Preparation Method of Carbon-Coated Nickel-Nitrogen Functionalized Carbon-Doped Titanium Nitride Monolithic Electrode

Abstract

A preparation method of a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode. The pretreated carbon cloth is used to prepare a titanium dioxide seed layer substrate through a titanium tetrachloride chemical bath method and high-temperature calcination; titanium isopropoxide solution is added, and after high-temperature hydrothermal treatment and high-temperature calcination, titanium dioxide nanorods are obtained; using the titanium dioxide nanorod substrate as a working electrode, a polyaniline film is deposited on the surface through cyclic voltammetry electrodeposition; and a nickel hydroxide film is prepared through constant current electrodeposition; a mixed solution of resorcinol and hexamethylenetetramine is added, and after high-temperature hydrothermal reaction, it is calcined at high temperature in an ammonia atmosphere to obtain the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode. This electrode has the advantages of simple preparation process, excellent capacitance contribution, and high heavy metal ion removal efficiency, etc., and can be applied to the efficient removal of low-concentration heavy metal ions in industrial wastewater, providing a new way for realizing high-performance and low-cost TiN-based CDI heavy metal wastewater purification technology.

Description

Technical Field

[0001] The present invention relates to a preparation method of a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode, belonging to the technical field of capacitive deionization electrode manufacturing processes in wastewater treatment. Background Art

[0002] Water resource shortage is the most severe challenge faced by human society. Industrial wastewater, with the characteristics of large volume, complex and variable water quality, and containing a lot of heavy metals, is the main source of current heavy metal pollutants in water bodies and has become an important issue that cannot be ignored in China's energy development strategy. In recent years, a large amount of industrial wastewater discharged from industries such as chemical fertilizers, batteries, paper-making, pesticides, coal, steel, and non-ferrous metal smelting has caused serious heavy metal ion pollution. It has the characteristics of high toxicity, carcinogenicity, and non-biodegradability. If directly discharged into the natural environment without treatment, it will lead to serious damage to the ecological system and water environmental pollution, and at the same time pose a serious threat to the survival of aquatic organisms and human health. Traditional purification technologies such as chemical precipitation method, membrane separation method, and ion exchange method have significant effects on the treatment of high-concentration wastewater, but are not good at effectively removing low-concentration heavy metal ions. Therefore, developing a high-efficiency, environmentally friendly, economical, and stable low-concentration heavy metal wastewater treatment technology is of great significance for solving the current freshwater crisis at home and abroad.

[0003] Capacitive deionization (CDI) is considered a simple and efficient new wastewater treatment technology and has been widely applied in the fields of heavy metal removal, organic pollutant purification, and sea / brackish water desalination. Compared with traditional wastewater treatment technologies, CDI technology has the advantages of low cost, high removal efficiency, simple process equipment, easy implementation, no secondary pollution, and environmental friendliness, providing a new way for the development of high-efficiency and low-cost heavy metal wastewater purification technologies. As we all know, the preparation of electrode materials with high theoretical capacitance, good structural stability, and high specific surface area is one of the key factors to obtain outstanding CDI removal performance.

[0004] Pseudocapacitive nanomaterials based on transition metal compounds (TMCs), including oxides, sulfides, carbides, phosphides, nitrides, etc., have been widely used in many fields such as lithium / sodium ion batteries, supercapacitors, seawater desalination, and wastewater purification due to their excellent electrical conductivity and high theoretical capacity. Among them, titanium nitride (TiN) has broad application prospects in the field of electrochemical energy storage / conversion technology due to its high electrical conductivity, high thermal conductivity, outstanding chemical stability, and low-temperature superconductivity. For example, Wu et al. reported a three-dimensional ordered mesoporous TiN powder electrode for the removal of sodium ions by CDI. It was found that the salt adsorption capacity of this electrode material was as high as 23.6 mg / g in a 500 mg / L NaCl solution, indicating the potential application advantages of TiN-based CDI electrodes in the removal of heavy metal ions. However, there is still a large gap between the ion adsorption capacity of the TiN electrodes reported in the current literature and their theoretical capacity, and the removal efficiency of low-concentration heavy metal ions still needs to be further improved, so it cannot meet the future industrial application of CDI wastewater purification technology. Therefore, the realization of highly efficient and stable novel heterostructured TiN-based CDI electrodes through techniques such as surface morphology / microstructure regulation, interface modification, and doping engineering has been a research hotspot at home and abroad in recent years. In addition, most of the CDI wastewater purification electrodes reported in the current literature are still mainly powder materials, and the CDI powder electrodes prepared by the traditional slurry coating method have disadvantages such as complex and time-consuming preparation processes, poor interface stability, and inability to recycle electrode materials, which further reduces their removal efficiency and cycle stability. Therefore, the development of a new preparation process for CDI wastewater purification electrodes is of great significance for the future industrial application of highly efficient and low-cost CDI wastewater purification technology. Summary of the Invention

[0005] The object of the present invention is to solve the technical defects of the existing complex and time-consuming preparation process of TiN-based CDI electrodes and their low removal efficiency for low-concentration heavy metal ions, and to provide a preparation method for a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode for the efficient removal of low-concentration heavy metal ions by applying CDI technology.

