Unveiling Electrochemical Reaction Pathways of CO2 Reduction to CN Species at S-Vacancies of MoS2.

Although C1 species such as CO and CH4 constitute the majority of CO2 reduction (CO2  R) products on known catalysts, recent experiments showed that 1-propanol with two C-C bonds is produced as the main CO2  R product on MoS2 single crystals in aqueous electrolytes. Herein, the CO2  R mechanism on MoS2 is investigated by using first-principle calculations. Focusing on S-vacancies (VS ) as the catalytic site, potential free-energy pathways to various CO2  R products are obtained by means of a computational hydrogen electrode model. The results underline the role of HCHO, which is one of the elemental C1 products, in opening pathways to CN species for N>1. Key steps to increase C-C bonds are the adsorption of HCHO at the VS site and binding of another HCHO to the adsorbed one. The predicted products and theoretical working potentials to open their pathways are consistent with experiments, which indicates that VS is an important active site for CO2  R on the MoS2 basal plane.