CO Oxidation on Electrified Platinum Surfaces in Acetonitrile/Water Solutions Studied by Sum Frequency Generation and Cyclic Voltammetry

Sum frequency generation (SFG) vibrational spectroscopy in combination with cyclic voltammetry (CV) was used to investigate the oxidation of carbon monoxide (CO) in acetonitrile (CH3CN)/water (H2O) solutions at the platinum (Pt) electrode surface. CO oxidation on Pt was studied as a function of water concentration and electrode potential. In electrolyte solutions containing small concentrations of water, a preoxidation wave was observed at +900 mV vs SCE whereby a small amount of the adsorbed CO was oxidized. This preoxidation wave was followed by the main oxidation of CO on Pt at approximately +1700 mV vs SCE. Spectroscopy and voltammetry data in these essentially nonaqueous electrolytes indicate an oxidation intermediate of CO to CO2 that was nearly parallel to the Pt electrode surface.