[0006] The present invention directly in-situ grows carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride nanorods with high surface area and porosity on the surface of a conductive substrate carbon cloth by using hydrothermal method, electrodeposition method, and high-temperature calcination method, and prepares a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode. This electrode has advantages such as high surface area, high electrical conductivity, high reusability, simple and easy preparation process, and excellent heavy metal ion removal performance, and can be applied to the efficient removal of low-concentration heavy metal ions in industrial wastewater, providing a new approach for realizing high-performance and low-cost TiN-based CDI heavy metal wastewater purification technology.

[0007] Technical solution of the present invention

[0008] A preparation method of a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode, comprising the following steps:

[0009] (1) Surface pretreatment of carbon cloth substrate

[0010] Soak the commercial carbon cloth in a nitric acid solution with a certain concentration for 8-12 h, and then ultrasonically treat it with acetone, ethanol and water in sequence and then dry it;

[0011] (2) Preparation of titanium dioxide seed layer

[0012] Place the carbon cloth substrate pretreated in step (1) obliquely in a container, keep an angle of 40-50° with the inner wall, add an aqueous TiCl4 solution, and place it in an electrothermal constant temperature blast drying oven for reaction at 70-80 °C for 1-2 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol and then dry it; then place it in a tube furnace and heat it to 350-500 °C for high-temperature calcination for 2-3 h to obtain a carbon cloth substrate with a titanium dioxide seed layer;

[0013] (3) Preparation of titanium dioxide nanorods by hydrothermal reaction

[0014] Place the carbon cloth substrate with the titanium dioxide seed layer obtained in step (2) in a reaction kettle, keep an angle of 40-50° with the inner wall, and add a uniformly mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven for high-temperature hydrothermal reaction at 140-180 °C. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol and then dry it; then place it in a tube furnace and heat it to 350-500 °C for high-temperature calcination for 1-3 h to obtain titanium dioxide nanorods on the carbon cloth substrate;

[0015] (4) Preparation of polyaniline@titanium dioxide nanorods

[0016] Use the carbon cloth substrate with titanium dioxide nanorods obtained in step (3) as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode to form a three-electrode system, and prepare a polyaniline film on the surface of the carbon cloth substrate with titanium dioxide nanorods by electrochemical deposition;

[0017] (5) Preparation of nickel hydroxide@polyaniline@titanium dioxide nanorods

[0018] Use the carbon cloth substrate with polyaniline@titanium dioxide nanorods obtained in step (4) as the working electrode and a platinum electrode as the counter electrode to form a two-electrode system, and further prepare a nickel hydroxide film on the surface of the carbon cloth substrate with polyaniline@titanium dioxide nanorods by electrochemical deposition;

[0019] (6) Preparation of carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode

[0020] Tilt the nickel hydroxide@polyaniline@titanium dioxide nanorod carbon cloth substrate obtained in step (5) in the reaction kettle at an angle of 40 - 50° with the inner wall, and add the carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for high-temperature hydrothermal reaction at 190 - 220 °C; after the reaction is completed, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it; finally, place it in a tube furnace and perform one-step high-temperature calcination at 800 - 1000 °C in an ammonia atmosphere to obtain a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0021] The specification of the carbon cloth in step (1) is: 8*10 cm 2 , the mass fraction of nitric acid is 35 wt.% - 50 wt.%, and the soaking temperature is 70 - 80 °C. The nitric acid chemical bath treatment process of the carbon cloth substrate is beneficial to improving its surface hydrophilicity.

[0022] The concentration of the TiCl4 aqueous solution in step (2) is 0.15 - 0.2 mol / L. The TiCl4 aqueous solution with a certain concentration is fully hydrolyzed under chemical bath conditions and calcined at high temperature in the air, which is beneficial to depositing a uniform, dense and well-crystalline titanium dioxide seed layer structure on the surface of the carbon cloth substrate, providing reaction sites for the further deposition of titanium dioxide nanorods on its surface.

[0023] The homogeneous mixed solution of titanium isopropoxide in step (3) contains concentrated hydrochloric acid, water and titanium isopropoxide components, and controls the volume ratio of concentrated hydrochloric acid, water and titanium isopropoxide to be 1:1.5:0.02 - 0.03. The concentrated hydrochloric acid, water and titanium isopropoxide with a certain volume ratio can react fully to grow uniform and dense titanium dioxide nanorods on the surface of the titanium dioxide seed layer substrate.

