-carbon catalysts in the OR reaction still falls short of practical application requirements. Therefore, there is an urgent need to develop cobalt-nitrogen-carbon catalysts with higher two-electron selectivity. The key to improving the two-electron selectivity of cobalt-nitrogen-carbon catalysts lies in the precise control of the electronic structure of their cobalt single-atom active sites. A suitable electronic structure can effectively optimize the adsorption energy of key intermediates in the OR reaction, thereby significantly improving the catalyst's two-electron selectivity. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst and its application in the electrosynthesis of hydrogen peroxide.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst includes the following preparation steps: S1. By weight, dissolve 1.5-2 parts of melamine and 0.5-0.8 parts of glucose in 50-55 parts of deionized water, add 0.05-0.1 parts of cobalt acetate and 1-2 parts of precursor modifier, and stir at 300-400 r / min for 25-30 min to obtain a uniform mixture. S2. Heat and stir the mixture obtained in step S1 until the water evaporates, dry it in an oven at 95-100℃ for 10-12 hours, then add it to a tube furnace, heat it from room temperature to 850-900℃, keep it at that temperature for 1-2 hours, and then grind it into powder to obtain the modified precursor material. S3. Add 180-200 parts of oxygen-functionalized modification liquid to the modified precursor material obtained in step S2, ultrasonically disperse for 25-30 min, stir at 300-400 r / min for 10-12 h in a water bath at 55-60℃, centrifuge and wash with deionized water until neutral, and dry for 10-12 h to obtain oxygen-functionalized cobalt-nitrogen-carbon catalyst; The preparation of precursor modifiers includes the following steps: S11. By mass, preheat 75-80 parts of deionized water in a water bath at 55-60℃ for 10-15 minutes, add 10-12 parts of urea and 0.5-1 parts of cyanuric acid, and stir at 250-300 r / min for 15-20 minutes. S12. Maintain a water bath temperature of 60°C, add 0.6-0.8 parts of citric acid and 0.4-0.5 parts of polyethylene glycol to the mixture obtained in step S11, stir at a speed of 300-350 r / min for 30-40 min until the solution is clear and transparent, and then cool naturally to room temperature to obtain the precursor modifier.

[0006] Preferably, the preparation of the oxygen-functionalized modified liquid includes the following steps: S31. Dissolve 0.5-0.6 parts of potassium dihydrogen phosphate in 20-30 parts of deionized water by weight, stir until completely dissolved, then add 0.1-0.3 parts of sodium dodecyl sulfate and 100-120 parts of dilute sulfuric acid to obtain a preliminary modified solution; S32. Add 2.5-3 parts of potassium persulfate to the preliminary modified solution obtained in step S31, and stir at 300-400 r / min for 15-20 min to obtain the secondary modified solution; S33. Add 0.2-0.5 parts ascorbic acid and 0.5-1 parts sodium bisulfate to the modified solution obtained in step S32, and stir at 300-350 r / min for 25-30 min to finally obtain the oxygen-functionalized modified solution.

[0007] Preferably, the heating temperature in step S2 is 80-85℃.

[0008] Preferably, in step S2, the heating is carried out under a nitrogen atmosphere, and the heating rate is 4-5℃ / min.

[0009] Preferably, the frequency of ultrasonic dispersion in step S3 is 40 kHz.

[0010] Preferably, the drying temperature in step S3 is 75-80°C.

[0011] Preferably, the mass concentration of dilute sulfuric acid in step S31 is 5%.

[0012] Application of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared according to the above method in the electrosynthesis of hydrogen peroxide.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a precursor modifier to form high-density, atomically dispersed, and stable active centers during high-temperature pyrolysis, significantly increasing the number of available electrocatalytic sites. The oxygen-functionalized modified liquid introduces oxygen-containing functional groups, effectively regulating the electronic structure of the Co active center, optimizing the adsorption energy of the key intermediate (*OOH) in the oxygen reduction reaction, and improving the catalyst's hydrogen peroxide selectivity.

