1.0, 2.0, and 5.0 wt% of rhodium and 2%RhBr 3 /TH were prepared
as described above for the chloroplatinate complexes. Again the
titania hydrate TH afforded photocatalysts which were very
active in the photodegradation of 4-CP, whereasHombikat 100
(Sachtleben) and P25 based materials were less efficient.
Maximum loading was observed at 5.0 wt% of rhodium whereas
the use of higher metal halide concentrations afforded powders
from which excess rhodium is completely removed during
washing.
A. CHARACTERIZATION
RhCl 3 /TH and RhBr 3 /TH have a pink and a dark yellow color,
respectively, and are surprisingly stable to desorption of the rho-
dium component as compared to chloroplatinate modifiedTH
(13,19,20). In aqueous suspension upon stirring either in the
dark or under irradiation with visible light, no dissolved rhodium
complex was detectable by UV–Vis absorption spectroscopy.
4-CP; 1.18 V
+- OH/OH–
ca. 2.4 V
VBCBO 2 /O 2 ––0.16 V- –0.28 V
2.93 VO 2 TiO 2 [Ti]OPtIVCl 4 L 4-CP–0.3 to –0.4 V
[Ti]OPtIIICl 4 Ln–hn[Ti]OPtCl^0 Cl 3 Ln–1.6 V+SCHEME 4. Potential diagram for 4.0%H 2 [PtCl 6 ]/TH at pH 7. All
potentials are given versus NHE.
VISIBLE LIGHT PHOTOCATALYSIS 385