Aerogel electrode material and method for preparing the same

Abstract

The application provides an aerogel electrode material and a preparation method thereof, and relates to the technical field of supercapacitor electrodes. The preparation method comprises the following steps: preparing a polystyrene template, then synthesizing ZIF-8 on the polystyrene template, obtaining SOM-ZIF-8 through chemical etching, compounding the SOM-ZIF-8 with MoS2 quantum dots, and then contacting the SOM-ZIF-8 with reduced graphene oxide to prepare a hydrogel, and finally freeze-drying to obtain the aerogel electrode material. The aerogel electrode material and the preparation method thereof can effectively solve the defects of the existing reduced graphene oxide, molybdenum disulfide quantum dots and binary composite system in supercapacitors, and can effectively balance the high power density and the high energy density while having high conductivity, high specific capacity, excellent rate performance and long cycle stability.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor electrode technology, and in particular to an aerogel electrode material and its preparation method. Background Technology

[0002] Supercapacitors have attracted much attention in the energy storage field due to their high power density, rapid charge-discharge capability, and long cycle life. However, existing electrode materials still face problems such as low specific capacity, insufficient ion transport efficiency, and poor structural stability. Although porous carbon materials have a high specific surface area, their disordered pore structure limits the rapid migration of ions; while transition metal oxides can provide pseudocapacitance, they have poor conductivity and are prone to aggregation. Therefore, it is crucial to develop electrode materials that combine ordered pore structure, high conductivity, and abundant active sites.

[0003] In recent years, reduced graphene oxide (rGO) has been frequently used as a conductive substrate for composite materials due to its excellent conductivity and mechanical strength. However, the inventors have discovered that although existing rGO substrates have high theoretical specific surface area and superior conductivity, the strong π-π stacking between rGO sheets easily leads to severe stacking during electrode fabrication and drying, resulting in a significant decrease in effective specific surface area and the burial of numerous active sites. Simultaneously, the single two-dimensional rGO sheet structure severely restricts the diffusion path of electrolyte ions. Ions mainly migrate horizontally between rGO layers, with vertical transport being greatly hindered, leading to slow ion diffusion kinetics and severe performance degradation at high rates. Furthermore, existing rGO-based electrodes are prone to gradual collapse of the electrode structure during cyclic charge-discharge, resulting in a rapid decrease in cycle stability.

[0004] Molybdenum disulfide (MoS2) quantum dots, due to their unique layered structure and abundant edge active sites, can significantly enhance the pseudocapacitive effect of materials. However, the inventors discovered that existing composite materials made of molybdenum disulfide quantum dots and reduced graphene oxide (RBO) used in supercapacitor electrodes suffer from low utilization of active sites and uneven local current density because the molybdenum disulfide quantum dots lack effective anchoring sites on the RBO substrate surface. More importantly, the binary composite system formed by molybdenum disulfide quantum dots and RBO lacks an effective synergistic energy storage mechanism—RBO mainly contributes to the double-layer capacitance, while molybdenum disulfide contributes to the pseudocapacitance; without synergistic bonding, the electrode struggles to achieve a balance between high power density and high energy density.

[0005] Based on this, an electrode material is provided to solve the problems of low effective specific surface area, obstructed vertical ion transport, and poor cycle stability due to the lack of a three-dimensional rigid framework caused by the π-π stacking of reduced graphene oxide sheets. At the same time, it solves the problems of agglomeration of molybdenum disulfide quantum dots due to the lack of effective anchoring sites, low utilization of active sites, and the lack of synergistic energy storage mechanism in binary composite systems. It can effectively balance high power density and high energy density while possessing high conductivity, high specific capacity, excellent rate performance and long cycle stability, which has important technical significance and research value. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides an aerogel electrode material and its preparation method. This method is based on an ordered large-microporous ZIF-8 framework as a carrier, molybdenum disulfide quantum dot modification, and graphene substrate to synergistically construct a three-dimensional porous electrode material with both high specific capacity and stability. It can effectively solve the defects of existing reduced graphene oxide, molybdenum disulfide quantum dots and their binary composite system in supercapacitors. It can effectively balance high power density and high energy density while possessing high conductivity, high specific capacity, excellent rate performance and long cycle stability.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing an aerogel electrode material includes the following steps: Step S01: Styrene, polyvinylpyrrolidone, and potassium persulfate solution are placed in deionized water. After stirring and reacting in an inert atmosphere, the solids are collected by centrifugation to obtain a polystyrene template. Step S02: Dissolve zinc nitrate hexahydrate and 2-methylimidazole in methanol to obtain a precursor solution; after impregnating the polystyrene template in the precursor solution, separate and collect the solids; after immersing the solids in a mixed solution of methanol and ammonia at room temperature and allowing them to stand, separate and collect the solids and dry them, then wash and dry them with tetrahydrofuran to obtain SOM-ZIF-8. Step S03: Place SOM-ZIF-8 in a MoS2 quantum dot dispersion, stir and react, then separate and collect the solids. After washing and drying, the solids are used to obtain the MoS2 / SOM-ZIF-8 complex. Step S04: Place the MoS2 / SOM-ZIF-8 composite in a reduced graphene oxide dispersion, stir and react, then centrifuge to collect the solid wet material. The solid wet material is washed and purified to obtain a purified gel precursor. The purified gel precursor is freeze-dried to obtain an aerogel electrode material.

[0008] Preferably, in step S01, the concentration of the potassium persulfate solution is 16-24 mg / mL; The mass-to-volume ratio of styrene, polyvinylpyrrolidone, potassium persulfate in the potassium persulfate solution, and deionized water is 6-14 mL: 0.1-0.3 g: 0.16-0.24 g: 100 mL.

[0009] Preferably, in step S01, the temperature of the stirring reaction is 70-75℃, and the stirring reaction time is 22-24h.

[0010] Preferably, in step S02, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole in the precursor solution is 1:1-5; and the molar concentration of zinc nitrate hexahydrate in the precursor solution is 0.6-0.7 mol / L. The mass-to-volume ratio of polystyrene template to precursor solution is 0.01-0.08 g: 1 mL.

