CN106098405B - A kind of three-dimensional rice shape TiO2/ graphene composite aquogel and preparation method thereof - Google Patents

Abstract

The invention discloses a three-dimensional rice-like TiO ₂ /graphene composite hydrogel and its preparation method, which adopts a simple and environmentally friendly one-step hydrothermal method, uses GO and TBT as raw materials, sodium citrate as a structure-directing agent, water and Ethanol is used as solvent for synthesis. The prepared hydrogel has a novel structure, and its macroscopic appearance is a black column with a diameter of about 1-2cm and a height of about 1-2cm; the microscopic appearance is rice-like TiO ₂ nanoparticles loaded on the graphene sheet, wherein TiO ₂ The diameter of nanoparticles is about 15-35nm, and the length is about 30-70nm; TiO ₂ nanoparticles and graphene sheets are interwoven into a network structure. The morphology and properties of the TiO ₂ /graphene composite hydrogel are controllable, that is, the formability and stability of the gel can be controlled by adjusting the amount of TBT added and the hydrothermal time. Meanwhile, the composite hydrogel not only possesses the respective intrinsic properties of _TiO2 nanoparticles and graphene, but is also able to generate novel synergistic effects.

Description

A three-dimensional rice-like TiO2/graphene composite hydrogel and its preparation method

technical field

The invention belongs to the technical field of material synthesis, and in particular relates to a three-dimensional rice-like TiO ₂ /graphene composite hydrogel and a preparation method thereof.

Background technique

Carbon materials have the advantages of good electrical conductivity, large specific surface area, high chemical stability, and the carbon network can provide an effective path for electron transfer, etc., which is an excellent electrochemical material. As a new member of the carbon family, graphene has attracted great attention in the field of materials science since its discovery in 2004. However, graphite electrodes have disadvantages such as easy disconnection of the circuit, easy deformation of the structure, and loss of initial capacity. To overcome these disadvantages, compounding inorganic nanoparticles with graphene may be an effective solution. TiO ₂ , as an important transition metal oxide, has shown great application potential in the fields of photocatalysis and energy storage due to its high activity, stability, non-toxicity, low price, and high theoretical specific capacity. For example, Qiu et al. synthesized TiO ₂ /graphene composites by one-step hydrothermal method (Jingxia Qiu, Chao Lai, Yazhou Wang. Chem. Eng. J., 2014, 256, 247-254), and applied it to lithium battery The results confirmed that the composite material has high specific capacitance, rate performance and cycle stability. The Chinese patent of authorized announcement number CN 102728337 B (application number 201210188887.2) discloses a preparation method of a _TiO2 /graphene composite material, specifically using sodium borohydride as a reducing agent and ammonium fluorotitanate as a titanium source. Prepared by liquid deposition. However, this method has the following disadvantages: the shape of the obtained TiO ₂ is nano-particles without special shape; sodium borohydride is a toxic reducing agent, which is not environmentally friendly; the preparation process is relatively complicated. The Chinese patent with the authorized announcement number CN 103545491 A (application number 201310441415.8) also discloses a preparation method of a TiO ₂ /graphene composite material, and uses it as a lithium battery negative electrode material. The results show that the composite material has good electrical conductivity, large electrochemical lithium storage capacity and good cycle stability. However, the post-processing process of this composite material is more complicated.

In the TiO ₂ /graphene composite materials reported above, due to the strong π-π interaction and van der Waals force between the two-dimensional graphene sheets, it is easy to cause irreversible aggregation and stacking, which greatly reduces the ratio of graphene. surface area, thereby limiting the interaction with _TiO2 nanoparticles.

