Structure and Bonding of the Water−Hydroxyl Mixed Phase on Pt(111)

Abstract

We combine low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and Auger electron spectroscopy (AES) with density functional theory (DFT) to reveal the structure and bonding of water−hydroxyl mixed layers adsorbed on Pt(111). We find that the stable water−hydroxyl adlayer forms a mixed phase of nearly coplanar hexamer structures resulting in (√3 × √3)R30° and (3 × 3) unit cells, respectively. In the asymmetric (3 × 3) structure the lateral O−O distances alternate between long and short bond lengths similar to the chemical bonding network for OH- ions in solution. The chemical driving force behind this similarity is discussed in a molecular orbital picture.