A micron-shaped flower-shaped composite metal oxide adsorption electrode material, its preparation method and application.

Abstract

This invention belongs to the field of environmental protection and water purification, specifically relating to a micron-shaped composite metal oxide adsorption electrode material, its preparation method, and its application. The electrode material of this invention is mainly composed of Co3O4 / CeO2@C, exhibiting a micron-shaped petal structure. Its preparation method uses PBA as a precursor, adding corresponding metal salts, and completing the precursor preparation under room temperature stirring. Subsequently, a low-temperature air calcination process yields the composite micron-shaped flower material. The material obtained by this invention consists of stacked petal-shaped micron sheets, exhibiting multi-level porosity, ultra-large specific surface area, and the interlacing of the petals and in-situ uniform carbon doping form an excellent conductive network and stable framework structure, endowing the electrode with excellent cycle stability and long-term operating performance. The material prepared in this invention performs superiorly in capacitive deionization applications in seawater desalination. Compared with the traditional synthesis conditions of carbon-based materials, it has strong universality and is more conducive to widespread application.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and water purification, specifically relating to a micron-sized flower-shaped composite metal oxide adsorption electrode material, its preparation method, and its application. Background Technology

[0002] As human civilization continues to evolve, many technologies that once propelled social progress are gradually becoming obsolete, and their potential negative effects are becoming increasingly prominent. For example, problems such as acid rain, light pollution, the greenhouse effect, and water pollution have profoundly impacted people's basic lives. Water is the source of life, and water resource protection is of paramount importance. However, the current water pollution situation is severe, and freshwater resources are becoming increasingly scarce. How to effectively reduce pollution and promote wastewater treatment and recycling has become an inevitable trend. Currently, widely used water purification technologies include reverse osmosis (RO), multi-stage flash evaporation (MSF), and electrodialysis (ED). Although these technologies are relatively mature, they still have shortcomings such as high energy consumption, complex operation, and potential secondary pollution. Against this backdrop, developing more efficient, low-energy-consumption, and environmentally friendly innovative desalination and water purification technologies is particularly crucial.

[0003] Electrochemical desalination (CDI) technology is considered a highly promising approach for future freshwater production due to its advantages such as low energy consumption and no secondary pollution. In the CDI system, cations and anions in the brine migrate and adsorb onto the cathode and anode respectively under the action of an applied electric field, thereby achieving water desalination. Electrode materials play a decisive role in the entire process. Current research mainly focuses on carbon-based electrode materials (such as biomass carbon, graphene, carbon nanotubes, etc.). These materials have excellent conductivity and high specific surface area, enabling rapid and efficient ion adsorption with low energy consumption. However, they still face two inherent problems in practical applications: (1) the preparation process is complex and costly, usually involving high-temperature pyrolysis, chemical vapor deposition (CVD), and soft and hard templates; (2) the cost and performance are mismatched. Since the salt storage mechanism of carbon-based materials mainly relies on double-layer capacitance, their salt adsorption capacity is relatively limited (usually less than 30 mg / g), making it difficult to achieve an effective return on investment in material preparation.

[0004] Therefore, how to develop highly active and easily synthesized adsorption electrode materials has become a key issue in promoting CDI technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a micron-sized flower-shaped composite metal oxide adsorption electrode material, its preparation method, and its application. A Prussian blue precursor (Co-Ce-PBA) is synthesized via a room-temperature chemical precipitation method using cobalt and cerium metal salts. Low-temperature air calcination yields Co3O4 / CeO2@C petal-shaped micron sheets, exhibiting hierarchical porosity and an ultra-large specific surface area. These morphological characteristics significantly enhance the migration and adsorption kinetics of ions in capacitive deionization technology. The interlaced arrangement of the petals and the in-situ uniform doping of carbon form an excellent conductive network and a stable framework structure, endowing the electrode with outstanding conductivity and long-term operating performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a micron-sized flower-shaped composite metal oxide adsorption electrode material. The active material is in the form of petal-shaped micron sheets, with uniform petals approximately 8 μm in length. The material exhibits a hierarchical porosity and possesses an ultra-large specific surface area and an ultra-thin sheet-like structure. Furthermore, the elemental ratio of cobalt (Co) to cerium (Ce) in the Co3O4 / CeO2@C nanoflower active material is approximately 1:1.5~2, and it is uniformly and densely distributed throughout the structure. The carbon phase forms a stable composite structure with the metal oxide through in-situ doping, and the synergistic effect of these three components optimizes the electrochemical performance of the material.

