Reaction pathways of ethanol electrooxidation on polycrystalline platinum catalysts in acidic electrolytes
2011
Kutz, Robert B. | Braunschweig, Björn | Mukherjee, Prabuddha | Behrens, Rachel L. | Dlott, Dana D. | Więckowski, Andrzej
Ethanol electrooxidation reaction (EOR) pathways on polycrystalline platinum were studied with broadband sum-frequency generation (BB-SFG) spectroscopy and electrochemistry in unprecedented detail and under working fuel cell conditions. We present the first observation of adsorbed acetate and co-adsorbed sulfuric acid anions with SFG and a discussion of their relation to the EOR. Surface-adsorbed intermediates such as CO on Pt atop sites and acetate are observed in both H₂SO₄ and HClO₄ solutions. However, CO molecules on bridge sites and sulfuric acid anions are found in H₂SO₄ only. At E<0.5V vs. Ag/AgCl, CO is the predominantly adsorbed species. Increasing the potential to E>0.5V results in the oxidative removal of CO and the adsorption of acetate anions. Experiments with isotopically labeled ethanol (¹²CH₃ ¹³CH₂OH) reveal information on the carbon–carbon bond cleavage and the subsequent CO formation. In particular, the methyl fragment (–¹²CHₓ) produces far less ¹²CO and suggests methyl electroreduction to methane and/or the persistence of –CHₓ on the Pt surface.
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