Adsorption, diffusion and dissociation of molecular oxygen at defected
TiO2(110) -- a DFT study.

Adsorption, diffusion and dissociation of molecular oxygen at defected TiO\ :sub:`2`\ (110) -- a DFT study.
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by M. D. Rasmussen, L. M. Molina and B. Hammer

J. Chem. Phys. **120**, 988 (2004).

Abstract
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The properties of reduced rutile TiO\ :sub:`2`\ (110) surfaces, as well
as the adsorption, diffusion, and dissociation of molecular oxygen are
investigated by means of density functional theory (DFT). The
O\ :sub:`2` molecule is found to bind strongly to bridging oxygen
vacancies, attaining a molecular state with an expanded O-O bond of 1.44
A. The molecular oxygen also binds (with somewhat shortened bond
lengths) to the five fold coordinated Ti atoms in the troughs between
the bridging oxygen rows, but *only when vacancies are present somewhere
in the surface*. In all cases, the magnetic moment of O\ :sub:`2` is
lost upon adsorption. The expanded bond lengths reveal together with
inspection of electron density and electronic density of state plots
that charging of the adsorbed molecular oxygen is of key importance in
forming the adsorption bond. The processes of O\ :sub:`2` diffusion from
a vacancy to a trough and O\ :sub:`2` dissociation at a vacancy are both
hindered by relative large barriers. However, we find that the presence
of neighbouring vacancies can strongly affect the ability of O\ :sub:`2`
to dissociate. The implications of this in connection with diffusion of
the bridging oxygen vacancies are discussed.