[0008] This invention designs and prepares a Co3O4 / CeO2@C petal-shaped micron-sized heterostructure. The staggered arrangement of the petals provides ample channels for ion migration, while the hierarchical porosity and ultra-large specific surface area significantly increase the adsorption active sites. The ultrathin sheet-like morphology effectively shortens the ion diffusion distance, directly improving the adsorption kinetic efficiency from a structural level. At the same time, the molar ratio of cobalt (Co) to cerium (Ce) is specified to be 1:1.5~2, ensuring that the bimetallic elements are uniformly and densely distributed in the material, laying the structural foundation for the synergistic effect.

[0009] In addition, by utilizing the high electrochemical activity of Co3O4 and the stable structural characteristics of CeO2, the bimetallic synergistic effect is achieved through precise molar ratio control, thereby accelerating the electron / ion transport rate. By leveraging the in-situ carbon doping during the pyrolysis of the Prussian blue precursor, a stable conductive network and framework structure are formed, which not only improves the conductivity of the material but also ensures the long-term operational stability of the electrode, thus solving the problem that it is difficult to balance conductivity and stability in traditional materials.

[0010] This invention provides a method for preparing a micron-sized flower-shaped composite metal oxide adsorption electrode material, the specific steps of which are as follows:

[0011] S1. Preparation of Co-Ce-PBA precursor: 1-3 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dispersed in a mixed solvent of 100-150 mL ethanol and 45-65 mL deionized water to obtain a uniformly dispersed solution A; under stirring conditions, 5-7.5 mL of 0.2 mol / L potassium hexacyanocobalaminate aqueous solution (K3Co(CN)6) was added dropwise to solution A, and after stirring for 10-15 minutes, the solution was allowed to stand at room temperature for 12-15 hours to form a precipitate.

[0012] S2. Preparation of composite metal oxide by low-temperature calcination: The precipitate obtained in step S1 is centrifuged, washed multiple times with ethanol, and dried overnight in an oven at 70~80℃; the dried product is heated to 350~400℃ at a heating rate of 3~5℃ / min, and calcined at this temperature for 6~8 hours. After cooling, Co3O4 / CeO2@C material is obtained, which is the micron flower-shaped composite metal oxide adsorption electrode material;

[0013] S3. Preparation of adsorption electrode: Grind the Co3O4 / CeO2@C material from step S2 into a fine powder, mix the Co3O4 / CeO2@C material, Ketjen black and PVDF adhesive in a weight ratio of 20:1:1, use N-methylpyrrolidone (NMP) as solvent, and stir evenly to form an electrode slurry; coat the slurry onto the surface of the current collector titanium sheet, and dry it in an oven to obtain the positive electrode for capacitor deionization.

[0014] The present invention also provides an application of a micron-shaped composite metal oxide adsorption electrode material, specifically, the negative electrode and a carbon-based positive electrode are assembled to form an asymmetric capacitive deionization (CDI) device, which can be used for the adsorption and removal of heavy metal ions in water to achieve water purification.

[0015] Beneficial effects of the present invention

[0016] (1) Structural innovation enables efficient adsorption: The prepared Co3O4 / CeO2@C material has a petal-shaped micron sheet structure with uniform petals of about 8 μm arranged in an interlaced manner. Combined with multi-level pores, ultra-large specific surface area and ultra-thin sheet morphology, it not only provides sufficient ion migration channels, but also significantly increases the adsorption active sites, while shortening the ion diffusion distance and greatly improving the adsorption kinetic efficiency.

