Monatomic cobalt doped graphite phase carbon nitride modified carbon electrode and preparation method and application thereof

Abstract

The invention provides a monatomic cobalt-doped graphite phase carbon nitride modified carbon electrode and a preparation method and application thereof, and belongs to the technical field. The prepared monatomic cobalt-doped graphite phase carbon nitride modified carbon electrode comprises a carbon electrode substrate and a cobalt-doped graphite phase carbon nitride catalytic layer. The oxygen-containing functional group of the carbon electrode and monatomic cobalt synergistically regulate and control the selectivity and activity of two-electron oxygen reduction, so that hydrogen peroxide is efficiently and stably generated by electro-catalyzing oxygen. The carbon electrode is applied to an electro-catalytic ozonation technology, H2O2 generated in situ reacts with ozone to generate hydroxyl radicals (OH), and monatomic cobalt and carbon nitride can also directly act on the ozone to generate OH, so that removal of new pollutants difficult to degrade is remarkably enhanced, and a theoretical basis and a technical support can be provided for remediation of the pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and in particular to a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, emerging contaminants (ECs) have been frequently detected in surface water, groundwater, and the effluent of the secondary sedimentation tank of sewage treatment plants. Although the concentrations of these ECs are relatively low (ng / L - μg / L) and do not cause sudden hazards (low acute toxicity), the coexistence of multiple ECs may produce synergistic effects, and long-term low-dose exposure will pose a potential threat to the ecological environment and human health. Therefore, there is an urgent need to develop advanced treatment technologies that can effectively remove ECs in water, continuously reduce environmental risks, and ensure water quality safety.

[0003] Electro-peroxone (EP electrocatalytic ozone) is an effective technology for removing ECs in water. By coupling ozone and electrochemical technologies, using the characteristics of carbon electrodes with high hydrogen evolution overpotential and low hydrogen peroxide decomposition activity, the oxygen (O2) mixed in ozone aeration is in-situ converted into H2O2 by cathodic reduction, and then through the peroxon reaction between H2O2 and O3, the conversion of O3 into •OH is strengthened, thereby realizing the efficient removal of refractory ECs. In addition, H2O2 can also quickly reduce hypobromite (BrO − , an important intermediate in the bromate generation process) to bromide ion (Br − ), effectively inhibiting the conversion of Br − in water into BrO3 − .

[0004] However, the EP electrocatalytic ozone technology has problems such as slow H2O2 generation rate, unstable yield, and short electrode life. How to efficiently and low-consumedly electrochemically reduce O2 to H2O2 at the cathode is the key to the EP electrocatalytic ozone technology. The electrochemical reduction of O2 to produce H2O2 mainly depends on the two-electron oxygen reduction reaction (ORR). O2 adsorbs on the electrode surface to form OOH*, and OOH* forms H2O2 through the two-electron OOR. At the same time, the four-electron OOR side reaction of OOH* also occurs. To increase the selectivity of the two-electron ORR, the Gibbs free energy of O* (ΔG(O*)) needs to be increased, which will inevitably cause an increase in the Gibbs free energy of OOH* (ΔG(OOH*)), resulting in a decrease in the activity of the two-electron ORR. Therefore, there has been a long-term trade-off between the selectivity and activity of electro-generated H2O2. A good electrode for electro-producing H2O2 should take into account both the selectivity and activity of the two-electron ORR, thereby improving the H2O2 generation rate and stability. Summary of the Invention

[0005] The object of the present invention is to provide a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode, its preparation method and application. The single-atom cobalt-doped graphitic carbon nitride modified carbon electrode can efficiently and stably generate H2O2, solving the problems of slow H2O2 generation rate and unstable yield of traditional carbon electrodes.

[0006] In order to achieve the above object of the invention, the present invention provides the following technical solutions: The present invention provides a preparation method of a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode, comprising the following steps: Mix carbon black, an alcohol solvent and a PTFE emulsion, sequentially perform evaporation treatment and rolling on the obtained mixture, place the obtained carbon paste on both sides of a nickel mesh, and perform pressing to obtain an electrode sheet; Perform first calcination on the electrode sheet to obtain a carbon substrate; Perform second calcination on a carbon and nitrogen source to obtain carbon nitride; Mix the carbon nitride, a cobalt source and water, sequentially perform freezing and freeze-drying on the obtained mixed solution, and then perform third calcination in a nitrogen atmosphere to obtain single-atom cobalt-doped carbon nitride; Mix the single-atom cobalt-doped carbon nitride with a dispersant, and compound the obtained dispersion with the carbon substrate to obtain a modified carbon electrode; After performing fourth calcination on the modified carbon electrode, sequentially repeat the steps of the compounding and the fourth calcination to obtain a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode.

