A polyaniline / Prussian blue / polyaniline composite electrode material and its preparation method and application

Abstract

The present invention provides a polyaniline / Prussian blue / polyaniline composite electrode material and its preparation method and application. The preparation method comprises the following steps: (1) forming a three-electrode system with a working electrode, a reference electrode, and a counter electrode, using an electrodeposition solution as an electrolyte, and performing an electrodeposition polymerization reaction on the surface of the working electrode to form a polyaniline conductive substrate; (2) placing the working electrode with a polyaniline layer deposited on the surface in a metal salt aqueous solution, first adding sodium citrate dihydrate, and then adding a potassium ferricyanide solution for reaction, thereby forming a Prussian blue layer on the surface of the polyaniline layer; (3) forming a three-electrode system with a working electrode with a polyaniline layer and a Prussian blue layer deposited on the surface, a reference electrode, and a counter electrode, using an electrodeposition solution as an electrolyte, and performing an electrodeposition polymerization reaction on the surface of the Prussian blue layer of the working electrode to form a polyaniline protective layer; thus, the polyaniline / Prussian blue / polyaniline composite electrode material is prepared. The composite material of the present invention has a higher desalination capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical desalination, in particular to a polyaniline / Prussian blue / polyaniline composite electrode material and a preparation method and application thereof. Background Art

[0002] Seawater and brackish water account for 98% of the water resources on the earth's surface. Drinkable water resources cannot meet people's needs. Solving the freshwater resource problem by desalinating brackish water is a promising development direction.

[0003] Currently, thermal, reverse osmosis, and electrodialysis methods are widely used for the sustainable utilization of water resources. Compared with traditional technologies, capacitive deionization (CDI) technology has the advantages of being environmentally friendly, low energy consumption, and miniaturized. Its basic principle is to apply an external electrostatic field so that the ions in the capacitive deionization device move in a directional manner toward the two ends of the electrode under the action of the electric field, and are then stored in the electrode material, thereby achieving the removal of ions from the salt solution. When the external electric field is eliminated or a reverse electric field is applied, the ions stored in the electrode material will be released into the solution, thereby achieving the recycling of the electrode material.

[0004] Improving the desalination capacity of CDI technology mainly relies on the development and design of new electrode materials. Generally speaking, CDI electrode materials should have high conductivity, good hydrophilicity, high specific surface area and narrow pore size distribution.

[0005] CDI electrode materials primarily consist of porous carbon materials and faradaic electrode materials. Carbon electrode materials achieve ion removal through double-layer adsorption. They possess high surface area, excellent conductivity, good hydrophilicity, and a suitable pore size distribution, but their desalination capacity is relatively low. Faradaic electrode materials primarily achieve desalination by embedding sodium ions into interstitial locations or atomic planes of the electrode material, or by chemically bonding to the electrode material. The main faradaic electrode materials currently used in CDI include transition metal carbides, transition metal oxides, and polyanionic compounds.

[0006] Prussian blue and its analogues are a class of MOF materials with the molecular formula A x M y [Fe(CN)₆]·nH₂O (0≤n≤2, A is an alkali metal ion, M is a transition metal ion), has a unique open-frame structure that provides large ion channels, allowing sodium ion insertion and extraction. It is non-toxic, inexpensive, environmentally friendly, and hydrophilic. However, its poor conductivity and stability prevent its direct application as a CDI electrode material. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a polyaniline / Prussian blue / polyaniline composite electrode material and its preparation method and application, so as to solve the problems of poor conductivity and stability of existing Prussian blue and its analogs, which cannot be directly used as CDI electrode materials.