[0014] 2. This invention improves the electrocatalytic oxygen reduction reaction activity and hydrogen peroxide selectivity through the synergistic effect of precursor modifiers and oxygen-functionalized modified liquids, exhibiting excellent electrochemical stability and structural durability while maintaining high activity. Furthermore, the process route of this invention is relatively simple, aligns with the development direction of green chemistry, and possesses good economic prospects. Attached Figure Description

[0015] Figure 1 This is a process flow diagram for the preparation of the oxygen-functionalized cobalt-nitrogen-carbon catalyst of the present invention; Figure 2 This is a process flow diagram for preparing the precursor modifier of the present invention; Figure 3 This is a process flow diagram for preparing the oxygen-functionalized modified liquid of the present invention; Figure 4 The oxygen reduction polarization curve of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 2 of this invention in a three-electrode (RRDE) system is shown. Figure 5 The H2O2 selectivity curve of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 2 of this invention in a three-electrode (RRDE) system is shown. Figure 6 The bar chart shows the H2O2 Faraday efficiency test results of the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 and Comparative Example 1 of this invention in a three-electrode gas diffusion flow electrolyzer. Figure 7 The bar chart shows the H2O2 space-time yield test results of the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 and Comparative Example 1 of this invention in a three-electrode gas diffusion flow electrolyzer. Figure 8The X-ray photoelectron fine spectrum (O1s electrons) of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared in Comparative Example 2 of this invention is shown in the figure. Figure 9 The X-ray photoelectron fine spectrum (O1s electrons) of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared in Example 1 of this invention is shown in the image. Figure 10 The X-ray photoelectron fine spectrum (O1s electrons) of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared in Example 2 of this invention is shown in the image. Figure 11 The X-ray photoelectron fine spectrum (O1s electrons) of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared in Example 3 of this invention is shown in the image. Figure 12 The X-ray diffraction pattern of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention; Figure 13 This is a transmission electron micrograph of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of the present invention; Figure 14 This is a scanning transmission electron microscopy image of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of the present invention in high-angle annular dark-field mode. Figure 15 The elemental distribution diagram of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention is based on energy-dispersive X-ray spectroscopy in scanning transmission mode. Figure 16 The fine structure spectrum (Fourier transform) of cobalt K-side extended X-ray absorption in the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention is shown. Detailed Implementation

[0016] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Please see Figures 1-16 The present invention provides a technical solution: Example 1 A method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst: Before preparing the oxygen-functionalized cobalt-nitrogen-carbon catalyst, the precursor modifier and the oxygen-functionalized modification solution are prepared first: The preparation of precursor modifiers includes the following steps: S11. Preheat 75g of deionized water in a water bath at 55℃ for 10min, add 10g of urea and 0.5g of cyanuric acid, and stir at 250r / min for 15min. S12. Maintain a water bath temperature of 60°C, add 0.6g citric acid and 0.4g polyethylene glycol (PEG-2000) to the mixture obtained in step S11, stir at 300r / min for 30min until the solution is clear and transparent, and then cool naturally to room temperature to obtain the precursor modifier.

[0018] The preparation of the oxygen-functionalized modified liquid includes the following steps: S31. Dissolve 0.5g of potassium dihydrogen phosphate in 20g of deionized water, stir until completely dissolved, then add 0.1g of sodium dodecyl sulfate and 100g of 5% dilute sulfuric acid to obtain a preliminary modified solution; S32. Add 2.5g of potassium persulfate to the preliminary modified solution obtained in step S31, and stir at 300r / min for 15min to obtain the secondary modified solution; S33. Add 0.2g ascorbic acid and 0.5g sodium bisulfate to the modified solution obtained in step S32, and stir at 300r / min for 25min to finally obtain the oxygen-functionalized modified solution.