Based on the above problems, some scientific workers began to study the three-dimensional structure of TiO ₂ /graphene composite materials, because the three-dimensional nanomaterials are porous network structures, large specific surface area, high mechanical strength, good chemical stability, and can be widely used In photocatalysis, electrochemistry and other fields. For example, Zhang et al. synthesized a three-dimensional TiO ₂ /graphene composite hydrogel by hydrothermal method (Zheye Zhang, Fei Xiao, Yunlong Guo.ACS Appl.Mater.Interfaces,2013,5(6):2227-2233), And it was used in the study of supercapacitors, and its electrochemical performance was significantly improved compared with pure graphene hydrogel. However, the _TiO2 nanoparticles used are P25 and have no special morphology, which limits further research on the properties of composite materials. The Chinese patent document with application publication number CN 102350335 A (application number 201110228170.1) discloses a method for preparing TiO ₂ /graphene composite hydrogel at room temperature. First, TiO ₂ is added to the graphene oxide aqueous solution containing the reducing agent at room temperature, and ultrasonically dispersed to obtain a precursor solution; then the obtained solution is left to stand at room temperature for 8-16 hours to obtain the product. The disadvantages of this invention: the reducing agent hydrazine hydrate used in the experimental process is toxic and not environmentally friendly; the shape and performance are uncontrollable; _TiO2 nanoparticles in the composite material are easy to agglomerate; it is not easy to recycle and reuse when photocatalytically degrading pollutants .

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the above methods, and provide a method for preparing a three-dimensional rice-like TiO ₂ /graphene composite hydrogel. The microscopic morphology of the as-prepared composite hydrogel is rice-like _TiO2 nanoparticles dispersed on graphene sheets. In the hydrothermal process, not only the morphology of _TiO2 can be effectively controlled, but also graphene oxide (GO) is reduced to graphene by high-temperature hydrothermal, which is green and environmentally friendly. The finally obtained gel network structure is novel; it has large specific surface area; excellent performance; the preparation method is simple and environment-friendly.

To achieve the above object, the present invention adopts the following technical solutions:

The invention provides a method for preparing a three-dimensional rice-like TiO ₂ /graphene composite hydrogel, comprising the following steps:

Using tetrabutyl titanate (TBT) as the titanium source, prepare TBT alcohol solution, then add the prepared TBT alcohol solution to the GO aqueous solution, mix well and add sodium citrate to control the directional growth of _TiO2 ; finally through hydrothermal Three-dimensional rice-like TiO ₂ /graphene composite hydrogels were obtained by self-assembly.

Although the above steps do not specifically limit specific conditional parameters, the inventive concept provided by the present invention is: adopt a simple and environmentally friendly one-step hydrothermal method, use GO and TBT as raw materials, sodium citrate as a structure-directing agent, and water and ethanol as solvents The synthesis is carried out, and the TiO _{2 /graphene composite hydrogel with a specific shape is obtained through the inventive concept, which provides a new synthesis idea for the preparation of TiO 2 /} graphene composite hydrogels with other shapes.

The preparation of GO in the present invention can adopt a variety of methods in the prior art, and here a modified Hummers method is selected for preparation. More importantly, the graphene in the present invention is obtained by thermal reduction without adding reducing agent, which is environmentally friendly. Its preparation method comprises the following steps:

①Put 1-3g graphite powder, 10-30mL concentrated sulfuric acid, 1-3g K ₂ S ₂ O ₈ , 1-3g P ₂ O ₅ into the beaker in turn, ultrasonicate for 5-10min, place in a water bath, heat to 75 ~85°C (preferably 80°C), stir for 4-8h, and cool to room temperature;

②Dilute the product of step ① with 500-1000mL distilled water and leave it overnight;

③ Suction filtration is performed on the diluted solution obtained in step ② to form a filter cake, and dry naturally overnight;

④Scrape the filter cake obtained in step ③ into a container, add 100-150mL of concentrated sulfuric acid, and sonicate for 0.5-1h;

⑤Under an ice bath, slowly add 5-15g of potassium permanganate to the ultrasonicated solution, control the temperature below 20°C, stir for 4-6h, then slowly raise the temperature to 35-50°C, stir and keep warm for 8-10h;

