Electro-catalysis water treatment system capable of realizing self-supply

Abstract

The invention discloses an electrocatalytic water treatment system capable of realizing self-supply, which comprises an anode, a cathode, a reference electrode and an electrolyte injected into an electrolytic bath, the anode is a Ti / IrO2 material, the cathode is a CoNP-N-C material, and the electrolyte is one of a sodium sulfate aqueous solution, sodium carbonate and sodium bicarbonate; the anode is connected with the cathode through a lead and external voltage, and the reference electrode is in contact with the electrolyte through a salt bridge; according to the system, through a cathode and anode coupling mechanism, O2 generated by an anode forms an oxygen saturated solution in an electrolyte, the diffusion resistance from O2 to a cathode reaction interface is reduced, and then the problems of high energy loss and low O2 utilization rate caused by the fact that air or O2 needs to be additionally pumped into the system due to low O2 solubility and slow diffusion of O2 in gas-liquid two phases are solved. Besides, under the condition of no additional air / O2, the system only needs lower potential, and the pollutants can be efficiently removed in a wider pH range.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis and relates to an electrocatalytic water treatment system capable of self - supply. Background Art

[0002] Electrochemical advanced oxidation processes (EAOPs) have the characteristics of strong versatility, simple operation, high degree of automation, and strong environmental compatibility, and have received extensive attention in recent years. The electro - Fenton technology occurring at the electrocatalytic cathode is one of the most promising technologies for treating organic wastewater. Its basic principle is that Fe 2+ reacts with H2O2 to generate highly oxidizing · OH, thereby achieving the purpose of degrading organic pollutants. H2O2 has poor self - stability and often poses great risks during storage and transportation. Moreover, the pH range in which Fe 2+ exists is relatively small, and iron sludge is often generated during the electrocatalytic process, causing secondary pollution. The Fenton - like reaction uses transition metal ions (copper ions, cobalt ions, manganese ions) or supported metal materials to replace Fe 2+ . These materials can also reduce O2 to H2O2 through the oxygen reduction reaction, and then reduce H2O2 to highly oxidizing · OH, 1 O2 and other highly reactive oxygen species. However, due to the low solubility and slow diffusion rate of oxygen at normal temperature and pressure, a large amount of air or oxygen often needs to be introduced into the reaction system during the water treatment process to ensure sufficient O2 supply. But due to the low utilization rate of O2, a large amount of energy is consumed.

[0003] During the electrocatalytic process, some oxidation reactions occur at the anode. Among them, the water oxidation reaction includes the reaction of generating · OH with 1 electron, generating H2O2 with 2 electrons, and generating O2 with 4 electrons. O2 and H2O2 are both key species in the electro - Fenton reaction. Therefore, coupling a cathode material with oxygen reduction activity and an anode material with water oxidation activity, and regulating the anode reaction type by adjusting the reaction conditions, is expected to solve the rate - limiting step of the generation and activation of H2O2 during the oxygen reduction process, realize the coupling of oxygen reduction and different water oxidation reactions, and provide O2 or H2O2 for the cathode oxygen reduction reaction to achieve efficient degradation of organic pollutants in wastewater. Summary of the Invention

[0004] In view of the above - mentioned technical problems, the present invention discloses an electrocatalytic water treatment system capable of self - supply, including an anode, a cathode, a reference electrode, and an electrolyte injected into the electrolytic cell. The anode is made of Ti / IrO2 material, and the cathode is Co NP-N-C material, and the electrolyte is one of aqueous sodium sulfate solution, sodium carbonate, and sodium bicarbonate; the anode is connected to the cathode through a wire under an external voltage, and the reference electrode is in contact with the electrolyte through a salt bridge; through the anode-cathode coupling mechanism, the O2 generated at the anode forms an oxygen-saturated solution in the electrolyte, reducing the diffusion resistance of O2 to the cathode reaction interface, thereby solving the problems of high energy consumption and low O2 utilization rate caused by the low solubility and slow diffusion of O2 in the gas-liquid two-phase, which requires additional pumping of air or O2 into the system. In addition, under the condition of no external air / O2, the system only requires a relatively low potential to achieve efficient removal of pollutants in a wide pH range.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An electrocatalytic water treatment system capable of realizing self-supply, including an anode, a cathode, a reference electrode, and an electrolyte injected into an electrolytic cell. The anode is made of Ti / IrO2 material, and the cathode is Co NP -N-C material, and the electrolyte injected into the electrolytic cell is one of aqueous sodium sulfate solution, sodium carbonate, and sodium bicarbonate; the anode is connected to the cathode through a wire under an external voltage; the reference electrode is in contact with the electrolyte through a salt bridge.