[0011] Preferably, in step S02, the immersion time of the polystyrene template in the precursor solution is 1-2 hours; The solid was immersed in a mixed solution of methanol and ammonia and left to stand at room temperature for 22-24 hours.

[0012] Preferably, in step S03, the concentration of the MoS2 quantum dot dispersion is 0.5-1 mg / mL; The mass-to-volume ratio of SOM-ZIF-8 to MoS2 quantum dot dispersion is 1-5 mg: 1 mL.

[0013] Preferably, in step S04, the concentration of the reduced graphene oxide dispersion is 0.5-0.6 mg / mL; The mass ratio of the MoS2 / SOM-ZIF-8 composite to the reduced graphene oxide dispersion is 100-300:20.

[0014] Further, in step S03, the method for preparing the MoS2 quantum dot dispersion is as follows: thioacetamide and sodium molybdate dihydrate are dissolved in deionized water and the pH is adjusted to 3.0; then ascorbic acid and polyvinylpyrrolidone are added, stirred evenly, and after hydrothermal reaction, the precipitate is removed by centrifugation, and the supernatant is dialyzed to obtain the MoS2 quantum dot dispersion.

[0015] Preferably, in the preparation of the MoS2 quantum dot dispersion, the mass ratio of thioacetamide, sodium molybdate dihydrate, ascorbic acid, and polyvinylpyrrolidone is 0.1-0.3g:0.15-0.3g:0.1-0.2g:0.1g; The hydrothermal reaction temperature is 100-300℃, and the hydrothermal reaction time is 16-20h.

[0016] An aerogel electrode material is prepared using the aforementioned preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the preparation of the aerogel electrode material of the present invention, SOM-ZIF-8 is prepared using styrene as a template. Compared with the traditional ZIF-8 powder, by adjusting the ratio of zinc nitrate hexahydrate, 2-methylimidazole and methanol, the sacrificial template method is used to perfectly combine the intrinsic advantages of ZIF-8 such as high specific surface area and abundant micropores with the epitaxial advantages such as specific surface area brought by hollow structure and excellent mass transfer kinetics brought by multi-level channels, thereby improving electrochemical performance and cycle stability.

[0018] (2) In the preparation of the aerogel electrode material of the present invention, by adjusting the ratio of SOM-ZIF-8 ordered macroporous framework and molybdenum disulfide quantum dots, MoS2 quantum dots are uniformly loaded on the SOM-ZIF-8 ordered macroporous framework, avoiding the aggregation of quantum dots, maximizing the exposure of their surface active sites, alleviating their volume changes during cycling, accelerating ion transport, and the ZIF-8 and MoS2 quantum dots interface are tightly bound, improving the electrode cycling stability and electrochemical performance.

[0019] (3) In the preparation of the aerogel electrode material of the present invention, SOM-ZIF-8, MoS2 quantum dots and rGO are cleverly combined by freeze drying to construct an aerogel electrode material based on an ordered large microporous ZIF-8 framework as a carrier, molybdenum disulfide quantum dot modification and reduced graphene oxide substrate in synergy; wherein, rGO constructs a three-dimensional continuous conductive pathway, electrons are rapidly transported through the rGO network, and ions rapidly reach the MoS2 active sites through the interlayer gaps of rGO and the multi-level pores of ZIF-8; the flexible sheets of rGO encapsulate or connect the MoS2 / SOM-ZIF-8 composite together to form an integral electrode structure with good mechanical strength, which avoids the active material from falling off the current collector during the cycle, optimizes the ion transport dynamics of the electrode, solves the problems of single substrate structure and insufficient conductivity, and constructs a three-dimensional porous electrode material with both high specific capacity and stability. Compared with the electrode material that simply uses ZIF-8 in the prior art, the substrate structure and active sites are richer, and the final specific capacitance is improved (at 0.2 Ag). -1 At a current density of 187.80 Fg, the specific capacitance can reach 187.80 Fg. -1 ). Attached Figure Description

[0020] Figure 1 Scanning electron microscope images of SOM-ZIF-8 prepared for Comparative Example 1 at different magnifications; where (a) is magnified by 20,000 times and (b) is magnified by 25,000 times.

[0021] Figure 2The images are scanning electron microscope images of the aerogel electrode material of Example 3 at different magnifications; where (a) is magnified by 20,000 times, (b) by 23,000 times, and (c) and (d) by 25,000 times.

[0022] Figure 3 The image shows the mapping diagram of the aerogel electrode material in Example 3; where (a)-(e) represent the distribution of C, N, Mo, Zn and S elements in the aerogel electrode material, respectively.

[0023] Figure 4 EDX elemental analysis of the aerogel electrode material in Example 3.

[0024] Figure 5 The figures are cyclic voltammetry test diagrams of the electrode materials of Comparative Example 1 and Example 3; wherein, (a) is the cyclic voltammetry test diagram of Comparative Example 1 and (b) is the cyclic voltammetry test diagram of Example 3.

[0025] Figure 6 The constant current charge-discharge test diagrams are for the electrode materials of Comparative Example 1 and Example 3; wherein, (a) is the constant current charge-discharge test diagram of Comparative Example 1, and (b) is the constant current charge-discharge test diagram of Example 3.

