MOFs / GO / CC composite material, preparation method and application

Abstract

The invention relates to the technical field of MOFs composite materials, and discloses an MOFs / GO / CC composite material, and a preparation method and application thereof. According to the method, carbon cloth is used as a working electrode and a graphene source, sulfate is used as an electrolyte, carbon is stripped through an electrochemical method to prepare a graphene oxide material, in the stripping process, the edge and the basal plane of the carbon cloth can be oxidized, an oxygen-containing functional group is introduced, and then meso-tetra (4-carboxyphenyl) porphin is used as an organic ligand to prepare the graphene oxide material. Co-TCPP is grown on the surface of the graphene modified carbon cloth electrode in situ through a solvothermal method. The preparation process is green and environment-friendly, and the obtained MOFs / GO / CC composite material makes up for the defects of poor energy storage performance and low surface activity when carbon cloth is used as an electrode material of a supercapacitor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of MOFs composite materials, and particularly relates to a MOFs / GO / CC composite material, a preparation method and application. BACKGROUND

[0002] At present, in the process of making the carbon cloth-based flexible electrode, strong oxidants need to be used, and compared with this, the strategy of introducing graphene into the carbon cloth is easier to realize the improvement of the capacitive performance. However, the preparation method of the commonly used graphene also needs to use dangerous reagents such as concentrated sulfuric acid and potassium permanganate, and many problems will be faced in the large-scale production. And for the carbon cloth-based composite material, the incompatibility of the pseudocapacitive material and the carbon cloth will cause the low performance of the final composite material.

[0003] As a new type of conductive metal-organic framework material, two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted much attention due to their high in-plane conjugation and strong interlayer coupling, and have shown broad application prospects. Although two-dimensional conductive MOFs have improved in terms of conductive performance compared to traditional MOF materials, their conductivity is still at a low level compared to traditional metal conductors and some high-performance conductive materials.

[0004] Therefore, it is necessary to use a green and safe method to electrochemically modify the carbon cloth, and to composite the carbon cloth with two-dimensional conjugated MOFs material with high electrochemical activity as a substrate to prepare a MOFs / graphene / carbon cloth composite material with excellent electrochemical performance. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art, and provides a MOFs / GO / CC composite material, a preparation method and application. The present application uses an electrochemical method to in-situ prepare GO at normal temperature and pressure, completely avoiding the traditional Hummers method (using strong oxidants and strong acids such as potassium permanganate and concentrated sulfuric acid) for preparing GO. The method is an environmentally friendly synthesis strategy; the present application directly grows active materials on the electrochemically exfoliated carbon cloth to form an integrated structure of "current collector-conductive layer (GO)-active material (MOF)", and the components are connected by chemical bonding (coordination bond, etc.), with strong bonding force and smooth electron transport path, effectively avoiding the shedding of active materials in the cycle and solving the inherent defects of the carbon cloth electrode; the present application specifically addresses the shortcomings of the carbon cloth as an electrode material, i.e. low energy storage performance and low surface activity, and greatly increases the specific surface area and electrochemically active sites by in-situ generating GO and growing MOFs, so that the carbon cloth is transformed from a common current collector into a high-performance electrode.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows: A preparation method of a MOFs / GO / CC composite material, comprising the following steps: Step (1), ultrasonic washing of carbon cloth, drying, to obtain washed carbon cloth; The washed carbon cloth is subjected to electrochemical exfoliation by an electrochemical method, and after exfoliation is completed, it is taken out, washed, and dried to obtain a GO / CC composite material; Step (2), placing the GO / CC composite material in a mixed solution of TCPP (meso-tetra(4-carboxyphenyl) porphyrin), PVP (polyvinylpyrrolidone) and Co(NO3)2•6H2O, and using a one-step hydrothermal method for reaction, and after the reaction is completed, a MOFs / GO / CC composite material is obtained.

[0007] Preferably, in the step (1), the ultrasonic washing operation comprises: sequentially ultrasonic washing the carbon cloth with acetone, ethanol and water for 25-30 min.

