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

The synthesis of ammonia (NH₃) from nitrogen (N₂) 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 Ti₃C₂T₂ 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 N₂ and to desorb NH₃ molecules. Of importance, the OH terminations on Ti₃C₂T₂ MXene can effectively enhance the N₂ adsorption and decrease the NH₃ adsorption for single atoms. Based on proposed criteria for promising SACs, our calculations further demonstrate that the Ni/Ti₃C₂O_0.19(OH)_1.81 exhibits reasonable thermodynamics and kinetics toward electrochemical nitrogen reduction.