[0026] Figure 7 This is a characterization diagram of the cyclic stability of the aerogel electrode material in Example 3. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] This invention provides a method for preparing an aerogel electrode material, comprising the following steps: Step S01: Styrene, polyvinylpyrrolidone, and potassium persulfate solution are placed in deionized water. After stirring and reacting in an inert atmosphere, the solids are collected by centrifugation to obtain a three-dimensional ordered polystyrene template. Step S02: Dissolve zinc nitrate hexahydrate and 2-methylimidazole in methanol to obtain a precursor solution; after impregnating the polystyrene template in the precursor solution, separate and collect the solids; after immersing the solids in a mixed solution of methanol and ammonia at room temperature and allowing them to stand, separate and collect the solids and dry them, then wash and dry them with tetrahydrofuran to obtain white powder SOM-ZIF-8. Step S03: Place SOM-ZIF-8 in a MoS2 quantum dot dispersion, stir and react, then separate and collect the solids. After washing and drying, the solids are used to obtain the MoS2 / SOM-ZIF-8 complex. Step S04: Place the MoS2 / SOM-ZIF-8 composite in a reduced graphene oxide dispersion, stir and react, then centrifuge to collect the solid wet material. The solid wet material is washed and purified to obtain a purified gel precursor. The purified gel precursor is freeze-dried to obtain an aerogel electrode material.

[0030] In this embodiment of the invention, a three-dimensional ordered polystyrene template is first prepared, and then SOM-ZIF-8 with ordered large micropores and high thermal stability is prepared using this polystyrene template. Its porous structure significantly improves ion diffusion kinetics. Then, MoS2 quantum dots are uniformly loaded onto the ordered large micropore framework of ZIF-8 to avoid quantum dot aggregation, maximize the exposure of their surface active sites, alleviate volume changes during cycling, and accelerate ion transport. Moreover, the tight bonding between ZIF-8 and MoS2 quantum dots at the interface can improve the electrode cycling stability and electrochemical performance. Then, through a freeze-drying process, a 3D aerogel is constructed based on the ordered large micropore ZIF-8 framework as a carrier, with molybdenum disulfide quantum dot modification and reduced graphene oxide substrate working synergistically. This allows ZIF-8 and MoS2 quantum dots to be uniformly inserted into the interlayer of reduced graphene oxide, effectively increasing the interlayer spacing and fundamentally suppressing π-π stacking. The process involves stacking layers to ensure full exposure of all active sites. It constructs a three-dimensional continuous conductive pathway using reduced graphene oxide, allowing electrons to rapidly transport through the reduced graphene oxide network and ions to quickly reach the MoS2 active sites via the interlayer gaps of reduced graphene oxide and the hierarchical channels of ZIF-8. Furthermore, the flexible sheets of reduced graphene oxide encapsulate or connect the MoS2 / SOM-ZIF-8 composite, forming a mechanically strong overall electrode structure that prevents the active material from detaching from the current collector during cycling, further optimizing the electrode's ion transport dynamics. The aforementioned techniques work synergistically to effectively address the shortcomings of existing reduced graphene oxide, molybdenum disulfide quantum dots, and their binary composite systems in supercapacitors. This approach effectively balances high power density and high energy density while maintaining high conductivity, high specific capacity, excellent rate performance, and long-cycle stability.

[0031] Preferably, in step S01, the concentration of potassium persulfate solution is 16-24 mg / mL; the mass-to-volume ratio of styrene, polyvinylpyrrolidone, potassium persulfate in potassium persulfate solution, and deionized water is 6-14 mL: 0.1-0.3 g: 0.16-0.24 g: 100 mL.

[0032] Preferably, in step S01, the temperature of the stirring reaction is 70-75℃, and the stirring reaction time is 22-24h.

[0033] Preferably, in step S02, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole in the precursor solution is 1:1-5; and the molar concentration of zinc nitrate hexahydrate in the precursor solution is 0.6-0.7 mol / L.

[0034] Preferably, in step S02, the mass-to-volume ratio of the polystyrene template to the precursor solution is 0.01-0.08 g:1 mL; and the immersion time of the polystyrene template in the precursor solution is 1-2 h.

[0035] Preferably, in step S02, the volume ratio of methanol to ammonia in the mixed solution is 1:0.8-1.2; the concentration of ammonia is 25-28 wt%; and the solid is immersed in the mixed solution of methanol and ammonia for 22-24 hours at room temperature.

[0036] Preferably, in step S03, the concentration of the MoS2 quantum dot dispersion is 0.5-1 mg / mL; the mass-to-volume ratio of SOM-ZIF-8 to the MoS2 quantum dot dispersion is 1-5 mg:1 mL.

[0037] Preferably, in step S04, the concentration of the reduced graphene oxide dispersion is 0.5-0.6 mg / mL; the mass ratio of the MoS2 / SOM-ZIF-8 composite to the reduced graphene oxide in the reduced graphene oxide dispersion is 100-300:20.

[0038] Preferably, in step S04, the stirring reaction time is 90-120 min.

[0039] Further, in step S03, the preparation method of MoS2 quantum dot dispersion is as follows: thioacetamide and sodium molybdate dihydrate are dissolved in deionized water and the pH is adjusted to 3.0; then ascorbic acid and polyvinylpyrrolidone are added, stirred evenly, and after hydrothermal reaction, the precipitate is removed by centrifugation, and the supernatant is dialyzed to obtain MoS2 quantum dot dispersion.

[0040] Preferably, in the preparation of the MoS2 quantum dot dispersion, the mass ratio of thioacetamide, sodium molybdate dihydrate, ascorbic acid, and polyvinylpyrrolidone is 0.1-0.3g:0.15-0.3g:0.1-0.2g:0.1g.

[0041] Preferably, in the preparation of the MoS2 quantum dot dispersion, the hydrothermal reaction temperature is 100-300℃ and the hydrothermal reaction time is 16-20h.

[0042] The present invention also provides an aerogel electrode material prepared by the aforementioned method.

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.

[0044] Example 1 This embodiment provides a method for preparing an aerogel electrode material, the specific steps of which are as follows: (1) Preparation of PS template: 6 mL of styrene, 0.1 g of polyvinylpyrrolidone (PVP), and 100 mL of deionized water were added to a round-bottom flask and bubbled with N2 for 20 min. The mixture was then stirred in an oil bath at 70 °C for 10 min to ensure thorough mixing. To initiate the polymerization of styrene, 10 mL of an aqueous solution containing 0.16 g of K2S2O8 was added to the flask over 20 min. The mixture was then refluxed and stirred at 800 rpm at 70 °C. After stirring for 24 h, the mixture was cooled to obtain monodisperse colloidal polystyrene (PS) spheres. Finally, the solids were collected by high-speed centrifugation to obtain a three-dimensionally ordered PS template.

