CN109354131B - Method for preparing electrochemical desalting electrode based on electrostatic spinning - Google Patents

Method for preparing electrochemical desalting electrode based on electrostatic spinning Download PDF

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CN109354131B
CN109354131B CN201811406650.0A CN201811406650A CN109354131B CN 109354131 B CN109354131 B CN 109354131B CN 201811406650 A CN201811406650 A CN 201811406650A CN 109354131 B CN109354131 B CN 109354131B
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施文慧
刘晓悦
沈江南
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Zhejiang University of Technology ZJUT
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
    • C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46133—Electrodes characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination

Abstract

The invention relates to the technical field of electrochemical desalination, and discloses a method for preparing an electrochemical desalination electrode based on electrostatic spinning aiming at the problems of poor conductivity and easy agglomeration of PB (polybutadiene), which comprises the steps of preparing a CNT/PAN (carbon nanotube/polyacrylonitrile) nanofiber membrane, preparing a PANI/CNT/PAN nanofiber membrane, preparing a PB/PANI/CNT hollow nanofiber membrane and preparing an EDI (electrochemical ionization) electrode. The invention adopts an electrostatic spinning method to prepare PAN fiber, wraps a layer of conductive polyaniline on the surface, synthesizes electronegative PB crystal on the surface to prepare PB/PANI/CNT/PAN nano fiber, and dissolves away PAN to form PB/PANI/CNT hollow fiber. The method combines PB and PANI/CNT, so that the material has high conductivity and a rapid ion transmission structure, the problems of poor conductivity and easy agglomeration of the PB material are solved, and the desalting capacity, the rate capability and the cycling stability of the PB material are improved.

Description

Method for preparing electrochemical desalting electrode based on electrostatic spinning
Technical Field
The invention relates to the technical field of electrochemical desalting, in particular to a method for preparing an electrochemical desalting electrode based on electrostatic spinning.
Background
The shortage of fresh water resources is becoming more and more serious due to the environmental pollution caused by the continuous increase of population and the rapid industrial development. The development of a green and efficient seawater desalination technology has important significance for relieving the water resource shortage condition of coastal water-deficient areas and islands in China and ensuring the sustainable utilization of water resources. At present, the widely used seawater desalination technologies mainly comprise a multi-effect distillation method, a reverse osmosis method, an electrodialysis method and the like, but the methods still have the problems of high energy consumption, high maintenance cost, environmental protection and the like.
The Capacitive Deionization (CDI) is a new water treatment technology, and has the advantages of low energy consumption, low cost, easy operation, no secondary pollution and the like,has attracted much attention in recent years. The technology is based on the principle of an electric double layer, and ions in a solution are moved to an electrode with opposite charges by applying an electric field, and the electric double layer is formed on the surface of the electrode. The electric double layer can absorb and store a large amount of ions, thereby achieving the aim of desalting. When the adsorption process is finished, the voltage is reversed or removed, and the ions adsorbed on the surface of the electrode return to the solution, so that the cyclic regeneration of the electrode is realized. Electrode materials are key components of the CDI technology, and generally, electrode materials should have the characteristics of high conductivity, good wettability, high specific surface area, narrow pore size distribution, and the like. The CDI electrode materials reported in the current research are mainly carbon nanomaterials represented by activated carbon, carbon aerogel, carbon nanotubes, graphene and the like. Since the carbon electrodes have limited electric adsorption capacity and an electric double layer overlapping effect occurs during the electric adsorption process, the desalting efficiency of the CDI is low and cannot meet the requirements of practical application. In order to improve the desalination efficiency, various new CDI systems were developed. Including Membrane Capacitive Deionization (MCDI), Hybrid Capacitive Deionization (HCDI) and flow electrode deionization (FCDI). Among them, the HCDI system combines CDI with a battery system, one side electrode is composed of activated carbon and adsorbs chloride ions by the double electric layer action, and one side electrode is composed of a battery type material and captures sodium ions by the chemical bond action, thus having high desalting efficiency and desalting capability. The battery-type anode material for sodium storage mainly includes metal oxides and sulfides. The metal oxide is CoO or MoO3、CuO、Fe2O3The theoretical capacity is high, but the material can expand in volume during circulation, which damages the structural integrity and results in poor stability and rate capability. The metal sulfide includes Sb2S3、Ni3S2、MoS2、FeS2And the like, the raw materials have wide sources and low price, but the defect of poor conductivity is also existed. Therefore, improving the conductivity, cyclability and rate capability of such battery type materials becomes an important research direction for improving the electrochemical performance of such materials.
Electrochemical Desalination (EDI) technology, which replaces the traditional carbon electrode material with a battery type material, applies constant current to two ends of the electrode to replace the traditional constant voltage mode, and in the range of water decomposition voltage, sodium ions enter a negative electrode through electrolyte during constant current charging, and electrons compensate to the negative electrode to ensure charge balance and perform reduction reaction with the electrode material to achieve the aim of desalination; during constant current discharge, the electrons are compensated and returned to the negative electrode to ensure charge balance, the negative electrode material loses electrons to generate oxidation reaction, and sodium ions are removed from the negative electrode to realize the cyclic regeneration of the electrode material.
Currently, a battery-type material commonly used in the EDI technology is Prussian Blue (PB) and its analog (PBA). The general chemical formula of PBA is AxM1[M2(CN)6]Wherein A represents a monovalent alkali metal ion, M1And M2Represents transition metal ions such as iron, manganese and nickel. The crystal is of a hexahydrate cubic structure, the transition metal is positioned on a substitute angle of an octahedron connected with the conjugated cyanide ions, and the unique open framework structure provides a larger ion channel, allows sodium ions to be inserted/extracted and has excellent electrochemical performance. In addition, PBAs have the advantages of no toxicity, low price, environmental protection, hydrophilicity and the like. However, the PB material has the problems of poor conductivity, easy agglomeration and the like, and when the PB material is used for an EDI positive electrode, the desalting capacity, rate capability and cycle stability of the PB material are still to be improved.
