CN106517171B - A kind of preparation method of graphene aerogel - Google Patents

Abstract

The invention provides a preparation method of graphene airgel, comprising the following steps: S1: adding graphene and amine-based polymers into a solvent and dispersing them to obtain a graphene dispersion; S2: freeze-drying the graphene dispersion liquid to obtain graphene airgel. The graphene airgel preparation method of the present invention uses the polymer containing amine group as graphene dispersant and structural cross-linking agent, at first utilizes the strong interaction between the amine group in the polymer and graphene to disperse the graphite in the solvent ene sheets, and then directly freeze-dry the graphene dispersion, in which the amine groups in the polymer cross-link the graphene sheets to form a structural skeleton after drying, thereby preparing an elastic graphene airgel with a porous structure. The invention directly prepares graphene airgel from graphene powder, has mild process conditions and simple steps, and can produce large-scale graphene airgel blocks on a large scale, and the obtained airgel has good adsorption characteristics and pressure resistance performance.

Description

A kind of preparation method of graphene airgel

technical field

The invention belongs to the technical field of nano-carbon material preparation, and relates to a preparation method of graphene airgel.

Background technique

Graphene airgel is a porous bulk material formed by interconnecting graphene nanosheets in three-dimensional space. Graphene airgel has low density (1-50mg/cm ³ ), high porosity (>50%), large specific surface area (100-1200m ² /g), good mechanical properties, elasticity, good conductivity, chemical Stable properties and other characteristics can be used as dielectric materials for clean energy storage (such as hydrogen, natural gas) and electrode materials for electric energy storage (such as supercapacitors), and also have important application prospects in the fields of heterogeneous catalysis, sewage treatment and sensors.

In order to obtain a bulk material with a porous structure, graphene aerogels are generally prepared by freeze-drying graphene hydrogels. However, graphene cannot be uniformly and stably dispersed in water, and it is difficult to prepare graphene hydrogel directly from graphene powder. Therefore, the currently reported methods are to prepare graphene hydrogels by self-assembly and reduction from graphene oxide, and then freeze-dry to obtain graphene aerogels. The reduction method is generally chemical reduction or hydrothermal reduction. For example, Zhang Xuetong proposed in "A Graphene Airgel and Its Preparation Method" (201010263656.4) to add a reducing agent to the graphene oxide dispersion to obtain graphene hydrogel, and then freeze-dry to prepare graphene airgel method, but the reduction process requires the introduction of toxic reducing agents such as hydrazine hydrate, which has potential safety hazards and is not conducive to the large-scale production of graphene aerogels. In the patent "A Preparation Method for Three-dimensional Self-assembled Graphene with High Adsorption" (201310110754.8), Gao Hui et al. proposed a hydrothermal method to self-assemble and simultaneously reduce graphene oxide sheets to obtain graphene hydrogel, and then freeze The method of drying graphene hydrogel to prepare graphene aerogel, hydrothermal reduction avoids the use of toxic reducing agents, but hydrothermal needs to be carried out in a closed container, which is not conducive to large-scale and large-scale preparation of graphene aerogel.

Therefore, the development of a technology suitable for large-scale preparation of graphene airgel will help promote the promotion and use of graphene airgel materials in the fields of energy and environmental protection.

Contents of the invention

In view of the above-mentioned shortcoming of prior art, the object of the present invention is to provide a kind of preparation method of graphene airgel, for solving the problem that the preparation method of graphene airgel in the prior art is not suitable for large-scale production .

In order to achieve the above-mentioned purpose and other related purposes, the invention provides a kind of preparation method of graphene airgel, comprising the following steps:

S1: adding graphene and amine-based polymers into the solvent and dispersing them to obtain a graphene dispersion;

S2: Freeze-drying the graphene dispersion to obtain graphene airgel.

As a preferred solution of the preparation method of the graphene airgel of the present invention, in the step S1, the graphene is selected from oxidation-reduction method, liquid phase exfoliation method, arc method, high temperature pyrolysis method And one or more graphene powders prepared by the chemical vapor deposition method.

As a preferred version of the preparation method of the graphene airgel of the present invention, in the step S1, the amino polymer is selected from chitosan, polyacrylamide, polyetherimide and polyaniline one or more of .

As a preferred version of the preparation method of the graphene airgel of the present invention, in the step S1, the solvent is selected from water, ethanol, isopropanol, N-methylpyrrolidone and N,N-dimethyl One or more of the base formamides.

As a preferred solution of the preparation method of the graphene airgel of the present invention, in the step S1, the mass ratio of the graphene, the amine-based polymer to the solvent is 1:0.1-2:5-100.