[0045] (2) Preparation of SOM-ZIF-8: 0.03 mol zinc nitrate hexahydrate and 0.03 mol 2-methylimidazole were dissolved in 45 mL of methanol solution to obtain the precursor solution. The PS template was immersed in the precursor solution for 1 h at a mass-to-volume ratio of 0.02 g / mL and degassed under vacuum for 10 min. The solid obtained by filtration was soaked in a 1:1 mixture of methanol and ammonia (25 wt%), degassed under vacuum, and then allowed to stand at room temperature for 24 h. The solid fragments were collected by filtration and dried. The solid was then soaked in tetrahydrofuran for one day to dissolve and remove the PS template. The solid was collected by centrifugation and dried at 110 °C overnight. The resulting white powder was SOM-ZIF-8.

[0046] (3) Preparation of MoS2 quantum dot dispersion: Weigh 0.15g of sodium molybdate dihydrate, add 40mL of deionized water, and stir magnetically until completely dissolved; weigh 0.15g of thioacetamide (TAA), slowly add it to the above solution, and stir for 15min until completely dissolved. Then add 1M HCl dropwise, monitor with a pH meter, and adjust the pH of the solution to 3.0. Then add 0.1g of ascorbic acid and 0.1g of PVP, and continue stirring for 30min. Then, transfer the mixed solution to a 50mL high-pressure hydrothermal reactor, seal the hydrothermal reactor, and react at 100℃ for 16h. After the reaction is completed, let the reactor cool naturally to room temperature. Centrifuge the product at 12000rpm for 30min and discard the bottom precipitate. Take the supernatant and put it into a dialysis bag, dialyze with 1L of deionized water for 48h (change the water every 8h) to remove residual salts. Finally, the dialysis product was filtered through a 0.22 μm filter membrane to obtain a clear MoS2 quantum dot dispersion with a MoS2 quantum dot concentration of 0.5 mg / mL.

[0047] (4) Preparation of MoS2 / SOM-ZIF-8 complex: 20 mg of SOM-ZIF-8 was added to 20 mL of MoS2 quantum dot dispersion, and the mixture was sonicated for 30 min to promote the quantum dots to enter the MOF channels; then the mixture was magnetically stirred to ensure that the quantum dots were fully adsorbed. The solid complex was collected by centrifugation at 6000 rpm for 10 min, washed three times with ethanol, and dried under vacuum at 60 °C for 6 h to obtain the MoS2 / SOM-ZIF-8 complex.

[0048] (5) Construction of aerogel: 200 mg MoS2 / SOM-ZIF-8 complex and 20 mg rGO were dispersed in 40 mL of deionized water by magnetic stirring and stirred at 300 rpm for 90 min to obtain a composite dispersion; the composite dispersion was centrifuged to collect solid wet material, and the obtained solid wet material was washed and purified with ethanol and deionized water in sequence to obtain a purified gel precursor; the purified gel precursor was freeze-dried in vacuum for 12 h to obtain MoS2@SOM-ZIF-8 / rGs, i.e. aerogel electrode material.

[0049] This embodiment also provides an aerogel electrode material prepared by the aforementioned method.

[0050] Example 2 This embodiment provides a method for preparing an aerogel electrode material, the specific steps of which are as follows: (1) Preparation of PS template: 8 mL of styrene, 0.2 g of polyvinylpyrrolidone (PVP), and 100 mL of deionized water were added to a round-bottom flask and bubbled with N2 for 20 min. The mixture was then stirred in an oil bath at 70 °C for 10 min to ensure thorough mixing. To initiate the polymerization of styrene, 10 mL of an aqueous solution containing 0.18 g of K2S2O8 was added to the flask over 20 min. The mixture was then refluxed and stirred at 800 rpm at 70 °C. After stirring for 24 h, the mixture was cooled to obtain monodisperse colloidal polystyrene (PS) spheres. Finally, the solids were collected by high-speed centrifugation to obtain a three-dimensionally ordered PS template.

[0051] (2) Preparation of SOM-ZIF-8: 0.03 mol zinc nitrate hexahydrate and 0.06 mol 2-methylimidazole were dissolved in 45 mL of methanol solution to obtain the precursor solution. The PS template was immersed in the precursor solution for 1 h at a mass-to-volume ratio of 0.03 g / mL and degassed under vacuum for 10 min. The solid obtained by filtration was soaked in a 1:1 mixture of methanol and ammonia (25 wt%), degassed under vacuum, and then allowed to stand at room temperature for 24 h. The solid fragments were collected by filtration and dried. The solid was then soaked in tetrahydrofuran for one day to dissolve and remove the PS template. The solid was collected by centrifugation and dried at 110 °C overnight. The resulting white powder was SOM-ZIF-8.

[0052] (3) Preparation of MoS2 quantum dot dispersion: Weigh 0.242 g of sodium molybdate dihydrate, add 40 mL of deionized water, and stir magnetically until completely dissolved; weigh 0.15 g of thioacetamide (TAA), slowly add it to the solution, and stir for 15 min until completely dissolved. Add 1 M HCl dropwise, monitor with a pH meter, and adjust the pH of the solution to 3.0. Then add 0.176 g of ascorbic acid and 0.1 g of PVP, and continue stirring for 30 min. Then, transfer the mixed solution to a 50 mL high-pressure hydrothermal reactor, seal the hydrothermal reactor, and react at 150 °C for 18 h. After the reaction is completed, let the reactor cool naturally to room temperature. Centrifuge the product at 12000 rpm for 30 min and discard the bottom precipitate. Take the supernatant and put it into a dialysis bag, dialyze with 1 L of deionized water for 48 h (change the water every 8 h) to remove residual salts. Finally, the dialysis product was filtered through a 0.22 μm filter membrane to obtain a clear MoS2 quantum dot dispersion with a MoS2 quantum dot concentration of 0.6 mg / mL.

