title: TiO2 anatase with a bandgap in the visible region.
abstract: TiO2 anatase plays a central role in energy and environmental research. A major bottleneck toward developing artificial photosynthesis with TiO2 is that it only absorbs ultraviolet light, owing to its large bandgap of 3.2 eV. If one could reduce the bandgap of anatase to the visible region, TiO2-based photocatalysis could become a competitive clean energy source. Here, using scanning tunneling microscopy and spectroscopy in conjunction with density functional theory calculations, we report the discovery of a highly reactive titanium-terminated anatase surface with a reduced bandgap of less than 2 eV, stretching into the red portion of the solar spectrum. By tuning the surface preparation conditions, we can reversibly switch between the standard anatase surface and the newly discovered low bandgap surface phase. The identification of a TiO2 anatase surface phase with a bandgap in the visible and high chemical reactivity has important implications for solar energy conversion, photocatalysis, and artificial photosynthesis.
authors.affiliation: Max Planck Institute for Solid State Research , Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Dette
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Pérez-Osorio
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Kley
authors.forename: Paul
authors.initials: P
authors.lastname: Punke
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Patrick
authors.forename: Peter
authors.initials: P
authors.lastname: Jacobson
authors.forename: Feliciano
authors.initials: F
authors.lastname: Giustino
authors.forename: Soon Jung
authors.initials: SJ
authors.lastname: Jung
authors.forename: Klaus
authors.initials: K
authors.lastname: Kern
mesh_terms: D008027:Light; D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D010788:Photosynthesis; D012993:Solar Energy; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium
keywords: Photocatalysis; TiO2 anatase; bandgap reduction to the visible; density functional theory; scanning tunneling microscopy and spectroscopy; titanium-terminated surface phase