Preparation and application of a porous bismuth ferrite material

Abstract

This invention discloses the preparation and application of a porous bismuth ferrite material. The preparation method includes the following steps: dissolving bismuth and iron salts in an acid solution to obtain a metal solution; adding a complexing agent and a pore-forming agent to the metal solution and mixing to obtain a precursor solution; heating the precursor solution to obtain a wet gel; drying the wet gel to obtain a dry gel; and calcining the dry gel under an inert atmosphere containing 6-10% oxygen to obtain the porous bismuth ferrite material. The porous bismuth ferrite electrode material of this invention not only solves the structural defects of traditional porous bismuth ferrite materials, such as small pore volume and insufficient utilization of active sites, but also fully utilizes its membrane capacitance characteristics and bimetallic synergistic effect, showing excellent application prospects in the field of capacitive deionization and chlorine removal.

Description

Technical Field

[0001] This invention relates to the preparation of an electrode active material, and more particularly to the preparation of a porous bismuth ferrite material and its application in the preparation of a capacitor deionization electrode. Background Technology

[0002] Capacitive deionization (CDI) is an emerging electrochemical water treatment technology that has been used to remove chloride ions from wastewater. CDI removes ions by applying a voltage between two electrodes, causing cations and anions in the solution to migrate and adsorb onto the electrode surface under the influence of the electric field. When the electrodes discharge or a reverse voltage is applied, the adsorbed ions are released, regenerating the electrodes. Compared to traditional water treatment methods, CDI technology offers advantages such as low energy consumption, simple operation, and good renewability. However, the core of CDI technology lies in the performance of the electrode materials. Currently used carbon-based electrode materials (such as activated carbon, carbon nanotubes, and graphene) mainly rely on the double-layer adsorption mechanism, exhibiting weak selectivity for anions, especially limited adsorption capacity for chloride ions. Furthermore, some electrode materials suffer from insufficient conductivity, low ion transport efficiency, and poor cycle stability during long-term operation, thus limiting the further application of CDI technology in chloride ion removal.

[0003] Ideal CDI electrode active materials should possess good electrical conductivity, high specific surface area, and strong chloride ion adsorption capacity. Porous bismuth ferrite, due to its porous structure and electrochemically active sites, is an excellent candidate material for CDI electrodes. However, although porous bismuth ferrite prepared by existing methods has a high specific surface area, its pore volume is low. Chlorinated aqueous solutions cannot effectively penetrate into the tiny channels inside the porous bismuth ferrite material, resulting in the active bismuth sites on the pore surface not being able to effectively contact chloride ions and perform electrochemical dechlorination. Most of the active bismuth sites remain idle. Therefore, CDI electrodes prepared from existing porous bismuth ferrite materials have a low chloride ion adsorption capacity in aqueous solutions, failing to fully utilize the advantages of porous bismuth ferrite materials. Summary of the Invention

[0004] Objectives of this invention: The objective of this invention is to provide a method for preparing porous bismuth ferrite materials, solving the problem of how to prepare porous bismuth ferrite materials with high pore volume. A second objective is to propose an application of porous bismuth ferrite materials in the preparation of capacitive deionization electrodes, solving the problem of how to prepare CDI electrodes with high chloride ion adsorption capacity. A third objective is to propose the application of capacitive deionization electrodes in the dechlorination of aqueous solutions, solving the problem of how to adsorb and remove chloride ions from aqueous solutions.

[0005] Technical solution: The present invention provides a method for preparing porous bismuth ferrite material, comprising the following steps: (1) Dissolve bismuth salt and iron salt in acid solution to obtain metal solution, add complexing agent and pore-forming agent to metal solution, mix well to obtain precursor solution; (2) The precursor solution is heated to react and a wet gel is obtained. The wet gel is dried to obtain a dry gel. (3) The dry gel was calcined under an inert atmosphere containing 6-10% oxygen to obtain porous bismuth ferrite material.

[0006] Preferably, in step (1), the bismuth salt includes at least one of bismuth nitrate and bismuth chloride, the iron salt includes at least one of ferric nitrate, ferric chloride, and ferric sulfate, the complexing agent includes at least one of citric acid, malic acid, and tartaric acid, the pore-forming agent is a mixture of at least one of P123, starch, and modified starch with urea, and the acid solution includes an aqueous solution of at least one of nitric acid, sulfuric acid, and hydrochloric acid.

