0.26 V in the case of 1%, 2%, and 4.0%H 2 [PtCl 6 ]/TH, respectively.
The reproducibility of quasi-Fermi potential and photocatalytic
activity measurements was in the range of 0.02 V and 10%,
respectively. Since the onset of the TiO 2 part in the 4.0%
H 2 [PtCl 6 ]/TH reflectance spectrum remains nearly unchanged,
the band gap is not altered and the anodic shift of the conduction
band edge is therefore accompanied by an anodic shift of the
valence band edge.
B. PHOTOCATALYTICDEGRADATION WITHARTIFICIAL
VISIBLELIGHT(l455 nm)
Figure 4 illustrates the photodegradation of 4-CP ( 32 ) with visi-
ble light. Since reaction rates increased with increasing
photocatalyst concentration, reaching a constant value at 0.5 g/L,
all experiments were conducted at this value ( 33 ). Whereas the
rutile based H 2 [PtCl 6 ]/Ald was inactive (Fig. 4, curve a), in accord
with the very small surface area and the trace amounts of
chemisorbed chloroplatinate, 1.1.%H 2 [PtCl 6 ]/P25 and 4.0%
H 2 [PtCl 6 ]/TH were active, inducing 50% degradation after 95 and
15 min, respectively (Fig. 4, curves b, c). 4.0%H 2 [PtCl 6 ]/TH also
initiated a fast mineralization as indicated by curve d in Fig. 4.
Since the mineralization process produces CO 2 ,H 2 O, and
HCl, the initial pH value of 3.4 decreased to 3.0 at 120 min
23456789101112–400–2000200400600c dU
ph(mV) versus Ag/AgClpHa bFIG. 3. Photovoltage recorded forTH(a), 1.0% (b), 2.0% (c), and 4.0%
H 2 [PtCl 6 ]/TH (d) suspensions in 0.1 M KNO 3 in the presence of (MV)Cl 2
irradiated with the full light of an XBO-lamp. The position of the inflec-
tion point pH 0 is marked with a dotted line.
VISIBLE LIGHT PHOTOCATALYSIS 381