Bonding Mechanism and Atomic Geometry of an Ordered Hydroxyl Overlayer on Pt(111)

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Abstract
Exposing water to a (2 × 2)−O precovered Pt(111) surface at 100 K and subsequently annealing at 155 K led to the formation of a well-ordered (√3 × √3)R30° overlayer. The structure of this overlayer is determined by DFT and full dynamical LEED calculations. There are two O containing groups per (√3 × √3)R30° unit cell and both occupy near on-top positions with a Pt−O bond length of (2.11 ± 0.04) Å. DFT calculations determined the hydrogen positions of the OH species and clearly indicate hydrogen bonds between the neighboring adsorbed OH groups whose interaction is mainly of electrostatic nature. A theoretical comparison with H2O shows the hybridization of OH on Pt(111) to be sp3.