Electric Field Effects in Electrochemical CO 2 Reduction

Electrochemical reduction of CO 2 has the potential to reduce greenhouse gas emissions while providing energy storage and producing chemical feedstocks. A mechanistic understanding of the process is crucial to the discovery of efficient catalysts, and an atomistic description of the electrochemical interface is a major challenge due to its complexity. Here, we examine the CO 2 → CO electrocatalytic pathway on Ag(111) using density functional theory (DFT) calculations and an explicit model of the electrochemical interface. We show that the electric field from solvated cations in the double layer and their corresponding image charges on the metal surface significantly stabilizes key intermediates—*CO 2 and *COOH. At the field-stabilized sites, the formation of *CO is rate-determining. We present a microkinetic model that incorporates field effects and electrochemical barriers from ab initio calculations. The computed polarization curves show reasonable agreement with experiment without fitting any parameters.