[0008] Preferably, in the step (1), the electrochemical exfoliation operation comprises: connecting the washed carbon cloth to an electrochemical workstation as a working electrode, Ag / AgCl as a reference electrode, and a platinum sheet electrode as a counter electrode, immersing the three electrodes in an electrolyte, applying a constant voltage of +1.5 to +2.5 V between the washed carbon cloth and the platinum sheet electrode, and performing electrochemical exfoliation for 10-12 min.

[0009] Further, the electrolyte is a 0.65-0.75 mol / L Na2SO4 aqueous solution.

[0010] Preferably, in the step (2), the solid-liquid ratio of the GO / CC composite material to the mixed solution of meso-tetra(4-carboxyphenyl) porphyrin, polyvinylpyrrolidone and Co(NO3)2•6H2O is 1 g: 150-160 mL; the mixed solution of TCPP (meso-tetra(4-carboxyphenyl) porphyrin), polyvinylpyrrolidone and Co(NO3)2•6H2O is prepared by mixing a mixed solution of meso-tetra(4-carboxyphenyl) porphyrin with a Co(NO3)2•6H2O solution; The mixed solution of meso-tetra(4-carboxyphenyl) porphyrin comprises the following steps: dissolving 8-10 mg of meso-tetra(4-carboxyphenyl) porphyrin and 15-20 mg of polyvinylpyrrolidone in 10-12 mL of a mixed solvent, and stirring uniformly; The Co(NO3)2•6H2O solution comprises the following steps: dissolving 0.0180-0.0185 g of Co(NO3)2•6H2O in 4-6 mL of a mixed solvent, and ultrasonic dissolving for 5-10 min; The above-mentioned mixed solvents are all prepared by mixing N,N-dimethylformamide and ethanol in a volume ratio of 3:1-3:1.3.

[0011] Preferably, in the step (2), the operation of the one-step hydrothermal method comprises: taking the mixed solution of meso-tetra(4-carboxyphenyl) porphyrin as solution A, and taking Co(NO3)2·6H2O solution as solution B; placing the GO / CC composite material in solution B for ultrasonic treatment for 20-30 min, then pouring the GO / CC composite material and solution B into solution A for stirring and mixing for 10-15 min, and then transferring the mixed solution of solution A and solution B and the GO / CC composite material into a high-pressure reaction kettle for reaction at 110-140 DEG C for 10-12 h.

[0012] Preferably, the MOFs / GO / CC composite material is prepared by the preparation method of the MOFs / GO / CC composite material as described above.

[0013] Preferably, the MOFs / GO / CC composite material is used in the field of electrochemical energy storage.

[0014] Compared with the prior art, the beneficial effects of the present application are embodied in: The present application prepares a graphene-modified carbon cloth electrode by a mild electrochemical method, and the method uses carbon cloth as a working electrode and graphene as a source, and a sulfate as an electrolyte, and graphene oxide material is prepared by the electrochemical method, and in the stripping process, the edges and basal planes of the carbon cloth are oxidized to introduce -COOH, -OH, C=O and other oxygen-containing functional groups, and these functional groups provide specific anchoring sites for metal ions (M + ), and the metal ions can be pre-adsorbed on the graphene surface through coordination to provide "seeds" for the heterogeneous nucleation of MOFs; and the presence of the graphene layer on the surface of the carbon cloth significantly increases the surface area of the carbon cloth and improves the hydrophilicity and electrochemical activity of the carbon cloth.

[0015] In the present application, meso-tetra(4-carboxyphenyl) porphyrin is used as an organic ligand, Co-TCPP is in-situ grown on the surface of the graphene-modified carbon cloth electrode by a hydrothermal method, and the GO / MOFs composite material is constructed, the high conductivity of the graphene makes up for the poor conductivity of most MOF materials, and the porosity and high activity of the MOF enrich the functions of the graphene.

