A density functional theory (DFT) study of graphene synthesis from graphite oxidation and exfoliation is presented. The calculated DFT results for O adsorption predict C=O as a most stable bond on the graphene oxide (GO) sheet. The obtained exfoliation energy for the graphene and the GO are 143 and similar to 70mJ/m(2) that verify easier exfoliation of the graphite oxide compared with the graphite. Furthermore, the DFT results show that for decreasing the exfoliation energy of the GO at least two layers of the graphite should be oxidized during the oxidation process. (C) 2010 Elsevier B.V. All rights reserved.