Photoinduced Dynamics at the Water/TiO_{2}(101) Interface.

We present a femtosecond time-resolved optical pump-soft x-ray probe photoemission study in which we follow the dynamics of charge transfer at the interface of water and anatase TiO_{2}(101). By combining our observation of transient oxygen O 1s core level peak shifts at submonolayer water coverages with Ehrenfest molecular dynamics simulations we find that ultrafast interfacial hole transfer from TiO_{2} to molecularly adsorbed water is completed within the 285 fs time resolution of the experiment. This is facilitated by the formation of a new hydrogen bond between an O_{2c} site at the surface and a physisorbed water molecule.

Reversible Ultrathin PtO Formation at the Buried Pt/YSZ(111) Interface Studied In Situ under Electrochemical Polarization.

Three different platinum oxides are observed by in situ X-ray diffraction during electrochemical potential cycles of platinum thin film model electrodes on yttria-stabilized zirconia (YSZ) at a temperature of 702 K in air. Scanning electron microscopy and atomic force microscopy performed before and after the in situ electrochemical X-ray experiments indicate that approximately 20% of the platinum electrode has locally delaminated from the substrate by forming pyramidlike blisters. The oxides and their locations are identified as (1) an ultrathin PtO at the buried Pt/YSZ interface, which forms reversibly upon anodic polarization; (2) polycrystalline β-PtO, which forms irreversibly upon anodic polarization on the inside of the blisters; and (3) an ultrathin α-PtO at the Pt/air interface, which forms by thermal oxidation and which does not depend on the electrochemical polarization.