A unifying mechanism for cation effect modulating C1 and C2 productions from CO 2 electroreduction.

Electrocatalysis, whose reaction venue locates at the catalyst-electrolyte interface, is controlled by the electron transfer across the electric double layer, envisaging a mechanistic link between the electron transfer rate and the electric double layer structure. A fine example is in the CO 2 reduction reaction, of which rate shows a strong dependence on the alkali metal cation (M + ) identity, but there is yet to be a unified molecular picture for that. Using quantum-mechanics-based atom-scale simulation, we herein scrutinize the M + -coupling capability to possible intermediates, and establish H + - and M + -associated ET mechanisms for CH 4 and CO/C 2 H 4 formations, respectively. These theoretical scenarios are successfully underpinned by Nernstian shifts of polarization curves with the H + or M + concentrations and the first-order kinetics of CO/C 2 H 4 formation on the electrode surface charge density. Our finding further rationalizes the merit of using Nafion-coated electrode for enhanced C2 production in terms of enhanced surface charge density.