Single Faceted Two-Dimensional Mo2C Electrocatalyst for Highly Efficient Nitrogen Fixation

Electrocatalytic reduction of N-2 to NH3 under an ambient atmosphere is highly desirable and extremely critical for energy-efficient nitrogen utilization. Inspired by the natural MoFe protein-based enzyme, the nitrogenase, we exploited this electrochemical process with a unique two-dimensional catalyst, namely, molybdenum carbide (Mo2C). The catalyst is synthesized through a chemical vapor deposition method, with a highly orientated (200) facet of the alpha-Mo2C phase. A remarkable Faradaic efficiency as high as 40.2% has been achieved on the (200) faceted alpha-Mo2C during the nitrogen reduction reaction (NRR). Density functional theory calculations confirm that rate-determining steps *NNH2 -> NNH3 and *NH -> *NH2 experience a low energy barrier on the (200) surface following the proton-electron coupled, distal associated mechanism. To protect Mo from leaching during the NRR process, we also grew layers of graphene on top of Mo2C, forming a chemically enduring two-dimensional heterostructured electrode.