[0008] To achieve the above-mentioned and other related purposes, the present invention provides a method for preparing a polyaniline / Prussian blue / polyaniline composite material, comprising the following steps:

[0009] (1) A three-electrode system consisting of a working electrode, a reference electrode, and a counter electrode is formed, and an electrodeposition solution is used as an electrolyte to form a polyaniline conductive substrate (PANI) by electrodeposition polymerization on the surface of the working electrode;

[0010] (2) placing the working electrode with a polyaniline layer deposited on the surface in a metal salt aqueous solution, first adding the ligand, and then adding potassium ferrocyanide solution to react, forming a Prussian blue layer (PB) on the surface of the polyaniline layer;

[0011] (3) A working electrode, a reference electrode, and a counter electrode with polyaniline layers and Prussian blue layers deposited on their surfaces are formed into a three-electrode system. An electrodeposition solution is used as an electrolyte to form a polyaniline protective layer (PANI) on the surface of the Prussian blue layer of the working electrode by electrodeposition polymerization reaction; thus, a polyaniline / Prussian blue / polyaniline composite electrode material (PANI / PB / PANI) is prepared.

[0012] In steps (1) and (3), the electrodeposition solution is a mixed aqueous solution of aniline monomer and acid.

[0013] The present invention first forms a polyaniline conductive substrate on the surface of the working electrode through an electrodeposition polymerization reaction, thereby improving the conductivity of the composite material and effectively preventing the agglomeration of Prussian blue layer particles; the intermediate interlayer Prussian blue layer has the effect of storing sodium ions, and the polyaniline protective layer has the function of protecting Prussian blue, thereby increasing the stability of the material. In addition, polyaniline has a certain ability to store chloride ions. The present application uses a composite electrode material with a sandwich structure formed by combining polyaniline and Prussian blue as a sodium storage electrode, thereby improving the sodium storage performance of the material and the cycle performance of the system.

[0014] Preferably, based on the total volume of the electrodeposition solution, the concentrations of the components in the electrodeposition solution are: 0.01 to 0.05 mol / mL of aniline monomer and 0.5 to 1.5 mol / mL of acid.

[0015] Preferably, based on the total volume of the electrodeposition solution, the concentrations of the components in the electrodeposition solution are: 0.01 to 0.05 mol / mL of aniline monomer and 0.5 to 1.5 mol / mL of acid.

[0016] Preferably, in steps (1) and (3), the current density of the electrodeposition polymerization reaction is 0.15 to 0.35 mA / cm 2 ; The time of electrodeposition polymerization reaction is 2 to 5 hours.

[0017] Preferably, in step (2), the metal salt aqueous solution contains Co 2+ 、Ni 2+ and Fe 3+ At least one of; the ligand is sodium citrate dihydrate.

[0018] Preferably, in step (2), the molar ratio of the metal salt, sodium citrate dihydrate and potassium ferricyanide in the metal salt aqueous solution is (1.5-2):(4.2-5):1.

[0019] Preferably, in step (2), the reaction temperature is 25-35° C., and the reaction time is 3-6 h.

[0020] Preferably, the working electrode is selected from one of FTO conductive glass, platinum sheet and carbon cloth; the reference electrode is an Ag / AgCl electrode; and the counter electrode is a platinum electrode.

[0021] Preferably, in step (1), the working electrode is carbon cloth, and the step of hydrophilizing the carbon cloth is further included before the reaction.

[0022] More preferably, the hydrophilic treatment of the carbon cloth includes treating the carbon cloth with mixed acid, which allows functional groups such as hydroxyl and carboxyl to grow on the surface of the carbon cloth, thereby increasing the hydrophilicity of the carbon cloth and facilitating the formation of a polyaniline conductive substrate.

[0023] More preferably, the mixed acid is a mixture of nitric acid and sulfuric acid in a volume ratio of (2-3):1.

[0024] The present invention also provides a polyaniline / Prussian blue / polyaniline composite electrode material prepared by the above preparation method. The composite material is a sandwich structure consisting of a polyaniline conductive substrate, Prussian blue and a polyaniline protective layer in sequence.

[0025] The present invention also provides an application of a polyaniline / Prussian blue / polyaniline composite electrode material as a sodium storage electrode in electrochemical desalination.

[0026] As described above, the present invention has the following beneficial effects: by combining polyaniline and Prussian blue to form a sandwich-structured composite electrode material as a sodium storage electrode, the sodium storage performance of the material is improved and the cycle performance of the system is improved; the preparation process of the present invention is simple, the process conditions are easy to control, and it is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1Shown is the SEM image of the PB / PANI electrode material prepared in step (3) of Example 1.

