Investigation of the titaniumdioxide–aqueous solution interface using XPS and cryogenics

The sorption of Na+ and Cl− electrolyte ions from an aqueous solution onto single crystal TiO2 has been the subject of an investigation using XPS in combination with in situ cryogenics. In particular the samples were decontaminated from adventitious carbon by annealing at 600 °C prior to the exposure to aqueous solution. Further, the subsequent transfer of the sample to the spectrometer was performed in a liquid nitrogen filled hollow sample holder in order to preserve the chemistry and structure at the sample surface. The presence of an ionic layer consisting of H2O, Na+ and Cl− has been confirmed using angular dependent XPS, where the electrolyte ions are distributed in at least 2–3 monolayers.