The chemical method first oxidizes graphite into graphite oxide by an oxidation reaction, and increases the interlayer spacing by introducing an oxygen-containing functional group on the carbon atom between the graphite layer and the layer, thereby weakening the interaction between the layers.
Common oxidation
The methods include Brodie method, Staudenmaier method and Hummers method [40]. The principle is that the graphite is treated with strong acid first.
A strong oxidizing agent is then added for oxidation.
The oxidized graphite is subjected to ultrasonic stripping to form graphene oxide, and then a reducing agent is added for reduction to obtain graphene.
Commonly used reducing agents are hydrazine hydrate, NaBH4 and strong base ultrasonic reduction. NaBH4 is expensive and easy to leave B element.
While the strong alkali ultrasonic reduction is simple and environmentally friendly, it is difficult to completely reduce it. After reduction, there is usually a large amount of residual oxygen-containing functional groups.
Therefore, it is common to use less expensive hydrazine hydrate to reduce graphite oxide. The advantages of hydrazine hydrate reduction are that the reducing ability is strong and the hydrazine hydrate is easy to volatilize, and no impurities remain in the product. In the reduction process, an appropriate amount of ammonia water is usually added to improve the reducing power of hydrazine hydrate.
On the other hand, the surface of graphene can be mutually repelled by a negative charge, thereby reducing the agglomeration of graphene.
Large-scale preparation of graphene can be achieved by chemical redox method, and the dispersion of the intermediate product graphene oxide in water is good.
It is easy to realize the modification and functionalization of graphene, so this method is often used in the research of composite materials and energy storage. But because of oxidation,
The loss of some carbon atoms during the ultrasonic process and the residual of the oxygen-containing functional groups during the reduction process tend to make the produced graphene contain more defects, which lowers its conductivity, thereby limiting its requirements for the quality of graphene. Application in .