Method for preparing supercapacitor electrode rGO-coated ZnWO4 based on assistance of nonionic surfactant

Abstract

The invention discloses a method for auxiliary preparation of a supercapacitor electrode rGO (at) ZnWO4 based on a nonionic surfactant. The preparation method comprises the following steps: S1, sequentially adding sodium tungstate dihydrate and zinc nitrate hexahydrate into a beaker, mixing to prepare a mixed solution I, adding a graphene oxide dispersion liquid into the mixed solution I, uniformly stirring, and carrying out a hydrothermal reaction; s2, centrifugally collecting a black precipitate from a product of the hydrothermal reaction, washing the black precipitate with deionized water and absolute ethyl alcohol for multiple times, and drying the black precipitate; s3, collecting the dried product, grinding into powder, weighing the powder, performing ultrasonic mixing on the powder and a nonionic surfactant PVP (Polyvinyl Pyrrolidone), and performing hydrothermal reaction on the mixed solution; and S4, after a hydrothermal reaction product is obtained, repeating the step S2, and finally obtaining the graphene / zinc tungstate rGO at ZnWO4 supercapacitor material under the regulation and control of PVP. The rGO-coated ZnWO4 is regulated and modified by using the nonionic surfactant, so that the rGO-coated ZnWO4 has excellent specific capacitance, cycling stability, high energy density and other performances.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor electrode materials, and specifically relates to a method for preparing a supercapacitor electrode rGO@ZnWO based on the assistance of a non-ionic surfactant. 4 Background Art

[0002] Supercapacitors are a new type of energy storage device because they can immediately provide a higher power density than batteries, while having a higher energy density than traditional dielectric capacitors. As an energy storage device with high power density, fast charge and discharge capabilities, and long cycle life, supercapacitors have received extensive attention in recent years. However, the specific capacitance and energy density of traditional supercapacitors still need to be further improved. Among them, ZnWO 4 As an inorganic compound, in terms of electrochemistry, it exhibits certain pseudocapacitance characteristics because zinc ions and tungsten ions can undergo redox reactions to store charges, providing a certain charge storage capacity for supercapacitors. However, from the current theoretical level, ZnWO 4 The specific capacity is only 600 mAh / g. In the actual operation scenario of low-rate charge and discharge, the actual specific capacity of this material drops to 420 mAh / g. In the application of electrochemical supercapacitors, as the active material zinc tungstate, after a certain number of cycles, the impedance at low frequencies will also increase significantly. After 1000 cycles, compared with the first cycle, the impedance at low frequencies increases significantly.

[0003] Patent document CN105047890A discloses a three-dimensional porous graphene composite material for the negative electrode of a lithium-ion battery. In this composite material, there is a synergistic effect between the graphene with a porous structure and the nano-ions, which can increase the lithium storage capacity while improving the cycle performance and rate capacity. However, the preparation process of this process is complex and requires high equipment requirements. Among them, for heat treatment reduction, the heating rate, holding time, pressure, atmosphere, etc. all have strict requirements. At the same time, its capacity attenuation problem is more obvious, with the first discharge capacity being 910 mAh / g and the capacity only about 200 mAh / g after 50 cycles. The reason may be the structural degradation and interfacial failure of the material system in the dynamic electrochemical environment.

[0004] Patent document CN111105934 discloses the preparation of ZnWO4 nanorods and their application in supercapacitors. In the patent, sodium dodecylbenzenesulfonate is used to prepare a rod-shaped zinc tungstate electrode, but the superiority of its rod-shaped nanomaterials in electron transport and storage is not fully utilized. Sodium dodecylbenzenesulfonate due to the strong oxidizing S 6+ and (SO 3 ) -1 with Zn 2+ / Zn​3+ Redox reactions may occur, leading to polarization. In reactions controlled by charge transfer, polarization increases the charge transfer resistance, causing the electrode's efficiency to significantly decline after multiple uses. The highest specific capacitance is 345.39 F / g.

