(228h) Identification of a Single-Atom Catalyst for Electrochemical Ammonia Synthesis Based on Transition Metal Doped Graphene-like GaN

The discovery of nitrogen reduction reaction (NRR) electrocatalysts with low overpotential and high selectivity towards ammonia could enable sustainable ammonia production. Although tremendous effort has been devoted to optimizing electrocatalysts for this reaction, candidates satisfying the above two characteristics under ambient conditions remain elusive. Via density functional theory with a semi-empirical dispersion correction and a mixed implicit plus explicit water solvation model, we evaluate the possibility of using a single-transition-metal (TM)-atom-doped graphene-like GaN (g-GaN) monolayer as an electrocatalyst for artificial nitrogen reduction. Our preliminary screening, based on adsorption of three key species namely, N₂, ^*NNH and ^*NH₂, suggests that, among 15 TMs investigated, the Mo-doped g-GaN (Mo@g-GaN) monolayer is the most promising. We followed this analysis by investigating possible NRR mechanisms on this Mo-based catalyst. We predict this catalyst to achieve a low overpotential of 0.42 V. Furthermore, we predict this catalyst to exhibit unprecedented selectivity toward ammonia synthesis over the competing hydrogen evolution reaction. Our study thus opens a new route for finding new artificial ammonia synthesis electrocatalysts based on single-atom catalysts.