Oxygen-induced changes to selectivity-determining steps in electrocatalytic CO2 reduction

Abstract

The state of the electrocatalyst surface—including the oxidation state of the catalyst and the presence of spectator species—is investigated on Cu surfaces with density functional theory in order to understand predicted ramifications on the selectivity and efficiency of CO₂ reduction. We examined the presence of oxygen-based species, including the fully oxidized Cu₂O surface, the partially oxidized Cu(110)–(2 × 1)O surface, and the presence of OH spectators. The relative oxygen binding strength among these surfaces can help to explain the experimentally observed selectivity change between CH₄ and CH₃OH on these electrodes; this suggests that the oxygen-binding strength may be a key parameter which predicts the thermodynamically preferred selectivity for pathways proceeding through a methoxy (CH₃O) intermediate. This study shows the importance of the local surface environment in the product selectivity of electrocatalysis, and suggests a simple descriptor that can aid in the design of improved electrocatalytic materials.