Molecular understanding of the critical role of alkali metal cations in initiating CO 2 electroreduction on Cu(100) surface.

Molecular understanding of the solid-liquid interface is challenging but essential to elucidate the role of the environment on the kinetics of electrochemical reactions. Alkali metal cations (M ⁺ ), as a vital component at the interface, are found to be necessary for the initiation of carbon dioxide reduction reaction (CO ₂ RR) on coinage metals, and the activity and selectivity of CO ₂ RR could be further enhanced with the cation changing from Li ⁺ to Cs ⁺ , while the underlying mechanisms are not well understood. Herein, using ab initio molecular dynamics simulations with explicit solvation and enhanced sampling methods, we systematically investigate the role of M ⁺ in CO ₂ RR on Cu surface. A monotonically decreasing CO ₂ activation barrier is obtained from Li ⁺ to Cs ⁺ , which is attributed to the different coordination abilities of M ⁺ with *CO ₂ . Furthermore, we show that the competing hydrogen evolution reaction must be considered simultaneously to understand the crucial role of alkali metal cations in CO ₂ RR on Cu surfaces, where H ⁺ is repelled from the interface and constrained by M ⁺ . Our results provide significant insights into the design of electrochemical environments and highlight the importance of explicitly including the solvation and competing reactions in theoretical simulations of CO ₂ RR.
(© 2024. The Author(s).)