[0007] In this invention, a mixture of starch and urea is used as a pore-forming agent. Under an oxygen-containing inert atmosphere, N-doped porous carbon is formed distributed within the porous framework of bismuth ferrite, thus constructing a three-dimensional porous structure with interconnected pores. This allows the porous bismuth ferrite material to possess both high specific surface area and high pore volume, resulting in excellent chloride ion adsorption and removal performance.

[0008] In some embodiments, the pore-forming agent is a mixture of starch and urea in a mass ratio of 1-4:1.

[0009] Preferably, in step (1), the molar ratio of Bi to Fe in the metal solution is 1-2:1-2; and the concentration of the acid solution is 5-15%.

[0010] Preferably, in step (2), the heating reaction is carried out at 70-90°C for at least 3 hours; the drying is carried out at 80-100°C for at least 6 hours.

[0011] Preferably, in step (3), the inert atmosphere containing 6-10% oxygen is a mixture of oxygen and argon, wherein the volume fraction of oxygen is 6-10%.

[0012] Preferably, in step (3), the calcination conditions are to raise the temperature to 500-700℃ at a rate of 3-7℃ / min and hold it for 3-10 hours.

[0013] The second aspect of this invention discloses the application of the porous bismuth ferrite material prepared by the above-described method in the preparation of capacitor deionization electrodes.

[0014] Preferably, the method for preparing a capacitor deionization electrode using the above-mentioned porous bismuth ferrite material includes the following steps: The porous bismuth ferrite material, conductive agent, binder and solvent are mixed and then ground and stirred to obtain electrode slurry; Electrode slurry is coated onto the surface of the current collector and dried to obtain a capacitor deionization electrode.

[0015] Preferably, the adhesive is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyacrylic acid, and polyvinyl alcohol, and the solvent includes N. The current collector is made of at least one of the following: methylpyrrolidone, dimethylformamide, ethanol, isopropanol, acetone, and water; the current collector material includes at least one of graphite paper, carbon cloth, carbon felt, graphene film, nickel mesh, stainless steel mesh, titanium mesh, nickel foam, aluminum foil, copper foil, titanium foil, and stainless steel foil; and the conductive agent includes at least one of conductive carbon black and polyaniline.

[0016] The third aspect of this invention discloses the use of a capacitor deionization electrode prepared by the above method to remove chlorine in an aqueous solution.

[0017] Specifically, the capacitor deionization electrode prepared by the above method is assembled into a capacitor deionization device, and the device is energized to treat a chlorine-containing aqueous solution to adsorb and remove chloride ions from the aqueous solution.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: In terms of electrochemical performance, the porous bismuth ferrite electrode prepared in this invention exhibits typical pseudocapacitive characteristics in 1M sodium chloride electrolyte. Cyclic voltammetry curves show symmetrical redox peaks, indicating that the electrode's energy storage mechanism involves Faraday redox reactions; the galvanostatic charge-discharge curves show a near-triangular symmetrical structure, confirming the electrode's good capacitive behavior and reversibility. Calculations show that the specific capacitance of the porous bismuth ferrite electrode reaches 311.8 F / g at a scan rate of 10 mV / s, significantly higher than that of bismuth ferrite electrodes prepared by conventional methods, indicating that the porous structure effectively enhances the material's charge storage capacity. Electrochemical impedance spectroscopy results show that the porous bismuth ferrite electrode has a low charge transfer resistance, which is beneficial for the rapid adsorption and desorption of chloride ions at the electrode-solution interface.

[0019] In terms of chloride removal performance, the porous bismuth ferrite electrode prepared in this invention exhibits highly efficient chloride ion removal capabilities. Using simulated chlorine-containing wastewater as the treatment target, under conditions of a 1.2V working voltage applied across the electrode and an initial solution conductivity of 1000 μS / cm, the porous bismuth ferrite electrode achieved an chloride ion adsorption capacity of 43.54 mg / g, demonstrating excellent chloride removal performance. The material exhibits good selective adsorption capacity for chloride ions, mainly attributed to the formation of interconnected three-dimensional pore structures through calcination of the dry gel in an oxygen-containing atmosphere using a specific pore-forming agent. This structure possesses both high specific surface area and high pore volume, allowing the chlorine-containing solution to fully fill the three-dimensional pore structure within the material, fully utilizing the bismuth ion active sites on the pore surface, and significantly improving the chloride ion adsorption efficiency. Furthermore, the high polarization characteristics of bismuth ions in the porous bismuth ferrite enhance the electrostatic capture ability of chloride ions, while the variable valence characteristics of iron ions enable in-situ transformation of adsorbed chloride ions, forming a synergistic chloride removal mechanism of adsorption and oxidation. Cyclic stability tests show that the electrode can maintain a high capacity retention rate after multiple adsorption-desorption cycles, demonstrating good cycle life.