[0016] In the present application, the MOFs / GO / CC composite material synthesized by the electrochemical stripping method and the hydrothermal method exhibits a specific capacitance of 2705 mF / cm 2The composite material has high specific capacitance and long cycle life, and the manufacturing process is green and environmentally friendly. It makes up for the shortcomings of carbon cloth as an electrode material of supercapacitors, such as poor energy storage performance and low surface activity. This opens up a new route for the application of pseudocapacitive supercapacitors in the field of energy storage. Attached Figure Description

[0017] Figure 1 The images show the (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP / GO / CC-110 composite material prepared in Example 1 of this invention under different current densities during energy storage performance testing. Figure 2 The images show (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP / GO / CC-120 composite material prepared in Example 2 of this invention under different current densities during energy storage performance testing. Figure 3 The images show (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP / GO / CC-130 composite material prepared in Example 3 of this invention under different current densities during energy storage performance testing. Figure 4 The images show the (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP / GO / CC-140 composite material prepared in Example 4 of this invention under different current densities during energy storage performance testing. Figure 5 The images show the (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP@GO / CC composite material prepared in Comparative Example 1 of this invention in energy storage performance testing at different current densities. Figure 6 The figures show (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-TCPP / CC composite material prepared in Comparative Example 2 of this invention at different current densities during energy storage performance testing. Figure 7 The images show the (a) constant current charge-discharge (CP) curves and (b) specific capacitance curves of the Co-BTB / GO / CC composite material prepared in Comparative Example 3 of this invention in energy storage performance testing at different current densities. Figure 8 This is a comparison of the cyclic voltammetry (CV) curves of the materials prepared in Example 3 of the present invention with those in Comparative Examples 4 and 5 at a scan rate of 5 mV / s. Figure 9These are scanning electron microscope (SEM) images of the materials prepared in Example 3, Comparative Examples 4 and 5 of the present invention; (a) is an SEM image of the untreated carbon cloth CC in Comparative Example 5; (b) is an SEM image of the carbon cloth GO / CC composite material after electrochemical exfoliation in Comparative Example 4; (c) and (d) are both SEM images of the Co-TCPP / GO / CC-130 composite material prepared in Example 3, wherein (c) is an SEM image at 20 μm and (d) is an SEM image at a 5 μm scale. Detailed Implementation

[0018] The present invention will be further illustrated below through specific embodiments. The following embodiments are specific implementations of the present invention, but the implementation of the present invention is not limited to the following embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

[0019] Example 1 This embodiment discloses a method for preparing MOFs / GO / CC composite materials, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; The GO / CC composite material was placed in solution B and sonicated for 30 min. Then, the GO / CC composite material and solution B were poured into solution A and stirred for 10 min. The mixture of solution A and solution B and the GO / CC composite material were transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 110 °C for 12 h. After the reaction was completed, the material was removed, rinsed three times each with ethanol and deionized water, and dried at 60 °C to obtain the MOFs / GO / CC composite material, denoted as Co-TCPP / GO / CC-110.

[0020] Example 2 This embodiment discloses a method for preparing MOFs / GO / CC composite materials, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; The GO / CC composite material was placed in solution B and sonicated for 30 min. Then, the GO / CC composite material and solution B were poured into solution A and stirred for 10 min. The mixture of solution A and solution B and the GO / CC composite material were transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 120°C for 12 h. After the reaction was completed, the material was removed, rinsed three times each with ethanol and deionized water, and dried at 60°C to obtain the MOFs / GO / CC composite material, denoted as Co-TCPP / GO / CC-120.

[0021] Example 3 This embodiment discloses a method for preparing MOFs / GO / CC composite materials, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; The GO / CC composite material was placed in solution B and sonicated for 30 min. Then, the GO / CC composite material and solution B were poured into solution A and stirred for 10 min. The mixture of solution A and solution B and the GO / CC composite material were transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 130 °C for 12 h. After the reaction was completed, the material was removed, rinsed three times each with ethanol and deionized water, and dried at 60 °C to obtain the MOFs / GO / CC composite material, denoted as Co-TCPP / GO / CC-130.

[0022] Example 4 This embodiment discloses a method for preparing MOFs / GO / CC composite materials, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; The GO / CC composite material was placed in solution B and sonicated for 30 min. Then, the GO / CC composite material and solution B were poured into solution A and stirred for 10 min. The mixture of solution A and solution B and the GO / CC composite material were transferred to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 140 °C for 12 h. After the reaction was completed, the material was removed, rinsed three times each with ethanol and deionized water, and dried at 60 °C to obtain the MOFs / GO / CC composite material, denoted as Co-TCPP / GO / CC-140.

