Copper bismuthate / porous carbon nitride composite electrode material and preparation method and application thereof

Abstract

The invention relates to a copper bismuthate / porous carbon nitride composite electrode material and a preparation method and application thereof, and belongs to the technical field of capacitive deionization desalination. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material comprises the following steps: uniformly mixing copper bismuthate and porous carbon nitride, adding a proper amount of ethanol, uniformly stirring, carrying out ultrasonic dispersion, and carrying out vacuum drying to remove a solvent to obtain a mixture; and calcining the mixture to obtain the copper bismuthate / porous carbon nitride composite electrode material. The copper bismuthate / porous carbon nitride composite material is adopted as the electrode material in the capacitive deionization technology, many limitations of a traditional electrode material in desalination performance, stability and service life are successfully overcome, and the overall performance of the CDI technology is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of capacitive deionization desalination, and particularly relates to a copper bismuthate / porous carbon nitride composite electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, with the rapid growth of the global population and the acceleration of the industrialization process, the problem of water resource shortage has become increasingly severe. The excessive consumption and pollution of fresh water resources have become an important challenge threatening the sustainable development of humanity. In this context, the development and application of seawater desalination technology are of great significance. However, a large amount of salt in seawater (such as chloride ions and sodium ions) not only seriously affects the potability of water but also causes many hazards to the environment and life. High-concentration chloride ions are highly harmful to the ecosystem. After infiltrating into the soil, they will cause salinization, damage the growth environment of crops, and result in reduced crop yields or even crop failures. At the same time, excessive intake of sodium ions will endanger human health, causing problems such as hypertension and cardiovascular diseases. In addition, the enrichment of sodium ions in water bodies will increase the water hardness, affect the quality of drinking water and industrial water, and cause problems such as pipeline scaling, posing multiple threats to the ecological environment and human life.

[0003] To address the above problems, desalination technologies have emerged. Their main goal is to remove salts from saline wastewater to make the water quality meet the standards of drinking water or industrial water. In the existing technologies, the main desalination methods include distillation, reverse osmosis, ion exchange, etc. Although these methods are technically mature, they generally have problems such as high energy consumption, membrane fouling, and high costs. In contrast, capacitive deionization (CDI) is a new type of water treatment technology that removes ions from water through the principle of electroadsorption and is particularly suitable for the desalination of low-salinity water bodies. The core principle of the CDI technology is to use the electric field formed on the electrode surface to adsorb cations and anions in water, and then release these ions by changing the direction of the electric field. Its working process can be divided into two stages: First, when a voltage is applied, the electrode adsorbs ions in water, similar to the charging process of a capacitor; then, when a reverse electric field is applied, the adsorbed ions are released, similar to the discharging process of a capacitor. By continuously cycling this process, the salts in the water are removed. However, the CDI technology is also limited by the performance of the electrode material. Currently, common materials such as activated carbon have problems such as insufficient specific surface area, low conductivity, and low durability. Therefore, the development of high-performance electrode materials has become the key to improving the efficiency of the CDI technology. Summary of the Invention

[0004] In view of this, the present application provides a copper bismuthate / porous carbon nitride composite electrode material, a preparation method thereof, and an application thereof. By using a hard template method to prepare porous carbon nitride, copper bismuthate and carbon nitride are uniformly combined in the microstructure to form a synergistic effect, significantly improving the ion adsorption capacity and electrochemical stability, and effectively overcoming the defects existing in the above-mentioned prior art.

[0005] In the first aspect of the present application, a preparation method of a copper bismuthate / porous carbon nitride composite electrode material is provided, including the following steps:

[0006] Uniformly mix copper bismuthate and porous carbon nitride, add an appropriate amount of ethanol and stir evenly, perform ultrasonic dispersion, and then carry out vacuum drying to remove the solvent to obtain a mixture; calcine the mixture to obtain a copper bismuthate / porous carbon nitride composite electrode material.

[0007] Copper bismuthate (CuBi2O4), as a metal oxide, has good electrical conductivity and high electrochemical stability, can provide abundant ion adsorption sites, and enhance the charge storage capacity of the electrode. However, its specific surface area is relatively small, which may limit its deionization performance. However, porous carbon nitride (g-C3N4) prepared by the hard template method has a relatively large specific surface area, can provide more ion adsorption sites, and has strong chemical stability. By compounding copper bismuthate and carbon nitride, the electrical conductivity of the material can be effectively improved, the specific surface area can be increased, and thus the deionization efficiency of the electrode can be enhanced. The excellent electrochemical performance of the composite material enables it to maintain high stability and strong ion selectivity during long-term cycling, and is particularly suitable for desalination of low-salinity water bodies. The composite electrode material exhibits high energy efficiency, long service life, and good environmental adaptability in capacitive deionization technology, and has broad application prospects. In addition, the copper bismuthate / carbon nitride (CuBi2O4 / g-C3N4) composite material can provide higher electrical conductivity and better ion adsorption capacity, further improving the performance of capacitive deionization technology, and has significant performance advantages and broad application prospects.

