Critical temperatures in the synthesis of graphene - like materials by thermal exfoliation - reduction of graphite oxide

We prepared a series of graphene-like materials by thermal exfoliation/reduction of a graphite oxide (GO) at temperatures between 127oC and 2400oC. The extent of the exfoliation and reduction of the GO at different temperatures, as well as the impact on the resultant graphene-like materials (TRGs), were studied through their chemical/structural characterization. The main oxygen loss was observed at 127oC during the blasting of the GO, which produced its exfoliation into monolayer functionalized TRG with hydroxyl groups and minor amounts of epoxy and carboxyl groups. Above 600oC, the reduction continued smoothly, with oxygen and hydrogen loss and the conversion of hybridized carbon atoms from sp into sp. 1000oC appears to be a critical temperature for the efficiency of the reduction process, as the resulting TRG contained less than 2% oxygen and 81.5% sp-carbon atoms. The materials obtained at 2000oC and 2400oC were almost oxygen-free and the layers exhibited a dramatic restoration of the pristine graphite structure, as confirmed by the increase in the average size of the sp-domains. The typical * Corresponding author: Fax. + 34 985 29 76 62; E-mail: [email protected] (Prof. R. Menéndez)