[0023] Comparative Example 1 This comparative example discloses a method for preparing Co-TCPP@GO / CC composite material, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; Solution B was poured into solution A and stirred for 10 minutes. The mixture of solution A and solution B was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 130°C for 12 hours. After the reaction was completed, the mixture was removed to obtain Co-TCPP material. 4 mg of Co-TCPP material, 1 mg of acetylene black powder, and 1 mg of PVDF binder were mixed and ground for 30 min, and then dispersed in 1~1.5 mL of NMP (N-methylpyrrolidone) to obtain Co-TCPP material slurry; Using GO / CC composite material as a substrate, Co-TCPP material slurry was uniformly coated onto GO / CC composite material at a coating amount of 2-3 mg. After coating, the material was dried, washed with ethanol and water, and dried again at 60℃ for 12 h to obtain Co-TCPP@GO / CC composite material, denoted as Co-TCPP@GO / CC.

[0024] Comparative Example 2 This comparative example discloses a method for preparing Co-TCPP / CC composite material, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was placed in a mixed solution of 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 3:1 and reacted at 100°C for 12 hours. After the reaction was completed, the cloth was removed, rinsed with deionized water 3 to 5 times, and then dried at 60°C to obtain the pretreated carbon cloth. Step (2): Dissolve 10 mg of TCPP (medium-tetra(4-carboxyphenyl)porphyrin) and 20 mg of PVP (polyvinylpyrrolidone) in 12 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), stir well to obtain solution A; dissolve 0.0182 g of Co(NO3)2•6H2O in 4 mL of a mixed solvent (DMF and ethanol in a volume ratio of 3:1), sonicate for 5 min to obtain solution B; The pretreated carbon cloth was ultrasonically treated in solution B for 30 min. Then, the pretreated carbon cloth and solution B were poured into solution A and stirred for 10 min. The mixture of solution A and solution B and the pretreated carbon cloth were transferred to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 130℃ for 12 h. After the reaction was completed, the mixture was taken out, rinsed three times each with ethanol and deionized water, and dried at 60℃ to obtain the Co-TCPP / CC composite material, denoted as Co-TCPP / CC.

[0025] Comparative Example 3 This comparative example discloses a method for preparing a Co-BTB / GO / CC composite material, including the following steps: Step (1): The carbon cloth with a specification of 1.5cm×1cm is ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After the exfoliation was completed, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material. Step (2): Dissolve 10 mg of H3BTB (1,3,5-tris(4-carboxyphenyl)benzene) and 25 mg of Co(NO3)2•6H2O in a mixed solvent of 15 mL DMF (N,N-dimethylformamide) and 0.5 mL acetic acid, and sonicate for 5 min to obtain a mixed solution; The GO / CC composite material and the mixed solution were transferred together to a high-pressure reactor lined with polytetrafluoroethylene and reacted at 170°C for 24 hours. After the reaction was completed, the material was removed, rinsed three times each with ethanol and deionized water, and dried at 60°C to obtain the Co-BTB / GO / CC composite material, denoted as Co-BTB / GO / CC.

[0026] Comparative Example 4 This comparative example discloses a method for preparing GO / CC composite material, including the following steps: The carbon cloth with a specification of 1.5cm×1cm was ultrasonically washed in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth. The washed carbon cloth was connected to an electrochemical workstation as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet electrode as the counter electrode. The three electrodes were immersed in a 0.7 mol / L Na2SO4 aqueous solution. A constant voltage of +2.5 V was applied between the washed carbon cloth and the platinum sheet electrode for electrochemical exfoliation for 10 min. After exfoliation, the carbon cloth was removed, rinsed three times with deionized water, and dried at 60 °C to obtain the GO / CC composite material, denoted as GO / CC.

[0027] Comparative Example 5 This comparative example discloses a pretreatment method for carbon cloth, including the following steps: A 1.5cm × 1cm carbon cloth was ultrasonically washed in acetone, anhydrous ethanol, and deionized water for 30 minutes in sequence, and then dried to obtain the washed carbon cloth, denoted as CC.