[0024] The high-temperature hydrothermal reaction time in step (3) is 9 - 12 h. The mixed solution of concentrated hydrochloric acid, water and titanium isopropoxide is easy to grow titanium dioxide nanorods on the surface of the titanium dioxide seed layer substrate under hydrothermal conditions, and at the same time, the morphology and film thickness of the titanium dioxide nanorods grown on the surface are changed by regulating the reaction temperature and time. If the temperature is too low or the reaction time is too short, the reaction is incomplete, resulting in fewer titanium dioxide nanorods on the substrate surface. If the temperature is too high, the reaction rate is too fast, which may lead to the formation of a large number of titanium dioxide massive aggregates, which is not conducive to the improvement of the electrode specific surface area.

[0025] The high-temperature calcination process of the titanium dioxide nanorods in step (3) is carried out in the air, and the heating rate is controlled at 2.5 - 5 °C / min. High-temperature calcination is beneficial to improving the crystallinity of the titanium dioxide nanorods. At the same time, control the calcination temperature at 350 - 500 °C. If the temperature is too low, it is not conducive to the improvement of the crystallinity of the titanium dioxide nanorods; if the temperature is too high, it will lead to local collapse of the titanium dioxide nanorod structure.

[0026] The cyclic voltammetry method is adopted for the electrochemical deposition method in the step (4). The voltage range is controlled to be -0.4 to 1.3 V, the scanning rate is 10 to 20 mV / s, and the number of scanning cycles is 20 to 30. The electrolyte solution is an aniline-sulfuric acid mixed solution, with the sulfuric acid concentration controlled to be 0.1 to 0.15 mol / L and the aniline concentration to be 0.1 to 0.3 mol / L. Through the cyclic voltammetry method of the three-electrode system, using a certain concentration of aniline as the electrolyte, by controlling the electrodeposition parameters, it is beneficial to deposit a polyaniline film with a certain thickness and uniform density on the surface of the titanium dioxide nanorod substrate.

[0027] The electrochemical deposition method in the step (5) is the constant current deposition method. The current density is controlled to be 2 to 8 mA / cm 2 , and the deposition time is 3 to 5 min. The electrolyte solution is a nickel nitrate solution, with the nickel nitrate concentration controlled to be 0.015 to 0.03 mol / L. Through the constant current deposition method of the two-electrode system, using a certain concentration of nickel nitrate as the electrolyte, by controlling the electrodeposition parameters, it is beneficial to deposit a nickel hydroxide film with a certain thickness and uniform density on the surface of the polyaniline@titanium dioxide nanorods.

[0028] The carbon precursor mixed solution in the step (6) contains components such as resorcinol, hexamethylenetetramine and water. The concentrations of resorcinol and hexamethylenetetramine are 0.4 to 1 mg / mL and 0.3 to 0.9 mg / mL respectively, and the mass ratio of resorcinol to hexamethylenetetramine is controlled to be 1:0.7 to 0.9. Resorcinol and hexamethylenetetramine at a certain concentration can fully react and form a uniform resorcinol / formaldehyde resin film on the surface of the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate.

[0029] The high-temperature hydrothermal reaction time in the step (6) is 24 to 28 h. Resorcinol and hexamethylenetetramine are prone to undergo a polycondensation reaction under high-temperature hydrothermal conditions to form a uniform resorcinol / formaldehyde resin film on the substrate surface. At the same time, the morphology and thickness of the film can be changed by regulating the reaction temperature and reaction time. If the temperature is too low or the reaction time is too short, the reaction is incomplete, resulting in uneven deposition of the resorcinol / formaldehyde resin film on the surface of the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate. If the temperature is too high, the reaction rate can be too fast, resulting in a large number of cracks on the electrode surface and a decrease in the film stability.

[0030] The high-temperature calcination process of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode in step (6) needs to be carried out in an ammonia atmosphere. The ammonia flow rate is 80-140 mL / min, the heating rate is controlled at 2.5-5 °C / min, and the holding time is 1-3 h. Ammonia needs to be continuously introduced during the calcination process, which is not only a necessary nitriding condition for the formation of titanium nitride, but also ammonia can promote the formation of nickel-nitrogen functionalized carbon under high-temperature action. At the same time, the calcination temperature is 800-1000 °C. If the temperature is too low, it is not conducive to the formation of titanium nitride and nickel-nitrogen functionalized carbon; if the temperature is too high, it will lead to local collapse of the titanium nitride nanorod structure.

[0031] Advantages and beneficial effects of the present invention

[0032] The present invention directly in-situ grows carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride nanorods with high surface area and porosity on the surface of a conductive substrate carbon cloth by using hydrothermal method, electrodeposition method and high-temperature calcination method, and prepares a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode, which is used in the field of capacitive wastewater purification. It has the following advantages:

[0033] First of all, this monolithic electrode not only effectively simplifies the electrode preparation process and avoids the use of insulating binders, which is beneficial to further improve the conductivity of the CDI electrode;

[0034] Secondly, the in-situ growth technology enhances the interfacial bonding force between the active material and the conductive substrate, which can effectively reduce the mass loss of the electrode material during the CDI process and improve the stability and reusability of the electrode.

