Hydrogen bonding steers the product selectivity of electrocatalytic CO reduction

Significance Many technologically interesting electrocatalytic reactions lead to a variety of products; that is, they exhibit poor product selectivity. Examples include the oxidations of ammonia and methane and the reductions of nitrogen and carbon dioxide. The poor selectivity hinders the adoption of these promising technologies. Improving the selectivity requires a molecular-level understanding of the factors that control these reaction processes. Herein, we investigated how the liquid reaction environment impacts the selectivity of the reduction of CO to ethylene, a prototypical process for multielectron–proton transfer reactions. We show that the intermolecular interaction between surface-adsorbed CO and interfacial water is critical for the formation of ethylene. This mechanistic insight is expected to guide the design of electrocatalytic interfaces with high product selectivity.