Reaction mechanisms for reduction of CO2 to CO on monolayer MoS2

Since the reduction of CO2 to fuels by consuming over-generated electricity, which can establish artificial carbon cycle and energy storage at the same time, extensive studies have been devoted to developing suitable catalysts for CO2 conversion in materials science. Recently, MoS2, a typical member of transition metal dichalcogenides, has been widely investigated for its high activity and low energy cost to catalyze CO2 reduction. In this work, we simulate the microscopic dynamic process of the CO2 reduction process in the framework of density functional theory (DFT). Our results reveal that Mo exposed edges of MoS2 are inclined to adsorb CO2 molecule and tend to catalytically reduce CO2 to CO. CO2 molecule is activated by two neighboring Mo atoms and the C-O double bond reconstructs in the adsorption process. The first proton/electron (H+ + e(-)) reaction taking place at MoS2 edges undergoes a different pathway from that on transition metal catalyst, contributing to the product selectivity towards CO. Finally, we demonstrate that desorption of CO from MoS2 edges is in virtue of unique diffusion process for adsorbed CO atoms.