[0020] In summary, the porous bismuth ferrite electrode material of the present invention not only solves the structural defects of traditional porous bismuth ferrite materials such as small pore volume and insufficient utilization of active sites, but also fully utilizes its membrane capacitance characteristics and bimetallic synergistic effect, showing excellent application prospects in the field of capacitive deionization and chlorine removal. Attached Figure Description

[0021] Figure 1 This is a comparison of adsorption curves for desalination tests of salt solutions with different conductivity using the porous bismuth ferrite material prepared in Example 1. Figure 2 The CDI cycle curves of the porous bismuth ferrite material prepared in Example 1 are shown below. Figure 3 Here is a SEM image of the porous bismuth ferrite prepared in Example 1; Figure 4 SEM image of the bismuth ferrite sample prepared in Comparative Example 7; Figure 5 This shows the relationship between the concentration and conductivity of NaCl solution. Detailed Implementation The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] Example 1: A method for preparing a porous bismuth ferrite material is as follows: (1) Weigh 2.425g of bismuth nitrate pentahydrate and 2.02g of ferric nitrate nonahydrate, dissolve them in 20mL of 10% nitric acid aqueous solution, and stir magnetically at room temperature until completely dissolved to obtain a transparent metal solution.

[0023] (2) Add 2.3g of citric acid to the metal solution as a complexing agent and continue stirring for 1h to allow the metal ions to fully complex with the citric acid to obtain a sol system.

[0024] (3) Mix 2g starch with 1g urea powder to obtain a pore-forming agent. Add the pore-forming agent to the sol system and stir continuously to make the pore-forming agent evenly dispersed in the sol system to obtain a precursor solution. (4) Place the beaker containing the above precursor solution in an 80°C constant temperature water bath and heat and stir for 4 hours. As the water gradually evaporates, the precursor solution transforms into a wet gel state. Transfer the obtained wet gel to a 90°C electric heating drying oven and dry for 12 hours to obtain a dry gel.

[0025] (5) The dried gel was placed in a muffle furnace and a mixture of oxygen and argon (oxygen volume fraction 8%) was introduced. Under this atmosphere, the temperature was increased to 500℃ at a rate of 5℃ / min and held for 5 hours for calcination treatment to completely decompose and remove the organic matter, while inducing the formation of bismuth ferrite crystal phase. After the furnace cooled naturally to room temperature, the product was collected and ground evenly to obtain bismuth ferrite powder with a porous structure, the microstructure of which is as follows. Figure 3 As shown.

[0026] Example 2: A method for preparing a porous bismuth ferrite material is as follows: (1) Weigh 2.425g of bismuth nitrate pentahydrate and 4.05g of ferric nitrate nonahydrate, dissolve them in 30mL of 5% nitric acid aqueous solution, and stir magnetically at room temperature until completely dissolved to obtain a transparent metal solution.

[0027] (2) Add 2.3g of citric acid to the metal solution as a complexing agent and continue stirring for 1h to allow the metal ions to fully complex with the citric acid to obtain a sol system.

[0028] (3) Mix 3g starch with 1g urea powder to obtain a pore-forming agent. Add the pore-forming agent to the sol system and stir continuously to make the pore-forming agent evenly dispersed in the sol system to obtain a precursor solution. (4) Place the beaker containing the above precursor solution in a 70°C constant temperature water bath and heat and stir for 8 hours. As the water gradually evaporates, the precursor solution transforms into a wet gel state. Transfer the obtained wet gel to an 80°C electric heating drying oven and dry for 24 hours to obtain a dry gel.

[0029] (5) The dried gel was placed in a muffle furnace and a mixture of oxygen and argon (oxygen volume fraction of 6%) was introduced. Under this atmosphere, the temperature was increased to 550°C at a rate of 3°C / min and held for 7 hours for calcination treatment to completely decompose and remove the organic matter, while inducing the formation of bismuth ferrite crystal phase. After the furnace chamber cooled naturally to room temperature, the product was collected and ground evenly to obtain bismuth ferrite powder with a porous structure.

