title: Band alignment of rutile and anatase TiO₂.
abstract: The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO₂. The discovery of the photolysis of water on the surface of TiO₂ in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO₂ (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.
authors.affiliation: University College London, Kathleen Lonsdale Materials Chemistry, 20 Gordon Street, London, WC1H OAJ, UK.
authors.forename: David O
authors.initials: DO
authors.lastname: Scanlon
authors.forename: Charles W
authors.initials: CW
authors.lastname: Dunnill
authors.forename: John
authors.initials: J
authors.lastname: Buckeridge
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Shevlin
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Logsdail
authors.forename: Scott M
authors.initials: SM
authors.lastname: Woodley
authors.forename: C Richard A
authors.initials: CR
authors.lastname: Catlow
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Powell
authors.forename: Robert G
authors.initials: RG
authors.lastname: Palgrave
authors.forename: Ivan P
authors.initials: IP
authors.lastname: Parkin
authors.forename: Graeme W
authors.initials: GW
authors.lastname: Watson
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Keal
authors.forename: Paul
authors.initials: P
authors.lastname: Sherwood
authors.forename: Aron
authors.initials: A
authors.lastname: Walsh
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Sokol
mesh_terms: D002384:Catalysis; D008956:Models, Chemical; D056951:Photoelectron Spectroscopy; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium