Probing Cation Effects on *CO Intermediates from Electroreduction of CO through Operando Raman Spectroscopy.

Cations in an electrolyte modulate microenvironments near the catalyst surface and affect product distribution from an electrochemical CO reduction reaction, and thus, their interaction with intermediate states has been tried to be probed. Herein, we directly observed the cation effect on *CO intermediates on the Cu(OH)-derived catalyst in real time through operando surface-enhanced Raman spectroscopy at high overpotentials (-1.0 V).