[0028] Experimental data characterization and performance testing like Figures 1-7 As shown in Table 1, the energy storage performance of the composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were tested respectively. The energy storage performance testing process specifically involved using a standard three-electrode system. The composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were used as the working electrode, the Hg / HgO electrode as the reference electrode, and a platinum sheet as the counter electrode. A 1 mol / L KOH aqueous solution was used as the electrolyte for capacitance performance testing. All tests were conducted on a CHI760F electrochemical workstation. Constant current charge-discharge (CP) curves were measured at different current densities, and the specific capacitance and rate performance were calculated.

[0029] Table 1. Specific capacitance of the composite materials prepared in the examples and comparative examples at different current densities.

[0030] Figure 1 The three-electrode system constructed from the Co-TCPP / GO / CC-110 composite material prepared in Example 1 is shown to operate at 1 mA / cm². 2 The specific capacitance at current density is 824 mF / cm 2 At 10mA / cm 2 The rate performance at current density is 69.5%; Figure 2 The three-electrode system constructed from the Co-TCPP / GO / CC-120 composite material prepared in Example 2 is shown to operate at 1 mA / cm². 2 The specific capacitance at current density is 2625 mF / cm 2 At 10mA / cm 2 The rate performance at current density is 85.8%; Figure 3 The three-electrode system constructed from the Co-TCPP / GO / CC-130 composite material prepared in Example 3 is shown to operate at 1 mA / cm². 2 The specific capacitance at current density is 2705 mF / cm 2 At 10mA / cm 2 The rate performance at current density is 86%; Figure 4 The three-electrode system constructed from the Co-TCPP / GO / CC-140 composite material prepared in Example 4 is shown to operate at 1 mA / cm². 2 The specific capacitance at the current density is 549.8 mF / cm. 2 At 10mA / cm 2 The rate performance at current density is 60.4%.

[0031] Depend on Figures 1-4As shown in Table 1, by comparing the specific capacitance values ​​of the Co-TCPP / GO / CC materials prepared in Examples 1-4, it was found that the Co-TCPP / GO / CC material prepared in Example 3 had the highest specific capacitance value. Furthermore, the difference in the preparation process between Examples 1-4 lies in the reaction temperature. This indicates that when preparing the Co-TCPP / GO / CC material with optimal performance, if the reaction temperature is too low, the bonding between Co-TCPP and GO / CC (carbon cloth) may rely on van der Waals forces or weak chemical interactions. At low temperatures, it is difficult to form strong chemical bonds, resulting in high resistance to interfacial charge transport and easy material detachment during the reaction. If the reaction temperature is too high, it may lead to partial thermal decomposition of the organic ligands (TCPP) in Co-TCPP or cause excessive aggregation of metal clusters, resulting in a reduction in active sites. In addition, high temperatures may cause excessive growth of MOF crystals, leading to agglomeration, reducing specific surface area and accessibility of active sites, thus affecting the specific capacitance value of the material.

[0032] Figure 5 The three-electrode system constructed from the Co-TCPP@GO / CC composite material prepared in Comparative Example 1 is shown to operate at 1 mA / cm². 2 The specific capacitance at the current density is 1203.1 mF / cm. 2 At 10mA / cm 2 The rate performance at current density is 52%; Figure 6 The three-electrode system constructed from the Co-TCPP / CC composite material prepared in Comparative Example 2 is shown to operate at 1 mA / cm. 2 The specific capacitance at the current density is 225.2 mF / cm. 2 At 10mA / cm 2 The rate performance at current density is 83.7%; Figure 7 The three-electrode system constructed from the Co-BTB / GO / CC composite material prepared in Comparative Example 3 shows that at 1 mA / cm 2 The specific capacitance at the current density is 118.3 mF / cm. 2 At 10mA / cm 2 The rate performance at current density is 81.2%.