[0028] Figure 2 Shown is the SEM image of the PANI / PB / PANI composite electrode material prepared in step (4) of Example 1.

[0029] Figure 3 Shown is the SEM image of the PB / PANI electrode material prepared in step (3) of Example 1 after being immersed in 1M HCl for 5 hours.

[0030] Figure 4 Shown is the FR-IT comparison diagram of the PANI electrode material prepared in step (2) of Example 1, the PB / PANI electrode material prepared in step (3), and the PANI / PB / PANI composite electrode material prepared in step (4).

[0031] Figure 5 Shown are XRD comparison diagrams of the p-CoHCF electrode material prepared in Comparative Example 1, the PB / PANI electrode material prepared in step (3) of Example 1, and the PANI / PB / PANI composite electrode material prepared in step (4).

[0032] Figure 6 Shown is the XRD pattern of carbon cloth.

[0033] Figure 7 The results show that the PANI electrode material prepared in step (2) of Example 1, the PB / PANI electrode material prepared in step (3) and the PANI / PB / PANI composite electrode material prepared in step (4) are significantly different at 5 mV s -1 CV comparison diagram at different scan rates.

[0034] Figure 8 Shown are CV graphs of the PANI / PB / PANI composite electrode material prepared in Example 1 at different scan rates.

[0035] Figure 9 Shown are CV graphs of the PB / PANI electrode material prepared in step (3) of Example 1 at different scan rates.

[0036] Figure 10 Shown are CV graphs of the p-CoHCF electrode prepared in Comparative Example 1 at different scan rates.

[0037] Figure 11 It shows the EIS graphs of the PB / PANI electrode material prepared in step (3) of Example 1, the PANI / PB / PANI composite electrode material prepared in step (4), and the p-CoHCF electrode prepared in Comparative Example 1. The auxiliary graph is an enlarged view of the high-frequency region.

[0038] Figure 12 Shown is the desalination capacity rate performance diagram of the PANI / PB / PANI composite electrode material prepared in Example 1 after being immersed in 1M HCl for different lengths of time.

[0039] Figure 13 The results show that the PB / PANI electrode material prepared in step (3) of Example 1, the PANI / PB / PANI composite electrode material prepared in step (4) and the p-CoHCF electrode prepared in Comparative Example 1 were -1 Desalination capacity rate performance diagram in NaCl solution.

[0040] Figure 14 The PANI / PB / PANI composite electrode material prepared in Example 1 is used as a symmetrical electrode at 750 mg / L -1 Desalination capacity rate performance diagram in NaCl solution.

[0041] Figure 15 The PANI / PB / PANI composite electrode material prepared in Example 1 was -1 In NaCl solution, 250 mA g -1 Long-cycle performance diagram at different current densities. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0044] Furthermore, it should be understood that the one or more method steps mentioned in the present invention do not exclude the presence of other method steps before or after the combination step, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the presence of other devices / apparatuses before or after the combination device / apparatus, or the insertion of other devices / apparatuses between two explicitly mentioned devices / apparatuses, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the present invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the present invention.

[0045] Example 1

[0046] The present invention provides a method for preparing a polyaniline / Prussian blue / polyaniline composite material, comprising the following steps:

[0047] (1) Hydrophilic treatment of carbon cloth: The carbon cloth is heated at 80°C for 4 hours in a mixed acid solution, wherein the mixed acid solution is a mixture of nitric acid and sulfuric acid with a volume ratio of 3:1; the mixed acid treatment causes functional groups such as hydroxyl and carboxyl groups to grow on the surface of the carbon cloth, thereby increasing the hydrophilicity of the carbon cloth;

