title: Heterojunction synergies in titania-supported gold photocatalysts: implications for solar hydrogen production.
abstract: The mixed-phase nature of P25 TiO2 (85 % anatase/15 % rutile) plays a key role in the high H2 production rates shown by Au/P25 TiO2 photocatalysts in alcohol/water systems. However, a full understanding of the synergistic charge transfer mechanisms between the TiO2 polymorphs that drive the high rates is yet to be realised. Here, we deconstruct P25 TiO2 into its component phases, functionalise the phases with Au nanoparticles and explore charge transfer in Au/TiO2 systems using EPR spectroscopy. EPR spectroscopy and photocatalytic data provide direct evidence that electrons excited across the rutile band gap move to anatase lattice traps through interfacial surface sites, which decreases electron-hole pair recombination and increases charge carrier availability for photoreactions. In particular, three-phase interfacial sites between Au, anatase and rutile appear to be H2 evolution "hot spots". The results isolate the origin of high photocatalytic H2 production rates seen in Au/P25 TiO2 systems.
authors.affiliation: School of Chemical Sciences, Science Centre, Building 301, 23 Symonds Street, Auckland 92019 (New Zealand). vjov001@aucklanduni.ac.nz.|The MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand). vjov001@aucklanduni.ac.nz.
authors.forename: Vedran
authors.initials: V
authors.lastname: Jovic
authors.affiliation: School of Chemical Sciences, Science Centre, Building 301, 23 Symonds Street, Auckland 92019 (New Zealand).|The MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand).|Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, MA 02215 (USA).
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Smith
authors.affiliation: Corporate Research and Innovation (CRI), Saudi Basic Industries Corporation (SABIC).
authors.forename: Hicham
authors.initials: H
authors.lastname: Idriss
authors.affiliation: School of Chemical Sciences, Science Centre, Building 301, 23 Symonds Street, Auckland 92019 (New Zealand). g.waterhouse@auckland.ac.nz.|The MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand). g.waterhouse@auckland.ac.nz.
authors.forename: Geoffrey I N
authors.initials: GI
authors.lastname: Waterhouse
mesh_terms: D002384:Catalysis; D006046:Gold / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D055668:Photochemical Processes; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: C009495:titanium dioxide; D006046:Gold; D006859:Hydrogen; D014025:Titanium
keywords: gold; hydrogen; photochemistry; supported catalysts; titanium