Reduction of graphene oxide means deoxygenation of graphene oxide(GO) via chemical and physical processes.Graphene oxide is a product of oxidation and exfoliation of graphite(G).Graphite has high C/O ratio of 6/1 to 8/1 and low surface area.
Graphite is multilayer conductive material while graphene oxide is semi conductive material which has C/O ratio of 2/1 .The main reason behind oxidation/exfoliation is to produce mono- to few-layer graphene oxide and increasing surface area.Within oxidation process ,graphite oxide lose most of conductive properties of graphite due to disordering of aromatic system. To restoring some or most conductive properties of graphite , reduction process must be performed .On reduction, reduced graphene oxide(rGO) restores aromatic π → π system and hence rGO may has high C/O ratio of 4/1 to 6/1 and also restores most conductive properties of graphite.