[0007] The cathode Co NP -N-C material should be loaded on a carbon material substrate such as carbon felt, carbon cloth, carbon paper or carbon fiber during use, and the loading amount is 1-5 mg·cm -2 .

[0008] As a limitation of the present invention, the electrolysis potential of the anode is 2.15-2.45 V, and the electrolysis potential of the cathode is -0.15-0.45 V.

[0009] As another limitation of the present invention, the concentration of the electrolyte is 0.05-1 M.

[0010] As a third limitation of the present invention, the preparation method of the cathode Co NP -N-C material is carried out in the following steps in sequence:

[0011] (1) Dissolve 0.873 g of cobalt nitrate hexahydrate in 30 mL of methanol to form a cobalt nitrate hexahydrate-methanol solution, dissolve 0.985 g of dimethylimidazole in 10 mL of methanol to form a dimethylimidazole-methanol solution, then pour the dimethylimidazole-methanol solution into the cobalt nitrate hexahydrate-methanol solution, stir at room temperature for 30 min, stand for 24 h, and wash with ethanol to obtain ZIF-67;

[0012] (2) Place ZIF-67 in a tubular furnace and calcine it under an inert gas atmosphere to obtain Co NP-N-C material.

[0013] As Co NP -N-C material preparation method is defined as follows. In step (2), the calcination temperature is 600 - 1000 °C, the heating rate is 5 °C / min, and the time is 3 - 6 h.

[0014] The present invention also has a limitation, characterized in that in step (2), the cathode Co NP -N-C material has a morphology of carbon-coated Co and N co-doped material.

[0015] In the present invention, the cathode material Co NP -N-C will generate a large number of oxygen defects during the calcination process, which is crucial for the adsorption and reduction of oxygen in the oxygen reduction process. Specifically: when heating at a heating rate of 5 °C / min during calcination, it is necessary to maintain a stable decomposition process and good crystal structure of ZIF-67 at this time. During the calcination process, the thermal decomposition and removal of organic ligands will occur, thereby generating a stable carbon skeleton structure. If the heating rate is less than 5 °C / min, the thermal decomposition of organic ligands will be too slow, resulting in over-sintering of the material. If the heating rate is greater than 5 °C / min, the thermal decomposition of organic ligands will be too fast, destroying the pore structure of the material; at the calcination temperature, the complete carbonization of organic ligands occurs, so that Co nanoparticles are evenly dispersed, forming an N-doped carbon skeleton structure. If the calcination temperature is less than 600 °C, partial decomposition of organic ligands will occur, resulting in incomplete carbonization of the material. If the calcination temperature is greater than 1000 °C, a highly graphitized carbon skeleton will be formed in the material, leading to high agglomeration of metal Co nanoparticles and loss of N doping; after holding for a period of time, highly dispersed Co and N can be formed on the surface of the material.

[0016] Co NP -N-C material has excellent oxygen reduction performance at -0.15 - 0.45 V (vs reversible hydrogen electrode). At the same time, due to the coupling effect between the cathode and anode, the theoretical voltage difference of the system is 0.55 V (1.23 - 0.68 V). The anode can also have excellent water oxidation ability at the corresponding anode potential. Co NP -N-C material generates a large number of oxygen defects during the calcination process. These oxygen vacancies can promote the combination of the cathode material and O2 and the generation of H2O2. In addition, Co NP -N-C material is coupled with a Ti / IrO2 anode as the cathode. The Ti / IrO2 shows excellent oxygen evolution performance. The oxygen generated by the Ti / IrO2 anode increases the O2 concentration in the electrolyte, overcoming the limitations of the low solubility and low diffusion rate of O2. And due to the NP abundant oxygen vacancies of CoNP -N-C materials, as the cathode materials of a self-supplying electrocatalytic water treatment system, can make full use of the O2 generated at the anode to achieve the O2 self-supply of the electrocatalytic water treatment system.