[0035] In addition, for the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared by the present invention, the unique highly open flower-like structure, the abundant nanopores on the surface of the nanorods and the nickel-nitrogen functionalized carbon coating layer are beneficial to improve the specific surface area and conductivity of the electrode and improve the removal efficiency of the electrode for low-concentration heavy metal ions.

[0036] In summary, the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared by the method of the present invention has the advantages of high surface area, high conductivity, high reusability, simple and efficient preparation process, excellent capacitance contribution and outstanding heavy metal ion removal performance, etc. It has a good application prospect in the field of industrial low-concentration heavy metal wastewater purification, and provides a new way for realizing high-performance and low-cost TiN-based CDI wastewater purification technology. Description of the drawings

[0037] Figure 1 SEM and TEM images of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in Example 1; among them, (a-c) are SEM images at different magnifications, and (d-f) are TEM images at different magnifications.

[0038] Figure 2 High-resolution XPS pattern of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in Example 1.

[0039] Figure 3 Cyclic voltammogram of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in Example 1.

[0040] Figure 4 Heavy metal ion removal efficiency diagram of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in Example 1. Detailed implementation method

[0041] Example 1

[0042] Preparation method of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode, the steps are as follows:

[0043] (1) Place the carbon cloth (8*10 cm 2 ) in a nitric acid solution at 80 °C with a mass fraction of 45 wt.%, soak for 10 h, then ultrasonically treat with acetone, ethanol and water for 30 min respectively, and dry at 70 °C for later use.

[0044] (2) Place the carbon cloth substrate pretreated in (1) obliquely in a beaker at an angle of 45° with the inner wall, add 25 mL of 0.2 mol / L TiCl4 aqueous solution, and place it in an electrothermal constant temperature blast drying oven at 70 °C for reaction for 2 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tube furnace and heat it up to 450 °C, and calcine it at high temperature in air for 2.5 h to obtain a titanium dioxide seed layer substrate.

[0045] (3) Add 10 mL of concentrated hydrochloric acid to 15 mL of water, then add 0.25 mL of titanium isopropoxide and ultrasonically treat for 30 min to form a uniform mixed solution of titanium isopropoxide. Then place the titanium dioxide seed layer substrate in (2) in a reaction kettle at an angle of 45° with the inner wall, and add the uniform mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven at 140 °C for high-temperature hydrothermal reaction for 12 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tube furnace and heat it up to 450 °C, control the heating rate at 4 °C / min, and calcine it at high temperature in air for 2 h to obtain titanium dioxide nanorods on the carbon cloth substrate.

[0046] (4) Using the titanium dioxide nanorod substrate obtained in the above (3) as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, a three-electrode system is formed. A polyaniline film is prepared on the surface of the carbon cloth substrate by cyclic voltammetry. Among them, the electrolyte is an aniline-sulfuric acid mixed solution with a concentration of 0.2 mol / L aniline and 0.1 mol / L sulfuric acid, the voltage range is -0.4 to 1.3 V, the scanning rate is 20 mV / s, and the number of scanning cycles is 25.

[0047] (5) Using the polyaniline@titanium dioxide nanorod substrate obtained in the above (4) as the working electrode and a platinum electrode as the counter electrode, a two-electrode system is formed. A nickel hydroxide film is further prepared on the surface of the carbon cloth substrate by constant current deposition method. Among them, the electrolyte is 0.03 mol / L nickel nitrate solution, and the current density is 2 mA / cm 2 , and the deposition time is 3 min.