Chinese patent application No. CN201810252823.1 discloses a capacitive desalination electrode and a preparation method thereof. According to the method, sodium titanate, sodium manganate, sodium cobaltate and a compound thereof are used as an embedded capacitive desalting cathode, a material capable of reacting with chloride ions is used as a positive electrode (such as carbon, Prussian blue, silver, bismuth oxychloride and the like) to form a double-ion de-embedding electrode, and the sodium ions and the chloride ions in the bitter alkali water/high salt water are embedded into corresponding electrodes in a chemical bond form, so that the desalting efficiency and the charge efficiency are greatly improved, and the double-electric-layer shielding effect, the co-ion effect and the like are well inhibited. However, the amount of desalting and the cycle stability thereof are still to be improved.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of a hollow nanofiber electrode material, which is simple to operate and easy to produce in mass. A large number of CNT/PAN fibers are prepared by an electrostatic spinning method, and a layer of chlorine-doped conductive polyaniline is wrapped on the surfaces of the fibers in an initiating polymerization mode. Due to the fact that polyaniline is positively charged, negative Prussian blue crystals can be attracted to be synthesized on the surface of the polyaniline, PB/PANI/CNT/PAN nano fibers can be prepared, and PB/PANI/CNT hollow fibers are formed by dissolving away PAN. According to the method, the PB is combined with PANI/CNT, so that the material has high conductivity and a rapid ion transmission structure, the problems of poor conductivity and easy agglomeration of the PB material are effectively solved, and the desalting capacity, the rate performance and the cycle stability of the PB material are improved.
The specific technical scheme of the invention is as follows: a method for preparing an electrochemical desalting electrode based on electrostatic spinning comprises the following steps:
(1) preparation of CNT/PAN electrospun nanofiber membranes: dissolving PAN in N, N-dimethylformamide to obtain a PAN solution, uniformly mixing a CNT dispersion liquid and the PAN solution, taking the obtained CNT/PAN dispersion liquid as an injection, and preparing a CNT/PAN electrostatic spinning nanofiber membrane by using an electrostatic spinning method;
(2) preparation of PANI/CNT/PAN nanofiber membranes: adding ammonium persulfate into a hydrochloric acid solution to prepare an initiator, placing the CNT/PAN nano-fiber membrane prepared in the step (1) into the hydrochloric acid solution, adding aniline, uniformly dispersing, adding the initiator to initiate polymerization, taking out a product after polymerization reaction, washing with deionized water and ethanol, and drying to obtain the PANI/CNT/PAN nano-fiber membrane;
(3) preparation of PB/PANI/CNT nanofiber membrane: putting the PANI/CNT/PAN nano-fiber membrane prepared in the step (2) into a ferric chloride solution, and slowly adding a potassium ferricyanide solution for reaction; repeatedly cleaning the obtained product by using deionized water and acetone, and drying in vacuum to obtain a PB/PANI/CNT/PAN nano fiber membrane; putting the obtained PB/PANI/CNT/PAN nanofiber membrane into DMF for repeated cleaning, and dissolving PAN to obtain a PB/PANI/CNT hollow nanofiber membrane;
(4) preparing an EDI electrode: and (3) taking the PB/PANI/CNT hollow nanofiber membrane prepared in the step (3) as an EDI negative electrode active material, taking activated carbon as an EDI positive electrode active material, taking polyvinylidene fluoride as a binder, taking conductive carbon black as a conductive agent, adding N-methyl pyrrolidone, repeatedly grinding to obtain a slurry, and uniformly coating the slurry on a graphite sheet to obtain the EDI electrode.
The invention utilizes an electrostatic spinning method to prepare a large amount of CNT/PAN fibers, and a layer of chlorine-doped conductive polyaniline is initiated and coated on the surfaces of the fibers in a polymerization manner. The polyaniline is positively charged and can attract the PB crystals with negative charge to synthesize on the surface of the polyaniline, so that the PB/PANI/CNT/PAN nano-fiber can be prepared, and the PB/PANI/CNT hollow fiber can be formed by dissolving away PAN. According to the method, the PB is combined with PANI/CNT, so that the material has high conductivity and a rapid ion transmission structure, the problems of poor conductivity and easy agglomeration of the PB material are effectively solved, and the desalting capacity, the rate performance and the cycle stability of the PB material are improved. And uniformly grinding the CNT/PANI/PB, conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone until slurry is coated on the carbon electrode, performing vacuum drying, then using the slurry as an EDI negative electrode, preparing an activated carbon electrode as a positive electrode by the same method, assembling the activated carbon electrode and a common anion-cation exchange membrane into an EDI module, circulating NaCl feed liquid through a peristaltic pump, and applying constant current to two ends of the electrode to realize the embedding/removing process of NaCl. The EDI negative electrode material prepared by the invention has higher desalting capacity, good rate capability and high cycle stability, and the capacity retention rate reaches up to 100%.
Preferably, in the step (1), the mass ratio of the PAN to the N, N-dimethylformamide is 1: 2.5-3.5, the concentration of the CNT in the CNT/PAN solution is 10-20 wt%, the concentration of the CNT dispersion is 25-35 wt%, the concentration of the PAN is 20-30 wt%, and the volume ratio of the CNT dispersion to the PAN solution is 0.9-1.1: 1.
According to the invention, the mass ratio of PAN to N, N-dimethylformamide is 1: 2.5-3.5, the concentration of PAN is 20-30 wt%, the concentration of CNT dispersion liquid is 25-35 wt%, and the concentration of CNT in CNT/PAN solution is 10-20 wt%, so that CNT in the prepared CNT/PAN electrostatic spinning nanofiber membrane is uniformly dispersed.
Preferably, in step (1), the electrospinning operating conditions are: the humidity is 35-45%, the voltage is 14-18 kV, the distance between a spinning nozzle and a receiving plate is 12-18 cm, and the injection speed is 0.2-0.4 mL/h.
Preferably, in the step (2), the concentration of the hydrochloric acid solution is 0.5-1.5 mol/L, the molar ratio of ammonium persulfate to aniline is 0.95-1.05: 1, and the volume ratio of aniline to hydrochloric acid solution is 0.045-0.047: 1.
Preferably, in the step (2), the area-to-volume ratio of the CNT/PAN nanofiber membrane to the hydrochloric acid solution is 4 x 4-5 x 5cm2:20mL。
Preferably, in the step (2), the volume ratio of the hydrochloric acid solution containing the CNT/PAN nanofiber membrane to the initiator is 1: 0.95-1.05, and the polymerization reaction time is 15-25 min.