[0008] Preferably, the preparation process of the copper bismuthate is as follows: Mix Cu(NO3)2·3H2O and Bi(NO3)3·5H2O in a molar ratio of 1:2, dissolve them in deionized water to obtain a uniform precursor solution; add an appropriate amount of alkaline solution to the precursor solution to adjust the pH to 7-8, and promote precipitation formation by heating in a water bath at 80°C; after suction filtration, washing, and drying, calcine the precipitate at 400-500°C for 1-3 hours to obtain copper bismuthate powder.

[0009] Preferably, the alkaline solution is selected from at least one of NH3·H2O, NaOH, KOH, and Na2CO3.

[0010] Preferably, the preparation process of the porous carbon nitride is as follows: disperse the silica nanosphere template in ethanol, add melamine, dry in an oven, and then heat it to 550 °C at a rate of 5 °C / min in a nitrogen atmosphere and pyrolyze for 2 - 4 hours to form a carbon nitride / template composite; then soak the carbon nitride / template composite in a 2 - 5 mol / L sodium hydroxide solution to remove the silica template, and finally wash it with deionized water until neutral and dry to obtain porous carbon nitride.

[0011] Preferably, the preparation process of the silica nanosphere template is as follows: first, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1, stir evenly, and then slowly drop tetraethyl orthosilicate (TEOS). Stir at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silica nanoparticles; after the reaction, collect the product by centrifugal separation, wash it with ethanol and deionized water multiple times to remove impurities, and finally dry it in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silica nanosphere template with uniform particle size.

[0012] Preferably, the time of ultrasonic dispersion is 0.5 - 1 hour; or

[0013] the calcination temperature is 300 °C and the calcination time is 1 hour; or

[0014] the mass ratio of cupric bismuthate to porous carbon nitride is (1 - 3):(1 - 3).

[0015] The second aspect of the present application also provides a cupric bismuthate / porous carbon nitride composite electrode material, which is the cupric bismuthate / porous carbon nitride composite electrode material prepared by the above method.

[0016] The third aspect of the present application also provides a preparation method of a cupric bismuthate / porous carbon nitride electrode plate, which is characterized in that the cupric bismuthate / porous carbon nitride composite electrode material described above is used, and it includes the following steps:

[0017] Mix the cupric bismuthate / porous carbon nitride composite electrode material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone solvent, and stir until the slurry is uniform; evenly coat the prepared slurry on a titanium plate, and then place it in an oven at 80 °C and dry for 12 hours to remove the solvent and cure the binder to obtain a cupric bismuthate / porous carbon nitride electrode plate.

[0018] The fourth aspect of the present application also provides a cupric bismuthate / porous carbon nitride electrode plate, which is the cupric bismuthate / porous carbon nitride electrode plate prepared by the above method.

[0019] The fifth aspect of the present application also provides an application of the cupric bismuthate / porous carbon nitride electrode plate as described above in capacitive deionization desalination, including the following steps:

[0020] A glass plate, a silicone gasket, a copper bismuthate / porous carbon nitride electrode plate are used as the positive electrode, a separator, and the copper bismuthate / porous carbon nitride electrode plate is used as the negative electrode at the same time. The silicone gasket and the glass plate are assembled in an orderly manner and fixed with special screws to prepare a CDI electrode; the prepared NaCl solution is introduced into the CDI electrode, and a low voltage is applied to generate an electric field on the electrode. The copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and are efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode, so that the ions are desorbed from the electrode surface, thereby restoring the adsorption capacity of the electrode.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) High desalination ability: The CuBi2O4 / g-C3N4 composite electrode material has excellent ion adsorption performance, and its porous structure and high specific surface area effectively improve the ion transport rate and adsorption capacity; under the condition of low salinity water treatment (such as 500mg / L NaCl solution), the adsorption capacity of the composite electrode material of the present application is significantly better than that of traditional activated carbon or graphite-based electrode materials.