[0017] In Co NP -N-C cathode and Ti / IrO2 anode coupled electrocatalytic treatment system, due to the coupling effect of the anode and cathode, when the Co NP -N-C cathode has a good cathode potential, the Ti / IrO2 anode can have excellent oxygen evolution performance. The Ti / IrO2 anode undergoes a 4-electron oxygen evolution reaction to produce O2, and the O2 dissolves in the electrolyte, increasing the O2 concentration in the electrolyte. The Co NP -N-C cathode has abundant oxygen vacancies, which can effectively adsorb O2 in the solution and reduce oxygen to H2O2. Since the Co NP -N-C Co nanoparticles are uniformly dispersed in the carbon layer, and the cobalt (Co) central metal atoms can form valence bond structures with nearby atoms. This structure can promote the charge transfer and charge coupling between the central metal and the ligand sites. Under the action of the Co NP -N-C material, H2O2 is in-situ activated into 1 O2 and ·OH, thus having high-efficient electrocatalytic water treatment ability.

[0018] As a whole, the above technical solutions of the present invention are closely related and interact with each other, jointly determining the morphological characteristics and performance of the product.

[0019] The above technical solutions have the following advantages or beneficial effects:

[0020] 1. The present invention utilizes the coupling of the anode and cathode to ensure the O2 supply during the oxygen reduction process at the cathode, without the need to introduce air or O2 into the reaction system from the outside, reducing energy consumption.

[0021] 2. The present invention realizes the synchronous generation of H2O2 at the anode and cathode through the electrolysis system and by controlling the anode and cathode potentials, improving the cumulative concentration and generation rate of H2O2.

[0022] 3. The present invention uses Co NP -N-C materials loaded on a carbon substrate as the cathode material, which can achieve the efficient degradation of pollutants in a wide pH range at a cathode potential of -0.15V - 0.45V.

[0023] Next, the technical solutions of the present invention will be further described in detail in conjunction with the accompanying drawings of the specification and the specific embodiments. Description of the Drawings

[0024] Figure 1Schematic diagram of degradation of the self - supply electro - catalytic water treatment system provided in Embodiments 1 - 3 of the present invention;

[0025] Figure 2 Co prepared in Embodiment 1 of the present invention NP XRD pattern of - N - C;

[0026] Figure 3 Co prepared in Embodiment 1 of the present invention NP Scanning electron microscope image and mapping image of Co - N - C, where: (a) is the scanning electron microscope image, (b) is the transmission electron microscope image, (c) is the lattice fringe spacing image, and (d) is the mapping image;

[0027] Figure 4 Co prepared in Embodiment 1 of the present invention NP Raman test pattern of - N - C;

[0028] Figure 5 Removal effect diagram of sulfamethazine by the self - supply electro - catalytic water treatment system provided in Embodiments 1 - 3 of the present invention;

[0029] Figure 6 Removal rate diagram of sulfamethazine and electrolyte dissolved oxygen diagram of the self - supply electro - catalytic water treatment system provided in Embodiments 1 - 3 of the present invention;

[0030] Figure 7 Removal effect and dissolved oxygen diagram of sulfamethazine by the electro - catalytic water treatment system provided in Comparative Example 1 of the present invention;

[0031] Figure 8 Removal effect and dissolved oxygen diagram of sulfamethazine by the electro - catalytic water treatment system provided in Comparative Example 2 of the present invention;

[0032] Figure 9 Electrochemical performance diagram of the anode material Ti / IrO₂ used in Embodiments 1 - 3 of the present invention;

[0033] Figure 10 Removal effect diagram of different pollutants by the electro - catalytic water treatment system provided in Embodiment 1 of the present invention;

[0034] Figure 11 Removal effect diagram of sulfamethazine by the electro - catalytic water treatment system provided in Embodiment 1 of the present invention under the condition of pH 0 - 11;

[0035] Figure 12 Stability performance diagram of the self - supply electro - catalytic water treatment system provided in Embodiment 1 of the present invention. Detailed implementation manners

[0036] The following embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected 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 efforts belong to the protection scope of the present invention.

[0037] In the present invention, unless otherwise specified, all devices, raw materials, etc. can be purchased from the market or are commonly used in this industry. The methods in the following embodiments are conventional methods in this field unless otherwise specified.