[0048] (2) Preparation of polyaniline conductive substrate: The carbon cloth treated with hydrophilization in step (1) was used as a working electrode (WE), and a three-electrode system was formed with a reference electrode (Ag / AgCl) (RE) and a counter electrode (platinum sheet) (CE). The electroplating solution was used as the electrolyte, and constant current electropolymerization was performed using an electrochemical workstation. The polyaniline conductive substrate was formed by electroplating polymerization on the surface of the working electrode, which was recorded as PANI electrode material. The concentrations of the components in the electroplating solution were: 0.02 mol / mL of aniline monomer and 1 mol / mL of acid; the volume ratio of aniline to hydrochloric acid was 0.019:1, and the current density of the electroplating polymerization reaction was 0.2 mA / cm 2 , the electrodeposition polymerization reaction was carried out for 2 hours; after the reaction was completed, it was washed with water and ethanol and then dried;

[0049] (3) The carbon with polyaniline conductive substrate deposited on the surface is arranged on the Co 2+ To a 0.03 mol / L cobalt chloride solution, 0.794 g of sodium citrate dihydrate was added, and then a 0.016 mol / L potassium ferricyanide solution was slowly added dropwise for reaction. The volume ratio of the cobalt chloride solution to the potassium ferricyanide solution was 1:1. The reaction was carried out at room temperature for 6 hours. The drying temperature was 70°C and the drying time was 12 hours. The obtained product was washed with deionized water and ethanol, and then vacuum dried to deposit a Prussian blue layer (PB) on a polyaniline conductive substrate, which was recorded as a PB / PANI electrode material.

[0050] (4) A carbon cloth with a polyaniline layer and a Prussian blue layer deposited on its surface was used as a working electrode (WE), and a three-electrode system was formed with a reference electrode (Ag / AgCl) (RE) and a counter electrode (platinum sheet) (CE). The electrodeposition solution was used as the electrolyte, and constant current electropolymerization was performed using an electrochemical workstation. The carbon cloth was placed in a hydrochloric acid solution with a concentration of 1 mol / L, and aniline monomer was added. After several hours, constant current electropolymerization was performed using an electrochemical workstation with a current density of 0.2 mA / cm 2After 1 hour of polymerization, the product was removed, washed with water and ethanol, and then vacuum-dried. A polyaniline protective layer (PANI) was formed on the surface of the Prussian blue layer by electrodeposition polymerization, thereby obtaining a polyaniline / Prussian blue / polyaniline composite electrode material (PANI / PB / PANI). A PANI / PB / PANI electrode was obtained.

[0051] Comparative Example 1

[0052] Comparative Example 1 differs from Example 1 in that step (2) is omitted, and a PANI conductive substrate and a polyaniline protective layer (PANI) are not grown on the carbon cloth surface. Instead, a Prussian blue layer (PB) is grown directly. The remaining processes are identical. The electrode material prepared in this comparative example is designated as a p-CoHCF electrode.

[0053] The electrode materials prepared in each step of the embodiment and the p-CoHCF electrode prepared in Comparative Example 1 were characterized by the following method:

[0054] The SEM test was carried out on a HIACHI SU-8010 field emission scanning electron microscope. The sample preparation method was as follows: a small amount of sample was attached to a cross-section support with conductive adhesive.

[0055] The XRD test was performed on a Panalytical X'Pert3 Powder. The sample to be tested was prepared as follows: the sample was cut to a suitable size, placed in a frosted groove of a quartz plate, and then tested.

[0056] CV and EIS tests were performed on an Autolab electrochemical workstation. The PANI / PB / PANI obtained in Example 1 was cut into 1×2 cm 2 The CV test uses a three-electrode system, with the electrode as the working electrode, the platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and 1M NaCl solution as the electrolyte. The voltage scan range is -0.2 to 1.1 V, and the scan rate is 2 to 50 mVs. -1 .

[0057] The EIS test also uses a three-electrode system with 1M NaCl as the electrolyte. The AC impedance test selects 10mV amplitude and the frequency range is set to 10 -2 -10 5 Preparation of activated carbon electrode: Activated carbon was used as the active material, carbon black and polyvinylidene fluoride were used as the conductive agent and binder, respectively, in a mass ratio of 8:1:1. A total of 10 mg was weighed, N-methylpyrrolidone was added dropwise, and the mixture was ground into a slurry. The slurry was then applied to a graphite sheet. The coating area was 3 × 3 cm. 2 .

