  Structural and electronic properties comparison between anatase, rutile and
monoclinic TiO2(B) titania polymorphs in bulk and related nanostructures
simulated by two-dimensional slabs has been performed by means of density
functional theory calculations. TiO2(B) was included due to experimental
results where it appears as a metastable phase during thermal annealing of low
content sodium layered titanate nanostructures obtained via hydrothermal
synthesis. Band gaps and surface energies are discussed confronting results
obtained by Plane Waves (PW) and Localized Basis Set methods (LCNAO), observing
an excellent agreement between both methodologies when considering floating
basis to calculate surfaces energies using LCAO. The computed formation energy
for the TiO2(B) (001) slab, as has been previously reported by Vittadini A. et
al., J. Phys. Chem. C 2009, 113 (44), 18973-18977, is in the order of the one
calculated for anatasa (101) which represents one of the most stable TiO2
surfaces. The adsorption of formic acid on (001) and (100) - less stable -
TiO2(B) dry facets was investigated as the first step for further evaluation of
TiO2(B) nanostructures for dye sensitized solar cells (DSSC) applications. The
results show that the bidentate dissociated configuration is the most stable
for both surfaces being the computed adsorption energy 0.76 eV and 1.35 eV for
(001) and (100) respectively. These results differ from what was previously
found for dry anatasa (101) where monodentate coordination prevails. The
evaluated reactivity of TiO2(B) slabs is comparable with anatase and indicates
that it could be a good adsorbent for common dyes used for Dye Sensitized Solar
Cells purposes.
