Anatase-Selective Photoluminescence Spectroscopy of P25 TiO₂ Nanoparticles: Different Effects of Oxygen Adsorption on the Band Bending of Anatase

Abstract

Photoluminescence (PL) spectroscopy was used to infer that oxygen adsorption changes the band bending of the anatase phase of TiO2 within P25 nanopowder in different ways. On the one hand, oxygen can adsorb through irreversible reaction with defects which reduces the intrinsic upward band bending at the TiO2 surface and results in increased PL emission. On the other hand, oxygen exposure also leads to molecular chemisorption that yields an outermost negative charge at the surface which increases the upward band bending of TiO2 and decreases the PL emission. Since band bending plays an active role in directing charge carrier migration to the surface, the finding that oxygen adsorption can have two different, and quite opposite, effects on the band bending of TiO2 provides a new perspective on how oxygen may influence photocatalytic reaction efficiencies.