[0058] CDI test: (a) This patent has no special requirements for anion and cation membranes. The selected anion membrane is heterogeneous ion exchange membrane type 1, and the cation exchange membrane is polyethylene heterogeneous ion exchange membrane type 1, both purchased from Hangzhou Lvhe Environmental Protection Technology Co., Ltd. The total dissolved solids (TDS) is 750 mg L -1 50 mL of sodium chloride solution was transferred to a beaker. The peristaltic pump speed was controlled at 100 mL min -1 After the solution conductivity no longer changes, turn on the power supply. Use a conductivity meter to monitor the conductivity in real time, recording it every 10 seconds.

[0059] Test results are shown in Figures 1 to 15 .

[0060] Figure 1 This is the SEM image of PB / PANI. PB grows in situ on PANI and presents a tightly distributed morphology, which is conducive to maintaining structural stability of the material during the charge and discharge process.

[0061] Figure 2 This is the SEM image of PANI / PB / PANI. It can be observed that Figure 1 , the surface of the material becomes rough, indicating that aniline can be adsorbed on the surface of the material and polymerized into continuous polyaniline.

[0062] Figure 3 The SEM image of PB / PANI after immersion in 1M HCl for 5 h shows that the hydrochloric acid treatment during the material synthesis process does not damage the structure of PB.

[0063] Figure 4 The FR-IT diagrams of PANI / PB / PANI, PB / PANI, and p-CoHCF are shown. In the infrared spectrum, the wavelengths at 1583 and 1496 cm -1 The C—C bond vibrations of the quinone and benzene rings are at 1294, 1144, and 3618 cm -1 The CN, C=N, and NH bond stretching vibration peaks of aromatic amines are 804 cm -1 The peak belongs to the out-of-plane CH bond bending vibration of the aromatic ring, which proves the successful polymerization of PANI.

[0064] Figure 5 The XRD patterns of PANI / PB / PANI, PB / PANI, and p-CoHCF are shown in Figure 2. The diffraction peaks at 17.5°, 24.9°, and 35.5° correspond to the (200), (220), and (400) planes of CoHCF, respectively. Figure 6 is the XRD pattern of carbon cloth. The carbon peaks of carbon cloth appear at 25° and 43°, which proves the formation of the microstructure of Prussian blue / polyaniline composite electrode material grown on carbon cloth.

[0065] Figure 7 PANI / PB / PANI, PB / PANI, p-CoHCF at 5mV s -1 CV plots at different scan rates. PANI / PB / PANI shows a larger integrated area, which is attributed to the synergistic effect of PANI and PB.

[0066] Figures 8-10 These are the CV graphs of PANI / PB / PANI, PB / PANI, and p-CoHCF at different scan rates.

[0067] Figure 11 These are the EIS traces of PANI / PB / PANI, PB / PANI, and p-CoHCF. The small quasi-semicircle diameter in the high-frequency range indicates the charge transfer resistance. The slanted line in the low-frequency region represents the Warburg impedance. This indicates that the introduction of PANI improves the conductivity of the composite.

[0068] Figure 12 Figure 2 shows the desalination capacity rate performance of PANI / PB / PANI samples obtained after soaking in 1M HCl for different times. The results show that hydrochloric acid treatment has a certain impact on the desalination performance of the PANI / PB / PANI composite electrode material. The PANI / PB / PANI composite electrode material obtained after soaking in hydrochloric acid for 5 hours has better desalination performance.

[0069] Figure 13 The figure shows the desalination capacity and rate performance of PANI / PB / PANI, PB / PANI, and p-CoHCF. Compared with the control sample, the PANI / PB / PANI composite electrode material shows higher desalination capacity and rate performance. -1 The current density can reach 160 mg g -1 desalination capacity.

[0070] Figure 14 This is a graph showing the desalination capacity rate performance when PANI / PB / PANI is used as a symmetrical electrode. Two PANI / PB / PANI electrodes are used for sodium storage and chlorine storage, respectively. Compared with activated carbon electrodes, the PANI on the surface of the PANI / PB / PANI electrode provides higher chlorine storage performance, thereby further improving the desalination capacity of the capacitive deionization device. At 100 mA g -1 The current density can reach 240mg g -1 desalination capacity.

