PNAS Plus Significance Statements

Chemical storage of solar energy can be achieved by electrochemical reduction of CO2 to CO and H2, and subsequent conversion of this mixture to fuels. Identifying optimal conditions for electrochemical cell operation requires knowledge of the CO2 reduction mechanism and the influence of all factors controlling cell performance. We report a multiscale model for predicting the current densities for H2 and CO formation from first principles. Our approach brings together a quantum-chemical analysis of the reaction pathway, a microkinetic model of the reaction dynamics, and a continuum model for mass transport of all species through the electrolyte. This model is essential for identifying a physically correct representation of product current densities dependence on the cell voltage and CO2 partial pressure. (See pp. E8812–E8821.)