High-efficiency carbon-based catalytic electrode and preparation method and application thereof

Abstract

The application discloses a kind of high-efficiency carbon-based catalytic electrode and its preparation method and application, electrode preparation method includes the following steps: carbon nanotube, polyvinylpyrrolidone and copper chloride are dissolved in organic solvent, stirring is made to be mixed evenly and heated to make solvent volatilize, then the mixture is heat-treated in nitrogen atmosphere by high-temperature pyrolysis method, obtain carbon-based single-atom catalyst precursor, then it is loaded on carbon felt using adhesive, obtain high-efficiency carbon-based catalytic electrode.The prepared electrode is used for electrochemical reaction and can efficiently remove dye, phenolic, antibiotic and other refractory organic pollutants in water, and the reaction mechanism is electron transfer path without additional free radicals.Especially, when the carbon-based electrode is used to remove organic pollutants in water, the removal effect is less affected by coexisting inorganic ions in water, easy to separate and recover, and the metal ion leaching is less, which shows excellent catalytic activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysis technology, in particular to a high-efficiency carbon-based catalytic electrode and a preparation method and application thereof. BACKGROUND

[0002] In recent decades, a variety of new chemicals have been designed and produced and widely used to meet the needs of rapid urbanization and industrialization of modern society. These chemicals may contaminate aquatic systems during production, use or disposal. At present, a variety of new chemicals have been detected in aquatic systems (rivers, lakes and oceans, etc.). However, some organic compounds (such as antibiotics, microplastics, artificial sweeteners, etc.) pose a potential threat to biological populations and human health due to their non-biodegradability, persistence and toxicity in nature. Physical treatment methods, such as membrane filtration, can remove such substances through steric exclusion, but this method cannot achieve their harmless degradation. Biological treatment methods can use microorganisms to oxidize and decompose organic matter in wastewater and convert it into stable and harmless substances. However, such methods are usually inefficient, complex to operate and unstable in effect. Chemical treatment methods are wastewater treatment methods that separate and remove organic pollutants in wastewater through chemical reactions and mass transfer and convert them into harmless substances. Among them, electrochemical method is one of the most effective wastewater treatment technologies, which can not only induce the production of highly active oxidative species (free radicals, etc.) by catalytic electrode to directly degrade or mineralize refractory and toxic organic pollutants into harmless products, but also can degrade organic matter through non-radical pathways such as electron transfer and singlet oxygen. The design of the catalytic electrode in the electrochemical method avoids the addition of powder catalysts, greatly solving the problem of difficult recovery of powder catalysts.

[0003] However, the water treatment process based on the free radical mechanism is easily disturbed by the coexisting inorganic ions in water, and cannot selectively remove organic pollutants in water. Therefore, the water treatment process based on the electron transfer pathway has gradually attracted attention. This pathway achieves rapid degradation of pollutants through directional migration of pollutant electrons, has little interference from coexisting substances in water and is highly selective for electron-rich pollutants, and is one of the effective means to address the problem of organic pollution in complex water quality.

[0004] In addition, in the existing catalytic electrode system, the reaction efficiency still has a lot of room for improvement due to the influence of the properties of the electrode itself. For example, the electrode material itself may have defects, such as lattice defects, dislocations, vacancies, etc. These defects will affect the electron transport and ion diffusion of the material, thereby affecting the rate and selectivity of the catalytic reaction. Carbon-based single-atom catalytic electrodes have attracted attention in the field of electrochemical water treatment due to their high metal atom utilization and high efficiency. Therefore, it is necessary to develop an efficient carbon-based single-atom catalytic electrode based on the electron transfer mechanism, which can improve the electrode activity and reaction rate while overcoming the defects of traditional catalytic electrodes, efficiently remove difficult-to-degrade organic pollutants in water, expand the application of carbon-based catalytic electrodes in sewage treatment, and achieve the goal of green and pollution-free protection of the water environment. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-efficiency carbon-based catalytic electrode and its preparation method and application. The electrode prepared by the present invention can be used for electrochemical oxidation to efficiently remove difficult-to-degrade organic pollutants in water, thereby achieving the purpose of efficient and green protection of the water environment.

[0006] The technical solution adopted by the present invention is: a method for preparing a high-efficiency carbon-based catalytic electrode, wherein the electrode is based on carbon felt, and the carbon nanotube single-atom catalyst precursor is stably and uniformly dispersed on the electrode surface through adhesion.