[0007] Preferably, the freezing and freeze-drying are sequentially replaced by hydrothermal reaction and air drying; the temperature of the hydrothermal reaction is 100-200 °C, and the time is 6-10 h.

[0008] Preferably, the mesh number of the nickel mesh is 200 mesh; the loading amount of the carbon paste on the nickel mesh is 0.03-0.05 g / cm 2 ; the temperature of the first calcination is 300-400 °C, and the time is 1-2 h.

[0009] Preferably, the carbon and nitrogen source includes urea, dicyandiamide or melamine; the temperature of the second calcination is 500-600 °C, and the time is 3-5 h.

[0010] Preferably, the cobalt source includes cobalt nitrate; the mass ratio of the carbon nitride to the cobalt source is 100:3.

[0011] Preferably, the temperature of the freezing is -80 °C, and the time is 6 h; the temperature of the third calcination is 500-600 °C, and the time is 1-2 h.

[0012] Preferably, the dispersant is a mixture of ethanol and PTFE emulsion; the dosage ratio of the single-atom cobalt-doped carbon nitride, ethanol and PTFE emulsion is 0.06 g:8 mL:140 μL; the density of the PTFE emulsion is 0.9 g / cm 3 .

[0013] Preferably, the temperature of the fourth calcination is 300-400 °C and the time is 1-2 h.

[0014] The present invention provides a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode prepared by the preparation method described in the above technical solution, including a carbon substrate and a single-atom cobalt-doped graphitic carbon nitride catalytic layer loaded on the carbon substrate.

[0015] The present invention provides an application of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode described in the above technical solution in electrocatalytic ozone degradation of new pollutants.

[0016] Compared with the prior art, the technical solution of the present application has the following beneficial effects: In the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode prepared by the present invention, oxygen-containing functional groups (such as carbonyl and carboxyl groups) in the carbon electrode make adjacent C atoms positively charged through O modification, promoting the combination of oxygen molecules and C active sites in a terminal adsorption mode, thus promoting the ORR to occur along the two-electron path and enhancing the selectivity of the two-electron ORR; at the same time, single-atom cobalt enhances the binding energy between the C active site and OOH* by regulating the adjacent C atomic environment, reduces the overpotential of the oxygen reduction reaction, and increases the two-electron ORR activity; therefore, under the action of current, the single-atom cobalt-doped carbon nitride modified carbon electrode can efficiently and stably convert O2 into H2O2. Therefore, the present invention co-regulates the two-electron ORR reaction through oxygen-containing functional groups and single-atom metal cobalt in the carbon electrode (carbon substrate, carbon nitride), so as to efficiently and stably electro-produce H2O2. Applying this electrode to the EP electrocatalytic ozone oxidation technology can achieve efficient removal of pollutants and effectively control the generation of disinfection by-products. On the one hand, in-situ generated H2O2 will react quickly with O3 to produce non-selective •OH. On the other hand, H2O2 can also reduce hypobromite (BrO – ) to bromide ion (Br – ), effectively inhibiting the conversion of Br – in water to BrO3 – . In addition, both single-atom cobalt and carbon nitride can catalyze the decomposition of ozone to produce •OH, thus significantly enhancing the removal of refractory pollutants (as shown in Figure 6 ).

