Titanium Dioxide: Energy Conversion, Photocatalysis and Isotope Labeling


Ladislav Kavan


 J. Heyrovsky Institute of Physical Chemistry, v.v.i. Academy of Sciences of the Czech Republic,
Dolejskova 3, 18223 Prague 8 (kavan@jh-inst.cas.cz)


Abstract


Titanium dioxide attracted considerable attention after the pioneering work of Fujishima and Honda
in 1972, which stems from several promising applications in solar cells, batteries, and
photocatalysis for environment protection. The dye sensitized solar cell is a low-cost, highly
efficient device to rival Si-based photovoltaics. It was discovered in 1991 by O’Regan and Graetzel
and their work triggered great academic and technological feedback during the next 2.5 decades. The
generic device is a liquid-junction photoelectrochemical cell with a dye sensitized nanocrystalline
TiO[2] photoanode. An alternative of this system is the solid-state dye sensitized solar cell in
which the photogenerated holes are transported by a solid conductive material.  Recently, this
concept developed into the methylammonium-lead-iodide perovskite solar cell achieving more than 20
% conversion efficiency. Accommodation of Li in TiO[2] (anatase), monoclinic TiO[2](B) and
particularly Li[4]Ti[5]O[12] (spinel) is readily applicable to the development of anodes for Li-ion
batteries, and possibly also No-ion batteries. The search for Na-ion batteries is motivated by the
expectation that the world supply of lithium could not be sufficient within the long-term horizon
to back up the growth of battery market for electromobiles and grid stabilization. Titania-based
photocatalysis is used for mineralization of environmental pollutants in air and water. We have
recently upgraded these studies by titania catalysts labeled by[ ]oxygen isotopes 16, 17, 18, each
in anatase and rutile forms. The products were characterized by Raman spectroscopy and by Raman
spectroelectrochemistry of Li-insertion. The second-order Raman scattering in rutile, and the
overlapping Raman features in anatase were addressed in detail.  The heterogeneous catalytic
processes at the interface of titania and gaseous reactants were investigated by high-resolution
FTIR spectroscopy in dark and upon UV-excitation.