[0007] A method for preparing a high-efficiency carbon-based catalytic electrode comprises the following steps:

[0008] 1) dissolving carbon nanotubes (CNTs), polyvinyl pyrrolidone (PVP) and copper metal salt (such as copper chloride CuCl2·2H2O) in ethanol, stirring to mix them evenly and heating to evaporate the ethanol;

[0009] 2) After the ethanol is completely evaporated, the mixture is placed in a tube furnace and heat-treated under a nitrogen atmosphere. After cooling, the mixture is treated with a dilute acid solution, and then washed with deionized water until the washing water is neutral. After drying, the mixture is obtained as a single-atom catalyst precursor based on carbon nanotubes, Cu-CNTs.

[0010] 3) The carbon nanotube single-atom catalyst precursor is dispersed in a solvent with a volume ratio of water to ethanol of 1:1, and an adhesive is added. Ultrasonication is performed to uniformly disperse the precursor, and the precursor is coated on a conductive graphite felt and dried.

[0011] 4) The obtained electrode can not only be used in the field of sewage treatment to degrade refractory organic pollutants in water, but can also be used for other electrocatalytic reactions.

[0012] Furthermore, the copper metal salt in step 1) is copper chloride, copper nitrate, or copper sulfate. The ratio of the copper metal salt (e.g., copper chloride CuCl2·2H2O) to carbon nanotubes (CNTs) is 1:12-5:12, and most preferably, the mass ratio of carbon nanotubes to copper metal salt is 6:1. The mass ratio of the copper metal salt (e.g., copper chloride CuCl2·2H2O) to polyvinyl pyrrolidone (PVP) is 1:24-5:24. Most preferably, the mass ratio of the copper metal salt to polyvinyl pyrrolidone is 1:12.

[0013] Furthermore, in step 1), the mixing and heating temperature is 60-80 degrees Celsius, and after the ethanol is completely volatilized, the remaining mixture is collected.

[0014] Furthermore, in step 2), the pyrolysis temperature is 600-900 degrees Celsius, preferably 900 degrees Celsius, and the heating rate is 2-10 degrees Celsius / minute, preferably 3 degrees Celsius / minute.

[0015] Furthermore, in step 2), the pyrolysis time is 1.5-4 hours, preferably 2 hours.

[0016] Furthermore, in step 2), the dilute acid solution is 0.5-1.5 mol / L dilute sulfuric acid or 0.5-1.5 mol / L dilute hydrochloric acid, and most preferably, the dilute acid solution is 1 mol / L dilute sulfuric acid or 1 mol / L dilute hydrochloric acid. The washing time is 2-4 hours, and then the washing is centrifuged with deionized water until the pH of the washing solution is 6-8.

[0017] Furthermore, in step 3), the adhesive is Nafion 117 solution, chitosan or resin (such as conductive adhesive), preferably Nafion 117 solution.

[0018] Furthermore, in step 3), the coating amount is 0-5 mg / m 2 , preferably 1 mg / m 2 .

[0019] Furthermore, in step 3), the carbon felt substrate is conductive graphite felt, carbon cloth, carbon paper, titanium felt or copper felt. The carbon felt substrate can be replaced by carbon cloth, carbon paper, titanium felt and copper felt, etc. The conductive carbon felt can be replaced by carbon paper and titanium felt to obtain Cu-CNTs@CF and Cu-CNTs@TiF, respectively, with a loading of 0-20 mg / m 2 .

[0020] Furthermore, the Cu atoms and N atoms in the electrode form a Cu-N4 coordination structure. The copper atoms and nitrogen atoms in the carbon-based catalytic electrode prepared by this method form a Cu-N4 coordination structure, distributed as single atoms on the electrode surface. This degrades organic matter via an electron transfer mechanism, without generating free radicals during the reaction. This electrode degrades organic matter using an electron transfer mechanism without generating free radicals. The electrode exhibits strong resistance to ionic interference and is highly adaptable to complex water bodies, making it suitable for electrochemical treatment of organic matter in wastewater and other electrochemical fields.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] The present invention uses a planar conductive material as a substrate and utilizes the coordination of nitrogen atoms in polyvinyl pyrrolidone with Cu to achieve stable loading of single Cu atoms. The entire preparation process, consisting of two main steps, pyrolysis and loading, is simple, efficient, and low-cost, with the potential for large-scale production. The preparation process does not generate waste, has high raw material utilization, and poses minimal environmental risk, making it an environmentally friendly chemical synthesis process.