[0048] (6) Add 10 mg of resorcinol and 7.5 mg of hexamethylenetetramine to 25 mL of water, stir until completely dissolved to prepare a carbon precursor mixed solution. Then tilt the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate obtained in the above (5) and place it in the reaction kettle at an angle of 45° with the inner wall, and add the carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for a hydrothermal reaction at 220 °C for 24 h; after the reaction is completed, take out the carbon cloth, rinse it with water and ethanol, and dry it at 70 °C; finally, place it in a tubular furnace, under the continuous protection of ammonia gas with a flow rate of 140 mL / min, control the heating rate to be 2.5 °C / min, heat up to 900 °C and keep it for 3 h to obtain a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0049] The SEM and TEM images of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in this example are as Figure 1 shown, where (a-c) are SEM images at different magnifications, and (d-f) are TEM images at different magnifications. As shown in the figure, a large number of porous nanorod arrays grow uniformly on the carbon cloth substrate, and the well-connected nanorods are assembled into a highly open flower-like structure in the entire electrode framework ( Figure 1 a-b, d). There are abundant nanopores on the surface of the titanium nitride nanorods, which not only helps to increase the specific surface area of the electrode, but also provides more channels for the rapid diffusion of heavy metal ions. At the same time, there is a relatively uniform nickel-nitrogen functionalized carbon coating layer on the surface of the titanium nitride nanorods ( Figure 1c, e). The lattice spacing of 0.24 nm in the high-resolution TEM image (1f) corresponds to the (111) characteristic crystal plane of the titanium nitride phase. In summary, the present invention uses the hydrothermal method, electrodeposition method, and high-temperature calcination method to directly in-situ grow carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride nanorods with high surface area and porosity on the surface of the conductive substrate carbon cloth, and prepares a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0050] The XPS diagram of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in this example is as Figure 2 shown. As shown in the figure, the high-resolution spectrogram results of Ti 2p ( Figure 2 a) and N 1s ( Figure 2 b) indicate the formation of the titanium nitride nanorod structure on the surface of the carbon cloth substrate. The N-C bond and N-Ni bond in the high-resolution N 1s spectrogram, and the C-N bond in the C 1s diagram ( Figure 2 c) and Ni 2p ( Figure 2 d) further prove the synthesis of the nickel-nitrogen functionalized carbon coating.

[0051] The specific capacitance and capacitance contribution of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in this example. Using a CHI-660E electrochemical workstation, the electrolyte is 1 mol / L NaCl solution, and the voltage range is -0.4 to 0.6 V. As shown in the figure, the specific capacitance of this electrode is greater than 120 F / g ( Figure 3 a) at a scan rate of 1 mV / s, and the capacitance contribution is as high as 91% ( Figure 3 b) at a scan rate of 5 mV / s.

[0052] The heavy metal ion removal efficiency diagram of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared in this example is as Figure 4 shown. The concentration of heavy metal ions at the outlet is determined by ICP-OES technology, and the removal efficiency of heavy metal ions of the electrode is further calculated. When the applied voltage is 1.2 V, the solution is a low-concentration heavy metal ion mixed solution (containing Cr 3+ , Fe 3 + , Pb 2+ , Cd 2+ , Cu 2+ , Ni 2+ and Na + , the single ion concentration is 10 mg / L, and the Na + concentration is 50 mg / L), the solution flow rate is 60 mL / min, and the heavy metal ion removal efficiency of the electrode is as Figure 4As shown. As shown in the figure, the average removal efficiency of heavy metal ions by the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode is as high as 99.6%, which is significantly higher than that of the N-C@TiN@CC electrode (87.3%) reported in the literature by this research group.

[0053] Example 2

[0054] (1) Place the carbon cloth (8*10 cm 2 ) in a nitric acid solution with a mass fraction of 50 wt.% at 70 °C for 8 h, and then ultrasonically treat it with acetone, ethanol, and water for 30 min respectively, and then dry it at 70 °C.

[0055] (2) Place the carbon cloth substrate pretreated in (1) above in a beaker at an angle of 45° to the inner wall, add 25 mL of 0.18 mol / L TiCl4 aqueous solution, and place it in an electrothermal constant temperature blast drying oven at 80 °C for 1 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it at 70 °C; then place it in a tube furnace and heat it to 350 °C, and calcine it at high temperature in air for 3 h to obtain a titanium dioxide seed layer substrate.

[0056] (3) Add 10 mL of concentrated hydrochloric acid to 15 mL of water, and then add 0.2 mL of titanium isopropoxide and ultrasonically treat it for 30 min to form a homogeneous mixed solution of titanium isopropoxide. Then place the titanium dioxide seed layer substrate in (2) above in a reaction kettle at an angle of 45° to the inner wall, and add the homogeneous mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven at 160 °C for high-temperature hydrothermal reaction for 10 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it at 70 °C; then place it in a tube furnace and heat it to 350 °C, control the heating rate to 3 °C / min, and calcine it at high temperature in air for 3 h to obtain titanium dioxide nanorods on the carbon cloth substrate.

[0057] (4) Using the titanium dioxide nanorod substrate obtained in (3) above as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, a three-electrode system is formed, and a polyaniline film is prepared on the surface of the carbon cloth substrate by cyclic voltammetry; among them, the electrolyte is an aniline-sulfuric acid mixed solution with a concentration of 0.1 mol / L aniline and 0.1 mol / L sulfuric acid, the voltage range is -0.4 to 1.3 V, the scanning rate is 15 mV / s, and the number of scanning cycles is 30.

[0058] (5) Using the polyaniline@titanium dioxide nanorod substrate obtained in (4) above as the working electrode and a platinum electrode as the counter electrode, a two-electrode system is formed, and a nickel hydroxide film is further prepared on the surface of the carbon cloth substrate by constant current deposition; among them, the electrolyte is 0.02 mol / L nickel nitrate solution, the current density is 4 mA / cm 2 , and the deposition time is 5 min.

