The chemical method firstly oxidizes graphite into graphite oxide by oxidation reaction, and increases the layer spacing by introducing oxygen containing functional groups on the carbon atoms between the graphite layers, thereby weakening the interaction between layers.

Common oxidation

The methods include Brodie method, Staudenmaier method and Hummers method [40]. The principle is to treat the graphite with strong acid first,

Then add strong oxidant for oxidation.

The oxidized graphite is stripped by ultrasonic to form graphene oxide, and then reduced by adding reducing agent to obtain graphene.

Common reducing agents include hydrazine hydrate, NaBH4 and strong alkali ultrasonic reduction. NaBH4 is expensive and easy to retain element B,

Although the strong alkali ultrasonic reduction is simple and environmentally friendly, it is difficult to reduce *, and a large number of oxygenated functional groups will remain after reduction,

Therefore, cheaper hydrazine hydrate is usually used to reduce graphite oxide. The advantage of hydrazine hydrate reduction is that hydrazine hydrate has strong reduction ability and is easy to volatilize, so there will be no impurities left in the product. In the reduction process, an appropriate amount of ammonia water is usually added to improve the reduction ability of hydrazine hydrate,

On the other hand, it can make the surfaces of graphene repel each other due to negative charges, thereby reducing the agglomeration of graphene.

Large scale preparation of graphene can be realized by chemical oxidation and reduction method, and the intermediate product graphene oxide has good dispersion in water,

It is easy to modify and functionalize graphene, so this method is often used in the research of composite materials and energy storage. But because of oxidation

The absence of some carbon atoms in the ultrasonic process and the residue of oxygen-containing functional groups in the reduction process often make the graphene produced contain more defects, which reduces its conductivity, thus limiting its application in the field of graphene with high quality requirements.