[0019] S1. Dissolve 1.5g of melamine and 0.5g of glucose in 50g of deionized water, add 0.05g of cobalt acetate and 1g of precursor modifier, and stir at 300r / min for 25min to obtain a uniform mixture. S2. The mixture obtained in step S1 is heated and stirred at 80°C until the water evaporates. After drying in an oven at 95°C for 10 hours, it is added to a tube furnace and heated from room temperature to 850°C at a heating rate of 4°C / min under a nitrogen atmosphere. After holding at this temperature for 1 hour, it is ground into powder to obtain the modified precursor material. S3. Add 180g of oxygen-functionalized modification liquid to the modified precursor material obtained in step S2, ultrasonically disperse at a frequency of 40kHz for 25min, stir at a speed of 300r / min for 10h in a water bath at 55℃, separate by centrifugation and wash with deionized water until neutral, and dry at 75℃ for 10h to obtain the oxygen-functionalized cobalt-nitrogen-carbon catalyst.

[0020] Example 2 A method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst: Before preparing the oxygen-functionalized cobalt-nitrogen-carbon catalyst, the precursor modifier and the oxygen-functionalized modification solution are prepared first: The preparation of precursor modifiers includes the following steps: S11. Preheat 80g of deionized water in a water bath at 60℃ for 15min, add 12g of urea and 1g of cyanuric acid, and stir at 300r / min for 20min. S12. Maintain a water bath temperature of 60°C, add 0.8g of citric acid and 0.5g of polyethylene glycol (PEG-2000) to the mixture obtained in step S11, stir at 350r / min for 40min until the solution is clear and transparent, and then cool naturally to room temperature to obtain the precursor modifier.

[0021] The preparation of the oxygen-functionalized modified liquid includes the following steps: S31. Dissolve 0.6g of potassium dihydrogen phosphate in 30g of deionized water, stir until completely dissolved, then add 0.3g of sodium dodecyl sulfate and 120g of 5% dilute sulfuric acid to obtain a preliminary modified solution; S32. Add 3g of potassium persulfate to the preliminary modified solution obtained in step S31, and stir at 400r / min for 20min to obtain the secondary modified solution; S33. Add 0.5g ascorbic acid and 1g sodium bisulfate to the modified solution obtained in step S32, and stir at 350r / min for 30min to finally obtain the oxygen-functionalized modified solution.

[0022] S1. Dissolve 2g of melamine and 0.8g of glucose in 55g of deionized water, add 0.1g of cobalt acetate and 2g of precursor modifier, and stir at 400r / min for 30min to obtain a uniform mixture; S2. The mixture obtained in step S1 is heated and stirred at 85°C until the water evaporates. After drying in an oven at 100°C for 12 hours, it is added to a tube furnace and heated from room temperature to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere. After holding at this temperature for 2 hours, it is ground into powder to obtain the modified precursor material. S3. Add 200g of oxygen-functionalized modification liquid to the modified precursor material obtained in step S2, ultrasonically disperse at a frequency of 40kHz for 30min, stir at a speed of 400r / min for 12h in a water bath at 60℃, separate by centrifugation and wash with deionized water until neutral, and dry at 80℃ for 12h to obtain the oxygen-functionalized cobalt-nitrogen-carbon catalyst.

[0023] Example 3 A method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst: Before preparing the oxygen-functionalized cobalt-nitrogen-carbon catalyst, the precursor modifier and the oxygen-functionalized modification solution are prepared first: The preparation of precursor modifiers includes the following steps: S11. Preheat 77g of deionized water in a water bath at 58℃ for 13min, add 11g of urea and 0.8g of cyanuric acid, and stir at 260r / min for 18min. S12. Maintain a water bath temperature of 60°C, add 0.7g citric acid and 0.45g polyethylene glycol (PEG-2000) to the mixture obtained in step S11, stir at 320r / min for 35min until the solution is clear and transparent, and then cool naturally to room temperature to obtain the precursor modifier.

[0024] The preparation of the oxygen-functionalized modified liquid includes the following steps: S31. Dissolve 0.55g of potassium dihydrogen phosphate in 25g of deionized water, stir until completely dissolved, then add 0.2g of sodium dodecyl sulfate and 110g of 5% dilute sulfuric acid to obtain a preliminary modified solution; S32. Add 2.8g of potassium persulfate to the preliminary modified solution obtained in step S31, and stir at 320r / min for 18min to obtain the secondary modified solution; S33. Add 0.4g ascorbic acid and 0.8g sodium bisulfate to the modified solution obtained in step S32, and stir at 320r / min for 28min to finally obtain the oxygen-functionalized modified solution.