[0023] (2) Excellent electrochemical stability: By optimizing the combination mode of copper bismuthate and carbon nitride, the composite electrode material shows excellent stability in high-intensity electrochemical cycles; experiments show that after 100 adsorption-release cycles, the performance of the composite electrode material only decreases by less than 5%, which is significantly better than traditional electrode materials, showing good long-term operation ability and service life.

[0024] (3) Low energy consumption operation: The present application can achieve efficient desalination under low voltage (1.2 - 1.6V), and the energy consumption is significantly lower than that of traditional reverse osmosis and ion exchange technologies; especially in the process of low salinity water treatment, the energy consumption reduction reaches more than 30%, greatly reducing the energy consumption and having significant economic benefits.

[0025] (4) Significant cost-effectiveness: The raw materials of the present application are widely sourced and have low costs, and at the same time the preparation process is simple and large-scale production can be realized; this makes the composite electrode material have significant economic competitiveness in practical applications. Description of the Drawings

[0026] To more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the present application or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0027] Figure 1 SEM image of the CuBi2O4 / g-C3N4 composite electrode material prepared in Example 1 of the present application;

[0028] Figure 2 Adsorption-desorption diagram of the CuBi2O4 / g-C3N4 composite electrode material prepared in Example 1 of the present application in a 500 mg / L NaCl solution;

[0029] Figure 3 BET diagrams of the CuBi2O4 / g-C3N4 composite electrode material and CuBi2O4 prepared in Example 1 of the present application, (a) N2 adsorption-desorption isotherm, (b) pore size distribution of the sample;

[0030] Figure 4 XRD diagram of the CuBi2O4 / g-C3N4 composite electrode material prepared in Example 1 of the present application. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the present application clearer, the following will clearly and completely describe the technical solutions in the present application in conjunction with the accompanying drawings in the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application fall within the scope of protection of the present application.

[0032] The experimental methods used in the embodiments of the present application are all conventional methods unless otherwise specified.

[0033] In the following embodiments, unless otherwise specified, all raw materials can be obtained through commercial purchase or conventional methods.

[0034] Example 1

[0035] (1) Dissolve 1 mmol of copper nitrate (Cu(NO3)2·3H2O) and 2 mmol of bismuth nitrate (Bi(NO3)3·5H2O) in 100 mL of high-purity water, and stir magnetically until completely dissolved to obtain a precursor solution; slowly add ammonia water to the precursor solution to adjust the pH of the solution to 7 - 8, and observe the formation of a light blue precipitate; after filtering the precipitate by suction, wash it alternately with ultrapure water and absolute ethanol 3 times to remove impurities; dry the washed precipitate in a vacuum at 80 °C for 12 hours, and then calcine it at 400 °C for 2 hours to obtain CuBi2O4 powder.

[0036] (2) First, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1, stir evenly, and then slowly add tetraethyl orthosilicate. Stir at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silicon dioxide nanoparticles; after the reaction is completed, collect the product by centrifugation, wash it repeatedly with ethanol and deionized water to remove impurities, and finally dry it in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silicon dioxide nanosphere template with uniform particle size; disperse 2 g of the silicon dioxide nanosphere template in 40 mL of ethanol, weigh 10 g of melamine and add it to the silicon dioxide nanosphere template solution, dry it in an oven at 80 °C, and then pyrolyze it in a nitrogen atmosphere at a heating rate of 5 °C / min to 550 °C for 3 hours to generate a carbon nitride / template composite; immerse the composite in a 2 mol / L sodium hydroxide solution to remove the silicon dioxide template, wash it with deionized water until neutral, and then place it in an oven to dry to obtain porous g-C3N4.

[0037] (3) Mix CuBi2O4 and porous g-C3N4 in a mass ratio of 1:1, add 20 mL of absolute ethanol, and stir magnetically for 30 minutes to fully mix the materials; disperse the mixed solution in an ultrasonic instrument for 30 minutes to ensure uniform particle distribution and avoid agglomeration; dry the mixed solution in a vacuum drying oven at 80 °C for 12 hours, and then calcine it at 300 °C for 1 hour to obtain the final CuBi2O4 / g-C3N4 composite material.

[0038] (4) Mix the CuBi2O4 / g-C3N4 composite material, conductive carbon black, and PVDF in a mass ratio of 8:1:1, add an appropriate amount of NMP and stir into a slurry, and use the doctor blade method to evenly coat the prepared slurry on the surface of the titanium plate to control the thickness of the active layer at about 100 μm to prepare a CuBi2O4 / g-C3N4 electrode plate.

