WO2019149018A1

WO2019149018A1 - Preparation method of reduced graphene oxide film

Info

Publication number: WO2019149018A1
Application number: PCT/CN2019/000012
Authority: WO
Inventors: 庄鹏宇
Original assignee: 庄鹏宇
Priority date: 2018-02-05
Filing date: 2019-01-21
Publication date: 2019-08-08
Also published as: CN110117003A

Abstract

Disclosed is a method for preparing a reduced graphene oxide film. First, a graphene oxide dispersion solution with or without a reducing agent is prepared. Then, a reduced graphene oxide film or a reduced graphene oxide gel is prepared by a hydrothermal reaction or solvothermal reaction. The reduced graphene oxide gel is converted into a reduced graphene oxide film by freeze-drying or supercritical drying. The prepared film is immersed in water or another solvent and then dried, thereby obtaining a thinner reduced graphene oxide film. The reduced graphene oxide film can be further reduced at a high temperature to obtain a reduced graphene oxide film having a higher degree of reduction and a more intact graphene crystalline structure.

Description

Preparation method of reduced graphene oxide film

Technical field

The invention relates to a preparation method of a reduced graphene oxide film.

Research Background

Membrane technology plays a vital role in the field of matter separation (Liu, G., et al., Chemical Society reviews, 2015, 44, 5016-5030). Among the many separation membranes, graphene membranes have attracted attention due to their extremely thin thickness while maintaining high mechanical strength and good water permeability (Koenig, SP, et al., Nature nanotechnology, 2012, 7, 728). -732; Surwade, SP, et al. Nature nanotechnology, 2015, 10, 459-464). However, direct preparation of high quality defect-free graphene films over large areas faces significant challenges (Su, Y. et al., Nature communications, 2014, 5, 4843). More and more people are turning to the preparation and research of graphene oxide films. Since graphene oxide introduces a large amount of functional groups such as a hydroxyl group, a carboxyl group or the like in the preparation thereof, graphene is excellent in water solubility. By preparing a graphene oxide solution, by vacuum filtration (Yang, Q. et al., Nature materials, 2017, 16, 1198-1202) or spin coating on a substrate (Nair, RR, et al., Science, 2012) , 335, 442-444), spraying (Morelos-Gomez, A. et al. Nature nanotechnology, 2017, 12, 1083-1088), casting (Chen, L. et al., Nature, 2017, 550, 380-383 The graphene oxide film is prepared in an equal manner. However, the graphene oxide layer spacing is about 1 nm, which is greater than most brine ionic radii (such as Na+, K+, Ca ²⁺ , Mg ^2+, etc.) and gas molecular diameter (such as hydrogen, oxygen, nitrogen, etc.), limiting The application of graphene oxide film in the field of material separation. Therefore, the obtained graphene oxide film is reduced by chemical reduction or thermal reduction, so that the graphene structure can be repaired to a certain extent, and the interlayer spacing is reduced, thereby applying it to the material separation such as seawater desalination ( Su, Y. et al., Nature communIcations, 2014, 5, 4843; Lin, LC & Grossman, JC, Nature communications, 2015, 6, 8355). However, the flexibility and stability of the reduced graphene oxide film produced by the prior art still need to be improved. The invention directly prepares a reduced graphene oxide film or a reduced graphene oxide gel film by hydrothermal reaction or solvothermal reaction, and combines supercritical drying or freeze-drying method to convert the reduced graphene oxide gel film into a reduced graphene oxide film. . The reduced graphene oxide film prepared by the method has good stability and can be compressed, and the flexibility can depend on the presence or absence of the supporting substrate and the flexibility of the supporting substrate, and the obtained reduced graphene oxide film can be further regulated by infiltration drying. The thickness of the film or the high temperature reduction further improves the degree of graphene reduction and structural perfection. The method is simple and universal. The reduced graphene oxide film developed by the invention has broad application prospects in the field of material separation. In addition, the reduced graphene oxide film developed by the present invention also has potential application value in the fields of supercapacitors, lithium ion batteries, sensors, and catalysis.

Summary of the invention

The object of the present invention is to provide a method for preparing a reduced graphene oxide film in view of the deficiencies of the existing methods for preparing a reduced graphene oxide film.

