Development of novel photoelectrode materials with improved charge separation properties

![CDATA[This investigation was aimed at identifying the scope for exploiting segregation phenomena to improve the ability of doped TiO2 to separate photo-generated charge carriers. By applying several controlled conditions of temperature and oxygen activity during the annealing of Nb-doped TiO2 (0.65 at.%), compositional gradients were imposed within the surface and nearsurface regions due to solute segregation. These compositional gradients were characterised using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), and then tested for charge separation abilities using surface photovoltage spectroscopy (SPS). This investigation has revealed that processing Nb-doped TiO2 under conditions that favour the depletion of Nb from the surface and near-surface region yields stronger charge separation. While this is attributed to the formation of a homo-junction that is providing additional driving force for charge separation, the altered impact of Nb5+ and related defect disorder may also play a role. This investigation has provided encouraging preliminary outcomes to stimulate further investigations.]]