By Renewable Energy Focus staff
The KIT Institute for Functional Interfaces (IFG) has looked at the conversion process using titanium oxide-based photocatalysts in the direct conversion of solar energy into chemical energy – for example hydrogen generation by water splitting.
With support from the universities of St Andrews (Scotland) and Bochum and Helmholtz-Forschungszentrum (German), the researchers have gathered new findings on the fundamental mechanisms of photochemistry on titanium dioxide (TiO2).
TiO2, or titania, is a photoactive material occurring in nature in the rutile and anatase modifications. Anatase modifications is being characterised by a ten times higher photochemical activity.
When the white TiO2 powder – also used as a pigment in plants and sunscreens – is exposed to light, electrons are excited and can, for example, split water into oxygen and hydrogen.
The researchers have also been able to determine the lifetime of the light-induced electronic excitations inside the TiO2 crystals.
Head of IFG, Professor Christof Wöll, says: “A short lifetime means that the excited electrons fall back again at once: We witness some kind of an internal short circuit. In the case of a long lifetime, the electrons remain in the excited state long enough to be able to reach the surface of the crystal and to induce chemical processes.”
He adds: “The objective is to develop photoactive materials with higher efficiencies and longer lifetimes.”