Synergizing Mo Single Atoms and Mo2C Nanoparticles on CNTs Synchronizes Selectivity and Activity of Electrocatalytic N2 Reduction to Ammonia

Previous research of molybdenum-based electrocatalysts for nitrogen reduction reaction (NRR) has been largely considered on either isolated Mo single atoms (MoSAs) or Mo carbide particles (e.g., Mo2 C) separately, while an integrated synergy (MoSAs-Mo2 C) of the two has never been considered. The theoretical calculations show that the Mo single atoms and Mo2 C nanoparticles exhibit, respectively, different catalytic hydrogen evolution reaction and NRR selectivity. Therefore, a new role-playing synergistic mechanism can be well enabled for the multistep NRR, when the two are combined on the same N-doped carbon nanotubes (NCNTs). This hypothesis is confirmed experimentally, where the MoSAs-Mo2 C assembled on NCNTs (MoSAs-Mo2 C/NCNTs) yields an ammonia formation rate of 16.1 µg h-1 cmcat-2 at -0.25 V versus reversible hydrogen electrode, which is about four times that by the Mo2 C alone (Mo2 C/NCNTs) and 4.5 times that by the MoSAs alone (MoSAs/NCNTs). Moreover, the Faradic efficiency of the MoSAs-Mo2 C/NCNTs is raised up to twofold and sevenfold of the Mo2 C/NCNTs and MoSAs/NCNTs, respectively. The MoSAs-Mo2 C/NCNTs also demonstrate outstanding stability by the almost unchanged catalytic performance over 10 h of the chronoamperometric test. The present study provides a promising new prototype of synchronizing the selectivity and activity for the multistep catalytic reactions.