Abstract
Excessive emission of CO2 has caused a critical greenhouse effect that is emerging as a major threat to the environment. Electrocatalytic reduction of CO2 is an advanced technology where chemically inert CO2 is reduced and can be used to produce value-added fuels or chemicals. In this work, the electrocatalytic performance of a single Cu atom embedded in a MoS2 monolayer with a sulfur vacancy for the electroreduction of CO2 is studied using density functional theory (DFT) with dispersion correction. The single Cu atom is stably located in the sulfur vacancy of the MoS2 monolayer. The multiple pathways explored here involve proton-electron pair transfer in the CO2 reduction reaction (CO2RR) to yield a variety of C1 products, such as HCOOH, CO, CH3OH and CH4. These pathways were examined using the corresponding free energy profiles and overpotentials. Among the different C1 products, CH4 formation is more favored via the following optimized pathway: *CO2 -> *OCHO -> *OCHOH -> *OCH2OH -> *OCH2 -> *OCH3 -> *OHCH3 -> *OH + CH4 -> H2O. The MoS2 monolayer with embedded Cu has enhanced CO2RR activity with an appreciably low overpotential compared to pristine MoS2. This study provides a deep understanding of the structure-reaction relationships and various mechanistic pathways of the CO2RR, and could aid in the design of high-performance single-atom electrocatalysts.