The concentration of the hydrochloric acid solution is 0.5-1.5 mol/L, the molar ratio of ammonium persulfate to aniline is 0.95-1.05: 1, the volume ratio of aniline to hydrochloric acid solution is 0.045-0.047: 1, and the area-to-volume ratio of the CNT/PAN nanofiber membrane to the hydrochloric acid solution is 4 x 4-5 x 5cm2When the volume is 20mL, the surface of the PAN fiber is uniformly coated with a layer of chlorine-doped conductive polyaniline, which is beneficial to synthesis of PB on the surface of the PAN fiber. When the amount of aniline is too small, it is difficult to form a continuous polyaniline layer, and it is difficult to form a hollow fiber having a complete structure after PAN dissolution in the subsequent step. Too much aniline forms too thick a polyaniline layer, which affects the dissolution rate of PAN.
Preferably, in the step (3), Fe is contained in the potassium ferricyanide solution and the ferric chloride solution3+The concentration is 0.010-0.015 mol/L.
Preferably, the volume ratio of the ferric chloride solution to the potassium ferricyanide solution is 3-5: 2. Fe in potassium ferricyanide solution and ferric chloride solution3+The concentration is the same, the volume ratio of ferric chloride solution to potassium ferricyanide solution is 3-5: 2, the potassium ferricyanide and ferric chloride react to generate PB, and PB crystals nucleate and grow uniformly on the surfaces of the PANI/CNT/PAN nanofibers.
Preferably, in the step (3), the reaction is carried out in an oil bath, the reaction temperature is 55-65 ℃, and the reaction time is 5-7 h; the drying temperature is 40-80 ℃, and the drying time is 9-15 h.
Preferably, in the step (4), the mass ratio of the negative electrode active material or the positive electrode active material to the binder and the conductive agent is 7-8: 1-1.5: 1.5, the mass-to-volume ratio of the negative electrode active material or the positive electrode active material to the N-methyl pyrrolidone is 1g: 8-10 mL, and the volume ratio is calculated according to the area of the graphite sheetIs 3X 3cm2And the coating amount of the slurry is 7-13 mg.
Compared with the prior art, the invention has the beneficial effects that:
(1) compared with the common PB nano particles, the PB crystal size grown on the PANI surface is reduced to 1/3, the PB crystal size is uniformly distributed on the PANI surface, the agglomeration phenomenon among the PB particles is effectively prevented, and meanwhile, the transmission rate of electrons in the PB/PANI/CNT electrostatic spinning nanofiber membrane is improved compared with that of a PB material because the doped PANI has good conductivity;
(2) on one hand, a PB/PANI/CNT continuous hollow tubular structure is obtained after polymer PAN is dissolved in DMF, on the other hand, the CNT plays a role in enhancing PANI redox reaction on the tube wall and the tube inside, the electron transmission rate is enhanced, and the performance of the PB/PANI/CNT/PAN electrostatic spinning nanofiber membrane is greatly improved compared with that of PB nanoparticles;
(3) the electrode has the advantages of wide source of raw materials required by electrode manufacturing, simple electrode preparation process, good circulation stability, low production cost and good application prospect in Electrochemical Deionization (EDI) desalination.
Drawings
FIG. 1 is an SEM image of PB crystals obtained in step (3) of comparative example 2 of a method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 2 is an SEM image of the CNT/PAN electrospun nanofiber membrane obtained in step (1) of example 1 of a method for preparing an electrochemical desalination electrode based on electrospinning according to the present invention;
FIG. 3 is an SEM image of the PANI/CNT/PAN nanofiber membrane prepared in step (2) of example 1 of the method for preparing an electrochemical desalination electrode based on electrospinning according to the present invention;
FIG. 4 is an SEM image of PB/PANI/CNT/PAN nanofiber membrane obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning according to the invention;
FIG. 5 is a high-magnification SEM image of the PB/PANI/CNT/PAN nanofiber membrane obtained in step (3) of comparative example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning according to the present invention;
FIG. 6 is an SEM image of a cross section of a PB/PANI/CNT hollow nanofiber membrane obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning according to the invention;
FIG. 7 is a high-magnification SEM image of a cross section of a PB/PANI/CNT hollow nanofiber membrane obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning according to the invention;
FIG. 8 is a high-power TEM image of PB/PANI/CNT hollow nanofibers obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 9 is an element distribution diagram of PB/PANI/CNT hollow nanofibers obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 10 is XRD patterns of PB crystals obtained in step (3) of comparative example 2 and PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 of a method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 11 is an infrared spectrum of CNT based on a method for preparing an electrochemical desalination electrode by electrospinning according to the present invention and PANI/CNT nanofibers obtained in step (1) of example 1;
FIG. 12 shows that the PB crystal obtained in step (3) of comparative example 2 and the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 of the method for preparing the electrochemical desalting electrode based on electrostatic spinning are 2-50 mv.s-1CV plot at scan rate;
FIG. 13 shows the PB crystals obtained in step (3) of comparative example 2 and the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning at 2 mv.s according to the present invention-1CV plot at scan rate;
FIG. 14 is an EIS diagram of PB crystals obtained in step (3) of comparative example 2 and PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 of a method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 15 shows the PB crystals obtained in step (3) of comparative example 2 and the PB/PANI/CNT nanofiber membrane obtained in step (3) of comparative example 1 of the method for preparing an electrochemical desalting electrode based on electrostatic spinning at 500 mA-g-1Discharge profile at current density;
FIG. 16 shows that the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 of the method for preparing the electrochemical desalting electrode based on electrostatic spinning is 0.125-5000 mA-g-1A charge-discharge curve at current density;
FIG. 17 shows the ratio of 0.125-5000 mA-g of the PB crystals obtained in step (3) of comparative example 2, the PANI/CNT nanofiber membrane obtained in step (3) of comparative example 1, and the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 in the method for preparing an electrochemical desalination electrode based on electrospinning according to the present invention-1Broken line comparison graph of discharge capacitance under current density;
FIG. 18 is a graph of EDI electro-adsorption behavior of other PB/PANI/CNT electrodes at different current densities obtained in example 1 of a method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention;
FIG. 19 is a line graph of EDI electro-adsorption capacity of PB/PANI/CNT electrode obtained in example 1 of the method for preparing electrochemical desalting electrode based on electrostatic spinning according to the present invention at different TDS;
FIG. 20 shows the PB crystals obtained in step (3) of comparative example 2 and the PB/PANI/CNT electrodes obtained in example 1 at 500 mA-g.g.in the method for preparing an electrochemical desalting electrode based on electrospinning according to the present invention-1And (5) performing electroadsorption capacity scatter diagram under the next 100 EDI cycles.
