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Title: The nature of interfaces and charge trapping sites in photocatalytic mixed-phase TiO{sub 2} from first principles modeling

Mixed phase rutile/anatase catalysts show increased reactivity compared with the pure phases alone. However, the mechanism causing this effect is not fully understood. The electronic properties of the interface and the relative energy of the electron in each phase play a key role in lowering the rate of recombination of electron hole pairs. Using density functional theory and the +U correction, we calculated the bands offsets between the phases taking into account the effect of the interface. Our model included several thousands atoms, and thus is a good representation of an interface between actual nanoparticles. We found rutile to have both higher conduction and valence band offsets than rutile, leading to an accumulation of electrons in the anatase phase accompanied by hole accumulation in the rutile phase. We also probed the electronic structure of our heterostructure and found a gap state caused by electrons localized in undercoordinated Ti atoms which were present within the interfacial region. Interfaces between bulk materials and between exposed surfaces both showed electron trapping at undercoordinated sites. These undercoordinated (typically four) atoms present localized electrons that could enable reduction reactions in the interfacial region, and could explain the increased reactivity of mixed-phase TiO{sub 2} photocatalyst materials.
Authors:
;  [1] ;  [2]
  1. Department of Chemical Engineering, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609 (United States)
  2. Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, Cork (Ireland)
Publication Date:
OSTI Identifier:
22415849
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ATOMS; CATALYSTS; COMPARATIVE EVALUATIONS; CORRECTIONS; DENSITY FUNCTIONAL METHOD; ELECTRONIC STRUCTURE; ELECTRONS; INTERFACES; NANOPARTICLES; PHOTOCATALYSIS; REACTIVITY; RECOMBINATION; REDUCTION; RUTILE; SURFACES; TITANIUM OXIDES; TRAPPING; VALENCE