[0038] Example 1

[0039] This embodiment provides an electrocatalytic water treatment system capable of self-supply, and its preparation process and steps are as follows:

[0040] (1) Preparation of cathode material

[0041] (1) Dissolve 0.873 g of cobalt nitrate hexahydrate in 30 mL of methanol, and dissolve 0.985 g of dimethylimidazole in 10 mL of methanol. Then pour the dimethylimidazole-methanol solution into the cobalt nitrate hexahydrate-methanol solution, stir at room temperature for 30 min, stand for 24 h, and wash with ethanol to obtain ZIF-67.

[0042] (2) Place ZIF-67 in a tubular furnace, and heat it from room temperature to 900 °C at a heating rate of 5 °C / min under an inert gas atmosphere, and keep it at this temperature for 5 h to obtain the cathode material Co NP -N-C.

[0043] (2) Preparation of electrocatalytic water treatment system

[0044] In this embodiment, Ti / IrO₂ is used as the anode, the prepared Co NP -N-C material is used as the cathode, and Ag / AgCl is used as the reference electrode. Among them, Co NP -N-C is loaded on a 2×2 cm -2 carbon cloth, and the loading amount is 3.75 mg·cm -2 . The electrolyte is a 50 mL, 50 mM Na₂SO₄ solution with pH = 7. Ti / IrO₂ is connected to Co NP -N-C through a wire by an external voltage, and at the same time forms a closed loop through the electrolyte; control the anode potential to be 2.35 V and the cathode potential to be 0.05 V, and do not expose air or O₂ into the system.

[0045] Example 2

[0046] This embodiment provides an electrocatalytic water treatment system capable of self-supply, and its preparation process and steps are as follows:

[0047] (I) Preparation of cathode material

[0048] (1) Dissolve 0.873 g of cobalt nitrate hexahydrate in 30 mL of methanol, and dissolve 0.985 g of dimethylimidazole in 10 mL of methanol. Then pour the dimethylimidazole-methanol solution into the cobalt nitrate hexahydrate-methanol solution, stir at room temperature for 30 min, stand for 24 h, and wash with ethanol to obtain ZIF-67;

[0049] (2) Place ZIF-67 in a tubular furnace, and heat it from room temperature to 600 °C at a heating rate of 5 °C / min under an inert gas atmosphere, and keep it at this temperature for 6 h to obtain the cathode material Co NP -N-C.

[0050] (II) Preparation of electrocatalytic water treatment system

[0051] In this embodiment, Ti / IrO2 is used as the anode, the prepared Co NP -N-C material is used as the cathode, and Ag / AgCl is used as the reference electrode. Among them, Co NP -N-C is loaded on a carbon cloth of 2×2 cm -2 , and the loading amount is 1 mg·cm -2 . The electrolyte is a 50 mL, 70 mM Na2SO4 solution with pH = 7. Ti / IrO2 is connected to Co NP -N-C through a wire under an external voltage, and at the same time forms a closed loop through the electrolyte. Control the anode potential to be 2.15 V and the cathode potential to be 0.45 V, and do not introduce air or O2 into the system.

[0052] Example 3

[0053] This embodiment provides an electrocatalytic water treatment system capable of self-supply, and its preparation process and steps are as follows:

[0054] (I) Preparation of cathode material

[0055] (1) Dissolve 0.873 g of cobalt nitrate hexahydrate in 30 mL of methanol, and dissolve 0.985 g of dimethylimidazole in 10 mL of methanol. Then pour the dimethylimidazole-methanol solution into the cobalt nitrate hexahydrate-methanol solution, stir at room temperature for 30 min, stand for 24 h, and wash with ethanol to obtain ZIF-67;

[0056] (2) Place ZIF-67 in a tubular furnace, and heat it from room temperature to 1000 °C at a heating rate of 5 °C / min under an inert gas atmosphere, and keep it at this temperature for 3 h to obtain the cathode material Co NP -N-C.

[0057] (II) Preparation of electrocatalytic water treatment system

[0058] In this example, Ti / IrO2 is used as the anode, Co NP -N-C as the cathode, and Ag / AgCl as the reference electrode, where Co NP -N-C is loaded on a 2×2 cm -2 carbon cloth with a loading amount of 5 mg·cm -2 . The electrolyte is a 50 mL, 1M Na2SO4 solution with pH = 7. Ti / IrO2 is connected to Co NP -N-C through a wire via an external voltage, and at the same time forms a closed loop through the electrolyte. The anode potential is controlled at 2.45 V, and the cathode potential is -0.15 V. No air or O2 is introduced into the system.