As a preferred solution of the preparation method of the graphene airgel of the present invention, in the step S1, the dispersion adopts one or more of ultrasound, stirring and shearing.

As a preferred version of the preparation method of the graphene airgel of the present invention, in the step S2, the freeze-drying temperature range is -50-0°C, the vacuum range is 1.3-13Pa, and the freeze-drying time is The range is 1~100h.

As a preferred solution of the method for preparing graphene airgel of the present invention, in the step S1, the graphene includes single-layer or multi-layer graphene.

As mentioned above, the preparation method of graphene airgel of the present invention has the following beneficial effects: the preparation method of graphene airgel of the present invention uses the polymer containing amine group as graphene dispersant and structural crosslinking agent, first Using the strong interaction between the amine groups in the polymer and graphene to disperse the graphene sheets in the solvent, and then directly freeze-drying the graphene dispersion, where the amine groups in the polymer cross-link the graphene sheets after drying The layers form a structural skeleton, thereby preparing elastic graphene aerogels with a porous structure. The graphene airgel preparation method of the present invention introduces an amine-containing polymer as a dispersant and a structural crosslinking agent at the same time, and directly prepares graphene airgel from graphene powder, with mild process conditions, simple steps, and scalable Large-scale graphene airgel blocks are produced. The obtained airgel has good adsorption characteristics and piezoresistive properties, and is expected to be applied in the fields of water pollution treatment and piezoresistive sensing.

Description of drawings

Fig. 1 shows the process flow diagram for the preparation method of graphene airgel of the present invention.

Fig. 2 shows the SEM image of the graphene airgel prepared in Example 1 for the preparation method of the graphene airgel of the present invention.

Fig. 3 shows the piezoresistive characteristic curve of the graphene airgel prepared in Example 1 for the preparation method of the graphene airgel of the present invention.

Fig. 4 shows the graphene airgel prepared in Example 1 for the preparation method of the graphene airgel of the present invention.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

See Figures 1 through 4. It should be noted that the diagrams provided in this embodiment are only schematically illustrating the basic idea of the present invention, and only the components related to the present invention are shown in the diagrams rather than the number, shape and shape of the components in actual implementation. Dimensional drawing, the type, quantity and proportion of each component can be changed arbitrarily during actual implementation, and the component layout type may also be more complicated.

The invention provides a kind of preparation method of graphene airgel, comprises the following steps:

S1: adding graphene and amine-based polymers into the solvent and dispersing them to obtain a graphene dispersion;

S2: Freeze-drying the graphene dispersion to obtain graphene airgel.

Specifically, in the step S1, the graphene is selected from one or more of the oxidation-reduction method, the liquid phase exfoliation method, the arc method, the high temperature pyrolysis method and the chemical vapor deposition method. Graphene powder. The graphene includes single-layer or multi-layer graphene.

Oxidation-re-reduction method to prepare graphene is based on natural graphite as raw material, using oxidation reaction (introducing carboxyl and hydroxyl groups on carbon atoms on the edge of graphite layers, oxygen-containing groups such as epoxy and carbonyl groups between layers) to weaken the interaction between graphite layers. function to increase the spacing, and then separate graphite oxide to obtain graphene oxide; then disperse graphene oxide (by means of high-speed centrifugation, ultrasound, etc.) into water or organic solvents to form a stable homogeneous sol, and then use reduction single or multilayer graphene. The reduction of hydrazine hydrate and ethylenediamine, which are widely used now, is a better reduction method, but these reducing agents are toxic and have many negative effects on the environment and human beings. Therefore, more researchers began to reduce graphene oxide with environmentally friendly reducing agents such as ascorbic acid, sodium citrate, and reducing amino acids. In addition, some strongly acidic substances have also been used to reduce graphene oxide to prepare graphene products, so that more and more graphene properties can be displayed. The biggest disadvantage of the redox method is that the prepared graphene has certain defects, because the graphene oxide obtained by oxidation with a strong oxidant may not be completely reduced, and may lose some properties, such as light transmittance, thermal conductivity, especially It is electrical conductivity, so the graphene obtained after reduction by some reducing agents is incomplete to a certain extent, that is, it is different from graphene in the strict sense. However, the redox method is cheap and can produce a large amount of graphene, so it has become the most commonly used method for preparing graphene.

The preparation of graphene by liquid phase exfoliation is usually directly adding graphite or expanded graphite (EG) (generally obtained by removing oxygen-containing groups on the surface by rapidly raising the temperature to above 1000°C) in some organic solvent or water, with the help of ultrasonic waves, heating or the action of airflow to prepare a single-layer or multi-layer graphene solution with a certain concentration.

