Study of Ethanol Electrooxidation in Alkaline Electrolytes with Isotope Labels and Sum-Frequency Generation

The ethanol electrococidation reaction (EOR) on polycrystalline Pt catalysts in alkaline solution was studied for the first time with broadband sum-frequency generation (BB-SFG) spectroscopy. We find that C-C bond cleavage and CO formation occur as early as 0.05 V versus reversible hydrogen electrode (RHE), and that CO is oxidized at similar to 0.45 V, which is 0.2 V lower than in acidic media. In order to track the oxidation of singlecarbon intermediates, we have monitored the oxidation of isotopically labeled ethanol ((CH3)-C-12 (CH2OH)-C-13). Surface-adsorbed (CO)-C-12 and (CO)-C-13 are observed and show very different potential-dependent behaviors. (CO)-C-13 molecules formed from preoxidized carbon species such as -CHxO, show the behavior expected from studies of CO-saturated alkaline media. (CO)-C-12, however, which is indicative of the oxidation of methyl-like species (-CHx) on the catalyst surface, is observed at unusually high potentials. The strongly adsorbed -CHx is not oixdatively removed from the surface until the electrode potential is swept past 0.65 V.