[0039] (5) Install the CuBi2O4 / g-C3N4 electrode plate in the CDI device (assemble the glass plate, silicone gasket, copper bismuthate / porous carbon nitride electrode plate as the positive electrode, separator, copper bismuthate / porous carbon nitride electrode plate as the negative electrode, silicone gasket, and glass plate in order, and fix them with special screws to prepare the CDI electrode), corresponding to the positive and negative electrodes. Pass the prepared 500 mg / L NaCl solution into the CDI device at a flow rate of 10 mL / min, flowing through the surface of the CuBi2O4 / g-C3N4 electrode. Turn on the power supply and set a constant voltage (1.2 V) for capacitive deionization desalination. During the operation, record the conductivity change of the water sample to evaluate the desalination efficiency (pass the prepared NaCl solution into the CDI electrode, apply a low voltage to generate an electric field on the electrode. The copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode, so that the ions desorb from the electrode surface, thereby restoring the adsorption capacity of the electrode).

[0040] Example 2

[0041] (1) Dissolve 1 mmol of copper nitrate (Cu(NO3)2·3H2O) and 2 mmol of bismuth nitrate (Bi(NO3)3·5H2O) in 100 mL of high-purity water, and magnetically stir until completely dissolved to obtain a precursor solution; slowly dropwise add ammonia water to the precursor solution to adjust the solution pH to 7-8, and observe the formation of a light blue precipitate; after filtering the precipitate by suction, wash it alternately with ultrapure water and absolute ethanol 3 times to remove impurities; vacuum dry the washed precipitate at 80 °C for 12 hours, and then calcine it at 400 °C for 2 hours to obtain CuBi2O4 powder.

[0042] (2) First, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1. After stirring evenly, slowly add tetraethyl orthosilicate dropwise, and stir at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silicon dioxide nanoparticles. After the reaction ends, collect the product by centrifugal separation, wash it with ethanol and deionized water multiple times to remove impurities, and finally dry it in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silicon dioxide nanosphere template with uniform particle size. Disperse 2 g of the silicon dioxide nanosphere template in 40 mL of ethanol, weigh 10 g of melamine and add it to the silicon dioxide nanosphere template solution, dry it in an oven at 80 °C, and then pyrolyze it in a nitrogen atmosphere at a heating rate of 5 °C / min to 550 °C for 3 hours to generate a carbon nitride / template composite. Immerse the composite in a 2 mol / L sodium hydroxide solution to remove the silicon dioxide template, wash it with deionized water until neutral, and then place it in an oven to dry to obtain porous g-C3N4.

[0043] (3) Mix CuBi2O4 and porous g-C3N4 in a mass ratio of 2:1, add 20 mL of absolute ethanol, and stir magnetically for 30 minutes to fully mix the materials. Place the mixed solution in an ultrasonic instrument and disperse it for 30 minutes to ensure uniform distribution of the particles and avoid agglomeration. Place the mixed solution in a vacuum drying oven at 80 °C and dry it for 12 hours, and then calcine it at 300 °C for 1 hour to obtain the final CuBi2O4 / g-C3N4 composite material.

[0044] (4) Mix the CuBi2O4 / g-C3N4 composite material, conductive carbon black, and PVDF in a mass ratio of 8:1:1, add an appropriate amount of NMP and stir to form a slurry. Use the doctor blade method to uniformly coat the prepared slurry on the surface of the titanium plate, and control the thickness of the active layer to be about 100 μm to prepare the CuBi2O4 / g-C3N4 electrode plate.

[0045] (5) Install the CuBi2O4 / g-C3N4 electrode plate in the CDI device (assemble the glass plate, silicone gasket, copper bismuthate / porous carbon nitride electrode plate as the positive electrode, separator, copper bismuthate / porous carbon nitride electrode plate as the negative electrode, silicone gasket, and glass plate in order, and fix them with special screws to prepare the CDI electrode), corresponding to the positive and negative electrodes. Pass the prepared 500 mg / L NaCl solution into the CDI device at a flow rate of 10 mL / min, flowing through the surface of the CuBi2O4 / g-C3N4 electrode. Turn on the power supply and set a constant voltage (1.2 V) for capacitive deionization desalination. During the operation, record the change in the conductivity of the water sample to evaluate the desalination efficiency (pass the prepared NaCl solution into the CDI electrode, apply a low voltage to generate an electric field on the electrode, the copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode and desorb the ions from the electrode surface, thereby restoring the adsorption capacity of the electrode).