[0005] Currently, no research on non-ionic surfactants for supercapacitor electrode materials rGO@ZnWO 4 has been found. Summary of the Invention

[0006] To overcome the above technical problems, the purpose of the present invention is to provide a method for preparing supercapacitor electrode rGO@ZnWO 4 using non-ionic surfactants as an aid. By using non-ionic surfactants to regulate and modify rGO@ZnWO 4 , it has excellent specific capacitance, cycle stability, high energy density, etc., while overcoming problems such as insufficient compounding, low specific capacitance, and poor performance stability caused by poor graphene dispersion in traditional graphene composites.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] A method for preparing supercapacitor electrode rGO@ZnWO 4 using non-ionic surfactants as an aid, comprising the following steps;

[0009] S1. Sodium tungstate dihydrate and zinc nitrate hexahydrate are successively added to a beaker and mixed to prepare mixed solution I. Then, graphene oxide dispersion is added to mixed solution I, and stirring is carried out at room temperature. After stirring evenly, hydrothermal reaction is carried out.

[0010] S2. The product of the hydrothermal reaction is centrifuged to collect the black precipitate, which is washed multiple times with deionized water and absolute ethanol and then dried.

[0011] S3. The dried product is collected, ground into powder, and a certain amount of the powder is weighed and ultrasonically mixed with non-ionic surfactant PVP (polyvinylpyrrolidone). The mixed solution is subjected to hydrothermal reaction.

[0012] S4. After obtaining the product of the hydrothermal reaction in step S3, step S2 is repeated to finally obtain the graphene / zinc tungstate rGO@ZnWO 4 supercapacitor material regulated by PVP (polyvinylpyrrolidone).

[0013] In the mixed solution I in S1, the molar ratio of sodium tungstate dihydrate to zinc nitrate hexahydrate is 1:1 - 1:1.5.

[0014] The graphene oxide aqueous dispersion described in S1 is prepared by dissolving 150-200 mg of graphene oxide in every 100 ml of deionized water.

[0015] The mass ratio of graphene oxide, sodium tungstate dihydrate, and zinc nitrate hexahydrate contained in the graphene oxide aqueous dispersion is 0.264-0.352:1.319:1.189-1.874.

[0016] In S1, the stirring time at room temperature is 30-45 min; the temperature in the reaction kettle is set at 140-160 °C, and the reaction time is 12-16 h.

[0017] In S3, the ultrasonic mixing time is 15-20 minutes, and the molar ratio of the powder to PVP is 1:0.75-2.

[0018] In S3, the ultrasonic mixing is carried out in the reaction kettle, the temperature in the reaction kettle is set at 60-80 °C, and the reaction time is 6-10 h.

[0019] Preparation of rGO@ZnWO supercapacitor electrodes assisted by non-ionic surfactants 4 It is a rod-like structure, showing long strip-shaped columns with uniform sizes. The rod-like contour can be clearly seen under local magnification, reflecting the one-dimensional directional growth characteristics through surface adsorption and crystal plane directional growth.

[0020] The polar groups in the pyrrolidone ring are adsorbed on the surface of zinc tungstate particles, inhibiting the excessive growth of crystals in specific directions, promoting the formation of a uniform nanostructure, and achieving the characteristics of dispersion stability and aggregation inhibition.

[0021] At the same time, the long-chain structure uses steric hindrance to prevent the van der Waals force between particles, avoiding lattice distortion caused by aggregation, and can coordinate with Zn 2+ or W 6+ to compensate for the lattice charge imbalance, reduce intrinsic defects such as oxygen vacancies, and thus achieve its structural stability.

[0022] Advantages of the present invention:

[0023] Graphene itself has poor dispersibility during compounding, and agglomeration is likely to occur, which will instead reduce the performance of the composite material; moreover, the oxygen-containing groups on the surface of graphene oxide are likely to remain after the hydrothermal reaction process, damaging the performance of the composite material; after using PVP (polyvinylpyrrolidone) as a non-ionic surfactant, as a dispersant, it can make the liquid fully wet each solid particle, replace the air in the particles, and further break the solid particles into smaller crystals to promote its composite reaction. As a reducing agent, it can fully reduce graphene oxide in the graphene system to rGO, repair the originally damaged conjugation of graphene, and improve its conductivity.