[0030] Example 3: A method for preparing a porous bismuth ferrite material is as follows: (1) Weigh 4.35g of bismuth chloride and 1.94g of ferric chloride, dissolve them in 40mL of 15% hydrochloric acid aqueous solution, and stir magnetically at room temperature until completely dissolved to obtain a transparent metal solution.

[0031] (2) Add 2.3g of citric acid to the metal solution as a complexing agent and continue stirring for 1h to allow the metal ions to fully complex with the citric acid to obtain a sol system.

[0032] (3) Mix 4g starch with 1g urea powder to obtain a pore-forming agent. Add the pore-forming agent to the sol system and stir continuously to make the pore-forming agent evenly dispersed in the sol system to obtain a precursor solution. (4) Place the beaker containing the above precursor solution in a 90°C constant temperature water bath and heat and stir for 3 hours. As the water gradually evaporates, the precursor solution transforms into a wet gel state. Transfer the obtained wet gel to a 100°C electric heating drying oven and dry for 6 hours to obtain a dry gel.

[0033] (5) The dried gel was placed in a muffle furnace and a mixture of oxygen and argon (oxygen volume fraction of 10%) was introduced. Under this atmosphere, the temperature was increased to 600°C at a rate of 7°C / min and held for 3 hours for calcination treatment to completely decompose and remove the organic matter, while inducing the formation of bismuth ferrite crystal phase. After the furnace chamber cooled naturally to room temperature, the product was collected and ground evenly to obtain bismuth ferrite powder with a porous structure.

[0034] Example 4: A method for preparing a porous bismuth ferrite material is as follows: (1) Weigh 2.425g of bismuth nitrate pentahydrate and 3.38g of ferric sulfate, dissolve them in 20mL of 12% nitric acid aqueous solution, and stir magnetically at room temperature until completely dissolved to obtain a transparent metal solution.

[0035] (2) Add 2.3g of citric acid to the metal solution as a complexing agent and continue stirring for 1h to allow the metal ions to fully complex with the citric acid to obtain a sol system.

[0036] (3) Mix 1g starch with 1g urea powder to obtain a pore-forming agent. Add the pore-forming agent to the sol system and stir continuously to make the pore-forming agent evenly dispersed in the sol system to obtain a precursor solution. (4) Place the beaker containing the above precursor solution in an 80°C constant temperature water bath and heat and stir for 6 hours. As the water gradually evaporates, the precursor solution transforms into a wet gel state. Transfer the obtained wet gel to a 90°C electric heating drying oven and dry for 12 hours to obtain a dry gel.

[0037] (5) The dry gel was placed in a muffle furnace and a mixture of oxygen and argon (7% oxygen by volume) was introduced. Under this atmosphere, the temperature was increased to 500°C at a rate of 5°C / min and held for 10 hours for calcination treatment to completely decompose and remove the organic matter, while inducing the formation of bismuth ferrite crystal phase. After the furnace cooled naturally to room temperature, the product was collected and ground evenly to obtain bismuth ferrite powder with a porous structure.

[0038] Comparative Example 1: Everything else is the same as in Example 1, except that: Starch is used as a pore-forming agent only; urea is not added.

[0039] Comparative Example 2: Everything else is the same as in Example 1, except that: Urea is used as the pore-forming agent only, without adding starch.

[0040] Comparative Example 3: Everything else is the same as in Example 1, except that... P123 was used as a pore-forming agent.

[0041] Comparative Example 4: Everything else is the same as in Example 1, except that: No pore-forming agent is added.

[0042] Comparative Example 5: Everything else is the same as in Example 1, except that: In step (5), the volume fraction of oxygen in the mixed gas is increased to 21%.

[0043] Comparative Example 6: Everything else is the same as in Example 1, except that: In step (5), the volume fraction of oxygen in the mixed gas is reduced to 3%.

[0044] Comparative Example 7: Bismuth ferrite powder was prepared by co-precipitation method, as follows: Weigh 2.425 g of bismuth nitrate pentahydrate and 2.02 g of ferric nitrate nonahydrate, add them to 100 mL of deionized water, and stir magnetically for 30 min until fully dissolved. Add 25 mL of 1 mol / L ammonia solution dropwise to the solution to completely precipitate the ferric and bismuth ions. After standing, discard the supernatant. Wash the precipitate with distilled water until the pH reaches 7.0-8.0. After filtration, dry the precipitate at 90℃ for 12 h, grind it thoroughly, and calcine it in a muffle furnace at 500℃ for 3 h to obtain bismuth ferrite powder. Its microstructure is shown in the figure below. Figure 4 As shown.