[0017] (2) Element synergistic optimization of electrochemical performance: The molar ratio of Co to Ce is precisely controlled to 1:1.5~2, so that the bimetallic elements are evenly and densely distributed. Combined with the high electrochemical activity of Co3O4 and the structural stability of CeO2, synergistic effect is achieved, and the electron / ion transport rate is accelerated. In-situ carbon doping forms a stable conductive network and framework structure, taking into account both the high conductivity of the material and the long-term operating stability. After 1000 electrochemical cycles, the specific capacitance retention rate reaches 91.12%.

[0018] (3) Excellent and stable desalination performance: The constructed asymmetric CDI device has outstanding desalination performance. After 300 cycles of adsorption-desorption in 500 mg / L NaCl solution and 1.2 V voltage, the performance retention rate reaches 96.8%, and the adsorption-desorption reversibility is good. The salt solution concentration is widely adaptable, and the unit desalination capacity increases steadily with the increase of concentration.

[0019] (4) Green and economical preparation process: The precursor is synthesized by room temperature chemical precipitation and the target material can be obtained by low temperature (350~400℃) air calcination. There is no need for complex processes such as high temperature pyrolysis and CVD. The process is simple and energy consumption is low. The raw materials are readily available and the cost is controllable. This solves the problems of complex preparation of traditional carbon-based electrode materials and mismatch between cost and performance, and is easy to scale up production.

[0020] (5) Broad application prospects: The materials and devices are suitable for the adsorption and removal of metal ions in water and water purification, which meets the needs of environmental protection and water resource recycling, and provides an efficient and low-cost electrode material solution for the industrial promotion of capacitive deionization technology. Attached Figure Description

[0021] Figure 1 The image shows a SEM image of the Co3O4 / CeO2@C material obtained in Example 1.

[0022] Figure 2 EDS image of the Co3O4 / CeO2@C material obtained in Example 1;

[0023] Figure 3 The image shows the XRD pattern of the Co3O4 / CeO2@C material obtained in Example 1.

[0024] Figure 4 The electrochemical cycling test diagram of the Co3O4 / CeO2@C material obtained in Example 1 is shown.

[0025] Figure 5 Figure 1 shows the reversible adsorption and desorption at different voltages of the Co3O4 / CeO2@C material obtained in Example 1.

[0026] Figure 6 This is a graph showing the desalination capacity of the Co3O4 / CeO2@C material obtained in Example 1 at different concentrations;

[0027] Figure 7 The diagram shows the cyclic desalination capacity of the Co3O4 / CeO2@C material obtained in Example 1.

[0028] Figure 8 The retention rate of materials after recycling in Examples 1, 4-6 and Comparative Examples 1-2 is given. Detailed Implementation

[0029] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to examples. The following content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the concept of the invention, they should all fall within the protection scope of the present invention.

[0030] The preparation method of the present invention will be described below through specific embodiments and comparative examples.

[0031] Example 1

[0032] A method for preparing a micron-sized flower-shaped composite metal oxide adsorption electrode material, the specific steps of which are as follows:

[0033] S1. Preparation of Co-Ce-PBA precursor: 2 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dispersed in a mixed solvent of 100 mL ethanol and 45 mL deionized water to obtain a uniformly dispersed solution A; under stirring conditions, 5 mL of 0.2 mol / L potassium hexacyanocobalaminate aqueous solution (K3Co(CN)6) was added dropwise to solution A, and after stirring for 10 minutes, the solution was allowed to stand at room temperature for 12 hours to form a precipitate.

[0034] S2. Preparation of composite metal oxide by low-temperature calcination: The precipitate obtained in step S1 was centrifuged, washed several times with ethanol, and dried overnight in an oven at 70°C; the dried product was heated to 350°C at a heating rate of 3°C / min and calcined at this temperature for 6 hours. After cooling, Co3O4 / CeO2@C material was obtained, which is the micron flower-shaped composite metal oxide adsorption electrode material.