The invention adopts hydrothermal reaction or solvothermal reaction to obtain a reduced graphene oxide film or a reduced graphene oxide gel, and then freeze-drying or supercritical drying of the reduced graphene oxide gel to obtain a reduced graphene oxide film. The obtained reduced graphene oxide film can also be obtained by infiltrating and drying in a solvent to obtain a thinner reduced graphene oxide film. The reduced graphene oxide film can be further reduced at a high temperature to obtain a reduced graphene oxide film having a higher degree of reduction of graphene and a more complete crystal structure. The obtained reduced graphene oxide film has good stability; the reduced graphene oxide film without the supporting substrate has good flexibility, and the flexibility of the reduced graphene oxide film supporting the substrate supports the flexibility of the substrate. The invention has the advantages of high universality, simple operation and green environmental protection.

A method for preparing a reduced graphene oxide film, comprising the steps of:

(1) Adding 0.1μm-100μm graphene oxide sheet to the liquid, stirring for 1h-96h, after ultrasonicing for 0h-24h (where ultrasonic is 0h, it means that no ultrasound can be selected), and the concentration is 1mg/mL-50mg. /mL graphene oxide dispersion; the liquid used is usually water, but it can also be other solvents such as methanol, ethanol, ethylene glycol, propanol, butanol, acetone, N, N-dimethylformamide, N, One or more of N-dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran, acetonitrile, hexamethylphosphoric triamide, dimethyl sulfoxide, pyridine, or a mixture with water;

(2) in step (1), the reducing agent may be optionally added to or not added to the graphene oxide dispersion;

(3) pouring the graphene oxide dispersion into the inner liner of the hydrothermal reaction kettle or the inner liner of the porous organic or inorganic film as the substrate, sealing the inner liner, and placing it in the reaction kettle. The amount of the dispersion to be poured therein is usually from 0.05 mL to 2 mL/cm ² , but is not limited to the amount of the above dispersion.

(4) Step (3) may also be carried out by pouring the graphene oxide dispersion into a glass container, and then sealing the glass container into the reactor lining, wherein the amount of the dispersed liquid is usually, but not limited to, 0.05 mL - 2 mL / cm ² .

(5) The reaction kettle is placed in a 60 ° C - 300 ° C vacuum oven for hydrothermal reaction or solvothermal reaction, the reaction time is usually 2h-48h, but not limited to the above time, to obtain unsupported or supported substrate reduction oxidation Graphene film or reduced graphene oxide gel;

(6) the reduced graphene oxide gel is freeze-dried or supercritically dried to obtain a reduced graphene oxide film;

(7) The reduced graphene oxide film obtained in the step (5) or (6) may be optionally dried in a solvent (usually water) and then dried to obtain a thinner film.

(8) The reduced graphene oxide film prepared in steps (5), (6), and (7) can be further reduced at a high temperature of from 300 ° C to 2500 ° C for 0.1 h to 24 h to obtain a higher degree of graphene reduction. A reduced crystalline graphene film with a more complete crystal structure.

The reducing agent is one or more of hydrazine hydrate, sodium borohydride, glucose, ascorbic acid, sodium ascorbate, ethylene glycol, diethylene glycol, hydroquinone, hydrobromic acid or acetic acid.

The reactor lining includes, but is not limited to, a lining made of glass, metal, polyethylene, polypropylene, para-polyphenylene, and polytetrafluoroethylene.

The organic film is mainly composed of polyolefin, polyester, polyamide, polyimide, polyacrylonitrile, polyurethane, polysulfone, polyurea, fluorinated polymer, silicon-containing polymer, cellulose acetate and their Composed of derivatives, copolymers or blends.

The inorganic film includes, but is not limited to, alumina, silica, titania, zirconia, alumina-ceria, titania-silica, silica-zirconia, titania-zirconia, zeolite. Membrane, molecular sieve membrane, glass membrane.

The invention has the beneficial effects compared with the prior art:

1. The present invention adopts hydrothermal reaction or solvothermal reaction method to directly prepare reduced graphene oxide film or reduced graphene oxide gel, and then combines supercritical drying method or freeze drying method to convert reduced graphene oxide gel into reducing oxidation. Graphene film is a brand new invention technology for preparing reduced graphene oxide film;

2. The invention has strong universality and the preparation process is simple and convenient;

3. The obtained reduced graphene oxide film can be further prepared by further dipping and drying in a solvent to obtain a thinner reduced graphene oxide film;

4. The obtained reduced graphene oxide film can be further reduced at a high temperature to obtain a reduced graphene oxide film having a higher degree of reduction and a more complete crystal structure of graphene;

5. The obtained reduced graphene oxide film has good stability and low density;

6. The reduced graphene oxide film of the unsupported substrate obtained is flexible; the flexibility of the reduced graphene oxide film with the supporting substrate depends on the flexibility of the supporting substrate.