[0045] The bismuth ferrite powder samples prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to tests for specific surface area, pore volume, and capacitance deionization and dechlorination. The method for capacitance deionization and dechlorination testing is as follows: Porous bismuth ferrite powder and polyaniline powder were dispersed in deionized water at a mass ratio of 10:1 and stirred continuously for 30 min, followed by ultrasonic treatment for 1 h. The mixture was centrifuged, the precipitate was retained, dried in an oven at 85℃, and then ground to obtain porous bismuth ferrite / polyaniline composite powder. Porous bismuth ferrite / polyaniline composite powder, conductive carbon black, and polyvinylidene fluoride were mixed at a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone was added, and the mixture was ground uniformly to obtain an electrode slurry. The prepared slurry was then uniformly coated onto the surface of a titanium plate using a blade coating method, with a coating thickness of 100 μm. The coated electrode was then placed in an 80℃ vacuum drying oven for 12 hours to remove the solvent and solidify the binder, thus obtaining a porous bismuth ferrite electrode.

[0046] Next, the glass plate, silicone pad, porous bismuth ferrite electrode plate as the positive electrode, the separator, the porous bismuth ferrite electrode plate as the negative electrode, the silicone pad, and the glass plate are assembled in sequence and fixed with special screws to form a capacitor deionization device.

[0047] Sodium chloride solutions with conductivity of 500, 1000, 2000, and 3000 μS / cm were prepared. These solutions were then passed into a capacitive deionization device at a flow rate of 10 mL / min. A dechlorination test was conducted by applying a working voltage of 1.2 V. The results are as follows: Figure 1 As shown, Figure 1 The results showed that, under solution conditions of 1000 μS / cm, the electrode made from the porous bismuth ferrite material in Example 1 exhibited the highest chloride ion adsorption capacity.

[0048] A sodium chloride solution with an initial conductivity of 1000 μS / cm was prepared as simulated chlorine-containing wastewater and introduced into the device at a flow rate of 10 mL / min. A working voltage of 1.2 V was applied for chlorine removal testing. The change in solution conductivity over time was recorded, and the adsorption behavior of the electrodes was observed. After adsorption saturation, the electrodes were regenerated by short-circuiting, releasing the adsorbed ions and completing the desorption process. The results are as follows: Figure 2 As shown, Figure 2 The results show that the CDI system can maintain good chloride ion removal performance after multiple cycles, indicating that the electrode made of the porous bismuth ferrite material in Example 1 has good stability and high capacitance retention.

[0049] To evaluate the chloride removal performance of bismuth ferrite materials, the conductivity of the NaCl solution was continuously monitored using a conductivity meter. The chloride ion adsorption capacity (SAC, mg / g) of the bismuth ferrite material was calculated based on the following formula:

[0050] Among them, C0 (mg / L) and C t(mg / L) represent the initial and final concentrations of the salt solution during the capacitor deionization process, respectively. V (L) represents the volume of the salt solution, and m (g) represents the mass of the electrode active material.

[0051] Before conducting CDI performance testing, a standard curve showing the relationship between NaCl solution concentration and conductivity was plotted (e.g., ...). Figure 5 As shown in the figure, C0 and C are calculated based on the standard curve and the measured conductivity of the NaCl solution. t .

[0052] The test results for each group are as follows: Table 1 Performance test results of different bismuth ferrite materials

[0053] As shown in Table 1, the bismuth ferrite powders prepared in Comparative Examples 2, 4, and 7 exhibit similar performance, but are significantly lower than those in Example 1. This indicates that when urea is used alone as a pore-forming agent to prepare bismuth ferrite powder, the lack of starch as a carbon source for forming porous carbon, coupled with the volatilization of nitrogen oxides generated by urea at high temperatures, prevents the formation of N-doped porous carbon in the bismuth ferrite material. Consequently, the specific surface area and pore volume of the bismuth ferrite material are both low, similar to those of Comparative Example 4 (without a pore-forming agent) and Comparative Example 7 (using a precipitation method). Therefore, urea itself does not have the function of optimizing the porous structure of bismuth ferrite materials or improving their electrochemical performance.

