A Molecular Understanding of the Gas-Phase Reduction and Doping of Graphene Oxide

Chemical reduction of graphene oxide represents an important route towards large-scale production of graphene sheets for many applications. Thus far, gas-phase reactions have been demonstrated to efficiently reduce graphene oxide, but a molecular understanding of the reaction processes is largely lacking. Here, using molecular dynamics simulations, we compare the reduction of graphene oxide in different environments. We find that NH3 affords more efficient reduction of hydroxyl and epoxide groups than H-2 and vacuum annealing partly due to lower energy barriers. Various reduction paths of oxygen groups in NH3 and H-2 are quantitatively identified. Furthermore, we show that with the combination of vacancies and oxygen groups, pyridinic- or pyrrolic-like nitrogen can readily be incorporated into graphene. All of these nitrogen configurations lead to n-doping of the graphene. Our results are consistent with many previous experiments and provide insights towards doping engineering of graphene.