DRAWINGS

1A and B are macroscopic photographs of a reduced graphene oxide film prepared by a typical embodiment of the present invention, and FIG. 1B illustrates that the density of the reduced graphene oxide film is low;

1C and D are respectively a curved photograph and a SEM photograph of a reduced graphene oxide film prepared by a typical embodiment of the present invention, and FIG. 1C illustrates that the reduced graphene oxide film is excellent in flexibility, and FIG. 1D illustrates that the surface area of the reduced graphene oxide film is small.

Detailed ways

The preparation method of the reduced graphene oxide film of the invention comprises the following steps:

(1) Adding a graphene oxide sheet having a size of 0.1 μm to 100 μm in a liquid, stirring for 1 h to 96 h, and after ultrasonicizing for 0 h to 24 h, preparing a graphene oxide dispersion having a concentration of 1 mg/mL to 50 mg/mL; It is water, but it can also be other solvents such as methanol, ethanol, ethylene glycol, propanol, butanol, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl a mixture of -2-pyrrolidone, tetrahydrofuran, acetonitrile, hexamethylphosphoric triamide, dimethyl sulfoxide, pyridine, or a mixture with water;

(3) Pour the graphene oxide dispersion into the inner liner of the hydrothermal reactor or the inner liner of the porous organic or inorganic membrane as the supporting substrate, seal the inner liner, and put it into the reaction kettle. The amount of the dispersion to be poured therein is usually from 0.05 mL to 2 mL/cm ² , but is not limited to the amount of the above dispersion.

(4) Step (3) may also be carried out by pouring the graphene oxide dispersion into a glass bottle, sealing the glass bottle into the reactor lining, wherein the amount of the poured liquid is usually but not limited to 0.05 mL - 2 mL / cm ² .

(7) The reduced graphene oxide film obtained in the step (5) or (6) may be optionally wetted in a solvent (usually water) and then dried to obtain a thinner film.

(8) The reduced graphene oxide film prepared in the step (5), (6) or (7) may be further reduced at a high temperature of from 300 ° C to 2500 ° C for 0.1 h to 24 h to obtain a higher degree of reduction and graphite. A more complete crystalline graphene oxide film.

The reducing agent comprises one or more of hydrazine hydrate, sodium borohydride, glucose, ascorbic acid, sodium ascorbate, ethylene glycol, diethylene glycol, hydrobromic acid or acetic acid, but is not limited to the above reducing agent.

The inorganic film includes, but is not limited to, alumina, silica, titania, zirconia, alumina-ceria, titania-silica, silica-zirconia, titania-zirconia, zeolite. Membrane, molecular sieve membrane, glass membrane, glass membrane.

The present invention is specifically described by the following examples, which are only used to further illustrate the present invention, and are not to be construed as limiting the scope of the present invention. Those skilled in the art will make some non-essential changes according to the contents of the above invention. Adjustments are all within the scope of protection of the present invention.

Example 1:

Step (a): Disperse 1 g of graphene oxide having a size of 8 μm in 200 mL of water, stir for 10 h, and ultrasonically for 2 min to obtain a graphene oxide dispersion;

Step (b): 3 mL of the graphene oxide dispersion obtained in the step a was poured into a polytetrafluoroethylene liner having a capacity of 50 mL, sealed, and placed in a reaction vessel.

Step (c): The reaction vessel in step b is sealed and placed in a vacuum oven at 120 ° C for 12 h to obtain a reduced graphene oxide hydrogel.

Step (d): The reduced graphene oxide hydrogel obtained in the step c is freeze-formed at -100 ° C, and freeze-dried to obtain a reduced graphene oxide film.

The reduced graphene oxide film obtained by the method has a thickness of 1-50 mm, a density of 4-10 mg/cm ³ , a compressibility of less than 80%, a curl, and a surface pore diameter of less than 500 nm.

Example 2:

Step (a): Disperse 1.2 g of graphene oxide having a size of 8 μm in 200 mL of water, stir for 10 h and ultrasonically for 2 min to obtain a graphene oxide dispersion;

Step (b): 1 mL of the graphene oxide dispersion obtained in the step a is poured into a 10 mL glass bottle, and after sealing, the glass bottle is placed in a 50 mL polytetrafluoroethylene liner, sealed, and placed in a reaction vessel.