⑥Then slowly add 100-300mL deionized water to the solution, stir at room temperature for 1.5-2.5h (preferably 2h); continue to add 500-700mL deionized water, stir for 1.5-2.5h (preferably 2h);

⑦ Then add 10-30mL hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5-1h and then stand at room temperature;

⑧ Pour off the supernatant of the solution obtained in ⑦, wash with HCl aqueous solution (the concentration is preferably 1mol L ^-1 ) to remove residual metal ions, and finally undergo repeated water washing, centrifugation and ultrasonication to obtain a nearly neutral GO aqueous solution, which is frozen Dried to obtain flake GO, which was ground into powder for later use.

The TBT alcohol solution in the present invention is a mixed solution of TBT and ethanol, and the specific operation method is: add TBT dropwise to absolute ethanol, and form mixed solution A after stirring. Note: The reaction temperature of the alcoholysis process is 30-40°C. The volume ratio of TBT to ethanol is: (0.16-0.76):(3-10).

In the present invention, the GO aqueous solution is mixed with ammonia water to form a mixed solution B. The specific operation is: prepare GO aqueous solution by ultrasonic stripping, then add ammonia water, stir well, and obtain mixed solution B. Among them, the concentration of GO aqueous solution is 1.5-3mg/mL, and the ultrasonic time is 0.5-2h.

Wherein, the volume of the TBT and ammonia water is (0.16-0.76):(0.5-1).

In the present invention, the mixed solution A is added to the mixed solution B, mixed uniformly, then sodium citrate is added, and stirred to form a mixed solution C, wherein the volume ratio of the mixed solution A to the mixed solution B is ( 3-10): (15-30). The stirring temperature is 30-40°C, and the stirring time is 2-4h (preferably 3h).

The preferred operation step is: adding the mixed solution A to the prepared mixed solution B dropwise under the condition of constant stirring. The purpose of this operation step is to enable GO to be more uniformly recombined with the titanium source.

The addition ratio of TBT and sodium citrate is (0.16-0.76)mL:(0.05-0.15)g.

In the present invention, the specific operation steps of hydrothermal self-assembly are as follows: transfer the mixed solution C to a polytetrafluoroethylene-lined autoclave, tighten the autoclave and put it into an oven for hydrothermal treatment. The kettle was naturally cooled to room temperature, and a three-dimensional rice-like TiO ₂ /graphene composite hydrogel was obtained. Among them, the hydrothermal temperature is 160-180°C, and the hydrothermal time is 6-24h, and the preferred condition is: 180°C for 12h.

The present invention uses the improved Hummers method to prepare GO, uses TBT as titanium source, sodium citrate as structure directing agent, and prepares three-dimensional TiO ₂ /graphene composite hydrogel by hydrothermal method. The characteristics of the composite hydrogel are: the macroscopic appearance is a black column with a diameter of 1-2cm and a height of 1-2cm _; Intertwined into a network structure, in which the diameter of TiO ₂ nanoparticles is 15-35nm, and the length is 30-70nm.

The beneficial effects of the present invention are:

(1) The present invention utilizes sodium citrate as a structure-directing agent, and the morphology of the synthesized three-dimensional _TiO2 /graphene composite hydrogel is that rice-like _TiO2 nanoparticles are loaded on graphene sheets, wherein the diameter of the _TiO2 nanoparticles is About 15-35nm, about 30-70nm long.

(2) In the three-dimensional TiO ₂ /graphene composite hydrogel prepared by the present invention, GO is reduced under high-temperature hydrothermal conditions without adding toxic reducing agents, which is green and environmentally friendly; the rice-like TiO ₂ particles have good dispersion and no The obvious agglomeration, which is beneficial to reduce the interfacial resistance during the charge transfer process, is ready for further applications.

(3) In the three-dimensional TiO ₂ /graphene composite hydrogel prepared by the present invention, the ratio of TiO ₂ to graphene can be controlled, and then the physical and chemical properties of the composite hydrogel can be optimized.

