Comprehensive Mechanism of CO2 Electroreduction on Non-Noble Metal Single-Atom Catalysts of Mo2CS2-MXene

In this work, a series of non-noble metal single-atom catalysts of Mo2CS2-MXene for CO2 reduction were systematically investigated by well-defined density-functional-theory (DFT) calculations. It is found that nine types of transitional metal (TM) supported Mo2CS2 (TM-Mo2CS2) are very stable, while eight can effectively inhibit the competitive hydrogen evolution reaction (HER). After comprehensively comparing the changes of free energy for each pathway in CO2 reduction reaction (CO2RR), it is found that the products of TM-Mo2CS2 are not completely CH4. Furthermore, Cr-, Fe-, Co- and Ni-Mo2CS2 are found to render excellent CO2RR catalytic activity, and their limiting potentials are in the range of 0.245-0.304 V. In particular, Fe-Mo2CS2 with a nitrogenase-like structure has the lowest limiting potential and the highest electrocatalytic activity. Ab initio molecular dynamics (AIMD) simulations have also proven that these kinds of single-atom catalysts with robust performance could exist stably at room temperature. Therefore, these single TM atoms anchored on the surface of MXenes can be profiled as a promising catalyst for the electrochemical reduction of CO2.