[0046] Example 3

[0047] (1) Dissolve 1 mmol of copper nitrate (Cu(NO3)2·3H2O) and 2 mmol of bismuth nitrate (Bi(NO3)3·5H2O) in 100 mL of high-purity water, and magnetically stir until completely dissolved to obtain a precursor solution; slowly dropwise add ammonia water to the precursor solution to adjust the solution pH to 7-8, and observe the formation of a light blue precipitate; after the precipitate is filtered by suction, wash it alternately with ultrapure water and absolute ethanol 3 times to remove impurities; vacuum dry the washed precipitate at 80 °C for 12 hours, and then calcine it at 400 °C for 2 hours to obtain CuBi2O4 powder.

[0048] (2) First, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1. After stirring evenly, slowly drop tetraethyl orthosilicate, and stir at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silicon dioxide nanoparticles. After the reaction ends, collect the product by centrifugal separation, wash it with ethanol and deionized water multiple times to remove impurities, and finally dry it in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silicon dioxide nanosphere template with uniform particle size. Disperse 2 g of the silicon dioxide nanosphere template in 40 mL of ethanol, weigh 10 g of melamine and add it to the silicon dioxide nanosphere template solution, dry it in an oven at 80 °C, and then pyrolyze it in a nitrogen atmosphere at a heating rate of 5 °C / min to 550 °C for 3 hours to generate a carbon nitride / template composite. Immerse the composite in a 2 mol / L sodium hydroxide solution to remove the silicon dioxide template, wash it with deionized water until neutral, and then place it in an oven to dry to obtain porous g-C3N4.

[0049] (3) Mix CuBi2O4 and porous g-C3N4 in a mass ratio of 1:2, add 20 mL of absolute ethanol, and stir with a magnetic stirrer for 30 minutes to fully mix the materials. Place the mixed solution in an ultrasonic instrument and disperse it for 30 minutes to ensure uniform distribution of the particles and avoid agglomeration. Place the mixed solution in a vacuum drying oven at 80 °C and dry it for 12 hours, and then calcine it at 300 °C for 1 hour to obtain the final CuBi2O4 / g-C3N4 composite material.

[0050] (4) Mix the CuBi2O4 / g-C3N4 composite material, conductive carbon black, and PVDF in a mass ratio of 8:1:1, add an appropriate amount of NMP and stir into a slurry. Use the doctor blade method to evenly coat the prepared slurry on the surface of the titanium plate, and control the thickness of the active layer to be about 100 μm to prepare the CuBi2O4 / g-C3N4 electrode plate.

[0051] (5) Install the CuBi2O4 / g-C3N4 electrode plate in the CDI device (assemble the glass plate, silicone gasket, copper bismuthate / porous carbon nitride electrode plate as the positive electrode, separator, copper bismuthate / porous carbon nitride electrode plate as the negative electrode, silicone gasket, and glass plate in order, and fix them with special screws to prepare the CDI electrode), corresponding to the positive and negative electrodes. Pass the prepared 500 mg / L NaCl solution into the CDI device at a flow rate of 10 mL / min, flowing through the surface of the CuBi2O4 / g-C3N4 electrode. Turn on the power supply and set a constant voltage (1.2 V) for capacitive deionization desalination. During the operation, record the conductivity change of the water sample to evaluate the desalination efficiency (pass the prepared NaCl solution into the CDI electrode, apply a low voltage to generate an electric field on the electrode. The copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode and desorb the ions from the electrode surface, thereby restoring the adsorption capacity of the electrode).

[0052] Example 4

[0053] (1) Dissolve 1 mmol of copper nitrate (Cu(NO3)2·3H2O) and 2 mmol of bismuth nitrate (Bi(NO3)3·5H2O) in 100 mL of high-purity water, and magnetically stir until completely dissolved to obtain a precursor solution; slowly add ammonia water to the precursor solution to adjust the solution pH to 7-8, and observe the formation of a light blue precipitate; after filtering the precipitate by suction, wash it alternately with ultrapure water and absolute ethanol 3 times to remove impurities; vacuum dry the washed precipitate at 80 °C for 12 hours, and then calcine it at 400 °C for 2 hours to obtain CuBi2O4 powder.