(4) The three-dimensional TiO ₂ /graphene composite hydrogel prepared by the present invention has a larger specific surface area, and the three-dimensional network structure constructed can shorten the diffusion and migration paths of electrolyte ions during charge and discharge, which is beneficial to electron transport, And then improve the application in the field of electrochemistry.

(5) The three-dimensional TiO ₂ /graphene composite hydrogel prepared by the present invention not only has the inherent properties of TiO ₂ and graphene, but also can produce novel synergistic effects. Compared with pure graphene hydrogel, the composite water The specific capacitance of the gel can reach 332.6F/g at a current density of 0.2A/g.

(6) The synthesis conditions of the present invention are mild, the raw materials are cheap and easy to obtain, and the process operation is simple and easy to implement, which provides a new synthesis idea for the preparation of TiO ₂ /graphene composite hydrogels with other morphologies.

The invention combines the sol-gel method and the hydrothermal method, mixes the TBT alcohol solution and the graphene aqueous solution, and successfully prepares the three-dimensional anatase TiO ₂ /graphene composite hydrogel. Rice-like _TiO2 nanoparticles are supported on graphene sheets without obvious aggregation. The morphology and properties of the TiO ₂ /graphene composite hydrogel are controllable, that is, the formability and stability of the gel can be controlled by adjusting the addition ratio of TBT to GO and the hydrothermal time. The morphology and physical and chemical properties of the composite gel showed certain regularity.

Description of drawings

Fig. 1 is the digital photo of the three-dimensional rice-like TiO ₂ /graphene composite hydrogel of Example 3 of the present invention;

Fig. 2 is the transmission electron microscope picture (TEM) of GO and _TiO2 /graphene composite hydrogel, wherein, a is the TEM of GO, b is the TEM of the _TiO2 /graphene composite hydrogel prepared in embodiment 3, c is the HRTEM of rice-like _TiO2 particles in the composite gel, d is the electron diffraction pattern of rice-like _TiO2 particles;

Fig. 3 is the field emission scanning electron microscope image (FESEM) of the aerogel formed by freeze-drying the TiO ₂ /graphene composite hydrogel prepared in Example 3 of the present invention;

Figure 4 is the X-ray diffraction pattern (XRD) of GO, pure graphene hydrogel and TiO ₂ /graphene composite hydrogel, where a is the XRD pattern of GO, and b is pure graphene hydrogel The XRD pattern of c is the XRD pattern of the TiO ₂ /graphene hydrogel prepared in Example 3;

Fig. 5 is the cyclic voltammetry curve (CV) of pure graphene hydrogel and TiO ₂ /graphene composite hydrogel, wherein, a is the CV figure of pure graphene hydrogel, and b is embodiment 3 CV diagram of the prepared TiO ₂ /graphene composite hydrogel;

Fig. 6 is the galvanostatic charge-discharge diagram (GCD) of pure graphene hydrogel and TiO ₂ /graphene composite hydrogel, wherein, a is the GCD diagram of pure graphene hydrogel, and b is embodiment 3 GCD diagram of the as-prepared _TiO2 /graphene hydrogel.

detailed description

The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

Example 1

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.16mL TBT into 5mL absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5mL ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 2

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.23mL TBT into 5mL absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5mL ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 3

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.30 mL of TBT into 5 mL of absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5 mL of ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

As shown in Figures 1, 2, 3 and 4, the macroscopic appearance of the graphene hydrogel prepared in the present embodiment 3 is a black column, with a diameter of about 1-2cm and a height of about 1-2cm; The rice-like TiO ₂ nanoparticles are evenly dispersed on the graphene sheet, wherein the TiO ₂ nanoparticles are anatase, with a diameter of about 15-35nm and a length of about 30-70nm; after the hydrogel is cold-dried into an aerogel It presents a three-dimensional porous network structure. It can be seen from Figures 5 and 6 that compared with the pure graphene hydrogel, the composite hydrogel synthesized in Example 3 exhibits superior electrochemical performance.

