Nanoparticulate double-heterojunction
photocatalysts comprising
TiO
2(Anatase)
/WO
3
/TiO
2(Rutile)
were
produced by a sol–gel method. The resulting photocatalysts
exhibit clear synergistic effects when tested toward the degradation
of methyl orange under both UV and visible light. Kinetic studies
indicate that the degradation rate on the best double-heterojunction
photocatalyst (10 wt % WO
3
-TiO
2
) depends mainly
on the amount of dye concentration, contrary to pure oxides in which
the degradation rate is limited by diffusion-controlled processes.
The synergistic effects were confirmed through systematic and careful
studies including holes and OH radical formation, X-ray diffraction,
electron microscopy, elemental analysis, UV–vis diffuse reflectance
spectroscopy, and surface area analysis. Our results indicate that
the successful formation of a double heterojunction in the TiO
2(Anatase)
/WO
3
/TiO
2(Rutile)
system leads
to enhanced photoactivity when compared to individual oxides and commercial
TiO
2
P25.