Non-Transition-Metal Catalytic System for N2 Reduction to NH3: A Density Functional Theory Study of Al-Doped Graphene

The prevalent catalysts for natural and artificial N 2 fixation are known to hinge upon transition-metal (TM) elements. Herein, we demonstrate by density functional theory that Al-doped graphene is a potential non-TM catalyst to convert N 2 to NH 3 in the presence of relatively mild proton/electron sources. In the integrated structure of the catalyst, the Al atom serves as a binding site and catalytic center while the graphene framework serves as an electron buffer during the successive proton/electron additions to N 2 and its various downstream N x H y intermediates. The initial hydrogenation of N 2 can readily take place via an internal H-transfer process with the assistance of a Li + ion as an additive. In view of the recurrence of H transfer in the first step of N 2 reduction observed in biological nitrogenases and other synthetic catalysts, this finding highlights the significance of heteroatom-assisted H transfer in the design of synthetic catalysts for N 2 fixation.