Example 4

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.56mL TBT into 5mL absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5mL ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 5

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.76mL TBT into 5mL absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5mL ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 6

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.30 mL of TBT into 5 mL of absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5 mL of ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 6 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 7

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.30 mL of TBT into 5 mL of absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5 mL of ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 18 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 8

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 40°C, slowly drop 0.30 mL of TBT into 5 mL of absolute ethanol, and stir to form a mixed solution A; prepare a 2 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.5 mL of ammonia water, and stir well to obtain a mixed solution B ; The mixed solution A is slowly added to the mixed solution B, then 0.08g of sodium citrate is added, and the stirring is continued for 3h to form a mixed solution C; the mixed solution C is transferred to a polytetrafluoroethylene-lined autoclave, and the Tighten the autoclave and place it in an oven, keep it warm at 180°C for 24 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / graphene composite hydrogel.

Example 9

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 30°C, slowly drop 0.30 mL of TBT into 3 mL of absolute ethanol, and stir to form a mixed solution A; prepare a 1.5 mg/mL GO aqueous solution by ultrasonication and stirring, then add 0.8 mL of ammonia water, and stir well to obtain a mixed solution B; slowly add the mixed solution A to the mixed solution B, then add 0.05g of sodium citrate, and continue to stir for 2h to form a mixed solution C; transfer the mixed solution C to a polytetrafluoroethylene-lined autoclave, and press the high pressure Tighten the reactor and place it in an oven, keep it warm at 170°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain three-dimensional TiO ₂ / Graphene composite hydrogels.

Example 10

(1) Preparation of GO aqueous solution

Add 3g of graphite powder, 30mL of concentrated sulfuric acid, 3g of K ₂ S ₂ O ₈ , and 3g of P ₂ O ₅ into the beaker in sequence, ultrasonicate for 5min, place in a water bath, heat to 80°C and stir for 6h, cool to room temperature; use 1000mL of distilled water Dilute and leave overnight; suction filter the obtained dilution to form a filter cake, and dry it overnight; scrape the filter cake into a small beaker with a medicine spoon, add 150 mL of concentrated sulfuric acid, stir, and sonicate for 1 hour; Slowly add 15g of potassium permanganate to the final solution, control the temperature to less than 20°C, stir for 4h, then slowly raise the temperature to 40°C, stir and keep warm for 8h; then slowly add 300mL deionized water to the solution, stir at room temperature for 2h; continue Add 700 mL of deionized water and stir for 2 h; then add 20 mL of hydrogen peroxide to obtain a bright yellow acidic GO aqueous solution, stir for 0.5 h and then let it stand; pour off the supernatant of the obtained solution, wash with 1 mol L ^-1 aqueous HCl solution to remove residual Finally, after repeated washing, centrifugation and ultrasonication, a nearly neutral GO aqueous solution was obtained; GO flakes were finally obtained by freeze-drying, which was ground into powder for later use.

(2) Synthesis of three-dimensional rice-like TiO ₂ /graphene composite hydrogel

At 35°C, slowly drop 0.30mL TBT into 10mL absolute ethanol, and stir to form a mixed solution A; prepare a 3mg/mL GO aqueous solution by ultrasonication and stirring, then add 1mL ammonia water, and stir well to obtain a mixed solution B; Slowly add the mixed solution A to the mixed solution B, then add 0.15g of sodium citrate, and continue stirring for 4h to form a mixed solution C; transfer the mixed solution C to a polytetrafluoroethylene-lined autoclave, and the autoclave Tighten it and place it in an oven, keep it warm at 160°C for 12 hours, cool the autoclave to room temperature naturally after the hydrothermal reaction, and obtain a black columnar object; wash the obtained columnar object several times to remove residual impurities, and obtain a three-dimensional TiO ₂ / Graphene composite hydrogels.