[0025] S1. Dissolve 1.8g of melamine and 0.7g of glucose in 53g of deionized water, add 0.08g of cobalt acetate and 1.5g of precursor modifier, and stir at 350r / min for 28min to obtain a homogeneous mixture; S2. The mixture obtained in step S1 is heated and stirred at 83°C until the water evaporates. After drying in an oven at 98°C for 11 hours, it is added to a tube furnace and heated from room temperature to 880°C at a heating rate of 4.5°C / min under a nitrogen atmosphere. After holding at this temperature for 1.5 hours, it is ground into powder to obtain the modified precursor material. S3. Add 190g of oxygen-functionalized modification liquid to the modified precursor material obtained in step S2, ultrasonically disperse at a frequency of 40kHz for 28min, stir at a speed of 350r / min for 11h in a water bath at 58℃, separate by centrifugation and wash with deionized water until neutral, and dry at 78℃ for 11h to obtain the oxygen-functionalized cobalt-nitrogen-carbon catalyst.

[0026] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that no precursor modifier was added in this comparative example; the other steps are exactly the same in Comparative Example 1 and Example 1.

[0027] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that no oxygen-functionalized modification liquid was added in this comparative example; the other steps are exactly the same in Comparative Example 2 and Example 1.

[0028] Performance testing: 1. The intrinsic electrocatalytic performance of the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 and Comparative Examples 1-2 was tested using a three-electrode rotating ring-disk electrode (RRDE): Ring disk electrode polishing treatment: The ring disk electrode is polished with alumina polishing powder (particle size 50nm), then cleaned with ultrapure water, and finally dried with a rubber bulb for later use. Slurry preparation: The dispersion system containing 2.94 mg catalyst, 705 μL ultrapure water, 705 μL ethanol and 22.5 μL Nafion (5 wt.%) was ultrasonically dispersed at room temperature for 20 min to obtain catalyst slurry; Working electrode preparation: 13 μL of catalyst slurry was dropped onto an area of ​​0.247 cm². 2 The glassy carbon electrode surface is dried at 50°C; Preparation of oxygen or argon saturated electrolyte: First, prepare a perchloric acid aqueous solution with a molar concentration of 0.1 mol / L, and then pass high-purity oxygen or argon into it for 10 minutes until the dissolved oxygen or argon in the electrolyte reaches saturation; Electrochemical testing: Graphite rods and mercury / mercurous sulfate (saturated potassium sulfate solution) were used as the counter and reference electrodes, respectively. First, the working electrode was continuously run in oxygen-saturated electrolyte at 0.05 V vs. RHE potential and 1600 rpm for 2 min to ensure complete surface wetting and stability. Then, the Pt ring electrode was subjected to cyclic voltammetry in argon-saturated electrolyte (0.05–1.0 V vs. RHE, potential scan rate of 100 mV / s, 20 cycles) to achieve ideal surface cleanliness. Finally, the electrolyte was replaced, and polarization curves and selectivity tests were performed. The oxidation voltage of the Pt ring electrode was kept constant at 1.25 V vs. RHE, and the electrode rotation speed was 1600 rpm.