[0035] S3. Preparation of adsorption electrode: Grind the above Co3O4 / CeO2@C material into fine powder, mix Co3O4 / CeO2@C, Ketjen black and PVDF adhesive in a weight ratio of 20:1:1, use N-methylpyrrolidone (NMP) as solvent, stir evenly to form electrode slurry; coat the slurry onto the surface of the current collector titanium sheet, and dry it in an oven to obtain the positive electrode for capacitor deionization.

[0036] Example 2

[0037] A method for preparing a micron-sized flower-shaped composite metal oxide adsorption electrode material, the specific steps of which are as follows:

[0038] S1. Preparation of Co-Ce-PBA precursor: 2.5 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dispersed in a mixed solvent of 120 mL ethanol and 50 mL deionized water to obtain a uniformly dispersed solution A; under stirring conditions, 6 mL of 0.2 mol / L potassium hexacyanocobalaminate aqueous solution (K3Co(CN)6) was added dropwise to solution A, and after stirring for 12 minutes, it was allowed to stand at room temperature for 13 hours to form a precipitate.

[0039] S2. Preparation of composite metal oxide by low-temperature calcination: The precipitate obtained in step S1 was centrifuged, washed several times with ethanol, and dried overnight in an oven at 75°C; the dried product was heated to 370°C at a heating rate of 4°C / min and calcined at this temperature for 7 hours. After cooling, Co3O4 / CeO2@C material was obtained, which is the micron flower-shaped composite metal oxide adsorption electrode material.

[0040] S3. Preparation of adsorption electrode: Grind the above Co3O4 / CeO2@C material into fine powder, mix Co3O4 / CeO2@C, Ketjen black and PVDF adhesive in a weight ratio of 20:1:1, use N-methylpyrrolidone (NMP) as solvent, stir evenly to form electrode slurry; coat the slurry onto the surface of the current collector titanium sheet, and dry it in an oven to obtain the positive electrode for capacitor deionization.

[0041] Example 3

[0042] This invention provides a method for preparing a micron-sized flower-shaped composite metal oxide adsorption electrode material, the specific steps of which are as follows:

[0043] S1. Preparation of Co-Ce-PBA precursor: 3 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dispersed in a mixed solvent of 150 mL ethanol and 65 mL deionized water to obtain a uniformly dispersed solution A; under stirring conditions, 7.5 mL of 0.2 mol / L potassium hexacyanocobalaminate aqueous solution (K3Co(CN)6) was added dropwise to solution A, and after stirring for 15 minutes, the solution was allowed to stand at room temperature for 15 hours to form a precipitate.

[0044] S2. Preparation of composite metal oxide by low-temperature calcination: The precipitate obtained in step S1 was centrifuged, washed several times with ethanol, and dried overnight in an oven at 80°C; the dried product was heated to 400°C at a heating rate of 5°C / min and calcined at this temperature for 8 hours. After cooling, Co3O4 / CeO2@C material was obtained, which is the micron flower-shaped composite metal oxide adsorption electrode material.

[0045] S3. Preparation of adsorption electrode: Grind the above Co3O4 / CeO2@C material into fine powder, mix Co3O4 / CeO2@C, Ketjen black and PVDF adhesive in a weight ratio of 20:1:1, use N-methylpyrrolidone (NMP) as solvent, stir evenly to form electrode slurry; coat the slurry onto the surface of the current collector titanium sheet, and dry it in an oven to obtain the positive electrode for capacitor deionization.

[0046] Example 4

[0047] The amount of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) added was changed to 1.0 mmol, and the procedure was the same as the remaining parameters and Example 1.

[0048] Example 5

[0049] The amount of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) added was changed to 1.5 mmol, and the procedure was the same as the remaining parameters and Example 1.

[0050] Example 6

[0051] The amount of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) added was changed to 2.5 mmol, and the procedure was the same as the remaining parameters and Example 1.

[0052] Comparative Example 1

[0053] Single Co-based oxide electrode material (Co3O4@C)

[0054] S1. Prepare 5 mL of 0.2 mol / L potassium hexacyanocobalaminate aqueous solution (K3Co(CN)6), and dry it to obtain the precursor powder sample.

