Ethanol Oxidation on Well-Ordered PtSn Surface Alloy on Pt(111) Electrode

Surface and subsurface structures of PtSn surface alloy on Pt(111) were determined using in situ scanning tunneling microscopy (STM) and X-ray diffraction. Different ordered structures of the PtSn alloy layer were observed by STM in HClO 4 at coverage of θ Sn ≤ 0.23. Superstructure of (√3 × √7)R19.1° with small domain size was formed at θ Sn = 0.23. This structure promoted the catalytic activity for the ethanol oxidation reaction with high durability. X-ray structural analysis showed that the ratio of Sn in the subsurface was below 3(2)%, The PtSn alloy layer was mainly formed at the surface of the Pt(111) electrode. The Sn atoms protruded by 0.02 nm from the Pt layer, which was similar to the surface structure of Pt 3 Sn(111). One Pt atom in the (√3 × √7)R19.1° structure contacts to one or two surrounding Sn atoms, which lead to the highest activity for the EOR.