[0023] The high-efficiency carbon-based catalytic electrode prepared by the present invention not only has the ability to electrochemically catalytically degrade organic pollutants, but also the good electrical conductivity of carbon nanotubes can effectively improve the efficiency of electron transfer during the catalytic process, so that the performance of the electrode is better than the electrodes currently reported for degrading organic pollutants, and has a good removal effect on various difficult-to-degrade organic pollutants such as dyes, phenols, and antibiotics. In particular, during the reaction, the efficient degradation of pollutants is achieved by directional migration of electrons without additional free radicals, overcoming the problem that the traditional free radical pathway is easily interfered by coexisting ions in water, and has strong adaptability to complex water quality and wide practicality. In summary, the preparation method of the high-efficiency carbon-based catalytic electrode described in the present invention is simple, low-cost, easy to operate, high catalytic activity, and low metal ion leaching. When the electrode is used for electrochemical degradation of difficult-to-degrade organic matter in water, it is easy to recycle and there is no need to add additional powder catalyst to the water body to be treated, which greatly reduces the secondary pollution of the water body and has good practical application prospects.

[0024] The electrodes prepared by the present invention can be used in electrochemical reactions to efficiently remove difficult-to-degrade organic pollutants such as dyes, phenols, and antibiotics from water. The reaction mechanism is an electron transfer pathway without the generation of additional free radicals. In particular, when used to remove organic pollutants from water, this carbon-based electrode is minimally affected by coexisting inorganic ions, is easily separated and recovered, and exhibits minimal metal ion leaching. It exhibits excellent catalytic activity and stability, and can efficiently remove organic pollutants such as bisphenol A from representative surface waters such as Taihu Lake and Poyang Lake, showing promising prospects for practical application. This electrode provides a new solution for green, efficient, and harmless water treatment strategies. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the X-ray diffraction spectrum and N2 isothermal adsorption-desorption curve of Cu-CNTs-900@CF;

[0026] Figure 2 is the scanning electron microscope image of Cu-CNTs-900@CF;

[0027] Figure 3 is the XPS spectrum of Cu element and N element of Cu-CNTs-900@CF;

[0028] Figure 4 is the degradation effect diagram of Cu-CNTs-900@CF on 2,4-para-chlorophenol (2,4-DCP), phenol (PE), tetracycline (TC) and bisphenol A (BPA), and the cyclic degradation diagram of bisphenol A;

[0029] Figure 5 is the scanning electron microscope image of Cu-CNTs-900@TiF and Cu-CNTs-900@CP;

[0030] Figure 6 is the degradation effect diagram of Cu-CNTs-900@TiF, Cu-CNTs-900@CP and Cu-CNTs-900@CF for removing bisphenol A in water by electrochemical oxidation device;

[0031] Figure 7 is the electron paramagnetic resonance spectrum of the inhibition of different quenching agents on Cu-CNTs-900@CF and the free radical capture;

[0032] Figure 8 is the removal rate of Cu-CNTs-900@CF on bisphenol A in typical anion solution and the removal rate of bisphenol A in different surface water. DETAILED DESCRIPTION

[0033] Embodiment: The present application will be further described in detail below in conjunction with examples. Those skilled in the art should understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. If the specific technology or condition is not specified in the examples, it is carried out according to the technology or condition described in the literature in the art or according to the product instruction. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by purchase.

[0034] Example 1: Preparation and application of Cu-CNTs-900@CF

[0035] Dissolve 60 mg of carbon nanotubes, 10 mg of copper chloride and 120 mg of polyvinyl pyrrolidone in 20 mL of ethanol and stir thoroughly to mix them evenly. Then heat it to 75 ° C, and after the ethanol is completely volatilized, collect the remaining mixture. Place the mixture in a porcelain boat, then put it into a tube furnace, and pyrolyze it at 900 ° C in a N2 atmosphere for 2 hours. After it is cooled to room temperature, wash it with 1 mol / L dilute sulfuric acid for 2 hours, then centrifuge and wash it with deionized water until the pH of the washing liquid is neutral, and centrifuge and dry it to obtain Cu-CNTs-900. Then disperse Cu-CNTs-900 in a mixed solution with a volume ratio of 1:1 between water and ethanol, add 0.5% volume fraction of Nation117 solution, and after ultrasonication for 30 minutes, evenly coat it on the conductive carbon felt with a loading of 1 mg / m 2 Then, the mixture was dried at 70°C to obtain the highly efficient carbon-based catalytic electrode Cu-CNTs-900@CF. Figure 1 As shown in the figure, the X-ray diffraction spectrum has two diffraction peaks at 26.2° and 43.2°, which are attributed to the (002) crystal plane and (004) crystal plane of graphite carbon, respectively. The N2 isothermal adsorption-desorption curve shows that the specific surface area of ​​the electrode is 3.05m 2 / g. The scanning electron microscope test results are as follows Figure 2 As shown, carbon nanotube catalysts are distributed on the carbon fibers of the carbon felt substrate, and copper is dispersed on the carbon nanotubes in the form of single atoms. Figure 3 Cu-N bonds appeared in the XPS diffraction pattern, indicating that Cu and N formed a Cu-N coordination structure.