[0054] (2) First, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1. After stirring evenly, slowly add tetraethyl orthosilicate dropwise, and stir at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silicon dioxide nanoparticles. After the reaction, collect the product by centrifugal separation, wash it with ethanol and deionized water multiple times to remove impurities, and finally dry it in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silicon dioxide nanosphere template with uniform particle size. Disperse 2 g of the silicon dioxide nanosphere template in 40 mL of ethanol, weigh 10 g of melamine and add it to the silicon dioxide nanosphere template solution, dry it in an oven at 80 °C, and then pyrolyze it at 5 °C / min to 550 °C in a nitrogen atmosphere for 3 hours to generate a carbon nitride / template composite. Immerse the composite in a 2 mol / L sodium hydroxide solution to remove the silicon dioxide template, wash it with deionized water until neutral, and then place it in an oven to dry to obtain porous g-C3N4.

[0055] (3) Mix CuBi2O4 and porous g-C3N4 in a mass ratio of 1:3, add 20 mL of absolute ethanol, and stir magnetically for 30 minutes to fully mix the materials. Place the mixed solution in an ultrasonic instrument and disperse it for 30 minutes to ensure uniform particle distribution and avoid agglomeration. Place the mixed solution in a vacuum drying oven at 80 °C and dry it for 12 hours, and then calcine it at 300 °C for 1 hour to obtain the final CuBi2O4 / g-C3N4 composite material.

[0056] (4) Mix the CuBi2O4 / g-C3N4 composite material, conductive carbon black, and PVDF in a mass ratio of 8:1:1, add an appropriate amount of NMP and stir it into a slurry. Use the doctor blade method to uniformly coat the prepared slurry on the surface of the titanium plate to control the thickness of the active layer at about 100 μm to obtain a CuBi2O4 / g-C3N4 electrode plate.

[0057] (5) Install the CuBi2O4 / g-C3N4 electrode plate in the CDI device (assemble the glass plate, silica gel gasket, copper bismuthate / porous carbon nitride electrode plate as the positive electrode, separator, copper bismuthate / porous carbon nitride electrode plate as the negative electrode, silica gel gasket, and glass plate in order, and fix them with special screws to prepare the CDI electrode), corresponding to the positive and negative electrodes. Pass the prepared 500 mg / L NaCl solution into the CDI device at a flow rate of 10 mL / min, flowing through the surface of the CuBi2O4 / g-C3N4 electrode. Turn on the power supply and set a constant voltage (1.2 V) for capacitive deionization desalination. During the operation, record the conductivity change of the water sample to evaluate the desalination efficiency (pass the prepared NaCl solution into the CDI electrode, apply a low voltage to generate an electric field on the electrode. The copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode, so that the ions desorb from the electrode surface, thereby restoring the adsorption capacity of the electrode).

[0058] Example 5

[0059] (1) Dissolve 1 mmol of copper nitrate (Cu(NO3)2·3H2O) and 2 mmol of bismuth nitrate (Bi(NO3)3·5H2O) in 100 mL of high-purity water, and stir magnetically until completely dissolved to obtain a precursor solution; slowly drop ammonia water into the precursor solution to adjust the solution pH to 7-8, and observe the formation of a light blue precipitate; after filtering the precipitate by suction, wash it alternately with ultrapure water and absolute ethanol 3 times to remove impurities; dry the washed precipitate in vacuo at 80 °C for 12 hours, and then calcine it at 400 °C for 2 hours to obtain CuBi2O4 powder.

[0060] (2) First, ethanol, deionized water, and ammonia water are mixed at a volume ratio of 10:3:1. After stirring evenly, tetraethyl orthosilicate is slowly added dropwise, and stirred at room temperature for 4 - 6 hours to hydrolyze and polycondense tetraethyl orthosilicate to form silicon dioxide nanoparticles; after the reaction ends, the product is collected by centrifugation, washed repeatedly with ethanol and deionized water to remove impurities, and finally dried in a vacuum drying oven at 60 - 80 °C for 12 hours to obtain a silicon dioxide nanosphere template with uniform particle size; 2 g of the silicon dioxide nanosphere template is dispersed in 40 mL of ethanol, 10 g of melamine is weighed and added to the silicon dioxide nanosphere template solution, dried in an oven at 80 °C, and then pyrolyzed at 5 °C / min to 550 °C in a nitrogen atmosphere for 3 hours to generate a carbon nitride / template composite; the composite is immersed in a 2 mol / L sodium hydroxide solution to remove the silicon dioxide template, washed with deionized water until neutral, and then placed in an oven to dry to obtain porous g-C3N4.