Detailed Description
The present invention will be further described with reference to the following examples. The devices, connections, and methods referred to in this disclosure are those known in the art, unless otherwise indicated.
Example 1
A method for preparing an electrochemical desalting electrode based on electrostatic spinning comprises the following steps:
(1) preparation of CNT/PAN electrospun nanofiber membranes: dissolving PAN in N, N-dimethylformamide to obtain a PAN solution, wherein the mass ratio of the PAN to the N, N-dimethylformamide is 1:3, uniformly mixing a CNT dispersion liquid with the concentration of 30wt% and a PAN solution with the concentration of 24wt% in a volume ratio of 1:1, taking the obtained CNT/PAN dispersion liquid as an injection, wherein the concentration of CNT in the CNT/PAN solution is 15wt%, and preparing a CNT/PAN electrostatic spinning nanofiber membrane by using an electrostatic spinning method; the electrostatic spinning operating conditions are as follows: the humidity was 40%, the voltage was 16kV, the distance between the spinneret and the receiving plate was 15cm, and the injection rate was 0.3 mL/h.
(2) Preparation of PANI/CNT/PAN nanofiber membranes: adding ammonium persulfate into a hydrochloric acid solution with the concentration of 1mol/L to prepare an initiator; putting the CNT/PAN nano-fiber membrane prepared in the step (1) into a hydrochloric acid solution with the concentration of 1mol/L, wherein the area-volume ratio of the CNT/PAN nano-fiber membrane to the hydrochloric acid solution is 5 multiplied by 5cm2Adding aniline into the solution 20mL, wherein the volume ratio of aniline to hydrochloric acid solution is 0.046:1, the molar ratio of ammonium persulfate to aniline is 1:1, uniformly dispersing, adding an initiator with the same volume to initiate polymerization, taking out a product after polymerization for 20min, washing the product with deionized water and ethanol, and drying the product to obtain the PANI/CNT/PAN nanofiber membrane;
(3) preparation of PB/PANI/CNT nanofiber membrane: putting the PANI/CNT/PAN nano-fiber membrane prepared in the step (2) into Fe3+Slowly adding Fe into ferric chloride solution with the concentration of 0.0125mol/L3+Reacting 0.0125mol/L potassium ferricyanide solution, wherein the volume ratio of ferric chloride solution to potassium ferricyanide solution is 2:1, the reaction is carried out in an oil bath, the reaction temperature is 60 ℃, and the reaction time is 6 hours; the drying temperature is 60 ℃, and the drying time is 12 hours; repeatedly cleaning the obtained product with deionized water and acetone, and drying in vacuum to obtain a PB/PANI/CNT/PAN nanofiber membrane; putting the obtained PB/PANI/CNT/PAN nanofiber membrane into DMF for repeated cleaning, and dissolving PAN to obtain the PB/PANI/CNT nanofiber membrane;
(4) preparing an EDI electrode: the PB/PANI/CNT electrostatic spinning nanofiber membrane prepared in the step (3) is EDI negativeThe cathode active material is prepared by taking activated carbon as an EDI cathode active material, taking polyvinylidene fluoride as a binder, taking conductive carbon black as a conductive agent, adding N-methyl pyrrolidone into the cathode active material or the cathode active material, the binder and the conductive agent in a mass ratio of 7.5:1.5:1.5, repeatedly grinding the cathode active material or the cathode active material, the binder and the conductive agent to obtain a slurry, uniformly coating the slurry on a graphite sheet, and uniformly coating the graphite sheet according to the graphite sheet area of 3 multiplied by 3cm2The amount of the slurry applied was 10mg, and an EDI electrode was prepared.
Example 2
A method for preparing an electrochemical desalting electrode based on electrostatic spinning comprises the following steps:
(1) preparation of CNT/PAN electrospun nanofiber membranes: dissolving PAN in N, N-dimethylformamide to obtain a PAN solution, wherein the mass ratio of the PAN to the N, N-dimethylformamide is 1:3.5, uniformly mixing a CNT dispersion liquid with the concentration of 35wt% and a PAN solution with the concentration of 30wt% in a volume ratio of 0.9:1, taking the obtained CNT/PAN dispersion liquid as an injection, wherein the concentration of CNT in the CNT/PAN solution is 20wt%, and preparing a CNT/PAN electrospun nanofiber membrane by using an electrospinning method; the electrostatic spinning operating conditions are as follows: the humidity was 35%, the voltage was 18kV, the distance between the spinneret and the receiving plate was 12cm, and the injection speed was 0.2 mL/h.
