Li insertion in sol-gel prepared Mn-doped TiO2 studied by electron spectroscopy in ultrahigh vacuum

The properties of a sol-gel prepared Mn-modified TiO2 film have been studied with X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy (PES) using synchrotron radiation. The chemical composition and oxidation state of the elements have been determined. The manganese content estimated by PES of the Mn-modified film is about 10% and both Mn2+ and Mn3+ are observed. Addition of Mn is found to modify the valence band edge. The Mn 3d states are found to extend about 1 eV into the TiO 2 band gap region. It is demonstrated that lithium insertion into the sol-gel film can be performed in a stepwise fashion in situ under ultrahigh vacuum (UHV) conditions. Lithium is distributed evenly throughout the entire film and leads to reduction of Mn3+ to Mn2+ followed by reduction of Ti4+ to Ti3+. The XAS and PES measurements give fully consistent results regarding the amount of inserted lithium.