[0059] (6) Add 10 mg of resorcinol and 9 mg of hexamethylenetetramine to 25 mL of water, stir until completely dissolved to prepare a carbon precursor mixed solution. Then, place the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate obtained in the above step (5) obliquely in the reaction kettle at an angle of 45° to the inner wall, and add the carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for a hydrothermal reaction at 200 °C for 26 h; after the reaction is completed, take out the carbon cloth, rinse it with water and ethanol, and dry it at 70 °C; finally, place it in a tubular furnace, under continuous protection of ammonia with a flow rate of 110 mL / min, control the heating rate at 4 °C / min, heat up to 950 °C and hold for 2 h to obtain a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0060] Test the specific capacitance and capacitance contribution of the above carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode. Using a CHI-660E electrochemical workstation, with an electrolyte of 1 mol / L NaCl solution and a voltage range of -0.4 to 0.6 V, the specific capacitance of this electrode is greater than 110 F / g at a scan rate of 1 mV / s, and the capacitance contribution is greater than 85% at a scan rate of 5 mV / s. The above-prepared electrode has a removal efficiency greater than 95% in a low-concentration heavy metal ion mixed solution (containing Cr 3+ , Fe 3+ , Pb 2+ , Cd 2+ , Cu 2+ , Ni 2+ and Na + , with a single ion concentration of 10 mg / L and a Na + concentration of 50 mg / L).

[0061] Example 3

[0062] (1) Place the carbon cloth (8 * 10 cm 2 ) in a nitric acid solution with a mass fraction of 35 wt.% at 80 °C for 12 h, then ultrasonically treat it with acetone, ethanol, and water for 30 min respectively, and dry it at 70 °C.

[0063] (2) Place the carbon cloth substrate pretreated in the above step (1) obliquely in a beaker at an angle of 45° to the inner wall, add 25 mL of 0.15 mol / L TiCl4 aqueous solution, and place it in an electrothermal constant temperature blast drying oven for a reaction at 75 °C for 1.5 h. After the reaction is completed, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tubular furnace and heat up to 500 °C, and calcine it at high temperature in air for 2 h to obtain a titanium dioxide seed layer substrate.

[0064] (3) Add 10 mL of concentrated hydrochloric acid to 15 mL of water, then add 0.3 mL of titanium isopropoxide and ultrasonically treat for 30 min to form a homogeneous mixed solution. Then place the titanium dioxide seed layer substrate obtained in the above (2) in a reaction kettle, keeping a 45° angle with the inner wall, and add the homogeneous mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven for a hydrothermal reaction at 180 °C for 9 h. After the reaction is completed, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tube furnace, heat it up to 500 °C, control the heating rate at 5 °C / min, and calcine it at high temperature in air for 1 h to obtain titanium dioxide nanorods on the carbon cloth substrate.

[0065] (4) Use the titanium dioxide nanorod substrate obtained in the above (3) as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode to form a three-electrode system, and prepare a polyaniline film on the surface of the carbon cloth substrate by cyclic voltammetry; among them, the electrolyte is an aniline-sulfuric acid mixed solution with a concentration of 0.3 mol / L aniline and 0.15 mol / L sulfuric acid, the voltage range is -0.4 to 1.3 V, the scanning rate is 10 mV / s, and the number of scanning cycles is 20.

[0066] (5) Use the polyaniline@titanium dioxide nanorod substrate obtained in the above (4) as the working electrode and a platinum electrode as the counter electrode to form a two-electrode system, and further load a nickel hydroxide film on the surface of the carbon cloth substrate by constant current deposition method; among them, the electrolyte is a 0.015 mol / L nickel nitrate solution, and the current density is 8 mA / cm 2 , and the deposition time is 4 min.

[0067] (6) Add 20 mg of resorcinol and 16 mg of hexamethylenetetramine to 25 mL of water, stir until completely dissolved to prepare a carbon precursor mixed solution. Then place the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate obtained in the above (5) obliquely in a reaction kettle, keeping a 45° angle with the inner wall, and add the carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for a hydrothermal reaction at 190 °C for 28 h; after the reaction is completed, take out the carbon cloth, rinse it with water and ethanol, and dry it at 70 °C; finally, place it in a tube furnace, under continuous protection of ammonia gas with a flow rate of 90 mL / min, control the heating rate at 5 °C / min, heat it up to 1000 °C and keep it for 1 h to prepare a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0068] Test the specific capacitance and capacitance contribution of the above carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode. Using a CHI-660E electrochemical workstation, with 1 mol / L NaCl solution as the electrolyte and a voltage range of -0.4 to 0.6 V, the specific capacitance of this electrode is greater than 100 F / g at a scan rate of 1 mV / s, and the capacitance contribution is greater than 80% at a scan rate of 5 mV / s. The above-prepared electrode has a removal efficiency greater than 93% in a mixed solution of heavy metal ions at low concentrations (including Cr 3+ , Fe 3+ , Pb 2+ , Cd 2+ , Cu 2+ , Ni 2+ and Na + , with a single ion concentration of 10 mg / L and a Na + concentration of 50 mg / L).