(2) Preparation of PANI/CNT/PAN nanofiber membranes: adding ammonium persulfate into a hydrochloric acid solution with the concentration of 1.5mol/L to prepare an initiator; putting the CNT/PAN nano-fiber membrane prepared in the step (1) into a hydrochloric acid solution with the concentration of 1.5mol/L, wherein the area-volume ratio of the CNT/PAN nano-fiber membrane to the hydrochloric acid solution is 4.5 multiplied by 4.5cm2Adding aniline into the solution 20mL, wherein the volume ratio of aniline to hydrochloric acid solution is 0.047:1, the molar ratio of ammonium persulfate to aniline is 1.05:1, uniformly dispersing, adding an equal volume of initiator to initiate polymerization, taking out a product after polymerizing for 25min, washing with deionized water and ethanol, and drying to obtain the PANI/CNT/PAN nanofiber membrane;
(3) preparation of PB/PANI/CNT nanofiber membrane: putting the PANI/CNT/PAN nano-fiber membrane prepared in the step (2) into Fe3+Slowly adding 0.015mol/L ferric chloride solutionInto Fe3+Reacting 0.015mol/L potassium ferricyanide solution, wherein the volume ratio of ferric chloride solution to potassium ferricyanide solution is 3:2, the reaction is carried out in an oil bath, the reaction temperature is 65 ℃, and the reaction time is 5 hours; the drying temperature is 40 ℃, and the drying time is 15 h; repeatedly cleaning the obtained product with deionized water and acetone, and drying in vacuum to obtain a PB/PANI/CNT/PAN nanofiber membrane; putting the obtained PB/PANI/CNT/PAN nanofiber membrane into DMF for repeated cleaning, and dissolving PAN to obtain the PB/PANI/CNT nanofiber membrane;
(4) preparing an EDI electrode: taking the PB/PANI/CNT electrostatic spinning nanofiber membrane prepared in the step (3) as an EDI negative electrode active material, taking activated carbon as an EDI positive electrode active material, taking polyvinylidene fluoride as a binder, taking conductive carbon black as a conductive agent, adding N-methyl pyrrolidone into the negative electrode active material or the positive electrode active material, the binder and the conductive agent in a mass ratio of 8:1:1.5, repeatedly grinding the mixture to obtain a paste, uniformly coating the paste on a graphite sheet, and uniformly coating the graphite sheet according to the area of the graphite sheet of 3 x 3cm, wherein the mass-volume ratio of the negative electrode active material or the positive electrode active material to the N-methyl pyrrolidone is 1g/9mL2The amount of the slurry applied was 13mg, and an EDI electrode was prepared.
Example 3
A method for preparing an electrochemical desalting electrode based on electrostatic spinning comprises the following steps:
(1) preparation of CNT/PAN electrospun nanofiber membranes: dissolving PAN in N, N-dimethylformamide to obtain a PAN solution, wherein the mass ratio of the PAN to the N, N-dimethylformamide is 1:2.5, uniformly mixing a CNT dispersion liquid with the concentration of 25wt% and a PAN solution with the concentration of 20wt% in a volume ratio of 1:1, taking the obtained CNT/PAN dispersion liquid as an injection, wherein the concentration of CNT in the CNT/PAN solution is 10wt%, and preparing a CNT/PAN electrospun nanofiber membrane by using an electrospinning method; the electrostatic spinning operating conditions are as follows: the humidity was 45%, the voltage was 14kV, the distance between the spinneret and the receiving plate was 18cm, and the injection rate was 0.4 mL/h.
(2) Preparation of PANI/CNT/PAN nanofiber membranes: adding ammonium persulfate into a hydrochloric acid solution with the concentration of 0.5mol/L to prepare an initiator; the CNT/PAN nano-fiber prepared in the step (1) is treatedThe fiber membrane is placed in hydrochloric acid solution with the concentration of 0.5mol/L, and the area-volume ratio of the CNT/PAN nano-fiber membrane to the hydrochloric acid solution is 4 multiplied by 4cm2Adding aniline into 20mL of the solution, wherein the volume ratio of aniline to hydrochloric acid solution is 0.045:1, the molar ratio of ammonium persulfate to aniline is 0.95:1, uniformly dispersing, adding an equal volume of initiator to initiate polymerization, taking out a product after polymerizing for 15min, washing with deionized water and ethanol, and drying to obtain the PANI/CNT/PAN nano-fiber membrane;
(3) preparation of PB/PANI/CNT nanofiber membrane: putting the PANI/CNT/PAN nano-fiber membrane prepared in the step (2) into Fe3+Slowly adding Fe into ferric chloride solution with the concentration of 0.010mol/L3+Reacting 0.010mol/L potassium ferricyanide solution, wherein the volume ratio of ferric chloride solution to potassium ferricyanide solution is 5:2, the reaction is carried out in an oil bath, the reaction temperature is 55 ℃, and the reaction time is 7 hours; the drying temperature is 60 ℃, and the drying time is 12 hours; repeatedly cleaning the obtained product with deionized water and acetone, and drying in vacuum to obtain a PB/PANI/CNT/PAN nanofiber membrane; putting the obtained PB/PANI/CNT/PAN nanofiber membrane into DMF for repeated cleaning, and dissolving PAN to obtain the PB/PANI/CNT nanofiber membrane;
(4) preparing an EDI electrode: taking the PB/PANI/CNT electrostatic spinning nanofiber membrane prepared in the step (3) as an EDI negative electrode active material, taking activated carbon as an EDI positive electrode active material, taking polyvinylidene fluoride as a binder, taking conductive carbon black as a conductive agent, adding N-methyl pyrrolidone into the negative electrode active material or the positive electrode active material, the binder and the conductive agent in a mass ratio of 7.5:1.5:1.5, repeatedly grinding the mixture to form slurry, uniformly coating the slurry on a graphite sheet, and uniformly coating the graphite sheet according to the area of the graphite sheet of 3 x 3cm, wherein the mass-volume ratio of the negative electrode active material or the positive electrode active material to the N-methyl pyrrolidone is 1g/10mL2The amount of the slurry applied was 7mg, and an EDI electrode was prepared.
Comparative example 1
Comparative example 1 differs from example 1 in that: in the step (3), the preparation method of the PANI/CNT nanofiber membrane comprises the following steps: and (3) putting the PANI/CNT/PAN nano-fiber membrane into a DMF solution, dissolving out PAN, repeatedly washing the obtained product by using deionized water and ethanol, and then drying the product in a vacuum oven at 60 ℃ for 12 hours to obtain the PANI/CNT nano-fiber membrane. The rest of the procedure was the same as in example 1.
Comparative example 2
Comparative example 2 differs from example 1 in that: in the step (3), the PANI/CNT/PAN nanofiber membrane is not added, standing is carried out for 20min after the reaction is finished, the supernatant is poured off, the obtained product is washed by deionized water for 3 times and acetone for 3 times, and then the product is dried in a vacuum oven at 60 ℃ for 12h, and finally the PB crystal is obtained. The rest of the procedure was the same as in example 1.
The properties of the intermediate product or electrode were examined by SEM, TEM, XRD, infrared spectroscopy, CV, EIS, charge and discharge and EDI analysis.
The detection method comprises the following steps:
SEM test was performed on a HIACHI SU-8010 field emission scanning electron microscope, and the sample preparation method was as follows: a small amount of samples are attached to the supporting table with the conductive adhesive section.
