The Selectivity Origins in Ag-Catalyzed CO 2 Electroreduction.

Ag exhibits high selectivity of electrochemical CO 2 reduction (CO 2 R) toward C 1 products, while the hydrogenation involving the concerted proton-electron transfer (CPET) or sequential electron-proton transfer (SEPT) mechanism is still in debate. Toward a better understanding of the Ag-catalyzed electrochemical CO 2 R, we employed a microkinetic model based on the Marcus electron transfer theory to thoroughly investigate the selectivity of C 1 products of electrochemical CO 2 R over the Ag(111) surface. We found that at an acidic condition of pH = 1.94, formate is the main product when U < -0.94 V via the CPET mechanism, whereas CO becomes the primary product when U > -0.94 V via the SEPT mechanism. Conversely, at an alkaline condition of pH = 13.95, formate is the main product following the SEPT mechanism. Our findings provide novel insights into the influence of external factors (applied potential and pH) on the product selectivity and hydrogenation mechanism of electrochemical CO 2 R.