Graphene is prepared by the arc method, using graphite rods as the negative and positive poles, and arc discharge is carried out under high current and hydrogen-containing atmosphere. During the arc discharge process, the anode graphite rods are continuously consumed, and single-layer or multi-layer graphene can be obtained in the inner wall area of the reaction chamber. Graphene. The arc method is a typical method that was first applied to the preparation of carbon nanotubes and fullerenes. The graphene graphite layer prepared by the arc method is regular and has a good crystal form. It is expected to obtain higher conductivity and better electrochemical properties. performance.

The most commonly used high-temperature pyrolysis method to prepare graphene is the silicon carbide high-temperature pyrolysis method. This method uses the high saturated vapor pressure difference between C and Si to heat the SiC crystal at high temperature, so that Si atoms are detached from the SiC crystal. The remaining C spontaneously recombine to form graphene. The advantage of this method is that graphene can be directly grown on semi-insulating substrates, and devices can be directly fabricated without transfer.

The chemical vapor deposition method uses carbon-containing compounds such as methane as a carbon source, and grows graphene through its pyrolysis on the surface of the substrate. The growth mechanism can be mainly divided into two types: (1) Carburizing and carburizing mechanism: For metal substrates with high carbon solubility such as nickel, the carbon atoms generated by the cracking of carbon sources penetrate into the metal substrate at high temperature, (2) Surface growth mechanism: For metal substrates such as copper with low carbon solubility, the carbon atoms generated by the cracking of gaseous carbon sources at high temperatures are adsorbed on the metal surface, Then nucleate and grow into "graphene islands", and through the two-dimensional growth of "graphene islands", a continuous graphene film is obtained. Because the CVD method is simple and easy to prepare graphene, the obtained graphene is of high quality, can grow in a large area, and is easier to transfer to various substrates, so this method is widely used in the preparation of graphene transistors and transparent conductive films. At present, it has gradually become the main method to prepare high-quality graphene.

Of course, in other embodiments, the graphene may also be graphene powder prepared by other methods, and the protection scope of the present invention should not be excessively limited here.

Specifically, in the step S1, the amino polymer is selected from one or more of chitosan, polyacrylamide, polyetherimide and polyaniline. The solvent is selected from one or more of water, ethanol, isopropanol, N-methylpyrrolidone and N,N-dimethylformamide. The mass ratio of the graphene, the amine-based polymer and the solvent is 1:0.1-2:5-100.

As shown in Figure 1, it is a process flow diagram of the preparation method of the graphene airgel of the present invention. The dispersion can use one or more of ultrasound, stirring and shearing. Among them, in ultrasonic dispersion, the ultrasonic frequency is 20-400kHz; in stirring dispersion, the stirring speed is 100-8000rpm; shear dispersion refers to letting the graphene powder quickly pass through the narrow gap between the stator and the mover of the shearing machine together with the solvent. The space promotes the mixing of the amino polymer and the graphene sheets through impact, tearing, etc., and opens the graphene aggregates, wherein the shearing speed is 100-18000rpm.

Due to the strong interaction between the amine groups in the polymer and the surface atoms of the graphene sheets, under operations such as ultrasound, stirring or shearing, the amine-based polymer molecules can penetrate into the agglomerated graphene sheets and open Graphene aggregates, and adsorbed on the surface of graphene sheets, so that the graphene sheets can no longer reunite, thereby stabilizing the dispersion of graphene in the corresponding solvent, the amine-based polymer can effectively disperse the graphene in the solvent lamellae.

Freeze-drying is also called sublimation drying. Materials can be frozen in a freezer first, and then vacuum-dried. They can also be frozen directly in a drying chamber by quickly evacuating them. The heat of vaporization required in the sublimation process is generally supplied by thermal radiation.

Specifically, in the step S2, the freeze-drying temperature range is -50-0° C., the vacuum range is 1.3-13 Pa, and the freeze-drying time range is 1-100 h. During the freeze-drying process, the amine-based polymer acts as a structural cross-linking agent, and the cross-linked graphene sheets form a structural skeleton. After a preset time of freeze-drying, an elastic graphene airgel with a porous structure can be obtained.

The graphene airgel preparation method of the present invention uses the polymer containing amine group as graphene dispersant and structural cross-linking agent, at first utilizes the strong interaction between the amine group in the polymer and graphene to disperse the graphite in the solvent ene sheets, and then directly freeze-dry the graphene dispersion, in which the amine groups in the polymer cross-link the graphene sheets to form a structural skeleton after drying, thereby preparing an elastic graphene airgel with a porous structure. The invention directly prepares graphene airgel from graphene powder, has mild process conditions and simple steps, and can produce large-scale graphene airgel blocks on a large scale.