[0017] The single-atom cobalt-doped graphitic carbon nitride modified carbon electrode of the present invention is applied to the EP electrocatalytic ozone oxidation system. In-situ generated H2O2, single-atom cobalt, and graphitic carbon nitride can all react with ozone to generate •OH, thus significantly enhancing the removal of refractory new pollutants. In addition, H2O2 can also reduce hypobromite (BrO – ) to bromide ion (Br – ), effectively inhibiting the conversion of Br – in water to BrO3 – and inhibiting the formation of disinfection by-products in water, providing technical support for the remediation of ECs and promoting the development of low-carbon, efficient, and green water treatment technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the preparation flow chart of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode of the present invention; Figure 2 are (a) X-ray diffraction pattern, (b) X-ray photoelectron spectroscopy C1s orbital, and (c) X-ray photoelectron spectroscopy Co2p orbital of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode prepared in Example 1; Figure 3 shows the influence of different carbon electrodes on the concentration of H2O2; Figure 4 is a comparison chart of the electrocatalytic ozone oxidation efficiency of different carbon electrodes for the removal of p-chlorobenzoic acid; Figure 5 shows the results of controlling the formation of bromate by the electrocatalytic ozone oxidation technology of different carbon electrodes; Figure 6 is the electrocatalytic ozone principle diagram of the single-atom cobalt-doped graphitic carbon nitride modified electrode of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] As Figure 1 shown, the present invention provides a preparation method of a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode, comprising the following steps: Mix carbon black, alcohol solvent, and PTFE emulsion, subject the obtained mixture to evaporation treatment and rolling in sequence, place the obtained carbon mud on both sides of a nickel mesh, and press to obtain an electrode sheet; Subject the electrode sheet to a first calcination to obtain a carbon substrate; Subject the carbon and nitrogen source to a second calcination to obtain graphitic carbon nitride; Mix the graphitic carbon nitride, cobalt source, and water, subject the obtained mixed solution to freezing and freeze-drying in sequence, and then perform a third calcination in a nitrogen atmosphere to obtain single-atom cobalt-doped graphitic carbon nitride; Mix the single-atom cobalt-doped graphitic carbon nitride with a dispersant, and compound the obtained dispersion with the carbon substrate to obtain a modified carbon electrode; After the fourth calcination of the modified carbon electrode, the steps of the above-mentioned compounding and the fourth calcination are sequentially repeated to obtain a single-atom cobalt-doped graphitic carbon nitride modified carbon electrode.

[0020] In the present invention, the alcohol solvent is preferably ethanol, and the density of the PTFE emulsion is preferably 0.9 g / cm 3 .

[0021] In the present invention, the dosage ratio of the carbon black, the alcohol solvent and the PTFE emulsion is preferably 6 g: 60 mL: 6 mL. The present invention utilizes the PTFE emulsion to play an adhesive role. The present invention preferably ultrasonically mixes the carbon black, the alcohol solvent and the PTFE emulsion for 40 min to obtain a mixture.

[0022] In the present invention, the temperature of the evaporation treatment is preferably 60-75 °C, more preferably 70 °C, and the time is preferably 10-20 min, more preferably 15 min. The present invention evaporates the alcohol solvent by heating with an electric furnace.

[0023] In the present invention, the thickness of the carbon mud is preferably 2 mm.

[0024] In the present invention, the mesh number of the nickel mesh is preferably 200 meshes; before use, the nickel mesh is preferably washed and dried in sequence; the loading amount of the carbon mud on the nickel mesh is preferably 0.03-0.05 g / cm 2 .

[0025] In the present invention, the pressure of the pressing is preferably 10-20 MPa, more preferably 15-20 MPa, and the time is preferably 1-2 min, more preferably 1-1.5 min.

[0026] In the present invention, the temperature of the first calcination is preferably 300-400 °C, more preferably 350-380 °C, and the time is preferably 1-2 h, more preferably 1 h.

[0027] In the present invention, the carbon and nitrogen source preferably includes urea, dicyandiamide or melamine.

[0028] In the present invention, the temperature of the second calcination is preferably 500-600 °C, more preferably 550 °C, and the time is preferably 3-5 h, more preferably 4 h.

[0029] In the present invention, the cobalt source preferably includes cobalt nitrate; the mass ratio of the graphitic carbon nitride to the cobalt source is preferably 100:3. The present invention has no special limitation on the dosage of the water, and it is only necessary to ensure sufficient mixing of the materials.

[0030] In the present invention, the temperature of freezing is preferably -80°C, and the time is preferably 6 h; the time of freeze-drying is preferably 48 h; the present invention has no requirement for the temperature of freeze-drying, and it can be carried out according to the conditions well-known in the art.

[0031] As another solution of the present invention, the freezing and freeze-drying are sequentially replaced by hydrothermal reaction and blow-drying; the temperature of the hydrothermal reaction is preferably 100 - 200°C, more preferably 180°C, and the time is preferably 6 - 10 h, more preferably 8 h; after the hydrothermal reaction is completed, it is cooled to room temperature, and the filter cake is filtered and blow-dried. The temperature of the blow-drying is preferably 60 - 80°C, more preferably 70°C, and the time is preferably 12 h.

