(124d) The Role of Surface Roughening in Improving the Selectivity of Copper for CO2 Electroreduction

Roughened copper electrodes, including those derived from cuprous oxide, have long been known to exhibit enhanced selectivity to C2+ products during CO2 electroreduction. However, the source of this enhancement has yet to be mechanistically rationalized. In this work, we present a theoretical study of roughened copper electrodes derived from cuprous oxide, phosphide, nitride, and sulfide. We utilize a carefully benchmarked effective medium theory potential to develop geometric models of the roughened electrodes on an unprecedented scale. Using semi-local density functional theory in conjunction with an implicit electrolyte representation, we determine binding energy distributions for several important reaction intermediates on each surface as a function of applied bias. We apply simple thermodynamic models to evaluate the role of surface roughening on selectivity among C1 and C2 products during CO2 electroreduction. Importantly, we find that moderately low index single crystal models lack the resolution necessary to reasonably reproduce the binding energies found on roughened electrodes, highlighting the need for careful experimentation when comparing to theory.