Abstract:
Since the discovery of water photolysis on a TiO2 electrode by Fujishima and Honda
in 1972, TiO2 has attracted extensive attention as an ideal photocatalytic material
because of its excellent properties such as high activity, good stability, nontoxicity and
low cost. Hence, it has been widely used in the fields of renewable energy and
ecological environmental protection. However, as a wide band gap oxide
semiconductor (Eg = 3.14 eV), brookite TiO2 can only show photocatalytic activity
under UV light irradiation (λ < 387.5 nm) that accounts for only a small portion of solar
energy (approximately 5 %), in contrast to visible light for a major part of solar energy
(approximately 45 %). Therefore, effectively utilizing sunlight is the most challenging
subject for the extensive application of TiO2 as a photocatalyst. Due to the unique d
electronic configuration and spectral characteristics of transition metals, transition
metal doping is one of the most effective approaches to extend the absorption edge
of TiO2 to the visible light region. This method of doping either inserts a new band into
the original band gap or modifies either the conduction band or valence band,
improving the photocatalytic activity of TiO2 to some degree. In this work, the
structural, electronic and optical properties of doped and undoped TiO2 (100), (110)
and (210) surfaces were performed using first principle calculations based on DFT
using a plane-wave pseudopotential method. The generalized gradient approximation
was used in the scheme of Perdew-Burke-Ernzerhof to describe the exchangecorrelation
functional as implemented in the Cambridge Sequential Total Energy
Package code in the Materials Studio of BIOVIA. The metal dopants shift the
absorption to longer wavelengths and improves optical absorbance in visible and near-
IR region. The un-doped (210) surface showed some activity in the visible and near
IR region.
