Termination-Accelerated Electrochemical Nitrogen Fixation on Single-Atom Catalysts Supported by MXenes.

The synthesis of ammonia (NH 3 ) from nitrogen (N 2 ) under ambient conditions is of great significance but hindered by the lack of highly efficient catalysts. By performing first-principles calculations, we have investigated the feasibility for employing a transition metal (TM) atom, supported on Ti 3 C 2 T 2 MXene with O/OH terminations, as a single-atom catalyst (SAC) for electrochemical nitrogen reduction. The potential catalytic performance of TM single atoms is evaluated by their adsorption behavior on the MXene, together with their ability to bind N 2 and to desorb NH 3 molecules. Of importance, the OH terminations on Ti 3 C 2 T 2 MXene can effectively enhance the N 2 adsorption and decrease the NH 3 adsorption for single atoms. Based on proposed criteria for promising SACs, our calculations further demonstrate that the Ni/Ti 3 C 2 O 0.19 (OH) 1.81 exhibits reasonable thermodynamics and kinetics toward electrochemical nitrogen reduction.