The TEM test is carried out on a JEM-100CX II type transmission electron microscope, and the sample preparation method comprises the following steps: a trace sample of the PB/PANI/CNT/PAN nanofiber membrane prepared in the step (3) of the example 1 is placed in a centrifuge tube filled with 1mL of absolute ethyl alcohol, then the centrifuge tube is placed in a water bath ultrasonic pool with the ultrasonic power of 250W for continuous ultrasonic treatment for 15min to obtain an ethanol phase dispersion liquid of the nanofiber, a small amount of dispersion liquid is dropped on the surface of a 230-mesh TEM (micro-porous carbon support membrane) micro-grid copper mesh, and then the dispersion liquid is dried in a 60-DEG C air-blast oven to obtain the nanofiber membrane. The TEM imaging voltage was 300 kV.
The XRD test is carried out on an X-ray diffractometer, and samples to be tested are prepared as follows: the PB/PANI/CNT/PAN nanofiber membrane prepared in the step (3) of example 1 and the PB crystal sample obtained in the comparative example 2 were taken, ground into powder, then laid out in a quartz plate frosted groove, and then flattened by using a glass slide until no obvious protrusions or gaps are formed, and then the test was carried out, wherein the scanning speed is 10 ℃ min-1。
The infrared measurements were performed on an infrared spectrometer and the samples were prepared as follows: grinding and tabletting a small amount of CNT powder and potassium bromide, wherein the wavelength range is 500-4000 cm-1The test was performed by the same method as for the PB/PANI/CNT/PAN nanofiber membrane sample obtained in comparative example 1.
CV tests were performed on a electrochemical workstation of type CHI 760, taking 8mg each of the PB/PANI/CNT/PAN nanofibrous membrane obtained in step (3) of example 1, the PB/PANI/CNT/PAN nanofibrous membrane obtained in comparative example 1 and the PB crystal sample obtained in comparative example 2, according to active substance: conductive carbon black: PVDF (polyvinylidene fluoride) in a mass ratio of 7: 1.5:1.5 mixing and then adding dropwise N-methyl pyrrolidone (NMP) solution and repeatedly grinding into uniform slurry. The slurry was uniformly applied to 6 pieces of 2X 1cm2Coated on a graphite sheet of 1X 1cm in area2. And (3) placing the electrode in a vacuum drying oven at 60 ℃, and drying for 12h in vacuum to remove the solvent to obtain the electrode slice. The CV test adopts a three-electrode system, an electrode plate is taken as a working electrode, a platinum sheet is taken as a counter electrode, Ag/AgCl is taken as a reference electrode, NaCl with the concentration of 1M is taken as electrolyte, the scanning voltage interval is-0.4-0.6V, and the scanning speed is 2-50 mv s-1。
EIS test is carried out on CHI 760 type electrochemical workstation, and the preparation method of the electrode plate is the same as CV test. The EIS analysis also adopts a three-electrode system, NaCl with the concentration of 1M is taken as electrolyte, the potential is 10mv, and the frequency range is 0.01-100 kHz.
The charge and discharge test is carried out on a CHI 760 type electrochemical workstation, the electrode plate preparation method and CV test charge and discharge analysis also adopt a three-electrode system, NaCl with the concentration of 1M is used as electrolyte, the voltage interval is-0.4-0.6, and the current density is 125-5000 mA.g-1。
Preparing an EDI electrode: the PB/PANI/CNT/PAN nanofiber membrane obtained in step (3) of example 1, the PB/PANI/CNT/PAN nanofiber membrane obtained in comparative example 1 and the PB crystal sample obtained in comparative example 2 were taken, each 8mg, as active material: conductive carbon black: PVDF (polyvinylidene fluoride) in a mass ratio of 7: 1.5:1.5 after mixing, the NMP solution was added dropwise and repeatedly ground to a uniform slurry. The slurry was uniformly coated on 8X 8cm2Coated on a graphite sheet having an area of 3X 3cm2. The electrode was placed in a vacuum oven at 60 ℃ and vacuum dried for 12h to remove the solvent, yielding an EDI negative side. The same preparation method is adopted, except that activated carbon is used as an active material, and the EDI positive electrode side is obtained.
The detection results are shown in the figures 1-20.
Fig. 1 is an SEM image of PB crystals obtained in step (3) of comparative example 2. It can be seen that the microstructure of the PB crystals is 200nm sized cubes and is heavily agglomerated. Fig. 2 is an SEM image of the CNT/PAN electrospun nanofiber membrane obtained in step (1) of example 1. It can be seen that the nanofibers are uniform in size, about 500nm in diameter, and the fiber surface is smooth, indicating that the CNTs are uniformly dispersed in the PAN nanofibers. Fig. 3 is an SEM image of the PANI/CNT/PAN nanofiber membrane prepared in step (2) of example 1. Compared with the graph shown in fig. 2, the surface of the nanofiber becomes rough, which indicates that PANI is uniformly coated on the CNT/PAN electrospun nanofiber, and the thickness of the PANI layer is 5-20 nm, which indicates that aniline can be adsorbed on the surface of the CNT/PAN electrospun nanofiber, and can be polymerized into a continuous polyaniline layer on the surface of the CNT/PAN electrospun nanofiber under the action of an initiator. FIG. 4 is an SEM image of the PB/PANI/CNT/PAN nanofiber membrane obtained in step (3) of example 1. The roughness degree of the nanofiber in the figure is higher, PB particles grow on the surface of the PANI/CNT/PAN nanofiber uniformly, the cubic structure is still maintained, the size is 70-90 nm, the distribution is uniform, and serious agglomeration does not occur. The PB crystals can nucleate on the surface of the polyaniline and grow uniformly.
FIG. 5 is a high power SEM image of the PB/PANI/CNT/PAN nanofiber membrane obtained in step (3) of example 1. The apparent hollow tubular structure can be observed in the figure, indicating that DMF can dissolve PAN but not PANI layer, therefore PANI can be used as a support layer of PB, and the hollow tubular structure of PB/PANI/CNT is maintained. FIG. 6 is an SEM image of a cross-section of the PB/PANI/CNT hollow nanofiber membrane obtained in step (3) of example 1. It can be observed that the PB/PANI/CNT nanofibers can maintain the morphology of CNT/PAN nanofibers and increase in diameter to 700 nm. The figure shows that the obvious hollow tubular structure is observed, the thickness of the tube wall is 70-90 nm and is consistent with the PB crystal size, and a part of CNT is remained in the tubular structure, which indicates that the CNT is successfully embedded in the tubular structure.
