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Presence of Gap States at Cu/TiO2 Anatase Surfaces: Consequences for the Photocatalytic Activity
journal contribution
posted on 2015-03-26, 00:00 authored by Nicola Seriani, Carlos Pinilla, Yanier CrespoCopper-modified titania is a system
of interest for its potential
for photocatalytic applications in the production of solar fuels.
Still, the role of copper in the process is unclear. In this work,
small copper clusters on the (101) and (100) surfaces of anatase have
been investigated by first-principles simulations based on density
functional theory, to shed light on their atomic and electronic structure,
and to understand their effect on the photocatalytic process. The
main effects of copper on the electronic structure are to provide
states above the edge of the valence band of titania and to lead to
the formation of midgap states. There are two types of midgap states,
respectively, associated with direct Cu–Ti bonds and to Ti3+ polarons. The latter are the result of charge donation from
copper and lie in the vicinity of the surface. Moreover, the copper
tetramer (Cu4) displays empty states at the bottom of the
conduction band that play a key role in accommodating excess electrons.
We discuss how these features should enhance the photoresponse of
TiO2, contribute to increase the lifetime of the photogenerated
electron–hole pairs and contribute to increase the activity
of this material for CO2 reduction, a key step in the photoproduction
of hydrocarbons.