[0053] (4) Preparation of MoS2 / SOM-ZIF-8 complex: 50 mg SOM-ZIF-8 was added to 20 mL of MoS2 quantum dot dispersion, and sonicated for 30 min to promote the quantum dots to enter the MOF channels; then magnetically stirred to ensure full adsorption of quantum dots. The solid complex was collected by centrifugation at 6000 rpm for 10 min, washed three times with ethanol, and dried under vacuum at 60 °C for 6 h to obtain the MoS2 / SOM-ZIF-8 complex.

[0054] (5) Construction of aerogel: 100 mg MoS2 / SOM-ZIF-8 complex and 20 mg rGO were dispersed in 40 mL of deionized water by magnetic stirring and stirred at 300 rpm for 90 min to obtain a composite dispersion; the composite dispersion was centrifuged to collect solid wet material, and the obtained solid wet material was washed and purified with ethanol and deionized water in sequence to obtain a purified gel precursor; the purified gel precursor was freeze-dried in vacuum for 12 h to obtain MoS2@SOM-ZIF-8 / rGs, i.e. aerogel electrode material.

[0055] This embodiment also provides an aerogel electrode material prepared by the aforementioned method.

[0056] Example 3 This embodiment provides a method for preparing an aerogel electrode material, the specific steps of which are as follows: (1) Preparation of PS template: 10 mL of styrene, 0.2 g of polyvinylpyrrolidone (PVP), and 100 mL of deionized water were added to a round-bottom flask and bubbled with N2 for 20 min. The mixture was then stirred in an oil bath at 70 °C for 10 min to ensure thorough mixing. To initiate the polymerization of styrene, 10 mL of an aqueous solution containing 0.2 g of K2S2O8 was added to the flask within 20 min. The mixture was then refluxed and stirred at 800 rpm at 70 °C. After stirring for 24 h, the mixture was cooled to obtain monodisperse colloidal polystyrene (PS) spheres. Finally, the solids were collected by high-speed centrifugation to obtain a three-dimensionally ordered PS template.

[0057] (2) Preparation of SOM-ZIF-8: 0.03 mol zinc nitrate hexahydrate and 0.09 mol 2-methylimidazole were dissolved in 45 mL of methanol solution to obtain the precursor solution. The PS template was immersed in the precursor solution for 1 h at a mass-to-volume ratio of 0.04 g / mL and degassed under vacuum for 10 min. The solid obtained by filtration was soaked in a 1:1 mixture of methanol and ammonia (25 wt%), degassed under vacuum, and then allowed to stand at room temperature for 24 h. The solid fragments were collected by filtration and dried. The solid was then soaked in tetrahydrofuran for one day to dissolve and remove the PS template. The solid was collected by centrifugation and dried at 110 °C overnight. The resulting white powder was SOM-ZIF-8.

[0058] (3) Preparation of MoS2 quantum dot dispersion: Weigh 0.242 g of sodium molybdate dihydrate, add 40 mL of deionized water, and stir magnetically until completely dissolved; weigh 0.15 g of thioacetamide (TAA), slowly add it to the above solution, and stir for 15 min until completely dissolved. Add 1 M HCl dropwise, and adjust the pH of the solution to 3.0 using a pH meter. Then add 0.176 g of ascorbic acid and 0.1 g of PVP, and continue stirring for 30 min. Then, transfer the mixed solution to a 50 mL high-pressure hydrothermal reactor, seal the hydrothermal reactor, and react at 200 °C for 18 h. After the reaction is completed, let the reactor cool naturally to room temperature. Centrifuge the product at 12000 rpm for 30 min and discard the bottom precipitate. Take the supernatant and put it into a dialysis bag, dialyze with 1 L of deionized water for 48 h (changing the water every 8 h) to remove residual salts. Finally, the dialysis product was filtered through a 0.22 μm filter membrane to obtain a clear MoS2 quantum dot dispersion with a MoS2 quantum dot concentration of 1 mg / mL.

[0059] (4) Preparation of MoS2 / SOM-ZIF-8 complex: 50 mg of SOM-ZIF-8 was added to 20 mL of MoS2 quantum dot dispersion. The mixture was sonicated for 30 min to promote quantum dot entry into the MOF channels. Then, the mixture was magnetically stirred to ensure complete adsorption of the quantum dots. The solid complex was collected by centrifugation at 6000 rpm for 10 min. The solid complex was washed three times with ethanol and dried under vacuum at 60 °C for 6 h to obtain the MoS2 / SOM-ZIF-8 complex.

[0060] (5) Construction of aerogel: 200 mg MoS2 / 3DSOM-ZIF-8 complex and 20 mg rGO were dispersed in 40 mL of deionized water by magnetic stirring and stirred at 300 rpm for 90 min to obtain a composite dispersion. The composite dispersion was centrifuged to collect the solid wet material. The obtained solid wet material was washed and purified with ethanol and deionized water in sequence to obtain a purified gel precursor. The purified gel precursor was freeze-dried in vacuum for 12 h to obtain MoS2@SOM-ZIF-8 / rGs, i.e. aerogel electrode material.

[0061] This embodiment also provides an aerogel electrode material prepared by the aforementioned method.

[0062] Example 4 This embodiment provides a method for preparing an aerogel electrode material, the specific steps of which are as follows: (1) Preparation of PS template: 12 mL of styrene, 0.3 g of polyvinylpyrrolidone (PVP), and 100 mL of deionized water were added to a round-bottom flask and bubbled with N2 for 20 min. The mixture was then stirred in an oil bath at 70 °C for 10 min to ensure thorough mixing. To initiate the polymerization of styrene, 10 mL of an aqueous solution containing 0.22 g of K2S2O8 was added to the flask over 20 min. The mixture was then refluxed and stirred at 800 rpm at 70 °C. After stirring for 24 h, the mixture was cooled to obtain monodisperse colloidal polystyrene (PS) spheres. Finally, the solids were collected by high-speed centrifugation to obtain a three-dimensionally ordered PS template.