[0029] 2. The activity and stability of the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 and Comparative Examples 1-2 under high current density were tested using a three-electrode gas diffusion flow electrolysis cell: Gas diffusion electrode preparation: Catalyst slurry was uniformly loaded onto 1*1cm carbon paper using ultrasonic spraying technology. 2 The central area (using carbon paper measuring 2.5*2.5cm) 2 The catalyst loading was 0.25 mg / cm³. 2 The Nafion content in the catalyst layer is 40 wt.%. Cathodic electrolyte preparation: Accurately prepare a sulfuric acid solution with a molar concentration of 0.5 mol / L, and use it as the cathodic electrolyte; Electrochemical testing: at a depth of 1.45*1.45cm 2 The iridium oxide catalyst layer served as the anode, and the cathode was a self-made gas diffusion electrode. One side of the catalyst-coated carbon paper was in contact with the electrolyte, and high-purity oxygen was introduced through the back of the carbon paper. The cathode / anode chambers were separated by a commercial proton exchange membrane; the distance between the cathode and anode electrodes was 3.5 mm. 150 mL of cathode electrolyte was transferred to the cathode storage bottle, and 150 mL of ultrapure water was added to the anode storage bottle. The peristaltic pump was turned on to fill the cathode / anode chambers with electrolyte and ultrapure water respectively; the flow rate of both chambers was set to 20 mL / min. Finally, different current densities (50, 100, 200 mA / cm²) were applied. 2 The above electrolytic cell system was subjected to constant current electrolysis test (anodic reaction: 2H2O→O2+4H) + +4e; Cathode reaction: O2 + 2H+ + +2e→H2O2); During continuous electrolysis, the electrolyte concentration in the cathode storage bottle was measured every 30 minutes (based on cerium sulfate spectrophotometry). The final data are shown in Table 1 below: Table 1. Results of electrocatalytic activity and H2O2 selectivity tests As can be seen from the test results in Table 1, the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 of this invention are superior to the comparative examples in terms of electrocatalytic activity and H2O2 selectivity. This indicates that the synergistic effect of the precursor modifier and the oxygen-functionalized modified liquid improves the electrocatalytic oxygen reduction reaction activity and hydrogen peroxide selectivity, and exhibits excellent electrochemical stability and structural durability while maintaining high activity.

[0030] Appendix Figure 4 and attached Figure 5 The figures show the oxygen reduction polarization curve and H2O2 selectivity curve of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 2 in a three-electrode (RRDE) system. It can be seen that after accelerated aging experiments (oxygen saturation, 0.1-0.7V, 100 mV / s, 10,000 cycles), the oxygen reduction half-wave potential and H2O2 selectivity of this catalyst decreased by only 28 mV and 2%, respectively, indicating that the catalyst has excellent durability.

[0031] Appendix Figure 6 and attached Figure 7The bar charts show the results of H2O2 Faradaic efficiency and space-time yield tests of the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 and Comparative Example 1 in a three-electrode gas diffusion flow electrolyzer. It can be seen that, compared to Comparative Example 1, the oxygen-functionalized cobalt-nitrogen-carbon catalysts obtained in Examples 1-3 show significant improvements in both H2O2 Faradaic efficiency and space-time yield, especially at 200 mA / cm². 2 At high current densities, the space-time yield of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 3 can reach 1.14 kg / (m³). 2 ·h), this performance indicator already has certain commercial value.

[0032] Appendix Figure 8-11 The images show the X-ray photoelectron spectroscopy (O1s electron) resolution diagrams of the oxygen-functionalized cobalt-nitrogen-carbon catalysts prepared in Comparative Example 2 and Examples 1-3 of this invention. It can be seen that after treatment with the oxygen-functionalized modification liquid, the relative content of CO functional groups on the catalyst surface significantly increases, indicating that the oxygen-functionalized modification liquid can effectively increase the number of hydroxyl (-OH) or epoxy (COC) groups on the catalyst surface.

[0033] Appendix Figure 12 The X-ray diffraction pattern of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention is shown below; Figure 13 This is a transmission electron micrograph of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of the present invention. (From the attached image) Figure 12 and 13 As can be seen from the above, the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in this invention does not contain any cobalt-based crystalline materials (such as cobalt metal nanoparticles); the catalyst is microscopically nanoparticle-shaped with a particle size of approximately 100 nm (see attached image). Figure 13 ).