[0032] In the present invention, the temperature of the third calcination is preferably 500 - 600°C, more preferably 550°C, and the time is preferably 1 - 2 h, more preferably 2 h.

[0033] In the present invention, single-atom cobalt is obtained through the freeze-drying process. Then, during the third calcination process, cobalt replaces part of the N on the carbon nitride, enabling cobalt to be anchored on the carbon nitride.

[0034] In the present invention, the dispersant is preferably a mixture of ethanol and PTFE emulsion; the dosage ratio of the single-atom cobalt-doped carbon nitride, ethanol, and PTFE emulsion is preferably 0.06 g:8 mL:140 μL; the density of the PTFE emulsion is preferably 0.9 g / cm 3 , where PTFE is used to bond the single-atom cobalt-doped carbon nitride on the surface of the carbon substrate.

[0035] In the present invention, the method of compounding the dispersion liquid with the carbon substrate is preferably spraying with an electrospray pen or ultrasonic impregnation; the caliber of the electrospray pen is preferably 0.5 mm.

[0036] In the present invention, the temperature of the fourth calcination is preferably 300 - 400°C, more preferably 350°C, and the time is preferably 1 - 2 h, more preferably 1 h.

[0037] After the fourth calcination is completed, the steps of compounding and the fourth calcination are sequentially repeated in the present invention to form a uniform layered single-atom cobalt-doped graphite-phase carbon nitride catalytic layer until the required loading amount is reached; the number of repetitions is preferably 2 - 3 times.

[0038] The present invention provides a single-atom cobalt-doped graphite-phase carbon nitride modified carbon electrode prepared by the preparation method described in the above technical solution, including a carbon substrate and a single-atom cobalt-doped graphite-phase carbon nitride catalytic layer loaded on the carbon substrate.

[0039] In the present invention, the loading amount of the single-atom cobalt-doped graphitic carbon nitride catalytic layer on the carbon substrate is preferably 0.008~0.012 g / cm 2 .

[0040] The single-atom cobalt-doped graphitic carbon nitride modified carbon electrode prepared by the present invention comprises a carbon electrode substrate and a cobalt-doped graphitic carbon nitride catalytic layer. The oxygen-containing functional groups of the carbon electrode and single-atom cobalt synergistically regulate the selectivity and activity of the two-electron oxygen reduction to achieve efficient and stable electrocatalytic generation of hydrogen peroxide from oxygen. Applying this carbon electrode to the electrocatalytic ozone oxidation technology, the in-situ generated H2O2 reacts with ozone to produce hydroxyl radicals (•OH), and single-atom cobalt and carbon nitride can also directly act on ozone to produce •OH, thereby significantly enhancing the removal of refractory new pollutants, which can provide a theoretical basis and technical support for the treatment of pollutants.

[0041] The present invention provides an application of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode described in the above technical solution in electrocatalytic ozone degradation of new pollutants.

[0042] The technical solution provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0043] In the embodiments, the reagents and materials used, if not otherwise specified, can be obtained by commercial purchase or prepared by conventional methods, and the instruments used can be obtained by commercial purchase. Embodiment