The hydrogels prepared in Examples 1-2 and 4-10 have no significant difference in their macroscopic and microscopic appearances from those in Example 3, all of which are rice-like _TiO2 particles loaded on graphene sheets. Among them, the rice-like _TiO2 particles have a diameter of about 15-35nm and a length of about 30-70nm.

Example 11

A supercapacitor, the electrode material of which is the three-dimensional TiO ₂ /graphene composite hydrogel in Example 3, has been verified by experiments, and the supercapacitor has good application in the field of electrochemistry.

The invention uses GO and TBT as raw materials, sodium citrate as a structure-directing agent, and adopts a simple and environmentally friendly hydrothermal method to synthesize a three-dimensional rice-like TiO ₂ /graphene composite hydrogel in one step. The formability and stability of the gel were regulated by changing the amount of TBT added and the hydrothermal time. At the same time, taking advantage of the advantages of the three-dimensional network structure, the prepared composite hydrogel was applied to the research of supercapacitors. The results showed that the TiO ₂ /graphene composite hydrogel has high specific capacitance, excellent rate performance and good cycle stability.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (7)

1. A kind of 1. three-dimensional rice shape TiO₂The preparation method of/graphene composite aquogel, it is characterized in that, comprise the following steps：

   With butyl titanate（TBT）For titanium source, TBT alcoholic solutions are prepared；The TBT alcoholic solutions are the mixed solution of TBT and ethanol, Concrete operation method is：TBT is added drop-wise in absolute ethyl alcohol, mixed solution A is formed after stirring；

   Then obtained TBT alcoholic solutions are added in the GO aqueous solution, sodium citrate is added to control TiO after well mixed₂Orientation Growth；Graphene oxide water solution adds ammoniacal liquor and is mixed to form mixed solution B；Wherein, the concentration of the GO aqueous solution is 1.5-3 mg/ mL；The volume of the TBT and ammoniacal liquor are (0.16-0.76):(0.5-1)；The addition ratio of the TBT and sodium citrate is (0.16-0.76) mL:(0.05-0.15) g；

   Three-dimensional rice shape TiO has been obtained finally by hydro-thermal self assembly₂/ graphene composite aquogel, wherein, hydrothermal temperature 160- 180 °C, the hydro-thermal time is 6-24 h；The macro morphology of obtained composite aquogel is diameter 1-2 cm, high 1-2 cm black Column；Microscopic appearance is rice shape TiO₂Nano-particle uniform load is mutually handed on graphene film between graphene film It is made into network structure, wherein TiO₂A diameter of 15-35 nm of nano-particle, a length of 30-70 nm.
2. 2. preparation method as claimed in claim 1, it is characterized in that：The volume ratio of the TBT and ethanol is：(0.16-0.76): (3-10)。
3. 3. preparation method as claimed in claim 1, it is characterized in that：The mixed solution A is added to described mixed solution B In, it is well mixed, is subsequently added into sodium citrate, stirring forms mixed solution C, wherein, the mixed solution A and mixed solution B Volume ratio be (3-10):(15-30).
4. 4. preparation method as claimed in claim 1, it is characterized in that：Mixed after adding sodium citrate, the stirring Temperature is 30-40 °C, and mixing time is 2-4 h.
5. 5. preparation method as claimed in claim 1, it is characterized in that：The hydrothermal condition：Hydrothermal temperature is 180 °C, hydro-thermal Time is 12 h.
6. 6. the three-dimensional rice shape TiO being prepared using the method any one of claim 1 ~ 5₂/ graphene compound water congealing Glue.
7. 7. hydrogel as claimed in claim 6, it is characterized in that：The macro morphology of the composite aquogel is diameter 1-2 cm, high 1-2 cm black column；Microscopic appearance is rice shape TiO₂Nano-particle uniform load is on graphene film, and graphene It is interweaved between piece and reticulates structure, wherein TiO₂A diameter of 15-35 nm of nano-particle, a length of 30-70 nm.