FIG. 7 is a high power SEM image of PB/PANI/CNT hollow nanofibers obtained in step (3) of example 1. The hollow structure of the nanofibers can be observed, indicating that the PAN inside the nanofibers has been completely removed. However, it is impossible to distinguish whether or not the CNTs exist inside the film under the depth contrast of the transmission electron microscope. FIG. 8 is a high power TEM image of PB/PANI/CNT hollow nanofibers obtained in step (3) of example 1. Nanofibers at high magnification show CNTs encapsulated in nanotubes. FIG. 9 is an element distribution diagram of the PB/PANI/CNT hollow nanofibers obtained in step (3) of example 1. The coexistence of Fe, C and N elements is shown, and the Fe, C and N elements are uniformly distributed in the hollow tubular structure of the nano fiber. The distribution of Fe element in the PB crystal is clear, and the hollow tubular structure of the PB/PANI/CNT nano fiber is further shown.
Fig. 10 is XRD patterns of PB crystals obtained in step (3) of comparative example 2 and PB/PANI/CNT nanofiber film obtained in step (3) of example 1. The peak packages of PB at 17 degrees, 24 degrees, 35 degrees and 39 degrees can be found on the corresponding diffraction peaks of PB/PANI/CNT. The PB is combined with PANI, the structure is complete, and the crystal image of the PB is not changed. FIG. 11 is an infrared spectrum of CNT and PANI/CNT nanofibers obtained in step (1) of example 1. 3460cm in the PANI/CNT infrared spectrogram-1Is the vibration absorption peak of N-H, 1560cm-1And 1480cm-11300cm corresponding to the quinoid absorption peak and the absorption peak of benzene ring structure of C-C bond-1And 1240cm-1Is at the absorption peak of corresponding aromatic amine Ar-N, 1110cm-1And 805cm-1Respectively representing the in-plane and out-of-plane bending vibration absorption peaks of the benzene ring. The successful synthesis of the chlorine doped polyaniline salt was demonstrated. CNT infrared spectrogram at 3460cm-1、2920cm-1And 2360cm-1The absorption peaks appeared there were all corresponding absorption peaks found in the infrared spectrum of PANI/CNT, indicating that CNT had been successfully doped into the hollow tubular structure of PANI.
FIG. 12 shows the ratio of 2-50 mV.s between the PB crystals obtained in step (3) of comparative example 2 and the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1-1CV curve at scan rate. A pair of redox peaks appears at the position of +0.1V, corresponding to the process of intercalation and deintercalation of sodium ions in the material, indicating that the capacitance is mainly provided by pseudocapacitance. The integrated area of the CV curve graph of the PB crystal is obviously smaller than that of the PB/PANI/CNT nano-fiber film under the same scanning speed, and the capacitance is controlled to be 221F-g-1Lifting to 302F g-1Due to the PANI as a support layer, the PB is formed into a nanofiber hollow tubular structure, and the ion transmission rate is improved. FIG. 13 shows the ratio of 2 mV. s for the PB obtained in step (3) of comparative example 2 and the PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1-1CV curve at scan rate. Corresponding capacitance of 117-302 F.g-1The multiplying power performance is improved to 38.7%. FIG. 14 is an EIS diagram of PB crystals obtained in step (3) of comparative example 2 and PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1. The small semicircular diameter of the high frequency region reflects the charge transfer resistance. The diagonal lines of the low frequency region represent the Warburg impedance. The slope of the PB/PANI/CNT nanofiber membrane is the highest in the low frequency region, which indicates that the PB/PANI/CNT nanofiber membrane has the best ion diffusion rate. The semi-circle diagram shown in the auxiliary diagram represents the equivalent series resistance of PB crystals and PB/PANI/CNT nanofiber films, respectively, of 3.04 Ω and 2.89 Ω, and the increase in capacitance is partly due to the decrease in resistance. Compared with a PB crystal, the PB/PANI/CNT nanofiber membrane has the advantages that the slope of a low-frequency region is increased, and the equivalent series resistance of a high-frequency region is reduced, which indicates that the PANI/CNT hollow tubular structure is favorable for reducing the resistance of a PB material. FIG. 15 shows the ratio of PB crystals obtained in step (3) of comparative example 2 and PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 at 500mA g-1Discharge profile at current density. In the figure, a PB crystal and a PB/PANI/CNT nanofiber membrane have a discharge platform between-0.1V and 0.3V, which corresponds to the sodium ion extraction process. The PB/PANI/CNT nanofiber membrane has the longest discharge time, which indicates that the PB/PANI/CNT nanofiber membrane has the highest discharge capacitance. FIG. 16 shows that the ratio of PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 is 0.125-5000 mA-g-1Charge and discharge curves at current density. The discharge capacitance corresponding to different current densities in the figure is 434.8-241 F.g-1The capacity retention rate was 55.5%. FIG. 17 is a graph of PB crystals obtained in step (3) of comparative example 2, PANI/CNT nanofiber membrane obtained in step (3) of comparative example 1, and PB/PANI/CNT nanofiber membrane obtained in step (3) of example 1 at 0.125-5000 mA-g-1The discharge capacity at current density is plotted against the line. The discharge capacitance of the PB crystal is 340-95.9F g-1The capacity retention rate is 28.2%; PANI/CNT nanofiber membraneA discharge capacity of 417 to 198.9 Fg-1The capacity retention rate is 48.5%, which shows that PANI/CNT is helpful to improve the rate capability of the PB crystal material.