The technical solution of the present invention will be described in detail below through specific examples.

Embodiment one

100 mg of graphene powder obtained by the oxidation-re-reduction method and 25 mg of chitosan were added to 100 mL of deionized water, and the graphene powder was completely dispersed in water by ultrasound to form a stable dispersion. Take the above-mentioned dispersion liquid and put it into a container, and freeze-dry it at -30°C and 1.5Pa for 24 hours to obtain a graphene airgel block. Figures 2, 3 and 4 are the SEM pictures of the obtained graphene airgel, the piezoresistive characteristic curve and the statistical chart of the adsorption capacity of different solvents, respectively. It can be seen that the graphene airgel obtained is a porous bulk material, has good pressure-sensitive properties, and has a large adsorption capacity (about 30-60 times its own weight) to water and some organic solvents. It is expected to be used as pressure sensitive sensor and water pollution treatment material.

Embodiment two

500 mg of graphene powder obtained by liquid phase exfoliation and 80 mg of polyaniline were added into 100 mL of deionized water, and the graphene powder was completely dispersed in water by ultrasonic waves to form a stable dispersion. Take the above-mentioned dispersion liquid and put it into a container, and freeze-dry it at -30°C and 1.5Pa for 36 hours to obtain a graphene airgel block.

Embodiment three

Add 100 mg of graphene powder obtained by the arc method and 50 mg of polyacrylamide into 100 mL of deionized water, and ultrasonically disperse the graphene powder in the water to form a stable dispersion. Take the above-mentioned dispersion liquid and put it into a container, and freeze-dry it at -40°C and 2Pa for 20 hours to obtain a graphene airgel block.

Embodiment Four

100 mg of graphene powder obtained by high temperature pyrolysis and 25 mg of polyetherimide were added to 100 mL of deionized water, and the graphene powder was completely dispersed in the water by ultrasound to form a stable dispersion. Take the above-mentioned dispersion liquid and put it into a container, and freeze-dry it at -25°C and 3Pa for 48 hours to obtain a graphene airgel block.

In summary, the graphene airgel preparation method of the present invention uses the polymer containing amine group as graphene dispersant and structural crosslinking agent, at first utilizes the strong interaction between the amine group in the polymer and graphene Disperse the graphene sheets in the solvent, and then directly freeze-dry the graphene dispersion, in which the amine groups in the polymer cross-link the graphene sheets to form a structural skeleton after drying, thereby preparing elastic graphene gas with a porous structure. gel. The graphene airgel preparation method of the present invention introduces an amine-containing polymer as a dispersant and a structural crosslinking agent at the same time, and directly prepares graphene airgel from graphene powder, with mild process conditions, simple steps, and scalable Large-scale graphene airgel blocks are produced. The obtained airgel has good adsorption characteristics and piezoresistive properties, and is expected to be applied in the fields of water pollution treatment and piezoresistive sensing. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (7)

1. a preparation method of graphene airgel, is characterized in that, comprises the following steps: S1: Add graphene and amine-based polymers into the solvent and disperse them to obtain a graphene dispersion. The amine-based polymers are selected from one of chitosan, polyacrylamide, polyetherimide and polyaniline. One or more, the amine-based polymer is used as a graphene dispersant; S2: Freeze-drying the graphene dispersion to obtain a graphene airgel, and the amine-based polymer is used as a graphene structure cross-linking agent. 2. the preparation method of graphene airgel according to claim 1, is characterized in that: in described step S1, described graphene is selected from and adopts oxidation-reduction method, liquid phase exfoliation method, electric arc method, Graphene powder prepared by one or more of high temperature pyrolysis method and chemical vapor deposition method. 3. the preparation method of graphene airgel according to claim 1 is characterized in that: in described step S1, described solvent is selected from water, ethanol, Virahol, N-methylpyrrolidone and N, One or more of N-dimethylformamide. 4. the preparation method of graphene airgel according to claim 1, is characterized in that: in described step S1, the mass ratio of described graphene, amine-based polymer and solvent is 1:0.1～2: 5~100. 5. The preparation method of graphene airgel according to claim 1, characterized in that: in the step S1, the dispersion adopts one or more of ultrasound, stirring and shearing. 6. The preparation method of graphene airgel according to claim 1, characterized in that: in the step S2, the temperature range of the freeze-drying is -50～0°C, and the vacuum range is 1.3～13Pa , Freeze-drying time range is 1 ~ 100h. 7. The preparation method of graphene airgel according to claim 1, characterized in that: in the step S1, the graphene comprises single-layer or multi-layer graphene.