[0061] (3) CuBi2O4 and porous g-C3N4 are mixed at a mass ratio of 3:1, 20 mL of anhydrous ethanol is added, and magnetic stirring is carried out for 30 minutes to fully mix the materials; the mixed solution is dispersed in an ultrasonic instrument for 30 minutes to ensure uniform distribution of the particles and avoid agglomeration; the mixed solution is placed in a vacuum drying oven at 80 °C and dried for 12 hours, and then calcined at 300 °C for 1 hour to obtain the final CuBi2O4 / g-C3N4 composite material.

[0062] (4) The CuBi2O4 / g-C3N4 composite material, conductive carbon black, and PVDF are mixed at a mass ratio of 8:1:1, an appropriate amount of NMP is added and stirred into a slurry, and the prepared slurry is evenly coated on the surface of a titanium plate by a doctor blade method to control the thickness of the active layer at about 100 μm, thus obtaining a CuBi2O4 / g-C3N4 electrode plate.

[0063] (5) Install the CuBi2O4 / g-C3N4 electrode plate in the CDI device (assemble the glass plate, silica gel gasket, copper bismuthate / porous carbon nitride electrode plate as the positive electrode, separator, and copper bismuthate / porous carbon nitride electrode plate as the negative electrode, silica gel gasket, and glass plate in order, and fix them with special screws to prepare the CDI electrode), corresponding to the positive and negative electrodes. Pass the prepared 500 mg / L NaCl solution into the CDI device at a flow rate of 10 mL / min, flowing through the surface of the CuBi2O4 / g-C3N4 electrode. Turn on the power supply and set a constant voltage (1.2 V) for capacitive deionization desalination. During the operation, record the conductivity change of the water sample to evaluate the desalination efficiency (pass the prepared NaCl solution into the CDI electrode, apply a low voltage to generate an electric field on the electrode, the copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and are efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode, so that the ions desorb from the electrode surface, thereby restoring the adsorption capacity of the electrode).

[0064] Test example

[0065] Figures 1-4 The CuBi2O4 / g-C3N4 samples used for characterization are all the CuBi2O4 / g-C3N4 composite electrode materials prepared in Example 1 of this application. Figure 4 XRD pattern of the CuBi2O4 / g-C3N4 sample prepared in Example 1, indicating that the CuBi2O4 / g-C3N4 composite material has been successfully synthesized. Figure 3 N2 adsorption-desorption isotherms and pore size distribution diagrams of CuBi2O4 and CuBi2O4 / g-C3N4. The samples all belong to type IV isotherms with H3-type hysteresis loops, indicating that the samples all have mesoporous structure characteristics. Experimental data show that the specific surface area of CuBi2O4 is 3.6442 m 2 / g, while the specific surface area of CuBi2O4 / g-C3N4 reaches 4.780 m 2 / g. Obviously, the specific surface area of CuBi2O4 / g-C3N4 has been significantly improved compared with CuBi2O4; in addition, from Figure 3As can be seen from (b), the pore diameter of CuBi2O4 is mainly concentrated in the range of 2-3 nm, and its average pore diameter is 14.6631 nm. The pore size distribution of CuBi2O4 / g-C3N4 is more extensive, mainly concentrated in the range of 2-4 nm, and the average pore diameter is 27.1323 nm. CuBi2O4 / g-C3N4 has a larger pore diameter, which provides it with a high adsorption capacity and stronger adsorption ability. Through a detailed analysis of the adsorption-desorption isotherm and the mesopore size distribution map, and combined with Figure 1 the SEM image of the CuBi2O4 / g-C3N4 sample in Figure 1 , it can be seen that the morphology of CuBi2O4 / g-C3N4 has a porous structure. Therefore, the following conclusion can be drawn: The CuBi2O4 / g-C3N4 composite material shows obvious advantages in terms of specific surface area, pore diameter, etc. The porous composite material is beneficial to the application of capacitive deionization desalination. As Figure 2 can be seen, during the charging process, due to the adsorption of ions in the solution, the solution conductivity decreases; during the discharging process, due to the desorption of ions in the solution, the solution conductivity increases. Obviously, the adsorption effect of CuBi2O4 / g-C3N4 is obvious. The porous structure increases the number of surface active adsorption sites, accelerates the ion diffusion and transport rate, and thus increases the desalination efficiency.