[0036] The high-efficiency carbon-based catalytic electrode of the present invention was used in an electrochemical oxidation device to remove organic pollutants in water. Specifically, a 4cm×6cm Cu-CNTs-900@CF electrode was used to treat bisphenol A in water. 1L of a 5μM organic matter solution was added to the anode, and 40mL of a 2.7g / L potassium persulfate solution was added to the cathode. The results are shown in Figure 2. Figure 4 As shown in the figure, the removal rate of several organic compounds reached 100%. And it can still maintain good performance after ten uses, indicating that it has excellent recyclability. Its reaction mechanism was tested by capture experiments and electron paramagnetic resonance technology. The results are as follows Figure 7 As shown, hydroxyl radicals, sulfate radicals and singlet oxygen scavengers have no effect on the degradation efficiency, and no corresponding free radicals are detected in the electron paramagnetic resonance spectrum, indicating that the electrode does not degrade organic matter through the above pathways, but degrades organic matter through the electron transfer pathway.

[0037] In addition, the electrode's ion resistance was tested, and the results were as follows: Figure 8As shown, the removal efficiency is almost unaffected in the removal experiments with different anions. The electrode was used to remove the simulated pollutant bisphenol A from actual surface waters such as Taihu Lake, Poyang Lake, and Xixi Wetland, with removal rates of 95.01%, 92.71%, and 94.67%, respectively, indicating its application prospects in real water.

[0038] Example 2: Preparation and Application of Cu-CNTs-800@CF

[0039] Dissolve 60 mg of carbon nanotubes, 10 mg of copper chloride and 120 mg of polyvinyl pyrrolidone in 20 mL of ethanol and stir thoroughly to mix them evenly. Then heat it to 75 ° C, and after the ethanol is completely volatilized, collect the remaining mixture. Place the mixture in a porcelain boat, then put it into a tube furnace, and pyrolyze it at 800 ° C in a N2 atmosphere for 2 hours. After it is cooled to room temperature, wash it with 1 mol / L dilute sulfuric acid for 2 hours, then centrifuge and wash it with deionized water until the pH of the washing liquid is neutral, and centrifuge and dry it to obtain Cu-CNTs-800. Then disperse Cu-CNTs-800 in a mixed solution with a volume ratio of 1:1 between water and ethanol, add 0.5% volume fraction of Nation117 solution, and after ultrasonication for 30 minutes, evenly coat it on the conductive carbon felt with a loading of 1 mg / m 2 The mixture was then dried at 70° C. to obtain the highly efficient carbon-based catalytic electrode Cu-CNTs-800@CF.

[0040] The high-efficiency carbon-based catalytic electrode described in this invention was used in an electrochemical oxidation device to remove organic pollutants from water. Specifically, a 2cm x 3cm Cu-CNTs-800@CF electrode was used to treat bisphenol A in water. 60mL of a 1.14mg / L bisphenol A solution was added to the anode, and 60mL of a 2.7g / L potassium persulfate solution was added to the cathode. Results showed that after 45 minutes, the bisphenol A removal rate reached 100%.

[0041] Example 3: Preparation and Application of Cu-CNTs-900@TiF

[0042] Dissolve 60 mg of carbon nanotubes, 10 mg of copper chloride and 120 mg of polyvinyl pyrrolidone in 20 mL of ethanol and stir thoroughly to mix them evenly. Then heat it to 75 ° C, and after the ethanol is completely volatilized, collect the remaining mixture. Place the mixture in a porcelain boat, then put it into a tube furnace, and pyrolyze it at 900 ° C in a N2 atmosphere for 2 hours. After it is cooled to room temperature, wash it with 1 mol / L dilute sulfuric acid for 2 hours, then centrifuge and wash it with deionized water until the pH of the washing liquid is neutral, and centrifuge and dry it to obtain Cu-CNTs-900. Then disperse Cu-CNTs-900 in a mixed solution with a volume ratio of 1:1 between water and ethanol, add 0.5% volume fraction of Nation117 solution, and after ultrasonication for 30 minutes, evenly coat it on titanium felt with a loading of 1 mg / m 2 Then it was dried at 70°C to obtain the high-efficiency carbon-based catalytic electrode Cu-CNTs-900@TiF. The scanning electron microscope test was performed on it, and the results were as follows: Figure 5 As shown in a, carbon nanotube precursors are evenly distributed on the titanium fiber.