[0024] The present invention prepares a modified rGO@ZnWO using a non-ionic surfactant. After synthesizing the graphene / tungsten zincate system, PVP is added for another hydrothermal treatment. During this process, first, the graphene oxide in the system is fully oxidized through the second hydrothermal reaction. Secondly, as a particle size regulator, PVP can change the size and shape of the system structure by adjusting the content of PVP, improving the density of the composite structure, making the structure more stable, and reducing the stress caused by volume changes of the electrode material during repeated charge and discharge processes, resulting in the collapse of the rGO@ZnWO 4 structure, and thus the impedance remains stable. 4 The prepared rGO@ZnWO modified under the action of PVP

[0025] material has good conductivity and a high specific capacitance. It avoids the poor reduction of graphene oxide in the graphene system, which weakens conductivity; it circumvents the phenomenon of agglomeration in the graphene system; at the same time, the addition of PVP makes the entire conductive structure system more three-dimensional, with dense and uniform atomic arrangement, forming a dense conductive network, enabling the impedance of the tungsten acid graphene system to remain stable after multiple charge and discharges, allowing rGO and ZnWO 4 to fully exert their performance and constructing an rGO@ZnWO 4 supercapacitor electrode material with excellent performance. Its performance indicators are: a specific capacitance as high as 1190 F / g, an energy density of 49.9 Wh / kg, and a capacitance retention rate of 97.4% after 1000 cycles. 4 BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the GCD curve of different types of tungsten zincate electrode materials in the present invention.

[0027] Figure 2 This is the GCD curve of different types of non-ionic surfactant graphene / tungsten zincate electrode materials in the present invention.

[0028] Figure 3 This is the EIS curve of different types of non-ionic surfactant graphene / tungsten zincate electrode materials in the present invention.

[0029] Figure 4 This is the capacitance retention rate diagram of the PVP-rGO@ZnWO4 electrode material in the present invention after 1000 cycles.

[0030] Figure 5 This is the XRD diffraction pattern of the PVP-rGO@ZnWO4 electrode material in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] ​The present invention will be further described in detail below with reference to the accompanying drawings.

[0032] The preparation method of the present invention realizes the controllable synthesis of high-performance graphene / zinc tungstate composites through stepwise hydrothermal reaction and surfactant regulation. In step S1, sodium tungstate dihydrate and zinc nitrate hexahydrate are mixed at a molar ratio of 1:1 to 1.5, and a graphene oxide (GO) dispersion is added. Through hydrothermal reaction at 140 - 160 °C for 12 - 16 hours, the metal ions are anchored by the oxygen-containing functional groups of GO, and ZnWO 4 nanocrystals are in-situ generated and part of GO is reduced to conductive rGO, forming an rGO@ZnWO 4 composite substrate. In step S2, impurities are removed by centrifugal washing, and a porous structure is retained after drying. In step S3, the product and PVP are ultrasonically mixed at a molar ratio of 1:0.75 to 2, and secondary hydrothermal reaction is carried out at 60 - 80 °C for 6 - 10 hours. By using the dispersion and morphology regulation effect of PVP, the aggregation of nanoparticles is inhibited and the interfacial binding between rGO and ZnWO 4 is enhanced. In step S4, washing and drying are repeated, and finally a supercapacitor material with high conductivity (continuous rGO network) and high pseudocapacitance activity synergy is obtained. The crystal growth, conductive network construction, and interfacial stability are balanced, enabling the material to have a high specific capacitance. At the same time, the long cycle life is improved by using the buffer volume effect of PVP.

