EFFECTS OF IODINE COATING AND DESORPTION ON THE RECONSTRUCTION OF A PT(110) ELECTRODE - A SCANNING-TUNNELING-MICROSCOPY STUDY

The structure of iodine adsorbed on a Pt(110) surface, formed by flame -annealing of the platinum crystal and quenching in iodine vapour, was investigated by scanning tunnelling microscopy (STM) in air and elect rolyte solutions. We find that the (1 x 2) reconstruction is lifted an d that a new structure is formed, characterized by a fourfold periodic ity in [1(1) over bar0$] and extended rows in the [001] direction and a pronounced elongation of steps in the [001] direction. The STM data are in accord with the (4 x 1) low-energy electron diffraction pattern recorded after transfer of the sample to ultra-high vacuum. In H2SO4 and NaOH solutions the iodine was desorbed at negative potentials, res ulting in an unreconstructed (1 x 1) surface and a change in surface t opography towards small rectangular, more isotropic terraces.