[0071] Figure 15 PANI / PB / PANI at 250mA -1Long-term cycle performance under current density. It can be seen that after 25 cycles, the desalination capacity of the PANI / PB / PANI electrode material has not decreased significantly, indicating that this sandwich structure PANI / PB / PANI composite electrode material has good stability.

[0072] Example 2

[0073] The difference between Example 2 and Example 1 is that the current density in steps (2) and (4) is different, specifically 0.05 mA cm 2 , the rest of the process is exactly the same.

[0074] Example 3

[0075] The difference between Example 3 and Example 1 is that the current density in steps (2) and (4) is different, specifically 0.4 mA cm 2 , the rest of the process is exactly the same.

[0076] Example 4

[0077] The difference between Example 4 and Example 1 is that the types of metal salt aqueous solutions in step (3) are different, specifically containing Ni 2+ The rest of the process is exactly the same.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing a polyaniline / Prussian blue / polyaniline composite electrode material, characterized in that: The following steps are involved: (1) A working electrode, a reference electrode, and a counter electrode are formed into a three-electrode system, and an electrodeposition solution is used as an electrolyte to form a polyaniline conductive substrate by electrodeposition polymerization reaction on the surface of the working electrode; (2) placing a working electrode with a polyaniline layer deposited on its surface in a metal salt aqueous solution, first adding sodium citrate dihydrate, and then adding potassium ferricyanide solution to react, thereby forming a Prussian blue layer on the surface of the polyaniline layer; (3) A working electrode, a reference electrode, and a counter electrode having a polyaniline layer and a Prussian blue layer deposited on the surface are formed into a three-electrode system, and an electrodeposition solution is used as an electrolyte to form a polyaniline protective layer by electrodeposition polymerization reaction on the surface of the Prussian blue layer of the working electrode; thus, a polyaniline / Prussian blue / polyaniline composite electrode material is prepared; In steps (1) and (3), the electrodeposition solution is a mixed aqueous solution of aniline monomer and acid.

2. The preparation method according to claim 1, wherein: Based on the total volume of the electrodeposition solution, the concentrations of the components in the electrodeposition solution are: 0.01 to 0.05 mol / L of aniline monomer and 0.5 to 1.5 mol / L of acid.

3. The preparation method according to claim 1, wherein: In steps (1) and (3), the current density of the electrodeposition polymerization reaction is 0.15 to 0.35 mA / cm 2 ; The time of electrodeposition polymerization reaction is 2 to 5 hours.

4. The preparation method according to claim 1, wherein: In step (2), the metal salt aqueous solution contains Co 2+ 、Ni 2+ and Fe 3+ At least one of .

5. The preparation method according to claim 4, characterized in that: In step (2), the molar ratio of the metal salt, sodium citrate dihydrate and potassium ferricyanide in the metal salt aqueous solution is (1.5-2): (4.2-5): 1; the reaction temperature is 25-35°C, and the reaction time is 3-6h.

6. The preparation method according to claim 1, wherein: The working electrode is selected from one of FTO conductive glass, platinum sheet and carbon cloth; the reference electrode is an Ag / AgCl electrode; and the counter electrode is a platinum electrode.

7. The preparation method according to claim 6, characterized in that: In step (1), the working electrode is carbon cloth, and the process of hydrophilizing the carbon cloth is also included before the reaction; the hydrophilizing treatment process of the carbon cloth includes treating the carbon cloth with a mixed acid; the mixed acid is a mixture of nitric acid and sulfuric acid in a volume ratio of (2 to 3):

1.

8. A polyaniline / Prussian blue / polyaniline composite electrode material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It is a sandwich structure consisting of a polyaniline conductive substrate, Prussian blue and a polyaniline protective layer.

9. Use of the polyaniline / Prussian blue / polyaniline composite electrode material as claimed in claim 8 as a sodium storage electrode in electrochemical desalination.

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