[0033] Example 1

[0034] The present embodiment provides a preparation method of a supercapacitor material of rGO@ZnWO4 based on a non-ionic surfactant, including the following steps:

[0035] S1. 1.319 g of sodium tungstate dihydrate and 1.189 g of zinc nitrate hexahydrate are successively added to a beaker containing 160 mL of deionized water, and magnetically stirred for 30 minutes to prepare a mixed solution I. Then, 88 mL of graphene oxide dispersion is added to the mixed solution I, and stirred at room temperature for 30 minutes. After stirring evenly, hydrothermal reaction is carried out.

[0036] The time of the hydrothermal reaction is 12 hours, and the temperature is 140 °C.

[0037] S2. The product of the hydrothermal reaction is centrifuged to collect the black precipitate, washed multiple times with deionized water and absolute ethanol, and dried for 8 hours at a temperature of 60 °C.

[0038] S3. The dried product is collected and ground into powder, and 0.649 g of the S2 product powder and 0.111 g of PVP (polyvinylpyrrolidone) are respectively added to 40 mL of deionized water and ultrasonically mixed for 15 minutes, and the mixed solution is subjected to hydrothermal reaction.

[0039] The hydrothermal reaction time is 6 hours and the temperature is 60 °C.

[0040] S4. Repeat step S2 to finally obtain a supercapacitor material of graphene / zinc tungstate regulated by PVP (polyvinylpyrrolidone).

[0041] The supercapacitor material of graphene / zinc tungstate obtained in this example has a maximum specific capacitance of 624.54 F / g and an AC impedance charge transfer resistance of 0.422 Ω.

[0042] Example 2

[0043] This example provides a preparation method for a supercapacitor material of rGO@ZnWO 4 including the following steps:

[0044] S1. Add 1.319 g of sodium tungstate dihydrate and 1.189 g of zinc nitrate hexahydrate to a beaker containing 160 mL of deionized water in sequence, stir magnetically for 30 minutes to prepare a mixed solution I, then add 88 mL of graphene oxide dispersion to the mixed solution I, stir at room temperature for 30 minutes, and perform hydrothermal reaction after stirring evenly.

[0045] The time of the hydrothermal reaction is 12 hours and the temperature is 140 °C.

[0046] S2. Centrifuge the product of the hydrothermal reaction to collect the black precipitate, wash it with deionized water and absolute ethanol for multiple times, and dry it. The drying time is 8 hours and the temperature is 60 °C.

[0047] S3. Collect and grind the dried product into powder, weigh 0.649 g of the S2 product powder and 0.364 g of CTAB (cetyltrimethylammonium bromide) and add them to 40 mL of deionized water respectively, ultrasonically mix for 15 minutes, and perform hydrothermal reaction on the mixed solution.

[0048] The hydrothermal reaction time is 10 hours and the temperature is 80 °C.

[0049] S4. Repeat step S2 to finally obtain a supercapacitor electrode material of graphene / zinc tungstate regulated by CTAB (cetyltrimethylammonium bromide).

[0050] The supercapacitor material of graphene / zinc tungstate obtained in this example has a maximum specific capacitance of 292.72 F / g and an AC impedance charge transfer resistance of 16.70 Ω.

[0051] Example 3

[0052] This example provides a preparation method for a supercapacitor material of rGO@ZnWO4 based on a non-ionic surfactant, including the following steps:

[0053] S1. Add 1.319 g of sodium tungstate dihydrate and 1.189 g of zinc nitrate hexahydrate successively into a beaker containing 160 mL of deionized water, stir magnetically for 30 minutes to prepare mixed solution I. Then add 88 mL of graphene oxide dispersion to mixed solution I, stir at room temperature for 30 minutes, and carry out hydrothermal reaction after stirring evenly.

[0054] The time of the hydrothermal reaction is 12 hours and the temperature is 140 °C.

[0055] S2. Centrifuge the product of the hydrothermal reaction to collect the black precipitate, wash it with deionized water and absolute ethanol for several times, and dry it for 8 hours at a temperature of 60 °C.