FIG. 18 is a graph of EDI electro-adsorption behavior of the PB/PANI/CNT electrode obtained in example 1 at different current densities. The PB/PANI/CNT removal rate is increased from 108.7 mg-g along with the increase of the current density-1Reduced to 66.7mg g-1This is due to incomplete reduction/oxidation of the PB crystals at higher current densities. Meanwhile, with the increase of the current density, the consumption time of the adsorption/desorption action is reduced, and the current density is 500mA · g-1When the capacity is high, the capacity of electric adsorption is up to 75.4 mg.g-1And the time consumption is low, therefore 500mA g is selected-1As a subsequent test current density. FIG. 19 is a line graph of EDI electro-adsorption capacity of the PB/PANI/CNT electrode obtained in example 1 at different TDS. It is clear that the adsorption capacity of PB/PANI/CNT electrode increases with the increase of NaCl concentration, and reaches 97.5mg g at 1000ppm-1Almost twice as much as 125 ppm. This is due to the fact that the higher the solution concentration, the higher the conductivity, the higher the electrochemical activity, resulting in higher electrochemical performance of the PB/PANI/CNT electrode. The PB/PANI/CNT electrode material has better application prospect in high-concentration seawater. FIG. 20 shows the PB crystals obtained in step (3) of comparative example 2 and the PB/PANI/CNT electrodes obtained in example 1 at 500mA g-1And (5) performing electroadsorption capacity scatter diagram under the next 100 EDI cycles. The electric adsorption capacity of the PB crystal has a slight trend of rising in the first 2-3 cycles because the electrode is in the activation stage and the electric adsorption capacity is 47mg g in the 3 rd-8 th cycle-1Reduced to 41mg g-1The trend of decline is reduced within 10-45 cycles, from 41mg g-1The concentration is reduced to 27mg g-1The electric adsorption capacity is maintained at 27 mg/g in cycles 40 to 100-1It shows that within 100 cycles, the stability of PB crystals is poor. The electric adsorption capacity of the PB/PANI/CNT electrode has a remarkable rising trend within the first 1-13 cycles and is from 71mg g-1Increased to 82mg g-1This is due to the electrode being in the activation phase. The electric adsorption capacity is hardly reduced in 13 th to 100 th cycles because of the nano particles dispersed on the hollow tubular surface of the PANI/CNTMore electron channels greatly promote electron conduction and accelerate the transportation of sodium ions. In addition, the PB is effectively prevented from being washed by high-speed water flow due to the fixing effect of the PANI/CNT layer. Indicating that the PB/PANI/CNT electrode has higher reversibility.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (10)

1. A method for preparing an electrochemical desalting electrode based on electrostatic spinning is characterized by comprising the following steps:
(1) preparation of CNT/PAN electrospun nanofiber membranes: dissolving PAN in N, N-dimethylformamide to obtain a PAN solution, uniformly mixing a CNT dispersion liquid and the PAN solution, taking the obtained CNT/PAN dispersion liquid as an injection, and preparing a CNT/PAN electrostatic spinning nanofiber membrane by using an electrostatic spinning method;
(2) preparation of PANI/CNT/PAN nanofiber membranes: adding ammonium persulfate into a hydrochloric acid solution to prepare an initiator, placing the CNT/PAN nano-fiber membrane prepared in the step (1) into the hydrochloric acid solution, adding aniline, uniformly dispersing, adding the initiator to initiate polymerization, taking out a product after polymerization reaction, washing with deionized water and ethanol, and drying to obtain the PANI/CNT/PAN nano-fiber membrane;
(3) preparation of PB/PANI/CNT nanofiber membrane: putting the PANI/CNT/PAN nano-fiber membrane prepared in the step (2) into a ferric chloride solution, and slowly adding a potassium ferricyanide solution for reaction; repeatedly cleaning the obtained product by using deionized water and acetone, and drying in vacuum to obtain a PB/PANI/CNT/PAN nano fiber membrane; putting the obtained PB/PANI/CNT/PAN nanofiber membrane into DMF for repeated cleaning, and dissolving PAN to obtain a PB/PANI/CNT hollow nanofiber membrane;
(4) preparing an EDI electrode: and (3) taking the PB/PANI/CNT hollow nanofiber membrane prepared in the step (3) as an EDI negative electrode active material, taking activated carbon as an EDI positive electrode active material, taking polyvinylidene fluoride as a binder, taking conductive carbon black as a conductive agent, adding N-methyl pyrrolidone, repeatedly grinding to obtain a slurry, and uniformly coating the slurry on a graphite sheet to obtain the EDI electrode.
2. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (1), the mass ratio of the PAN to the N, N-dimethylformamide is 1: 2.5-3.5, the concentration of the CNT in the CNT/PAN solution is 10-20 wt%, the concentration of the CNT dispersion liquid is 25-35 wt%, the concentration of the PAN is 20-30 wt%, and the volume ratio of the CNT dispersion liquid to the PAN solution is 0.9-1.1: 1.
3. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (1), the electrostatic spinning operation conditions are as follows: the humidity is 35-45%, the voltage is 14-18 kV, the distance between a spinning nozzle and a receiving plate is 12-18 cm, and the injection speed is 0.2-0.4 mL/h.
4. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (2), the concentration of the hydrochloric acid solution is 0.5-1.5 mol/L, the molar ratio of ammonium persulfate to aniline is 0.95-1.05: 1, and the volume ratio of aniline to hydrochloric acid solution is 0.045-0.047: 1.
5. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (2), the area-volume ratio of the CNT/PAN nano-fiber membrane to the hydrochloric acid solution is 4 x 4-5 x 5cm2:20mL。
6. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (2), the volume ratio of the hydrochloric acid solution containing the CNT/PAN nano-fiber membrane to the initiator is 1: 0.95-1.05, and the polymerization reaction time is 15-25 min.
7. The method of claim 1, wherein the electrochemical dehydration is based on electrostatic spinningA method of salt electrode, characterized by: in the step (3), Fe in the potassium ferricyanide solution and the ferric chloride solution3+The concentration is 0.010-0.015 mol/L.
8. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 7, wherein: the volume ratio of the ferric chloride solution to the potassium ferricyanide solution is 3-5: 2.
9. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (3), the reaction is carried out in an oil bath, the reaction temperature is 55-65 ℃, and the reaction time is 5-7 h; the drying temperature is 40-80 ℃, and the drying time is 9-15 h.
10. The method for preparing the electrochemical desalting electrode based on electrostatic spinning as claimed in claim 1, wherein: in the step (4), the mass ratio of the negative electrode active material or the positive electrode active material to the binder and the conductive agent is 7-8: 1-1.5: 1.5, the mass-volume ratio of the negative electrode active material or the positive electrode active material to the N-methyl pyrrolidone is 1g: 8-10 mL, and the area of the graphite sheet is 3 x 3cm2And the coating amount of the slurry is 7-13 mg.
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