The chemical method first oxidizes graphite to graphite oxide by an oxidation reaction, and increases the layer spacing by introducing an oxygen-containing functional group on the carbon atoms between the graphite layer and the layer, thereby weakening the interaction between the layers.
Methods include Brodie's method, Staudenmaier's method, and Hummers' method . The principle is that graphite is first treated with strong acid.
Then add a strong oxidizing agent for oxidation.
The oxidized graphite is formed into graphene oxide by ultrasonic exfoliation, and then added with a reducing agent for reduction, thereby obtaining graphene.
The commonly used reducing agents are hydrazine hydrate, NaBH4, and strong alkali ultrasonic reduction. NaBH4 is expensive due to its high price and it easily retains B elements.
Ultrasonic reduction of strong bases is simple and environmentally friendly, but it is difficult to restore completely, and there are usually a large number of residual oxygen-containing functional groups after reduction.
Therefore, the cheaper hydrazine hydrate is generally used to reduce the graphite oxide. The advantage of hydrazine hydrate reduction is that the reducing capacity is strong and the hydrazine hydrate is easy to evaporate, and no impurities remain in the product. In the reduction process, an appropriate amount of ammonia water is usually added, on the one hand, the reducing capacity of the hydrazine hydrate is increased.
On the other hand, the surface of the graphene can be mutually repelled due to negative charge, thereby reducing graphene agglomeration.
The large-scale preparation of graphene can be achieved through chemical redox, and the dispersion of the intermediate graphene oxide in water is better.
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 absence of some carbon atoms in the ultrasonic process and the residue of oxygen-containing functional groups during the reduction process often make the resulting graphene contain more defects, lowering its conductivity, and thus limiting its requirement for high quality of graphene. Application.