[0069] Example 4

[0070] (1) Immerse the carbon cloth (8*10 cm 2 ) in a nitric acid solution with a mass fraction of 35 wt.% at 80 °C for 8 h, then ultrasonically treat it with acetone, ethanol, and water for 30 min respectively, and dry it at 70 °C.

[0071] (2) Place the carbon cloth substrate pretreated in the above (1) obliquely in a beaker at an angle of 45° with the inner wall, add 25 mL of 0.15 mol / L TiCl4 aqueous solution, and place it in an electrothermal constant temperature blast drying oven at 70 °C for 1 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tube furnace, heat it up to 350 °C, and calcine it at high temperature in air for 2 h to obtain a titanium dioxide seed layer substrate.

[0072] (3) Add 10 mL of concentrated hydrochloric acid to 15 mL of water, then add 0.2 mL of titanium isopropoxide and ultrasonically treat it for 30 min to form a homogeneous mixed solution. Then place the titanium dioxide seed layer substrate in the above (2) in a reaction kettle at an angle of 45° with the inner wall, and add the homogeneous mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven at 140 °C for high-temperature hydrothermal reaction for 9 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and dry it at 70 °C; then place it in a tube furnace, heat it up to 350 °C, control the heating rate at 3 °C / min, and calcine it at high temperature in air for 1 h to obtain titanium dioxide nanorods on the carbon cloth substrate.

[0073] (4) Using the titanium dioxide nanorod substrate obtained in the above (3) as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode, a three-electrode system is formed, and a polyaniline film is prepared on the surface of the carbon cloth substrate by cyclic voltammetry; wherein, the electrolyte is an aniline-sulfuric acid mixed solution with a concentration of 0.1 mol / L aniline and 0.1 mol / L sulfuric acid, the voltage range is -0.4 to 1.3 V, the scanning rate is 10 mV / s, and the number of scanning cycles is 20.

[0074] (5) Using the polyaniline@titanium dioxide nanorod substrate obtained in the above (4) as the working electrode and a platinum electrode as the counter electrode, a two-electrode system is formed, and nickel hydroxide film is further loaded on the surface of the carbon cloth substrate by constant current deposition method; wherein the electrolyte is 0.02 mol / L nickel nitrate solution, and the current density is 2 mA / cm 2 , and the deposition time is 3 min.

[0075] (6) Add 20 mg of resorcinol and 16 mg of hexamethylenetetramine to 25 mL of water, stir until completely dissolved to prepare a carbon precursor mixed solution. Then tilt the nickel hydroxide@polyaniline@titanium dioxide nanorod substrate obtained in the above (5) in the reaction kettle, keep an angle of 45° with the inner wall, and add the carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for hydrothermal reaction at 190 °C for 24 h; after the reaction is completed, take out the carbon cloth, rinse it with water and ethanol, and dry it at 70 °C; finally, place it in a tubular furnace, under the continuous protection of ammonia with a flow rate of 80 mL / min, control the heating rate at 5 °C / min, heat up to 900 °C and keep it for 1 h to obtain a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

[0076] Test the specific capacitance and capacitance contribution of the above carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode. Using a CHI-660E type electrochemical workstation, the electrolyte is 1 mol / L NaCl solution, the voltage range is -0.4 to 0.6 V, the specific capacitance of this electrode is greater than 90 F / g at a scanning rate of 1 mV / s, and the capacitance contribution is greater than 76% at a scanning rate of 5 mV / s. The removal efficiency of the above prepared electrode in a low-concentration heavy metal ion mixed solution (including Cr 3+ , Fe 3+ , Pb 2+ , Cd 2+ , Cu 2+ , Ni 2+ and Na + , the single ion concentration is 10 mg / L, and the Na + concentration is 50 mg / L) is greater than 90%.

