Surface Density-of-States Engineering of Anatase TiO₂ by Small Polyols for Enhanced Visible-Light Photocurrent...

Enhancement of visible-light photocurrent generation by sol-gel anatase TiO₂ films was achieved by binding small polyol molecules to the TiO₂ surface. Binding ethylene glycol onto the surface, enhancement factors up to 2.8 were found in visible-light photocurrent generation experiments. Density functional theory calculations identified midgap energy states that emerge as a result of the binding of a range of polyols to the TiO₂ surface. The presence and energy of the midgap state is predicted to depend sensitively on the structure of the polyol, correlating well with the photocurrent generation results. Together, these results suggest a new, facile, and cost-effective route to precise surface band gap engineering of TiO₂ toward visible-light-induced photocatalysis and energy storage.