[0033] Depend on Figure 5 As shown in Table 1, the Co-TCPP@GO / CC composite material prepared in Comparative Example 1 has good specific capacitance but poor rate performance at current densities of 1, 2, 4, 6, 8 and 10 mA / cm². 2 The specific capacitances at those times were 1203.1, 1086.2, 931.6, 816, 711.1, and 626 mF / cm, respectively. 2 Its specific capacitance starts from a low current density of 1 mA / cm² 2 Increase 10 times to 10 mA / cm 2At that time, the capacitance retention rate was 52%. Although it has a relatively high specific capacitance and capacitance retention rate, it is still at a lower level compared to the composite material prepared in Example 3. This indicates that compared to a simple mixture of two materials, the composite material formed by the interaction of Co-TCPP and GO / CC can produce a stronger synergistic effect, thereby significantly optimizing the energy storage performance of the material.

[0034] Depend on Figure 6 As shown in Table 1, the Co-TCPP / CC composite material prepared in Comparative Example 2 exhibits good rate capability but poor specific capacitance at current densities of 1, 2, 4, 6, 8, and 10 mA / cm². 2 The specific capacitances at the following times were 225.2, 223.6, 211.8, 205.9, 196.4 and 188.6 mF / cm, respectively. 2 Its specific capacitance starts from a low current density of 1 mA / cm² 2 Increase 10 times to 10 mA / cm 2 At that time, the capacitance retention rate was 83.7%. This indicates that GO (graphene oxide), as an intermediate layer, greatly optimized the electronic conduction path and mass transport channel of Co-TCPP, while also producing a synergistic effect with Co-TCPP. In contrast, the surface of the bare CC in Comparative Example 2 is mainly inert carbon material with fewer chemical functional groups. The growth of MOF on it may rely more on physical adsorption, resulting in weak binding force, uneven distribution, and easy detachment from the substrate, leading to the lower specific capacity of Comparative Example 2.

[0035] Depend on Figure 7 As shown in Table 1, the Co-BTB / GO / CC composite material prepared in Comparative Example 3 exhibits good rate capability but poor specific capacitance at current densities of 1, 2, 4, 6, 8, and 10 mA / cm². 2 The specific capacitances at those times were 118.3, 111.5, 107.7, 106.2, 100, and 96 mF / cm, respectively. 2 Its specific capacitance starts from a low current density of 1 mA / cm² 2 Increase 10 times to 10 mA / cm 2 At that time, the capacitance retention was 81.2%. This indicates that the large conjugated structure of TCPP facilitates efficient electron transport with the GO substrate and optimizes the electronic structure of the active center. Although the BTB ligand used in Comparative Example 3 also has a benzene ring, its degree of conjugation and planarity are far inferior to the porphyrin macrocycle. Its π-π interaction with GO may be weaker, resulting in a lower specific capacity.

[0036] Figure 8The graph shows a comparison of the cyclic voltammetry (CV) curves of the materials prepared in Example 3 of this invention, and Comparative Examples 4 and 5, at a scan rate of 5 mV / s. The graph shows that the curve for the carbon cloth is almost a flat straight line, indicating that the carbon cloth itself does not exhibit significant redox activity. The GO / CC curve shows a weak redox peak, indicating that it has some electrochemical activity, but it is very weak. In contrast, the CV curve of the composite material has the largest and sharpest redox peak, indicating that the introduction of two-dimensional conjugated MOFs greatly enhances the electrochemical activity of the material, suggesting that the oxidation reaction of this material is reversible and rapid.

[0037] Figure 9 These are scanning electron microscope (SEM) images of the materials prepared in Example 3, Comparative Examples 4 and 5 of this invention. Figure 9 As shown, Figure 9 (a) is a scanning electron microscope image of the untreated carbon cloth CC in Comparative Example 5. The carbon fiber has a complete and smooth surface with a small number of structure-related grooves, which is typical of carbon fiber structure. Figure 9 (b) is a scanning electron microscope image of the carbon cloth GO / CC composite material after electrochemical exfoliation in Comparative Example 4. The original small grooves on the carbon fiber surface become less distinct. This is because the exfoliation of carbon fibers initially occurs at the gaps between the graphite layers. After surface exfoliation, the part above the groove will be clearly exfoliated. The exfoliation layer can increase the surface area of ​​the carbon cloth to a certain extent, but the increased surface area is not enough to bring about a major change in the performance of the carbon cloth. Figure 9 (c) Figure 9 (d) is a scanning electron microscope image of the Co-TCPP / GO / CC-130 composite material prepared in Example 3. The image shows that these well-aligned Co-TCPP nanosheets grow uniformly on the GO / CC surface, forming a stable network structure with a large number of open spaces. This unique structure greatly promotes rapid and efficient ion charge transfer and electron transport by providing a shorter mass transfer distance.