[0054] In Comparative Example 1, starch was used as a pore-forming agent. In an atmosphere where the oxygen content was lower than that of air, most of the starch was carbonized into porous carbon, and a small part was oxidized to form carbon dioxide and water volatilization. Therefore, a porous structure was formed inside the bismuth ferrite material, which resulted in a significant increase in specific surface area. However, due to the lack of nitrogen doping by urea and the pore-expanding effect of decomposition gas, the pores inside the composite material were narrow and the connectivity was poor. As a result, the increase in pore volume was smaller than that in Comparative Example 4, and the chloride ion adsorption capacity declined.

[0055] In Comparative Example 3, P123 was used as a pore-forming agent. Although it can form a porous structure in bismuth ferrite material and has a higher specific surface area than in Example 1, it still cannot solve the problem of narrow pores and poor connectivity. As a result, the increase in pore volume is small and the chloride ion adsorption capacity is low.

[0056] When excessive oxygen content was used in Comparative Example 5, most of the starch and urea were oxidized and decomposed into gas volatilization at high temperature, resulting in less porous carbon formation or collapse and poor porous structure formation. Although Comparative Example 4 could also improve the specific surface area and pore volume, the improvement was extremely limited, and its electrochemical performance was also only slightly improved.

[0057] When the oxygen content in Comparative Example 6 was too low, the gas produced by urea decomposition was reduced, and most of it was N-doped into porous carbon. Under anaerobic conditions, almost all of the starch was converted into porous carbon. Due to the lack of gas to open up and expand the pores, and the excessive generation of porous carbon to block the macropores, the narrow and unconnected pore channels resulted in a low pore volume, but a high specific surface area. The low pore volume resulted in poor electrochemical performance of the bismuth ferrite.

Claims

1. A method for preparing a porous bismuth ferrite material, characterized in that, Includes the following steps: (1) Dissolve bismuth salt and iron salt in acid solution to obtain metal solution, add complexing agent and pore-forming agent to metal solution, mix well to obtain precursor solution; (2) The precursor solution is heated to react and a wet gel is obtained. The wet gel is dried to obtain a dry gel. (3) The dry gel was calcined under an inert atmosphere containing 6-10% oxygen to obtain porous bismuth ferrite material.

2. The method for preparing porous bismuth ferrite material according to claim 1, characterized in that, In step (1), the bismuth salt includes at least one of bismuth nitrate and bismuth chloride, the iron salt includes at least one of ferric nitrate, ferric chloride, and ferric sulfate, the complexing agent includes at least one of citric acid, malic acid, and tartaric acid, the pore-forming agent is a mixture of at least one of P123, starch, and modified starch with urea, and the acid solution includes an aqueous solution of at least one of nitric acid, sulfuric acid, and hydrochloric acid.

3. The method for preparing porous bismuth ferrite material according to claim 1, characterized in that, In step (1), the molar ratio of Bi to Fe in the metal solution is 1-2:1-2; the concentration of the acid solution is 5-15%.

4. The method for preparing porous bismuth ferrite material according to claim 1, characterized in that, In step (2), the heating reaction is carried out at 70-90℃ for at least 3 hours; the drying is carried out at 80-100℃ for at least 6 hours.

5. The method for preparing porous bismuth ferrite material according to claim 1, characterized in that, In step (3), the inert atmosphere containing 6-10% oxygen is a mixture of oxygen and argon, wherein the volume fraction of oxygen is 6-10%.

6. The method for preparing porous bismuth ferrite material according to claim 1, characterized in that, In step (3), the calcination conditions are to raise the temperature to 500-700℃ at a rate of 3-7℃ / min and hold it for 3-10 hours.

7. The application of the porous bismuth ferrite material prepared by the preparation method according to any one of claims 1-6 in the preparation of capacitor deionization electrodes.

8. The application according to claim 7, characterized in that, Includes the following steps: The porous bismuth ferrite material, conductive agent, binder and solvent are mixed and then ground and stirred to obtain electrode slurry; Electrode slurry is coated onto the surface of the current collector and dried to obtain a capacitor deionization electrode.

9. The application according to claim 8, characterized in that, The adhesive may be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyacrylic acid, and polyvinyl alcohol, and the solvent includes N. The current collector is made of at least one of the following: methylpyrrolidone, dimethylformamide, ethanol, isopropanol, acetone, and water; the current collector material includes at least one of graphite paper, carbon cloth, carbon felt, graphene film, nickel mesh, stainless steel mesh, titanium mesh, nickel foam, aluminum foil, copper foil, titanium foil, and stainless steel foil; and the conductive agent includes at least one of conductive carbon black and polyaniline.

10. The application of the capacitive deionization electrode prepared according to claim 7 in the dechlorination of aqueous solution.

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