[0066] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A preparation method of a copper bismuthate / porous carbon nitride composite electrode material, characterized in that, It includes the following steps: Uniformly mix cupric bismuthate and porous carbon nitride, add an appropriate amount of ethanol and stir evenly. After ultrasonic dispersion, conduct vacuum drying to remove the solvent to obtain a mixture; calcine the mixture to obtain a cupric bismuthate / porous carbon nitride composite electrode material.

2. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material according to claim 1, wherein The preparation process of the cupric bismuthate is as follows: Mix Cu(NO3)2·3H2O and Bi(NO3)3·5H2O in a molar ratio of 1:2, dissolve them in deionized water to obtain a uniform precursor solution; Add an appropriate amount of alkaline solution to the precursor solution to adjust the pH to 7-8, and promote the formation of precipitation by heating in a water bath at 80°C; after suction filtration, washing, and drying, calcine the precipitate at 400-500°C for 1-3 hours to obtain cupric bismuthate powder.

3. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material according to claim 2, characterized in that, The alkaline solution is selected from at least one of NH3·H2O, NaOH, KOH, and Na2CO3.

4. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material according to claim 1, characterized in that, The preparation process of the porous carbon nitride is as follows: Disperse the silica nanosphere template in ethanol, add melamine, dry in an oven, and then pyrolyze at 5°C / min to 550°C in a nitrogen atmosphere for 2-4 hours to generate a carbon nitride / template composite; then soak the carbon nitride / template composite in a 2-5 mol / L sodium hydroxide solution to remove the silica template, and finally wash with deionized water to neutrality and dry to obtain porous carbon nitride.

5. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material according to claim 4, characterized in that, The preparation process of the silica nanosphere template is as follows: First, mix ethanol, deionized water, and ammonia water in a volume ratio of 10:3:1, stir evenly, and then slowly drop tetraethyl orthosilicate. Stir at room temperature for 4-6 hours to hydrolyze and polycondense tetraethyl orthosilicate to generate silica nanoparticles; after the reaction ends, collect the product by centrifugal separation, wash it with ethanol and deionized water multiple times to remove impurities, and finally dry it in a vacuum drying oven at 60-80°C for 12 hours to obtain a silica nanosphere template with uniform particle size.

6. The preparation method of the copper bismuthate / porous carbon nitride composite electrode material according to claim 1, wherein, The time of ultrasonic dispersion is 0.5-1 hour; or The calcination temperature is 300°C and the calcination time is 1 hour; or The mass ratio of cupric bismuthate to porous carbon nitride is (1-3):(1-3).

7. A copper bismuthate / porous carbon nitride composite electrode material, characterized in that, A cupric bismuthate / porous carbon nitride composite electrode material prepared by the method according to any one of claims 1-6.

8. A preparation method of a copper bismuthate / porous carbon nitride electrode plate, characterized in that Using the cupric bismuthate / porous carbon nitride composite electrode material according to claim 7, it includes the following steps: Mix the cupric bismuthate / porous carbon nitride composite electrode material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone solvent, and stir until the slurry is uniform; uniformly coat the prepared slurry on a titanium plate, and then place it in an oven at 80°C to dry for 12 hours to remove the solvent and cure the binder to obtain a cupric bismuthate / porous carbon nitride electrode plate.

9. A copper bismuthate / porous carbon nitride electrode plate, characterized in that, A cupric bismuthate / porous carbon nitride electrode plate prepared by the method according to claim 8.

10. Application of the copper bismuthate / porous carbon nitride electrode plate as described in claim 9 in capacitive deionization desalination, characterized in that, It includes the following steps: The glass plate, silicone gasket, copper bismuthate / porous carbon nitride electrode plate are assembled in order as the positive electrode, separator, and copper bismuthate / porous carbon nitride electrode plate simultaneously as the negative electrode, silicone gasket, and glass plate, and are fixed with special screws to prepare a CDI electrode; the prepared NaCl solution is introduced into the CDI electrode, and a low voltage is applied to generate an electric field on the electrode. The copper bismuthate / porous carbon nitride electrode plate with a positive voltage adsorbs anions in the water body, and the negative electrode adsorbs cations; under the action of the electric field, ions are driven to the electrode surface and are efficiently adsorbed through the high specific surface area and porous structure of the copper bismuthate / porous carbon nitride composite electrode material, thereby gradually reducing the salt concentration in the water body to achieve the purpose of desalination; when the electrode adsorption reaches the saturation state, the power supply is reversely charged or the power supply is stopped to release the ions adsorbed on the electrode, so that the ions are desorbed from the electrode surface, thereby restoring the adsorption capacity of the electrode.

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