Unveiling Electrochemical Reaction Pathways of CO 2 Reduction to C N Species at S‐Vacancies of MoS 2

Although C 1 species such as CO and CH 4 constitute the majority of CO 2 reduction (CO 2  R) products on known catalysts, recent experiments showed that 1‐propanol with two C−C bonds is produced as the main CO 2  R product on MoS 2 single crystals in aqueous electrolytes. Herein, the CO 2  R mechanism on MoS 2 is investigated by using first‐principle calculations. Focusing on S‐vacancies ( V S ) as the catalytic site, potential free‐energy pathways to various CO 2  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 C 1 products, in opening pathways to C N species for N >1. Key steps to increase C−C bonds are the adsorption of HCHO at the V S 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 V S is an important active site for CO 2  R on the MoS 2 basal plane.