Graphene Oxide-Supported Transition Metal Catalysts for Di-Nitrogen Reduction

Developing single metal atom catalysts with high stability and efficiency for the electroreduction of dinitrogen (N-2) to ammonia (NH3) has attracted extensive attention but remains a challenge. In this work, we employed density functional theory calculations to design the first graphene oxide (GO)-supported transition metal catalysts (TM@GO) for N-2 fixation. Both single TM atoms and trimers (TM = Pt, Cu, Ni, and Co) are considered. The calculated results show that owing to the active sites provided by the epoxy functional group, GO can serve as an ideal substrate to stabilize TM atoms, as it affords larger binding energies and higher diffusion barriers, compared to pristine graphene. The strong interaction of TMs with GO is ascribed to the large polarization of the positive charges on deposited TM atoms. Deposited TM3 trimers possess higher stability than single TM atoms. Interestingly, Ni-3@GO exhibits the highest electrocatalytic activity for converting N-2 to NH3 among the TM atoms considered. The predicted reaction pathways show that the reduction of N-2 to NH3 at deposited TMs follows a Heyrovsky associative rather than a dissociative mechanism.