Investigating the effect of graphite pretreatment and contribution of the oxidizer in the synthesis of graphite oxide by hummers approach

Abstract

Graphite oxide (GrO), the precursor of graphene oxide (GO) has been prepared by pre-treating graphite in a mixture of nitric and sulfuric acid, followed by chemical oxidation by a modified Hummers approach. The effect of pretreatment, KMnO4, and sulfuric acid on the chemical oxidation reaction was observed by characterizing GrO specimens on the bulk scale. KMnO4 oxidizes the carbon atoms by withdrawing electrons, instead of penetrating between the stacked carbon layers and directly interacting with the carbon atoms. Sulfuric acid and water molecules penetrate the interlayers of carbon planes and form the functionalities by nucleophilic attack on the charged carbon atoms. The pretreatment of graphite induces a small number of moieties, distributed evenly across the entire domain, serving as the primary reaction site of chemical oxidation. The inclusion of a small amount of functionalities marginally increases the lattice spacing and mildly intercalates the stacked carbon layers, facilitating the diffusion of acid and water molecules in the later step. The prepared GrO possesses only 24% graphitic carbon atoms and 11-layer of carbon stacking, confirming significant oxidation and intercalation.