[0063] (2) Preparation of SOM-ZIF-8: 0.03 mol zinc nitrate hexahydrate and 0.12 mol 2-methylimidazole were dissolved in 45 mL of methanol solution to obtain the precursor solution. The PS template was immersed in the precursor solution for 1 h at a mass-to-volume ratio of 0.07 g / mL and degassed under vacuum for 10 min. The solid obtained by filtration was soaked in a 1:1 mixture of methanol and ammonia (25 wt%), degassed under vacuum, and then allowed to stand at room temperature for 24 h. The solid fragments were collected by filtration and dried. The solid was then soaked in tetrahydrofuran for one day to dissolve and remove the PS template. The solid was collected by centrifugation and dried at 110 °C overnight. The resulting white powder was SOM-ZIF-8.

[0064] (3) Preparation of MoS2 quantum dot dispersion: Weigh 0.3g of sodium molybdate dihydrate, add 40mL of deionized water, and stir magnetically until completely dissolved; weigh 0.15g of thioacetamide (TAA), slowly add it to the above solution, and stir for 15min until completely dissolved. Add 1MHCl dropwise, monitor with a pH meter, and adjust the pH of the solution to 3.0. Then add 0.2g of ascorbic acid and 0.1g of PVP, and continue stirring for 30min. Then, transfer the mixed solution to a 50mL high-pressure hydrothermal reactor, seal the hydrothermal reactor, and react at 250℃ for 20h. After the reaction is completed, let the reactor cool naturally to room temperature. Centrifuge the product at 12000rpm for 30min and discard the bottom precipitate. Take the supernatant and put it into a dialysis bag, dialyze with 1L of deionized water for 48h (change the water every 8h) to remove residual salts. Finally, the dialysis product was filtered through a 0.22 μm filter membrane to obtain a clear MoS2 quantum dot dispersion with a MoS2 quantum dot concentration of 0.8 mg / mL.

[0065] (4) Preparation of MoS2 / SOM-ZIF-8 complex: 100 mg SOM-ZIF-8 was added to 20 mL of MoS2 quantum dot dispersion, and sonicated for 30 min to promote the quantum dots to enter the MOF channels; then magnetically stirred to ensure full adsorption of quantum dots. After centrifugation at 6000 rpm for 10 min, the solid complex was collected, washed three times with ethanol, and dried under vacuum at 60 °C for 6 h to obtain the MoS2 / SOM-ZIF-8 complex.

[0066] (5) Construction of aerogel: 300 mg MoS2 / 3DSOM-ZIF-8 complex and 20 mg rGO were dispersed in 40 mL of deionized water by magnetic stirring and stirred at 300 rpm for 90 min to obtain a composite dispersion. The composite dispersion was centrifuged to collect the solid wet material. The obtained solid wet material was washed and purified with ethanol and deionized water in sequence to obtain a purified gel precursor. The purified gel precursor was freeze-dried in vacuum for 12 h to obtain MoS2@SOM-ZIF-8 / rGs, i.e. aerogel electrode material.

[0067] This embodiment also provides an aerogel electrode material prepared by the aforementioned method.

[0068] Example 5 This embodiment provides a method for preparing an aerogel electrode material, the specific steps of which are as follows: (1) Preparation of PS template: 14 mL of styrene, 0.3 g of polyvinylpyrrolidone (PVP), and 100 mL of deionized water were added to a round-bottom flask and bubbled with N2 for 20 min. The mixture was then stirred in an oil bath at 70 °C for 10 min to ensure thorough mixing. To initiate the polymerization of styrene, 10 mL of an aqueous solution containing 0.24 g of K2S2O8 was added to the flask over 20 min. The mixture was then refluxed and stirred at 800 rpm at 70 °C. After stirring for 24 h, the mixture was cooled to obtain monodisperse colloidal polystyrene (PS) spheres. Finally, the solids were collected by high-speed centrifugation to obtain a three-dimensionally ordered PS template.

[0069] (2) Preparation of SOM-ZIF-8: 0.03 mol zinc nitrate hexahydrate and 0.15 mol 2-methylimidazole were dissolved in 45 mL of methanol solution to obtain the precursor solution. The PS template was immersed in the precursor solution for 1 h at a mass-to-volume ratio of 0.08 g / mL and degassed under vacuum for 10 min. The solid obtained by filtration was soaked in a 1:1 mixture of methanol and ammonia (25 wt%), degassed under vacuum, and then allowed to stand at room temperature for 24 h. The solid fragments were collected by filtration and dried. The solid was then soaked in tetrahydrofuran for one day to dissolve and remove the PS template. The solid was collected by centrifugation and dried at 110 °C overnight. The resulting white powder was SOM-ZIF-8.

[0070] (3) Preparation of MoS2 quantum dot dispersion: Weigh 0.3g of sodium molybdate dihydrate, add 40mL of deionized water, and stir magnetically until completely dissolved; weigh 0.15g of thioacetamide (TAA), slowly add it to the above solution, and stir for 15min until completely dissolved. Add 1MHCl dropwise, monitor with a pH meter, and adjust the pH of the solution to 3.0. Then add 0.2g of ascorbic acid and 0.1g of PVP, and continue stirring for 30min. Then, transfer the mixed solution to a 50mL high-pressure hydrothermal reactor, seal the hydrothermal reactor, and react at 300℃ for 20h. After the reaction is completed, let the reactor cool naturally to room temperature. Centrifuge the product at 12000rpm for 30min and discard the bottom precipitate. Take the supernatant and put it into a dialysis bag, dialyze with 1L of deionized water for 48h (change the water every 8h) to remove residual salts. Finally, the dialysis product was filtered through a 0.22 μm filter membrane to obtain a clear MoS2 quantum dot dispersion with a MoS2 quantum dot concentration of 0.9 mg / mL.

