Search

TiO2anatase plays a central role in energy and environmentalresearch. A major bottleneck toward developing artificial photosynthesiswith TiO2is that it only absorbs ultraviolet light, owingto its large bandgap of 3.2 eV. If one could reduce the bandgap ofanatase to the visible region, TiO2-based photocatalysiscould become a competitive clean energy source. Here, using scanningtunneling microscopy and spectroscopy in conjunction with densityfunctional theory calculations, we report the discovery of a highlyreactive titanium-terminated anatase surface with a reduced bandgapof less than 2 eV, stretching into the red portion of the solar spectrum.By tuning the surface preparation conditions, we can reversibly switchbetween the standard anatase surface and the newly discovered lowbandgap surface phase. The identification of a TiO2anatasesurface phase with a bandgap in the visible and high chemical reactivityhas important implications for solar energy conversion, photocatalysis,and artificial photosynthesis. [ABSTRACT FROM AUTHOR]