posted on 2015-09-24, 00:00authored byJolla Kullgren, Bálint Aradi, Thomas Frauenheim, Ladislav Kavan, Peter Deák
The synergic effect of mixing rutile
(R) and anatase (A) crystals
in photocatalysis is often attributed to a staggered alignment of
the band structures, but it is widely disputed whether the conduction
band edge of rutile or that of anatase is higher. Photoelectron spectroscopy
(PES) supports the former, and flat-band potential (FBP) measurements
the latter. Theoretical alignment of the bulk band structures as well
as calculated offsets across actual interfaces support the PES data.
The theoretical study presented here shows that the FBP data can be
explained by taking into account the adsorption of OH– and H+ ions in the electrolyte solution. We conclude
that, in the case of nanopowders applied in photocatalysis, the dipole
layer created by surface adsorption and the one at the R/A interface
both have an influence on the alignment, and the end result may change
from experiment to experiment.