[0059] Comparative example

[0060] In order to explore the influence of different parameters in the preparation process of the present invention on the performance of the products of the present invention, the following comparative experiments were specifically carried out. The following comparative examples respectively provide different electrocatalytic hydrolysis systems, specifically as follows:

[0061] Comparative example 1

[0062] This comparative example provides an electrocatalytic hydrolysis system. The preparation process is similar to that of Example 1, except that the non-aeration condition is changed to O2 saturation or N2 saturation.

[0063] Comparative example 2

[0064] This comparative example uses pure carbon cloth (CC) as the cathode material. The preparation process is similar to that of Example 1, except that the cathode Co NP -N-C material is replaced with pure CC without loading other materials.

[0065] Performance test

[0066] The above Examples 1-3 and the comparative examples were subjected to performance tests, and the specific results are as follows.

[0067] As Figure 1 , the degradation schematic diagram of the electrocatalytic water treatment system capable of realizing self-supply provided by Examples 1-3 of the present invention is shown. It can be seen from the figure that Ti / IrO2 is used as the anode, and H2O molecules in the electrolyte undergo a 4-electron oxygen evolution reaction on the surface of the Ti / IrO2 anode to generate O2. O2 diffuses to the Co NP -N-C cathode surface to undergo an oxygen reduction reaction, generating · OH, 1 O2 and then degrading pollutants.

[0068] AsFigure 2 , the XRD pattern of Co NP -N-C prepared in Example 1 of the present invention. It can be seen from the figure that three peaks are shown at 44.22°, 51.52°, and 75.85°, which are consistent with the characteristic peaks of metallic Co, indicating that Co 2+ is reduced to metallic Co during the carbonization process. The peak at 20.5° corresponds to the amorphous carbon peak, indicating the formation of the carbon skeleton; through the scanning electron microscope images and mapping images [as shown in Figure 3 (a)-(d) in it], it can be seen that nitrogen atoms are uniformly distributed throughout the carbon layer, and cobalt nanoparticles and oxygen are embedded in the nitrogen-doped carbon layer. This evidence confirms the successful preparation of the Co, N co-doped carbon-based material; in addition, through Raman testing (as shown in Figure 4 ), it can also be seen that Co NP -N-C has a good degree of graphitization, and the characteristic peak of oxygen vacancies is observed at 600 cm -1 .

[0069] As shown in Figure 5 , it is the removal effect diagram of sulfamethazine by the self-powered electrocatalytic water treatment system provided in Examples 1-3 of the present invention. It can be seen from the figure that as the cathode potential increases, the removal effect of sulfamethazine gradually increases, from 72% to 98%.

[0070] As shown in Figure 6 , it is the removal rate diagram of sulfamethazine and the electrolyte dissolved oxygen diagram of the self-powered electrocatalytic water treatment system provided in Examples 1-3 of the present invention. It can be seen from the figure that at 0.05V and -0.15V Co NP -N-C has a higher removal rate of sulfamethazine, and at the same time, the oxygen evolution amount of the Ti / IrO2 anode increases.

[0071] As shown in Figure 7 , it is the removal effect and dissolved oxygen diagram of sulfamethazine by the electrocatalytic water treatment system provided in Comparative Example 1. It can be seen from the figure that in the case of O2 saturation or N2 saturation, the removal rate of sulfamethazine can reach 90% and 70%, which indicates that even in the case of O2 saturation or N2 saturation, the removal rate of sulfamethazine by this system is still very high. This is because under the condition of O2 saturation, sufficient O2 can be provided for the oxygen reduction reaction at the cathode. However, when O2 reaches saturation, to a certain extent, it inhibits the oxygen evolution reaction of the Ti / IrO2 anode, resulting in a reduction in the coupling performance of the system and a decrease in the removal effect of sulfamethazine compared to the case without O2 / air supply; under the condition of N2 saturation, the oxygen evolution reaction of Ti / IrO2 will be further inhibited, resulting in a reduction in the removal effect of sulfamethazine to 70%.