[0071] (4) Preparation of MoS2 / SOM-ZIF-8 complex: 100 mg SOM-ZIF-8 was added to 20 mL of MoS2 quantum dot dispersion. The mixture was sonicated for 30 min to promote quantum dot entry into the MOF channels. Then, the mixture was magnetically stirred to ensure complete adsorption of the quantum dots. The solid complex was collected by centrifugation at 6000 rpm for 10 min. The solid complex was washed three times with ethanol and dried under vacuum at 60 °C for 6 h to obtain the MoS2 / SOM-ZIF-8 complex.

[0072] (5) Construction of aerogel: 300 mg MoS2 / 3DSOM-ZIF-8 complex and 20 mg rGO were dispersed in 40 mL of deionized water by magnetic stirring and stirred at 300 rpm for 90 min to obtain a composite dispersion. The composite dispersion was centrifuged to collect the solid wet material. The obtained solid wet material was washed and purified with ethanol and deionized water in sequence to obtain a purified gel precursor. The purified gel precursor was freeze-dried in vacuum for 12 h to obtain MoS2@SOM-ZIF-8 / rGs, i.e. aerogel electrode material.

[0073] This embodiment also provides an aerogel electrode material prepared by the aforementioned method.

[0074] Comparative Example 1 This comparative example adopts the technical solution of Example 3, the difference being that steps (3), (4), and (5) are omitted.

[0075] Comparative Example 2 This comparative example adopts the technical solution of Example 3. The difference is that in step (4), the dosage of SOM-ZIF-8 is increased from 50mg to 120mg.

[0076] Experimental Example 1 At room temperature, the electrochemical performance of the electrode materials in Examples 1-5 and Comparative Examples 1-2 was tested using a CHI760E electrochemical workstation (Shanghai Chenhua Instrument Factory, China) with 6.0M KOH solution as the electrolyte. Specifically, each aerogel electrode material was coated onto nickel foam metal, with the coating amount controlled at 1 mg / cm³. 2 After coating, the electrode is pressed into a current collector. In the traditional three-electrode system, the aforementioned coated nickel metal current collector is used as the working electrode, a platinum wire electrode as the auxiliary electrode, and a mercury oxide electrode as the reference electrode. Cyclic voltammetry (CV) tests are performed at different scan rates within a voltage range of 0V to 0.5V. Within the 0-0.5V voltage range, at 0.2Ag... -1 Up to 1.6Ag -1Constant current charge-discharge (GCD) tests were performed at different current densities. The specific capacitance (C) was calculated from the charge-discharge curves at different current densities using the following equation. s ):

[0077] In the formula, ΔU(V) is the voltage window, m(g) is the mass of the electrode material, I(A) is the current during the discharge process, and Δt(S) is the discharge time.

[0078] The performance characterization results of the electrode materials in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1: Table 1. Summary of Electrode Material Performance Characterization Results for Examples 1-5 and Comparative Examples 1-2

[0079] As shown in Table 1, the aerogel electrode material based on ordered large microporous ZIF-8 and reduced graphene oxide prepared in Example 3 exhibits a high specific capacitance. This is attributed to the synergistic design of the ordered microporous structure of 3DSOM-ZIF-8, the layered structure of molybdenum disulfide (MoS2) quantum dots, and reduced graphene oxide (rGO) to construct a three-dimensional porous aerogel electrode material with high specific capacitance, excellent flexibility, and stability, enabling the composite electrode material to maintain high efficiency during long-term cycling.

[0080] As can be seen from the performance of Comparative Example 1, SOM-ZIF-8 has extremely low intrinsic electronic conductivity, limited ion diffusion paths, and a single energy storage mechanism. Compared with Example 3, it reflects that the present invention can effectively achieve rapid ion diffusion and obtain a comprehensive leap in electrode performance by constructing an ordered microporous structure of 3DSOM-ZIF-8, a layered structure of molybdenum disulfide (MoS2) quantum dots, and a synergistic electrode material of reduced graphene oxide (rGO).

[0081] As can be seen from the performance of Comparative Example 2, increasing the amount of SOM-ZIF-8 white powder did not improve the performance of the final electrode material. Analysis shows that this is because increasing the amount of SOM-ZIF-8 white powder can prevent MoS2 quantum dots from entering the MOF channels effectively, thus failing to promote electrolyte penetration and ion diffusion and thus failing to improve the ion transport rate.

[0082] Compared with the nitrogen-phosphorus co-doped porous carbon P@ZIF-8 electrode material disclosed in Chinese patent CN112735838A, the aerogel electrode materials of Examples 1-5 of this invention exhibit significantly improved performance. Analysis reveals that while the core-shell structure and heteroatom doping achieve some performance enhancement, the high-temperature carbonization of ZIF-8 and polymer microspheres inevitably leads to inherent defects such as reduced electronic conductivity, severe pore structure collapse, insufficient cycle stability due to a lack of long-range conductive framework, relatively limited pseudocapacitive contribution, and high interfacial resistance. This invention, by using ordered large-microporous SOM-ZIF-8 single crystals prepared with a polystyrene template as a carrier, and constructing a three-dimensional porous aerogel through physical mixing and self-assembly with reduced graphene oxide and MoS2 quantum dots, systematically overcomes all the defects of the electrode material in the comparative patent, achieving a significantly superior synergistic effect.

[0083] The microstructure of the electrode materials of Comparative Example 1 and Example 3 was characterized using a scanning electron microscope (SEM, ZEISS Supra 55), and the results are as follows: Figure 1 and Figure 2 As shown. Figure 1 It can be seen that the SOM-ZIF-8 synthesized using polystyrene as a template in Comparative Example 1 has ordered large micropores (2-5 nm structure). Figure 2 It can be seen that after SOM-ZIF-8 is doped with quantum dots and then combined with rGO dispersion to form MoS2@SOM-ZIF-8 / rGs (i.e. aerogel electrode material), large pores of 100-500nm are formed between the graphene sheets, which is conducive to the transport and diffusion of ions.

