Surface chemistry of reduced graphene oxide: H-atom transfer reactions

Highlights: • Ab initio simulations of the surface of reduced graphene oxide were carried out. • The goal was to study formation of good leaving groups (GLG): CO, CO₂, H₂O etc. • The dynamical simulations were initiated at 300 K as well as at 1373 K. • It was established that the reactions of H-atom transfer enhanced formation of GLG. In the present work, the surface chemistry of reduced graphene oxide, modified with hydrocarbon, hydroxyl, aldehyde and carboxyl groups is studied by means of computational chemistry. The simulations by ab-initio molecular dynamics show that the reactions depend on the proximity of chemical groups and possibilities for H-atom transfer and gas evolution. Defects in close proximity can also promote certain reactions, especially in case of good leaving groups as products (CO₂, H₂O, CH₃OH, CO). Parts of the surface, rich in sp² carbon atoms (i.e. regular graphene surface) can significantly decrease the scission energy of CC bonds from the leaving groups, compared to gas phase ethane molecule or to the corresponding CC- bonds located at the edge (or defect) of the two-dimensional carbon material. This effect is caused by the unpaired electron, formed after bond dissociation, joining the global π system and restoring of the regular graphene structure. Decarboxylation reactions are found to be energetically favorable at both edge and surface. Generally, reactions at the edge are found to be disfavored energetically if they involve the participation of a C atom from the surface of the two-dimensional carbon material.