[0034] Appendix Figure 14 The image shows a scanning transmission electron microscopy (STEM) image of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention in high-angle annular dark-field mode; (See attached image) Figure 15 The elemental distribution diagram of the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention, based on energy-dispersive X-ray spectroscopy in scanning transmission mode; (See attached image) Figure 16 The fine structure spectrum (Fourier transform) of cobalt K-edge extended X-ray absorption in the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in Example 1 of this invention is shown. High-resolution scanning transmission characterization results with spherical aberration correction are also presented. Figure 14 The results show that the catalyst surface contains a large number of atomic-level bright spots, which correspond to single cobalt atoms; combined with the elemental distribution results ( Figure 15 It can be inferred that cobalt single atoms most likely form the so-called Co-N with nitrogen atoms. xCoordination structure, which is the main active site for the electrocatalytic oxygen reduction reaction. Fourier transform extended X-ray absorption fine structure spectrum (...) Figure 16 The analysis results further confirm that the oxygen-functionalized cobalt-nitrogen-carbon catalyst obtained in this invention is a cobalt single-atom catalyst.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst, characterized in that, The preparation steps include the following: S1. By weight, dissolve 1.5-2 parts of melamine and 0.5-0.8 parts of glucose in 50-55 parts of deionized water, add 0.05-0.1 parts of cobalt acetate and 1-2 parts of precursor modifier, and stir at 300-400 r / min for 25-30 min to obtain a uniform mixture. S2. Heat and stir the mixture obtained in step S1 until the water evaporates, dry it in an oven at 95-100℃ for 10-12 hours, then add it to a tube furnace, heat it from room temperature to 850-900℃, keep it at that temperature for 1-2 hours, and then grind it into powder to obtain the modified precursor material. S3. Add 180-200 parts of oxygen-functionalized modification liquid to the modified precursor material obtained in step S2, ultrasonically disperse for 25-30 min, stir at 300-400 r / min for 10-12 h in a water bath at 55-60℃, centrifuge and wash with deionized water until neutral, and dry for 10-12 h to obtain oxygen-functionalized cobalt-nitrogen-carbon catalyst; The preparation of the precursor modifier includes the following steps: S11. By mass, preheat 75-80 parts of deionized water in a water bath at 55-60℃ for 10-15 minutes, add 10-12 parts of urea and 0.5-1 parts of cyanuric acid, and stir at 250-300 r / min for 15-20 minutes. S12. Maintain a water bath temperature of 60°C, add 0.6-0.8 parts of citric acid and 0.4-0.5 parts of polyethylene glycol to the mixture obtained in step S11, stir at a speed of 300-350 r / min for 30-40 min until the solution is clear and transparent, and then cool naturally to room temperature to obtain the precursor modifier.

2. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 1, characterized in that, The preparation of the oxygen-functionalized modified liquid includes the following steps: S31. Dissolve 0.5-0.6 parts of potassium dihydrogen phosphate in 20-30 parts of deionized water by weight, stir until completely dissolved, then add 0.1-0.3 parts of sodium dodecyl sulfate and 100-120 parts of dilute sulfuric acid to obtain a preliminary modified solution; S32. Add 2.5-3 parts of potassium persulfate to the preliminary modified solution obtained in step S31, and stir at 300-400 r / min for 15-20 min to obtain the secondary modified solution; S33. Add 0.2-0.5 parts ascorbic acid and 0.5-1 parts sodium bisulfate to the modified solution obtained in step S32, and stir at 300-350 r / min for 25-30 min to finally obtain the oxygen-functionalized modified solution.

3. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 1, characterized in that, The heating temperature in step S2 is 80-85℃.

4. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 1, characterized in that, In step S2, the temperature is increased under a nitrogen atmosphere at a rate of 4-5 °C / min.

5. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 1, characterized in that, In step S3, the frequency of ultrasonic dispersion is 40 kHz.

6. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 1, characterized in that, The drying temperature in step S3 is 75-80℃.

7. The method for preparing an oxygen-functionalized cobalt-nitrogen-carbon catalyst according to claim 2, characterized in that, The mass concentration of dilute sulfuric acid in step S31 is 5%.

8. The application of the oxygen-functionalized cobalt-nitrogen-carbon catalyst prepared by any one of claims 1-7 in the electrosynthesis of hydrogen peroxide.

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