Influence of Graphite Source on Chemical Oxidative Reactivity

Abstract

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 °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 % 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 μeV 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.

From graphite to porous graphene-like nanosheets for high rate lithium-ion batteries

“…Natural graphite (NG) is widely present on Earth, especially in the northeast of China, and it has a good conductivity and layered structure. Expandable graphite (EG) is derived from NG after a simple treatment; as EG has a larger interlayer distance than NG, some functional composites can be introduced into the interlayer of NG [42,43]. Based on these considerations, in a previous study, we synthesized mesoporous carbon/graphite nanosheet composites by intercalating resol prepolymer into the EG interlayer, followed by the exfoliation of EG through in situ polymerization and carbonization processes [44].…”

Geographical and Geological Origin of Natural Graphite Heavily Influence the Electrical and Electrochemical Properties of Chemically Modified Graphenes

“…No relationship was found between the defect density of the starting graphite and the extent of oxidation of GO, as suggested by ap revious study. [33] Instead, ad irect correlationb etween the purity of the starting natural graphite and extent of oxidation of the resultant GO was observed. Small quantities of sulfur and nitrogen were also present in the GOs, and arose from covalently bondedo rganosulfates, inorganic sulfates, and/or residual adsorbed sulfuric and nitric acid during synthesis.…”

Synthesis, Structure, and Characterizations

“…In addition, due to the inherent defects and complexity of the structure, the precise oxidation mechanism in those reactions is hard to elucidate. Chen et al observed that the product from the highest crystallinity graphite offers best transport for electrons and holes [ 28 ]. Kim et al also prepared GO from three different graphite sources with modifi ed Hummer's method and observed disparities in sheet size distributions [ 30 ].…”