Efficiency of different methods of oxidation of graphite: a key route of graphene preparation

Abstract

Oxidation of graphite is the first important step for the industrial-scale preparation of graphene by a top-down method using graphite as a starting material. In this study, graphite was oxidized by thermal, chemical (sulphuric acid, ozone, peracetic acid, benzoyl peroxide), thermo-chemical (heat treatment in the presence of sulphuric acid) and mechano-chemical (sonication with sulphuric acid in ozone environment) methods and the efficiency of different oxidation methods was studied through different characterization techniques and crystal simulation. From the results, it was evident that the maximum percentage of functional groups (1.8%) was introduced without much breaking the hexagonal graphitic structure when a mixture of graphite and benzoyl peroxide (1:20 w/w) was heated at 110 °C for 15 min. However, the maximum percentage of defects was generated through the introduction of functional groups as well as breaking of the hexagonal graphitic structure when graphite was sonicated with sulphuric acid (1:10 w/w) in ozone environment at 80 °C for 15 min. The crystal simulation result revealed that virgin graphite has monoclinic symmetry, but after oxidation with BPO it has converted to triclinic crystal symmetry with a significant increase in unit-cell volume from 738.6 Ǻ 3 to 1655.8 Ǻ 3 .