Surface electrochemistry of CO on Pt(110)-(1x2) and Pt(110)-(1x1) surfaces

A new type of flame-annealing method has been developed for the preparation of surfaces having either fcc(110)-(1x1) or fcc(110)-(1 x 2) symmetry. In situ X-ray scattering studies show that both the Pt(110)-(1 x 2) and Pt(110)-(1 x 1) surfaces are stable in the potential region between 0 and 1.0 V. Adsorption of CO on the (1 x 2) surface in solution does not induce the (1 x 2)-->(1 x 1) transition that is observed in UHV upon adsorption of CO. Nominally identical saturation coverages of hydrogen (H-upd) and COad are observed on the two surfaces, implying that two H-upd atoms or two COad molecules are adsorbed per unit cell of the reconstructed (1 x 2) surface. A significant increase in the interatomic spacing between the first and second layer of the reconstructed (1 x 2) surface occurs upon hydrogen adsorption to full coverage. Occupation of subsurface sites for H-upd are inferred from this result. The (1 x 2) surface is found to have a much higher catalytic activity for the electro-oxidation of CO; the anodic oxidation of either COad or dissolved COgas occurs at approximate to 0.3 V lower potential on the (1 x 2) than the (1 x 1) surface. (C) 1997 Elsevier Science B.V.