[0072] As shown in Figure 8, The removal effect of sulfamethazine and dissolved oxygen of the electrocatalytic water treatment system provided in Comparative Example 2. It can be seen from the figure that when CC is used as the electrocatalytic cathode, the removal rate of sulfamethazine is only 47%, and the dissolved oxygen during the electrocatalytic process remains constant and shows no obvious increase, further proving that Co NP -N-C cathode and Ti / IrO2 anode coupled electrocatalytic treatment system can not only achieve self-supply of oxygen during the electrocatalytic process, but also promote the oxygen reduction performance of the Co NP -N-C cathode and the oxygen evolution performance of the Ti / IrO2 anode at the same time.

[0073] The LSV test was carried out on the anode material Ti / IrO2 used in Examples 1-3 of the present invention under the conditions of O2 self-supply and O2 supply using an electrochemical workstation. The results are as Figure 9 shown. It can be seen from the figure that under the condition of O2 self-supply, Ti / IrO2 has a lower overpotential and Tafel slope, indicating that it has good oxygen evolution performance.

[0074] As Figure 10 , the removal effect diagram of different pollutants by the electrocatalytic water treatment system provided in Example 1 of the present invention. It can be seen from the figure that the removal rates of tetracycline, rhodamine B, methylene blue and 2,4-dichlorophenol by this system can all reach more than 80%, indicating that this system is applicable to the removal of various pollutants.

[0075] As Figure 11 , the removal effect diagram of sulfamethazine by the electrocatalytic water treatment system provided in Example 1 of the present invention under the condition of pH 0-11. It can be seen from the figure that even under strong alkaline conditions, the removal of sulfamethazine can still reach 80%, indicating that this system is applicable to a wide pH range.

[0076] The chronopotentiometry measurement was carried out on the degradation system provided in Example 1 of the present invention at a current density of 7.5 mA·cm -2 for 24 hours. The results are as Figure 12 shown. When the Co NP -N-C is recycled 10 times, the removal of sulfamethazine can still reach 65%. And during the chronopotentiometry test, the cathode and anode potentials remain stable, indicating that the self-supply electrocatalytic water treatment system provided by the present invention has stability and can be reused.

[0077] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An electrocatalytic water treatment system capable of realizing self-supply, comprising an anode, a cathode, a reference electrode, and an electrolyte injected into an electrolytic cell, characterized in that, The anode is made of Ti / IrO2 material, and the cathode is Co NP -N-C material. The reference electrode is an Ag / AgCl electrode or a saturated calomel electrode. The electrolyte injected into the electrolytic cell is one of sodium sulfate solution, sodium carbonate solution, and sodium bicarbonate solution. The anode is connected to the cathode through a wire via an external voltage; The reference electrode is in contact with the electrolyte through a salt bridge.

2. The electrocatalytic water treatment system capable of self-supply according to claim 1, wherein The electrolysis potential of the anode is 2.15 - 2.45 V, and the electrolysis potential of the cathode is -0.15 - 0.45 V.

3. The electrocatalytic water treatment system capable of self-supply according to claim 1, wherein The concentration of the electrolyte is 0.05 - 1 M.

4. A self-supplying electrocatalytic water treatment system according to claim 1, characterized in that, The cathode Co NP -N-C material preparation method is carried out in sequence according to the following steps: (1) Dissolve 0.873 g of cobalt nitrate hexahydrate in 30 mL of methanol to form a cobalt nitrate hexahydrate - methanol solution, and dissolve 0.985 g of dimethylimidazole in 10 mL of methanol to form a dimethylimidazole - methanol solution. Then pour the dimethylimidazole - methanol solution into the cobalt nitrate hexahydrate - methanol solution, stir at room temperature for 30 min, stand for 24 h, and obtain ZIF - 67 after washing with ethanol. (2) Place ZIF-67 in a tubular furnace and calcine it under an inert gas atmosphere to obtain Co NP -N-C material.

5. The electrocatalytic water treatment system capable of self-supply according to claim 4, wherein In step (2), the calcination temperature is 600 - 1000 °C, the heating rate is 5 °C / min, and the time is 3 - 6 h.

6. The electrocatalytic water treatment system capable of self-supply according to claim 4, wherein In step (2), the prepared Co NP -N-C material is a carbon-coated Co and N co-doped material.

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