[0055] The steps are the same as those in the remaining parameters and Example 1.

[0056] Comparative Example 2:

[0057] Single Ce-based oxide electrode material (CeO2@C)

[0058] S1. 2 mmol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dispersed in a mixed solvent of 100 mL ethanol and 45 mL deionized water, and dried to obtain the precursor powder sample.

[0059] The steps are the same as those in the remaining parameters and Example 1.

[0060] Applications and Testing

[0061] 1. Electrochemical performance testing of Co3O4 / CeO2@C electrode

[0062] The CHI 660E electrochemical workstation was used to conduct charge-discharge cycle tests on a three-electrode system with the following electrode materials: reference electrode silver / silver chloride, counter electrode platinum mesh, and working electrode active material composite electrode. The current density was 1 A / g, the voltage window was -0.6 V to 0.6 V, and the electrolyte was 1.0 mol / L sodium chloride solution.

[0063] 2. Electrochemical desalination test of Co3O4 / CeO2@C electrode

[0064] The CHI 660E electrochemical workstation was used to conduct charge-discharge cycle tests on the electrode materials (silver / silver chloride reference electrode, platinum mesh counter electrode, and active material composite electrode) in a three-electrode system. The current density was 1 A / g, the voltage window was -0.6 V to 0.6 V, and the electrolyte was 1.0 mol / L sodium chloride solution.

[0065] Figure 1 The image shows a SEM image of the Co3O4 / CeO2@C material obtained in Example 1. The active material is in the form of petal-shaped micron flakes with uniform petals and a length of about 8 μm. The material exhibits a multi-level pore structure with a large specific surface area and an ultra-thin sheet-like structure.

[0066] Figure 2 The image shows the EDS spectrum of the Co3O4 / CeO2@C material obtained in Example 1. From the energy spectrum, it can be analyzed that the elements of cobalt (Co) and cerium (Ce) are evenly and densely distributed throughout the structure.

[0067] Figure 3The image shows the XRD pattern of the Co3O4 / CeO2@C material obtained in Example 1. As can be seen from the image, the characteristic diffraction peaks in the spectrum correspond one-to-one with the standard cards for Co3O4 and CeO2, and all characteristic peaks are sharp and clear, indicating good crystallinity of the material. Furthermore, no diffraction peaks of cobalt, cerium, or other impurity phases are observed in the spectrum, proving that the pure-phase composite structure of Co3O4 and CeO2 was successfully synthesized using the method of this invention. Simultaneously, no obvious carbon phase diffraction peaks were observed, suggesting that the in-situ doped carbon is uniformly dispersed in an amorphous form within the metal oxide matrix, forming a stable composite structure with the metal oxide. This is consistent with the description in the invention that "the carbon phase forms a stable composite structure with the metal oxide through in-situ doping."

[0068] Figure 4 The cyclic charge-discharge (GCD) curves and cyclic voltammetry curves show that after 1000 cycles of GCD testing, the triangular curve characteristics did not change significantly, and the specific capacitance retention rate reached 91.12%, which strongly demonstrates the excellent stability of the electrode in electrochemical experiments.

[0069] 2. Electroadsorption performance test of Co3O4 / CeO2@C electrode

[0070] To test the adsorption effect of this invention on ions in salt solutions, an asymmetric capacitive deionization adsorption device was constructed using the Co3O4 / CeO2@C electrode from Example 1 and activated carbon. Desalination experiments were conducted under different conditions, and the corresponding performance was tested.

[0071] Figure 5 The data for treating a 500 mg / L NaCl salt solution with the Co3O4 / CeO2@C electrode prepared in Example 1 at different voltages are presented. The results show that adsorption and desorption can occur reversibly, demonstrating the material's regeneration capability. Furthermore, the decrease in conductivity and the desalination capacity gradually increase with increasing voltage.

[0072] Figure 6 The data for processing salt solutions of different concentrations with the Co3O4 / CeO2@C electrode prepared in Example 1 at a voltage of 1.2V shows that the amount of salt removed per unit increases with the increase of salt solution concentration.