[0044] The preparation method of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode provided in this embodiment is as follows: 1) Cut a nickel mesh with a specification of 200 meshes, wash and dry it; 2) Weigh 6 g of carbon black in a beaker, add 60 mL of ethanol and 6 mL of PTFE emulsion (density 0.9 g / cm 3 ), and ultrasonically mix for 40 min to obtain a mixture; 3) After heating the mixture in step 2) with an electric furnace at 70 °C for 15 min to evaporate ethanol, roll it into a carbon paste with a thickness of 2 mm, place the obtained carbon paste on both sides of the nickel mesh, and the loading amount of the carbon paste on the nickel mesh is 0.04 g / cm 2 , and press for 1 min at 20 MPa to obtain an electrode sheet; 4) Place the electrode sheet prepared in step 3) in a muffle furnace and calcine it at a high temperature. The calcination temperature is 350 °C and the calcination time is 1 h to obtain a carbon substrate; 5) Weigh 10 g of urea, put it into a crucible, and calcine it at a high temperature in a muffle furnace. The calcination temperature is 550 °C and the calcination time is 4 h to obtain pale yellow carbon nitride; 6) Weigh 0.5 g of carbon nitride and 0.015 g of cobalt nitrate in a beaker, add 30 mL of ultrapure water, stir rapidly for 1 h, and ultrasonicate in an ice bath for 30 min; 7) Transfer the mixed solution obtained in step 6) to a refrigerator for freezing. The freezing temperature is -80 °C and the freezing time is 6 h. Then, freeze-dry for 48 h; 8) Place the powder obtained in step 7) in a porcelain boat, and perform high-temperature calcination in a tubular furnace under a nitrogen atmosphere. The calcination temperature is 550 °C and the calcination time is 2 h to obtain a single-atom cobalt-doped carbon nitride catalyst; 9) Disperse 0.06 g of the single-atom cobalt-doped carbon nitride catalyst prepared above in a mixed solution of 8 mL of ethanol and 140 μL of PTFE emulsion (density 0.9 g / cm 3 ) to obtain a catalyst mixed solution; use an electrospray pen with a caliber of 0.5 mm to uniformly spray the catalyst mixed solution onto the carbon substrate; 10) Place the modified carbon electrode prepared in step 9) in a muffle furnace and perform high-temperature calcination. The calcination temperature is 350 °C and the calcination time is 1 h; 11) Repeat steps 9) and 10) until the required loading amount is reached to obtain a single-atom cobalt-doped graphite-phase carbon nitride modified carbon electrode. The loading amount of the single-atom cobalt-doped carbon nitride catalyst is 0.01 g / cm 2 , denoted as C-PTFE / g-C3N4 / Co. Example

[0045] The difference from Example 1 is that: in step 5), 10 g of urea is replaced by 7 g of dicyandiamide, and other steps and parameters are the same as those in Example 1. Example

[0046] The difference from Example 1 is that: in step 5), 10 g of urea is replaced by 7 g of melamine, and other steps and parameters are the same as those in Example 1. Example

[0047] The difference from Example 1 is that: in step 7), freezing + freeze-drying is replaced by hydrothermal + forced-air drying. The hydrothermal reaction temperature is 180 °C and the time is 8 h. After the reaction ends and the temperature drops to room temperature, filter and perform forced-air drying on the filter cake at a temperature of 70 °C for 12 h, and other steps and parameters are the same as those in Example 1. Example

[0048] The difference from Example 1 is that: in step 9), electrospray pen spraying is replaced by ultrasonic impregnation. Immerse the carbon substrate in the catalyst mixed solution and ultrasonicate at room temperature for 1 h, and other steps and parameters are the same as those in Example 1.

[0049] Comparative Example 1 In Example 1, the carbon substrate is labeled as the traditional carbon electrode C-PTFE, and this electrode contains oxygen-containing functional groups such as -C=O and -COOH.

[0050] Comparative Example 2 The carbon nitride prepared in step 5) of Example 1 was used to prepare the catalyst mixture according to step 9), and then it was sprayed onto the carbon substrate by an electrospray pen, with a loading amount of 0.01 g / cm 2 , obtaining a carbon electrode, denoted as C-PTFE / g-C3N4.

[0051] Characterization and performance testing Figure 2 Figure for the characterization of the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode prepared in Example 1. (a) X-ray diffraction pattern, (b) X-ray photoelectron spectroscopy C1s orbital, (c) X-ray photoelectron spectroscopy Co2p orbital; from Figure 2 it can be seen that 26.6° and 44.7° are two characteristic peaks of carbon nitride. The single-atom cobalt-doped graphitic carbon nitride modified carbon electrode contains oxygen-containing functional groups such as -C-O, -C=O, and -COOH, and the existence forms of single-atom cobalt include Co 2+ and Co 3+ .

[0052] Figure 3 Figure for the influence of different carbon electrodes on the concentration of H2O2; reaction conditions: platinum anode = 2×2 cm 2 , carbon cathode (different carbon electrodes) = 2×3 cm 2 , current = 30 mA; from Figure 3 the comparison can be seen that, compared with the traditional carbon electrode C-PTFE and the C-PTFE / g-C3N4 electrode, the rate of H2O2 generation and the yield are faster and higher under the action of the C-PTFE / g-C3N4 / Co electrode prepared in Example 1. This indicates that the single-atom cobalt-doped graphitic carbon nitride modified carbon electrode of the present invention co-regulates the two-electron ORR reaction through oxygen-containing functional groups and single-atom metal cobalt.