Claims

1. A preparation method of a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode, characterized in that, It includes the following steps: (1) Surface pretreatment of the carbon cloth substrate Soak the commercial carbon cloth in nitric acid solution for 8 - 12 h, then ultrasonically treat it successively with acetone, ethanol and water, and then dry it; (2) Growth of the titanium dioxide seed layer Place the carbon cloth substrate pretreated in step (1) obliquely in a beaker container, with an angle of 40 - 50° with the inner wall, add an aqueous TiCl4 solution, and place it in an electrothermal constant temperature blast drying oven for reaction at 70 - 80°C for 1 - 2 h. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it; then place it in a tube furnace and heat it to 350 - 500°C for high-temperature calcination in air for 2 - 3 h to obtain a carbon cloth substrate with a titanium dioxide seed layer; (3) Preparation of titanium dioxide nanorods by hydrothermal reaction Place the carbon cloth substrate with the titanium dioxide seed layer in step (2) in a reaction kettle, with an angle of 40 - 50° with the inner wall, and add a homogeneous mixed solution of titanium isopropoxide; place the reaction kettle in an electrothermal constant temperature blast drying oven for high-temperature hydrothermal reaction at 140 - 180°C. After the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it; then place it in a tube furnace and heat it to 350 - 500°C for high-temperature calcination for 1 - 3 h to obtain titanium dioxide nanorods on the carbon cloth substrate; (4) Preparation of polyaniline@titanium dioxide nanorods Use the carbon cloth substrate with titanium dioxide nanorods obtained in step (3) as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode to form a three-electrode system, and prepare a polyaniline thin film on the surface of the carbon cloth substrate with titanium dioxide nanorods by electrochemical deposition; (5) Preparation of nickel hydroxide@polyaniline@titanium dioxide nanorods Use the carbon cloth substrate with polyaniline@titanium dioxide nanorods obtained in step (4) as the working electrode and a platinum electrode as the counter electrode to form a two-electrode system, and further prepare a nickel hydroxide thin film on the surface of the carbon cloth substrate with polyaniline@titanium dioxide nanorods by electrochemical deposition; (6) Preparation of a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode Place the carbon cloth substrate with nickel hydroxide@polyaniline@titanium dioxide nanorods obtained in step (5) obliquely in a reaction kettle, with an angle of 40 - 50° with the inner wall, and add a carbon precursor mixed solution; place the reaction kettle in an electrothermal constant temperature blast drying oven for high-temperature hydrothermal reaction at 190 - 220°C; after the reaction, take out the carbon cloth substrate, rinse it with water and ethanol, and then dry it; finally, place it in a tube furnace and perform one-step high-temperature calcination at 800 - 1000°C in an ammonia atmosphere to obtain a carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic capacitive wastewater purification electrode.

2. The preparation method according to claim 1, characterized in that, The specifications of the carbon cloth in step (1) are: 8*10 cm 2 , the mass fraction of nitric acid is 35 wt.% to 50 wt.%, and the soaking temperature is 70 to 80 °C.

3. The preparation method according to claim 1, characterized in that, The concentration of the TiCl4 aqueous solution in step (2) is 0.15 - 0.2 mol / L.

4. The preparation method according to claim 1, characterized in that, The homogeneous mixed solution of titanium isopropoxide in step (3) contains concentrated hydrochloric acid, water and titanium isopropoxide components, and controls the volume ratio of concentrated hydrochloric acid, water and titanium isopropoxide to be 1:1.5:0.02 - 0.03; the time of the high-temperature hydrothermal reaction is 9 - 12 h, the high-temperature calcination process is carried out in air, and the heating rate is controlled at 2.5 - 5°C / min.

5. The preparation method according to claim 1, characterized in that, In the electrochemically depositing method in step (4), cyclic voltammetry is adopted, the voltage range is controlled to be -0.4 to 1.3 V, the scanning rate is 10 to 20 mV / s, and the number of scanning cycles is 20 to 30; the electrolyte solution is an aniline-sulfuric acid mixed solution, the concentration of sulfuric acid is controlled to be 0.1 to 0.15 mol / L, and the concentration of aniline is 0.1 to 0.3 mol / L.

6. The preparation method according to claim 1, characterized in that, The electrochemically depositing method in the step (5) is a constant current deposition method, and the current density is controlled to be 2-8 mA / cm 2 , the deposition time is 3-5 min; the electrolyte is a nickel nitrate solution, and the concentration of nickel nitrate is controlled to be 0.015-0.03 mol / L.

7. The preparation method according to claim 1, characterized in that, The carbon precursor mixed solution in step (6) contains resorcinol, hexamethylenetetramine and water. The concentrations of resorcinol and hexamethylenetetramine are 0.4 to 1 mg / mL and 0.3 to 0.9 mg / mL respectively, and the mass ratio of resorcinol to hexamethylenetetramine is controlled to be 1:0.7 to 0.

9.

8. The preparation method according to claim 1, characterized in that, The time of the high-temperature hydrothermal reaction in step (6) is 24 to 28 h.

9. The preparation method according to claim 1, characterized in that, The high-temperature calcination process of the carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode in step (6) needs to be realized in an ammonia atmosphere, the heating rate is controlled to be 2.5 to 5 °C / min, the ammonia gas flow rate is 80 to 140 mL / min, and the heat preservation time is 1 to 3 h.

10. The carbon-coated nickel-nitrogen functionalized carbon-doped titanium nitride monolithic electrode prepared by the method according to any one of claims 1 to 9.

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