Abstract
The presence of alkali metal cations in the electrolyte substantially affects the reactivity and selectivity of electrochemical carbon dioxide (CO(2)) reduction (CO(2)R). This study examines the role of cations in CO(2)R on single-crystal and polycrystalline Au under controlled mass-transport conditions. It establishes that CO(2) adsorption is the rate-determining step regardless of cation type or surface structure. Density functional theory calculations show that electron transfer occurs to a solvated CO(2)-cation complex. A more positive potential of zero charge enhances CO(2)R activity only on Au with similar surface coordination. The symmetry factor (β) of the rate-determining step varies with surface structure and cation identity, with density functional theory calculations indicating β's sensitivity to surface and double-layer structures. These findings emphasize the importance of both surface and double-layer structures in understanding cation effects on CO(2)R.