The reason
for such a limited photocatalytic activity of bare TiO2 may be due to the recombination between the photogenerated charges or
by the low adsorption of MB and/or an impeded desorption of reaction
products or carbonaceous poisoning species. The beneficial effect
of coupled TiO2/WO3 nanoparticles may be due to the higher
number of photons absorbed. Additionally, due to the location of
the conduction band edge of WO3 and TiO2 the photogenerated
electrons in the TiO2 can be transferred to WO3, slowing electron–
hole recombination processes. The electrons injected into
WO3 can be employed to reduce the material itself to W(V) from
W(VI) W6þ þ e
ðTiO2ÞCB ! W5þ. Thus WO3 can help in trapping
photogenerated electrons (limiting electron–hole recombination
processes)