| Abstract
| - Charge migration between electron trapping sites within the mixed-phase titania photocatalyst Degussa P25has been studied. In addition to previously described lattice electron trapping sites on both anatase and rutilephases, surface electron trapping sites and an anatase−rutile interface trapping site specific to Degussa P25are identified. The relationship between these sites and recombination with surface hole trapping sites is alsodetermined. It is experimentally shown that upon band-gap illumination holes appear at the surface andpreferentially recombine with electrons in surface trapping sites. These findings indicate that in mixed-phaseTiO2, such as Degussa P25, photogenerated holes are trapped exclusively on the particle surface, whilephotogenerated electrons are trapped within the nanoparticle lattice. Recombination reactions are dominatedby surface reactions that follow charge migration. These findings indicate that, in mixed-phase TiO2, such asDegussa P25, a random flight mechanism of recombination predominates. Such knowledge simplifies themechanistic mathematical models used for process design and points the way for improving future oxidativetitania catalysts.
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