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

• Published in: The journal of physical chemistry letters 2011-09, Vol.2 (17), p.2236-2240
• Main Authors: Kutz, Robert B, Braunschweig, Björn, Mukherjee, Prabuddha, Dlott, Dana D, Wieckowski, Andrzej
• Format: Article
• Language: English
• Subjects: Surfaces, Interfaces, Catalysis
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/jz200957e

The ethanol electrooxidation 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 ∼0.45 V, which is 0.2 V lower than in acidic media. In order to track the oxidation of single-carbon intermediates, we have monitored the oxidation of isotopically labeled ethanol (12CH3 13CH2OH). Surface-adsorbed 12CO and 13CO are observed and show very different potential-dependent behaviors. 13CO molecules formed from preoxidized carbon species such as −CH x O, show the behavior expected from studies of CO-saturated alkaline media. 12CO, however, which is indicative of the oxidation of methyl-like species (−CH x ) on the catalyst surface, is observed at unusually high potentials. The strongly adsorbed −CH x is not oxidatively removed from the surface until the electrode potential is swept past 0.65 V.