[0056] S3. Collect the dried product and grind it into powder. Weigh 0.649 g of the product powder of S2 and 0.348 g of SDBS (sodium dodecylbenzenesulfonate) and add them into 40 mL of deionized water respectively, and ultrasonically mix for 15 minutes. Then carry out hydrothermal reaction on the mixed solution.

[0057] The time of the hydrothermal reaction is 10 hours and the temperature is 80 °C.

[0058] S4. Repeat step S2 to finally obtain the supercapacitor material of graphene / zinc tungstate regulated by SDBS (sodium dodecylbenzenesulfonate).

[0059] The supercapacitor material of graphene / zinc tungstate obtained through this example has a maximum specific capacitance of 200 F / g and an AC impedance charge transfer resistance of 5.24 Ω.

[0060] Example 4

[0061] This example provides a preparation method of a supercapacitor electrode material based on a non-ionic surfactant rGO@ZnWO 4 including the following steps:

[0062] S1. Add 1.319 g of sodium tungstate dihydrate and 1.189 g of zinc nitrate hexahydrate successively into a beaker containing 160 mL of deionized water, stir magnetically for 30 minutes to prepare mixed solution I. Then add 176 mL of graphene oxide dispersion to mixed solution I, stir at room temperature for 30 minutes, and carry out hydrothermal reaction after stirring evenly.

[0063] The time of the hydrothermal reaction is 12 hours and the temperature is 160 °C.

[0064] S2. Centrifuge the product of the hydrothermal reaction to collect the black precipitate, wash it with deionized water and absolute ethanol for several times, and dry it for 8 hours at a temperature of 60 °C.

[0065] S3. Collect and grind the dried product into powder, and weigh 0.671 g of the S2 product powder and 0.222 g of PVP (polyvinylpyrrolidone) and add them to 40 mL of deionized water respectively, then ultrasonically mix for 15 minutes, and perform hydrothermal reaction on the mixed solution.

[0066] The hydrothermal reaction time is 10 hours and the temperature is 80 °C.

[0067] S4. Repeat step S2 to finally obtain a supercapacitor electrode material of graphene / zinc tungstate regulated by PVP (polyvinylpyrrolidone).

[0068] For the supercapacitor material of graphene / zinc tungstate obtained in this example, the highest specific capacitance is 1190 F / g, and the charge transfer resistance of the AC impedance is 0.403 Ω.

[0069] Example 5

[0070] This example provides a preparation method of an rGO@ZnWO supercapacitor electrode material based on a non-ionic surfactant, including the following steps: 4 The preparation method of the supercapacitor electrode material of rGO@ZnWO based on a non-ionic surfactant includes the following steps:

[0071] S1. Add 1.319 g of sodium tungstate dihydrate and 1.189 g of zinc nitrate hexahydrate to a beaker containing 160 mL of deionized water in sequence, stir magnetically for 30 minutes to prepare mixed solution I, then add 176 mL of graphene oxide dispersion to the mixed solution I, stir at room temperature for 30 minutes, and perform hydrothermal reaction after stirring evenly.

[0072] The time of the hydrothermal reaction is 12 hours and the temperature is 160 °C.

[0073] S2. Centrifuge the product of the hydrothermal reaction to collect the black precipitate, wash it with deionized water and absolute ethanol for many times, and perform drying. The drying time is 8 hours and the temperature is 60 °C.

[0074] S3. Collect and grind the dried product into powder, and weigh 0.671 g of the S2 product powder and 0.333 g of PVP (polyvinylpyrrolidone) and add them to 40 mL of deionized water respectively, then ultrasonically mix for 15 minutes, and perform hydrothermal reaction on the mixed solution.

[0075] The hydrothermal reaction time is 10 hours and the temperature is 80 °C.

[0076] S4. Repeat step S2 to finally obtain a supercapacitor material of graphene / zinc tungstate regulated by PVP (polyvinylpyrrolidone).

[0077] The supercapacitor material of graphene / zinc tungstate obtained through this embodiment has a maximum specific capacitance of 405.81 F / g and an AC impedance charge transfer resistance of 0.388 Ω.