[0073] Figure 7 The data for the Co3O4 / CeO2@C electrode prepared in Example 1 are obtained from a cyclic adsorption-desorption experiment conducted at a voltage of 1.2 V and a NaCl salt solution of 500 mg / L. As can be seen from the figure, after 300 cycles of testing, the adsorption-desorption performance of the electrode reached 96.8% of the retention rate in the first cycle, which is sufficient to show that the material has stable performance and can be used in long-term desalination equipment.

[0074] Figure 8The figure shows the cycle retention rate of the electrode materials after application in Examples 1, 4-6 and Comparative Examples 1-2. As can be seen from the figure, Ce and Co have a synergistic effect, and their performance is significantly higher when they coexist than when they exist as a single element. In addition, the performance is best when the molar ratio of Co to Ce is 1:1.5-2.

[0075] As can be seen from the above electrochemical and electroadsorption performance test results, the electrode active material involved in this invention not only has a high electroadsorption capacity for metal ions in salt solutions, but also performs well in long-term cycle tests. The desalination equipment is simple to manufacture, the material synthesis is green and environmentally friendly, and the process cost is low, which has broad development prospects.

Claims

1. A method for preparing a microflower-type composite metal oxide adsorbing electrode material, characterized in that, The method comprises the following steps: S1. Preparing Co-Ce-PBA precursor: dispersing 1-3 mmol Ce(NO3)3·6H2O in a mixed solvent of 100-150 mL of ethanol and 45-65 mL of deionized water to obtain solution A; under stirring, 5-7.5 mL of K3Co(CN)6 with a concentration of 0.2 mol / L is added dropwise into solution A, stirring, and standing at room temperature to form a precipitate product; S2. Preparing composite metal oxide by low-temperature calcination: the precipitate product obtained in step S1 is centrifuged and washed with ethanol for multiple times, and then dried in an oven at 70-80℃ overnight; the dried product is heated to 350-400℃, and calcined at constant temperature for 6-8 hours, and then cooled to obtain Co3O4 / CeO2@C material, which is a micron flower type composite metal oxide adsorption electrode material; S3. Preparing adsorption electrode: the Co3O4 / CeO2@C material in step S2 is ground into fine powder, and the Co3O4 / CeO2@C material, Ketjen black and adhesive PVDF are mixed to form electrode slurry by stirring with NMP as solvent; the slurry is coated on the surface of the current collector titanium sheet, and then dried to obtain a negative electrode for capacitive deionization; The micron flower type composite metal oxide adsorption electrode material in step S2 is petal-shaped microparticle, with uniform petals and a length of about 8 μm; the material has a multi-level pore structure, a super large specific surface area and a super thin sheet structure, and the element ratio of Co to Ce is 1:1.5-2, which is uniformly and densely distributed in the whole structure, and the carbon phase forms a stable composite structure with the metal oxide by in-situ doping.

2. The production method according to claim 1, characterized by, The stirring time in step S1 is 10-15 minutes, and the standing time at room temperature is 12-15 hours.

3. The preparation method according to claim 1, characterized in that, The heating rate of the temperature rise in step S2 is 3-5℃ / min.

4. The method of claim 1, wherein, The mass ratio of the Co3O4 / CeO2@C material, Ketjen black and adhesive PVDF in step S3 is 20:1:

1.

5. A microflower type composite metal oxide adsorbing electrode material, characterized in that, Prepared by the method in any one of claims 1-4.

6. The use of the microflower composite metal oxide adsorbent electrode material of claim 5, characterized in that, The positive electrode prepared from the material and the carbon material-based negative electrode are assembled to form an asymmetric capacitive deionization device, which is used for adsorption and removal of metal ions in water and water resource purification.

7. Use according to claim 6, characterized in that, The asymmetric capacitive deionization device has a performance retention rate of ≥96.8% after 300 cycles of adsorption-desorption under the condition of 500 mg / L NaCl solution and 1.2 V voltage.

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