[0053] Figure 4 Figure for the comparison of the electrocatalytic ozonation performance of different carbon electrodes for the removal of 4-chlorobenzoic acid; O3 represents the traditional ozonation process, reaction conditions: platinum anode = 2×2 cm 2 , carbon cathode (different carbon electrodes) = 2×3 cm 2 , current = 30 mA, ozone dosage = 1.0 mgO3 / mgDOC; from Figure 4 it can be seen that when the modified carbon electrode of the present invention is applied to the EP electrocatalytic ozonation system, the removal efficiency of 4-chlorobenzoic acid is significantly better than that of the traditional carbon electrode.

[0054] Figure 5Results of controlling bromate formation by electrocatalytic ozonation technology using different carbon electrodes; Reaction conditions: platinum anode = 2×2 cm 2 , carbon cathode = 2×3 cm 2 , current = 30 mA, ozone dosage = 1.0 mgO3 / mgDOC; It can be seen from Figure 5 that the modified carbon electrode of the present invention is applied to the EP electrocatalytic ozonation system, and the concentration of bromate in water is significantly reduced.

[0055] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a single-atom cobalt-doped graphite-phase carbon nitride-modified carbon electrode, characterized in that: The following steps are involved: Mixing carbon black, alcohol solvent and PTFE emulsion, evaporating and rolling the obtained mixture in sequence, placing the obtained carbon mud on both sides of the nickel mesh, and pressing to obtain an electrode sheet; The electrode sheet is subjected to a first calcination to obtain a carbon substrate; The carbon-nitrogen source is subjected to a second calcination to obtain carbon nitride; The carbon nitride, the cobalt source and water are mixed, the obtained mixed solution is sequentially frozen and freeze-dried, and then a third calcination is performed in a nitrogen atmosphere to obtain single-atom cobalt-doped carbon nitride; The single-atom cobalt-doped carbon nitride is mixed with a dispersant, and the obtained dispersion is compounded with a carbon substrate to obtain a modified carbon electrode; After the modified carbon electrode is calcined for the fourth time, the steps of compounding and calcining for the fourth time are repeated in sequence to obtain a single-atom cobalt-doped graphite-phase carbon nitride modified carbon electrode.

2. The preparation method according to claim 1, characterized in that: The freezing and freeze drying are replaced by hydrothermal reaction and forced air drying in sequence; the temperature of the hydrothermal reaction is 100-200° C. and the time is 6-10 h.

3. The preparation method according to claim 1 or 2, characterized in that: The mesh number of the nickel mesh is 200 mesh; the loading amount of the carbon mud on the nickel mesh is 0.03-0.05 g / cm 2 ; The temperature of the first calcination is 300~400 ℃ and the time is 1~2h.

4. The preparation method according to claim 1 or 2, characterized in that: The carbon and nitrogen source includes urea, dicyandiamide or melamine; the temperature of the second calcination is 500-600°C and the time is 3-5 hours.

5. The preparation method according to claim 1 or 2, characterized in that: The cobalt source includes cobalt nitrate; the mass ratio of the carbon nitride to the cobalt source is 100:

3.

6. The preparation method according to claim 1 or 2, characterized in that: The freezing temperature is -80°C for 6 hours; the third calcination temperature is 500-600°C for 1-2 hours.

7. The preparation method according to claim 1 or 2, characterized in that: The dispersant is a mixture of ethanol and PTFE emulsion; the dosage ratio of the single-atom cobalt-doped carbon nitride, ethanol and PTFE emulsion is 0.06 g:8 mL:140 μL; the density of the PTFE emulsion is 0.9 g / cm 3 .

8. The preparation method according to claim 1 or 2, characterized in that: The fourth calcination is performed at a temperature of 300-400° C. and for a time of 1-2 h.

9. The single-atom cobalt-doped graphite-phase carbon nitride-modified carbon electrode prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The invention comprises a carbon substrate and a single-atom cobalt-doped graphite-phase carbon nitride catalyst layer supported on the carbon substrate.

10. Use of the single-atom cobalt-doped graphite-phase carbon nitride-modified carbon electrode according to claim 9 in electrocatalytic ozone degradation of new pollutants.

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