[0078] The above results show that the comprehensive performance of the supercapacitor material based on non-ionic surfactant rGO@ZnWO prepared by the steps and methods of Example 4 is optimal. 4

[0079] The prepared rGO@ZnWO modified under the action of PVP 4 material has good conductivity and high specific capacitance. It avoids the phenomenon that graphene oxide in the graphene system is difficult to be fully reduced, which weakens the conductivity; it avoids the agglomeration phenomenon in the graphene system; at the same time, it also makes the impedance of the tungstenic acid system remain stable after multiple charge and discharge cycles, enabling rGO and ZnWO 4 These two substances can give full play to their performance and construct a supercapacitor electrode material with excellent performance. Its performance indicators are: maximum specific capacity of 1190 F / g, energy density of 49.9 Wh / kg, and capacitance retention rate of 97.4% after 1000 cycles.

Claims

1. A method for preparing supercapacitor electrode rGO@ZnWO4 based on non-ionic surfactant, characterized in that: The steps include: S1. Sodium tungstate dihydrate and zinc nitrate hexahydrate are sequentially added to a beaker and mixed to prepare a mixed solution I, and then the graphene oxide dispersion is added to the mixed solution I, and stirred at room temperature, and a hydrothermal reaction is performed after the stirring is uniform; S2. The product of the hydrothermal reaction was centrifuged to collect the black precipitate, which was washed several times with deionized water and anhydrous ethanol, and then dried; S3. The dried product was collected and ground into powder, and the powder was weighed and ultrasonically mixed with a nonionic surfactant PVP, and the mixed solution was subjected to a hydrothermal reaction; S4. After obtaining the hydrothermal reaction product of step S3, repeat step S2 to finally obtain the supercapacitor material of graphene / zinc tungstate rGO@ZnWO4 regulated by PVP.

2. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant assistance according to claim 1, characterized in that: The molar ratio of sodium tungstate dihydrate to zinc nitrate hexahydrate in the mixed solution I described in S1 is 1:1-1:1.

5.

3. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant as claimed in claim 1, characterized in that: The graphene oxide aqueous dispersion described in S1 is prepared by dissolving 150 to 200 mg of graphene oxide in every 100 ml of deionized water.

4. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant as claimed in claim 1, characterized in that: The mass ratio of graphene oxide to sodium tungstate dihydrate and zinc nitrate hexahydrate contained in the graphene oxide aqueous dispersion is 0.264-0.352:1.319:1.189-1.

874.

5. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant as claimed in claim 1, characterized in that: The stirring time at room temperature in S1 is 30 to 45 minutes; the temperature setting degree in the reactor is 140 to 160° C., and the reaction time is 12 to 16 hours.

6. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant assistance according to claim 1, characterized in that: The S3 ultrasonic mixing time is 15 to 20 minutes, and the molar ratio of the powder to PVP is 1:0.75-2.

7. The method for preparing supercapacitor electrode rGO@ZnWO4 based on nonionic surfactant as claimed in claim 1, characterized in that: The ultrasonic mixing in S3 is carried out in a reactor, the temperature in the reactor is set at 60-80° C., and the reaction time is 6-10 hours.

8. Preparation of supercapacitor electrode rGO@ZnWO4 based on non-ionic surfactant, characterized in that: It is a rod-like structure, in the shape of long columns with uniform size, and has the characteristics of one-dimensional directional growth through surface adsorption and crystal plane directional growth; The polar groups in the pyrrolidone ring are adsorbed on the surface of zinc tungstate particles to inhibit the excessive growth of crystals in a specific direction, promote the formation of uniform nanostructures, and achieve dispersion stability and anti-agglomeration characteristics; At the same time, the long chain structure uses steric hindrance to prevent the van der Waals force between particles and avoid lattice distortion caused by agglomeration. 2+ or W 6+ Coordination, compensation for lattice charge imbalance, and reduction of intrinsic defects such as oxygen vacancies, thereby achieving structural stability.

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