[0038] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing MOFs / GO / CC composite materials, characterized in that, Includes the following steps: Step (1): Ultrasonically wash the carbon cloth and dry it to obtain the washed carbon cloth; The washed carbon cloth was electrochemically peeled off using an electrochemical method. After peeling, it was taken out, washed, and dried to obtain the GO / CC composite material. Step (2): Place the GO / CC composite material in a mixed solution of methyl-tetra(4-carboxyphenyl)porphyrin, polyvinylpyrrolidone and Co(NO3)2•6H2O, and react it using a one-step hydrothermal method. After the reaction is completed, remove the material to obtain the MOFs / GO / CC composite material.

2. The method for preparing a MOFs / GO / CC composite material according to claim 1, characterized in that, In step (1), the ultrasonic washing operation includes: ultrasonically washing the carbon cloth with acetone, ethanol and water in sequence.

3. The method for preparing a MOFs / GO / CC composite material according to claim 1, characterized in that, In step (1), the electrochemical stripping operation includes: connecting the washed carbon cloth to the electrochemical workstation as the working electrode, immersing the working electrode, reference electrode, and counter electrode in the electrolyte, applying a constant voltage of +1.5~+2.5 V between the working electrode and the counter electrode, and performing electrochemical stripping for 10~15 min.

4. The method for preparing a MOFs / GO / CC composite material according to claim 3, characterized in that, In the electrochemical stripping operation in step (1), the reference electrode is Ag / AgCl; the counter electrode is a platinum sheet electrode; and the electrolyte is a 0.65~0.75mol / L Na2SO4 aqueous solution.

5. The method for preparing a MOFs / GO / CC composite material according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the GO / CC composite material to the mixed solution of 1g:150mL~160mL is 1g:150mL~160mL. The mixed solution of 1g:150mL~160mL is prepared by mixing the mixed solution of 1g:150mL~160mL with the Co(NO3)2•6H2O solution.

6. The method for preparing a MOFs / GO / CC composite material according to claim 5, characterized in that, In step (2): The mixture of methyl-tetra(4-carboxyphenyl)porphyrin is prepared by the following steps: dissolving 8-10 mg of methyl-tetra(4-carboxyphenyl)porphyrin and 15-20 mg of polyvinylpyrrolidone in 10-12 mL of mixed solvent and stirring until homogeneous; The Co(NO3)2•6H2O solution is prepared by the following steps: dissolving 0.0180~0.0185g of Co(NO3)2•6H2O in 4~6mL of mixed solvent and sonicating for 5~10min; The above-mentioned mixed solvents were all prepared by mixing N,N-dimethylformamide and ethanol in a volume ratio of 3:1 to 3:1.

3.

7. The method for preparing a MOFs / GO / CC composite material according to claim 1, wherein step (2), the one-step hydrothermal method includes: The mixture of 1,4-tetra(4-carboxyphenyl)porphyrin was used as solution A, and the Co(NO3)2•6H2O solution was used as solution B. The GO / CC composite material was placed in solution B and ultrasonically treated for 20-30 min. Then, the GO / CC composite material and solution B were poured into solution A and stirred for 10-15 min to react.

8. The method for preparing a MOFs / GO / CC composite material according to claim 7, wherein in step (2), the reaction conditions are: reacting at 110~140℃ for 10~12h.

9. A MOFs / GO / CC composite material prepared by the method for preparing MOFs / GO / CC composite materials as described in any one of claims 1 to 8.

10. An application of the MOFs / GO / CC composite material as described in claim 9 in the field of electrochemical energy storage.

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