[0043] The high-efficiency carbon-based catalytic electrode of the present invention was used in an electrochemical oxidation device to remove organic pollutants in water. Specifically, a 2cm×3cm Cu-CNTs-900@TiF electrode was used to treat bisphenol A in water. 60mL of a 1.14mg / L bisphenol A solution was added to the anode, and 60mL of a 2.7g / L potassium persulfate solution was added to the cathode. The results are shown in Figure 2. Figure 6 As shown, after 60 minutes, the removal rate of bisphenol A reached 70%.

[0044] Example 4: Preparation of Cu-CNTs-800@CP

[0045] Dissolve 60 mg of carbon nanotubes, 10 mg of copper chloride and 120 mg of polyvinyl pyrrolidone in 20 mL of ethanol and stir thoroughly to mix them evenly. Then heat it to 75 ° C, and after the ethanol is completely volatilized, collect the remaining mixture. Place the mixture in a porcelain boat, then put it into a tube furnace, and pyrolyze it at 800 ° C in a N2 atmosphere for 2 hours. After it is cooled to room temperature, wash it with 1 mol / L dilute sulfuric acid for 2 hours, then centrifuge and wash it with deionized water until the pH of the washing liquid is neutral, and centrifuge and dry it to obtain Cu-CNTs-800. Then disperse Cu-CNTs-800 in a mixed solution with a volume ratio of 1:1 between water and ethanol, add 0.5% volume fraction of Nation117 solution, and after ultrasonication for 30 minutes, evenly coat it on conductive carbon paper with a loading amount of 1 mg / m 2 Then it was dried at 70°C to obtain the highly efficient carbon-based catalytic electrode Cu-CNTs-800@CP. Scanning electron microscopy was performed on it, and the results were as follows: Figure 5 As shown in b, carbon nanotube precursors are evenly distributed on the carbon fibers.

[0046] The high-efficiency carbon-based catalytic electrode of the present invention was used in an electrochemical oxidation device to remove organic pollutants in water. Specifically, a 2cm×3cm Cu-CNTs-800@CP electrode was used to treat bisphenol A in water. 60mL of a 1.14mg / L bisphenol A solution was added to the anode, and 60mL of a 2.7g / L potassium persulfate solution was added to the cathode. The results are shown in Figure 2. Figure 5 As shown in Figure b, after 60 minutes, the removal rate of bisphenol A reached 55%.

Claims

1. A method for preparing a high-efficiency carbon-based catalytic electrode, characterized in that: The steps include: 1) Dissolve carbon nanotubes, polyvinyl pyrrolidone, and copper salt in ethanol, mix, and heat to volatilize the ethanol; 2) After the ethanol has completely evaporated, the mixture is placed in a tube furnace and heat-treated by pyrolysis under a nitrogen atmosphere. After cooling, the mixture is treated with a dilute acid solution, then washed with deionized water until the washing water is neutral, and dried to obtain Cu-CNTs, a single-atom catalyst precursor based on carbon nanotubes. 3) The single-atom catalyst precursor Cu-CNTs based on carbon nanotubes was dispersed in a mixed solvent of water and ethanol, and an adhesive was added. It was evenly dispersed by ultrasonication, and then coated on a carbon felt substrate and dried to obtain a high-efficiency carbon-based catalytic electrode.

2. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 1), the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes; The copper salt is copper chloride, copper nitrate or copper sulfate.

3. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 1), the mass ratio of the copper salt to polyvinyl pyrrolidone is 1-5:24; The mass ratio of the copper salt to the carbon nanotubes is 1-5:

12.

4. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 1), the temperature of the mixing and heating is 60-80°C.

5. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 2), the heat treatment temperature is 600-900 degrees Celsius, the heat treatment time is 1.5-4 hours, and the heating rate is 2-10 degrees / minute.

6. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 2), the dilute acid solution is 0.5-1.5 mol / L dilute sulfuric acid or 0.5-1.5 mol / L dilute hydrochloric acid.

7. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 3), the adhesive is Nafion 117, chitosan or conductive adhesive.

8. The method for preparing a high-efficiency carbon-based catalytic electrode according to claim 1, characterized in that: In step 3), the carbon felt substrate is conductive graphite felt, carbon cloth, carbon paper, titanium felt or copper felt.

9. A high-efficiency carbon-based catalytic electrode prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the high-efficiency carbon-based catalytic electrode according to claim 9 in degrading refractory organic pollutants in water during sewage treatment.

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