On-Line Mass Spectrometry for Ethanol Oxidation on Well-Defined Sn/Pt(hkl) Electrode Surfaces

Onset potentials of ethanol oxidation reaction (EOR) and potential-dependent evolution of gaseous products from well-defined Sn/Pt(hkl) electrode surfaces were investigated. The electrode surfaces were prepared by vacuum deposition of Sn on a Pt(hkl) single-crystal substrate in ultra-high vacuum. The EOR onset potentials of anodic currents for Sn/Pt(hkl) shifted to lower potentials in comparison to unmodified Pt(hkl). Online electrochemical mass spectrometry (OLEMS) analysis of the gaseous products formed on the Sn/Pt(hkl) surfaces showed that acetaldehyde, rather than CO2, was generated at lower applied voltages and that the product evolution was sensitive to the atomic arrangement of the surface Pt (Pt(hkl)). EOR anodic current measurements and OLEMS analysis showed that EOR onset potential is the lowest for Sn/Pt(110). The findings can be attributed to the effectiveness of Pt(110) steps in ethanol C-C bond cleavage and an ensemble effect of the Pt and Sn atoms against CO poisoning.