[0084] Elemental analysis of the aerogel electrode material prepared in Example 3 was performed using a scanning electron microscope (SEM, ZEISS Supra 55). The results are as follows: Figure 3 and 4 As shown in the figure, the uniform distribution and proportion of C, N, Mo, Zn, and S elements in the sample indicate that ZIF-8, MoS2, and rGO are well combined and very uniformly dispersed, which allows the active sites to be better displayed during electrochemical testing, thereby improving electrochemical performance.

[0085] Figure 5 The figures show the electrical performance test results for the samples, where a is the cyclic voltammetry test result for the SOM-ZIF-8 sample of Comparative Example 1; and b is the cyclic voltammetry test result for the aerogel electrode material of Example 3. From... Figure 5As can be seen, the CV curves of both samples exhibit a hybrid energy storage mechanism combining characteristics of double-layer capacitance and pseudo-capacitance. The current response of the samples increases with increasing scan rate, and the redox peaks gradually broaden under the influence of hysteresis kinetics. Compared to Comparative Example 1, Example 3 shows a larger CV curve area, indicating a larger specific capacitance; at the same scan rate, the current response is significantly greater; the redox peaks are relatively sharp, with larger peak currents and relatively lower polarization; and it can still maintain certain redox characteristics at high scan rates, demonstrating superior rate performance.

[0086] Figure 6 The figures show the constant current charge-discharge test results for the samples, where a is the constant current charge-discharge test result for the SOM-ZIF-8 sample of Comparative Example 1; and b is the constant current charge-discharge test result for the aerogel electrode material of Example 3. Figure 6 As can be seen, at high current densities, the ion diffusion rate cannot adequately adapt to the rapid reaction of the active material; therefore, the specific capacitance of the material decreases with increasing current density. At 0.2 Ag... -1 Below, the specific capacitance of the SOM-ZIF-8 sample in Comparative Example 1 is 82.74 Fg. -1 The specific capacitance of the aerogel electrode material in Example 3 is 187.8 Fg. -1 This invention demonstrates that the aerogel electrode material and its preparation method, through the synergistic construction of an ordered macroporous ZIF-8 framework as a carrier, molybdenum disulfide quantum dot modification, and a graphene substrate, provide the electrode material with high conductivity, high specific surface area, and abundant redox active sites.

[0087] Figure 7 The figure shows the cyclic stability characterization of the aerogel electrode material in Example 3. It can be seen that after 6000 cycles of cyclic stability testing, its specific capacitance only decreased by 7% compared to the initial value.

[0088] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0089] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an aerogel electrode material, characterized in that, Includes the following steps: Step S01: Styrene, polyvinylpyrrolidone, and potassium persulfate solution are placed in deionized water. After stirring and reacting in an inert atmosphere, the solids are collected by centrifugation to obtain a polystyrene template. Step S02: Dissolve zinc nitrate hexahydrate and 2-methylimidazole in methanol to obtain a precursor solution; after impregnating the polystyrene template in the precursor solution, separate and collect the solids; after immersing the solids in a mixed solution of methanol and ammonia at room temperature and allowing them to stand, separate and collect the solids and dry them, then wash and dry them with tetrahydrofuran to obtain SOM-ZIF-8. Step S03: Place SOM-ZIF-8 in a MoS2 quantum dot dispersion, stir and react, then separate and collect the solids. After washing and drying, the solids are used to obtain the MoS2 / SOM-ZIF-8 complex. Step S04: Place the MoS2 / SOM-ZIF-8 composite in a reduced graphene oxide dispersion, stir and react, then centrifuge to collect the solid wet material. The solid wet material is washed and purified to obtain a purified gel precursor. The purified gel precursor is freeze-dried to obtain an aerogel electrode material.

2. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S01, the concentration of potassium persulfate solution is 16-24 mg / mL; The mass-to-volume ratio of styrene, polyvinylpyrrolidone, potassium persulfate in the potassium persulfate solution, and deionized water is 6-14 mL: 0.1-0.3 g: 0.16-0.24 g: 100 mL.

3. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S01, the temperature of the stirring reaction is 70-75℃, and the stirring reaction time is 22-24h.

4. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S02, the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole in the precursor solution is 1:1-5; the molar concentration of zinc nitrate hexahydrate in the precursor solution is 0.6-0.7 mol / L. The mass-to-volume ratio of polystyrene template to precursor solution is 0.01-0.08 g: 1 mL.

5. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S02, the polystyrene template is immersed in the precursor solution for 1-2 hours. The solid was immersed in a mixed solution of methanol and ammonia and left to stand at room temperature for 22-24 hours.

6. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S03, the concentration of the MoS2 quantum dot dispersion is 0.5-1 mg / mL; The mass-to-volume ratio of SOM-ZIF-8 to MoS2 quantum dot dispersion is 1-5 mg: 1 mL.

7. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S04, the concentration of the reduced graphene oxide dispersion is 0.5-0.6 mg / mL; The mass ratio of the MoS2 / SOM-ZIF-8 composite to the reduced graphene oxide dispersion is 100-300:

20.

8. The method for preparing the aerogel electrode material according to claim 1, characterized in that, In step S03, the preparation method of MoS2 quantum dot dispersion is as follows: thioacetamide and sodium molybdate dihydrate are dissolved in deionized water and the pH is adjusted to 3.0; then ascorbic acid and polyvinylpyrrolidone are added, stirred evenly, and after hydrothermal reaction, the precipitate is removed by centrifugation, and the supernatant is dialyzed to obtain MoS2 quantum dot dispersion.

9. The method for preparing the aerogel electrode material according to claim 8, characterized in that, In the preparation of the MoS2 quantum dot dispersion, the mass ratio of thioacetamide, sodium molybdate dihydrate, ascorbic acid, and polyvinylpyrrolidone is 0.1-0.3g:0.15-0.3g:0.1-0.2g:0.1g; The hydrothermal reaction temperature is 100-300℃, and the hydrothermal reaction time is 16-20h.

10. An aerogel electrode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

Images