Step (d): The reduced graphene oxide hydrogel obtained in the step c is freeze-formed at -30 ° C, and freeze-dried to obtain a reduced graphene oxide film.

The reduced graphene oxide film obtained by the method has a thickness of 0.5-30 mm, a density of 2-5 mg/cm ³ , a compressibility of more than 50%, a bendability, and a surface pore diameter of less than 500 nm.

Example 3:

Step (a): Disperse 1 g of graphene oxide having a size of 8 μm in 200 mL of water, stir for 10 h and ultrasonically for 2 min to obtain a graphene oxide dispersion;

Step (b): Put a cellulose acetate film directly of 2.96 cm into a polytetrafluoroethylene inner liner having a capacity of 50 mL and an inner diameter of 2.96 cm as a substrate, and then pour 3 mL of the graphene oxide dispersion obtained in the step a, and seal it. After lining, put it into the reaction kettle.

Step (c): The reaction vessel in step b is sealed and placed in a vacuum oven at 130 ° C for 12 h to obtain a reduced graphene oxide hydrogel.

The reduced graphene oxide film obtained by the method has a supporting substrate, and the reduced graphene oxide film has a thickness of 1-50 mm, a density of 4-8 mg/cm ³ , a compressibility of more than 30%, a curl, and a surface pore diameter of less than 500 nm. .

The above-mentioned embodiments are intended to be illustrative of the present invention and are not intended to be construed as limiting the scope of the present invention. Any modifications or variations of the present invention are intended to be included within the scope of the present invention.

Claims

A method for preparing a reduced graphene oxide film, comprising the steps of:

(1) adding a graphene oxide sheet to a liquid to prepare a certain concentration of graphene oxide dispersion;

(2) in step (1), the reducing agent may or may not be added to the graphene oxide dispersion;

(3) pouring the graphene oxide dispersion into the reaction vessel, and after sealing, the reaction vessel is subjected to hydrothermal reaction or solvothermal reaction at a certain temperature to obtain a reduced graphene oxide film or a reduced graphene oxide gel;

(4) The reduced graphene oxide gel in the step (3) is subjected to freeze-drying or supercritical drying to obtain a reduced graphene oxide film.
The method for preparing a reduced graphene oxide film according to claim 1, wherein in the step (1), the liquid is mainly composed of water, methanol, ethanol, ethylene glycol, propanol, butanol, acetone. , N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran, acetonitrile, hexamethylphosphoric triamide, dimethyl sulfoxide, pyridine One or more mixed compositions.
The method for producing a reduced graphene oxide film according to claim 1, wherein the size of the graphene oxide in the step (1) is usually from 0.1 μm to 100 μm.
The method for preparing a reduced graphene oxide film according to claim 1, wherein the concentration of the graphene oxide dispersion in the step (1) is generally from 1 mg/mL to 50 mg/mL.
The method for preparing a reduced graphene oxide film according to claim 1, wherein in the step (2), the reducing agent is mainly composed of hydrazine hydrate, sodium borohydride, glucose, ascorbic acid, sodium ascorbate, and ethylene glycol. One or more of diethylene glycol, hydroquinone, hydrobromic acid or acetic acid.
The method for preparing a reduced graphene oxide film according to claim 1, wherein in the step (3), the reaction vessel comprises glass, metal, polyethylene, polypropylene, para-polyphenylene, polytetrafluoroethylene. A container made of a vinyl material and a reaction vessel equipped with a liner made of the above material.
The method for preparing a reduced graphene oxide film according to claim 1, wherein a certain temperature in the step (3) generally refers to 60 ° C to 300 ° C, and the reaction time is usually 6 h to 24 h.
A method for producing a reduced graphene oxide film according to claim 1, wherein the amount of the graphene oxide dispersion poured in the step (3) is 0.05 mL to 2 mL/cm 2 .
The method for preparing a reduced graphene oxide film according to claim 1, wherein the reduced graphene oxide film obtained in the step (4) is further infiltrated and dried in a solvent (usually water) to obtain a thinner Reducing the graphene oxide film;
The reduced graphene oxide film prepared in claims 1 and 9 can also be further reduced at a high temperature from 300 ° C to 2500 ° C to obtain a reduced graphene oxide film having a higher degree of reduction and a more complete crystal structure of graphene.