Single atom-supported MXene: how single-atomic-site catalysts tune the high activity and selectivity of electrochemical nitrogen fixation

A central topic for the electrocatalytic N 2 reduction reaction (ENRR) lies in the search for facile electrocatalysts under ambient conditions. Inspired by recent works on stabilizing single atoms with Ti 3 C 2 T x MXene nanosheets, herein, we designed a series of single atoms supported on Ti 2 CO 2 and Mo 2 CO 2 MXene monolayers as efficient electrocatalysts for the ENRR by a well-defined first-principles calculation. Our calculation results revealed that single Ru or Mo atom anchored Mo 2 CO 2 or Ti 2 CO 2 possessed high ENRR activity, and the calculated limiting potentials of Ti 2 CO 2 were more negative than those of Mo 2 CO 2 due to the high conductivity of Mo 2 CO 2 . Moreover, N 2 can be efficiently reduced to NH 3 on Ti@Mo 2 CO 2 via different reaction mechanisms with a record limiting potential (−0.64 V). Furthermore, the activity and selectivity of the ENRR on Mo@Mo 2 CO 2 were evaluated by comparing the Gibbs free energy of each dinitrogen and hydrogen as well as the first dinitrogen protonation and hydrogen adsorption. We found that N 2 reduction proceeds via a distal or hybrid mechanism with an overpotential down to 0.16 or 0.19 V, indicating Mo@Mo 2 CO 2 as a robust electrocatalyst for the ENRR. This work opens up an exciting new avenue for the rational design of high-efficiency MXene-based nanocomposites for artificial N 2 fixation. A series of single atom supported on Ti 2 CO 2 and Mo 2 CO 2 MXenes were systematically explored as efficient electrocatalysts for electro-catalytic N 2 reduction. We demonstrate that Ru and Mo atoms anchored MXenes are highly activity.