(472d) DFT Studies of Electrochemical Reduction of CO2 On Cu Electrodes
Electrocatalytic reduction of CO2 to alcohols would provide a synthetic sustainable way to convert renewable energy sources to transport fuels, however, large overpotentials and inability to control product selectivity are significant barriers to application. To date only Cu electrodes have shown significant hydrocarbon products but at relatively high overpotentials. Interestingly, methane and ethylene are the dominant products instead of methanol. Furthermore, the product distribution is sensitive to the Cu facet and morphology. Understanding these selectivity features and identifying the key reaction steps for CO2 reduction on Cu electrodes will be an important step in designing improved catalysts. We will report the results of a systematic density functional theory (DFT) study to evaluate the potential-dependent barriers of elementary steps for CO2electroreduction on the Cu(111) surface that incorporates the role of water solvation in a computationally tractable manner.
We find that O–H bond formation reactions occur through water-assisted H-shuttling, whereas C–H bond formation occurs via direct bonding with adsorbed H on the Cu(111) surface with negligible H2O involvement. Furthermore, CO reduction to COH or CHO intermediate is the key selectivity step for production of methane/ethylene over methanol. Methane formation goes through a COH intermediate, which eventually reduces to CHx species that can produce both methane and ethylene as observed experimentally. We will also present ongoing work on the impact of additional solvation, other copper facets and step edges, coverage effects, as well as exploring other potential materials for CO2 electrocatalytic reduction.