Influence of Graphite Source on Chemical Oxidative Reactivity

Although all graphites share the same idealized chemical structure, marked differences in fact exist between their reactivities, such as the propensity for oxidation, that need to be taken into consideration for the development of applications. Here we show that five different commercially sourced natural and synthetic graphites differ significantly in their response to a modified Staudenmaier oxidation that produces substoichiometric graphene oxides (sub-GOx). The dominant oxidation product is hydroxyl groups, which can be dehydrate to epoxy groups under mild heating even below 120 degrees C. The extent of oxidation correlates broadly with the defect band intensity in the starting graphites as measured by Raman spectroscopy. FTIR shows there is a significant concentration of H defects at the 96 atom level. The results suggest that defects in the graphite plane are more prevalent than previously thought. Finally, the properties of the thermally reduced sub-GOx are also different. The product from the least defective starting graphite ultimately exhibits the lowest activation energies for both electron and hole transport, of the order of 10 mu eV below 25 K, that is characteristic of band-like transport. These results are important because they show that the quality of the starting graphite significantly affects the properties of the derived products.