  A simple refluxing wet-chemical approach is employed for fabricating
In2S3/Pt-TiO2 heterogeneous catalysts for hydrogen generation under visible
light irradiation. When the mass ratio between Pt-TiO2 and cubic-phased In2S3
(denoted as In2S3/Pt-TiO2) is two, the composite catalyst shows the highest
hydrogen production, which exhibits an 82-fold enhancement over in-situ
deposited Pt-In2S3. UV-vis diffuse reflectance and valence band X-ray
photoelectron spectra elucidate that the conduction band of In2S3 is 0.3 eV
more negative compared to that of TiO2, favoring charge separation in the
nanocomposites. Photoelectrochemical transient photo-current measurements and
optical pump - terahertz probe spectroscopic studies further corroborate the
charge separation in In2S3/Pt-TiO2. The migration of photo-induced electrons
from the In2S3 conduction band to the TiO2 conduction band and subsequently
into the Pt nanoparticles is found to occur within 5 picoseconds. Based on the
experimental evidence, a charge separation process is proposed which accounts
for the enhanced activity exhibited by the In2S3/Pt-TiO2 composite catalysts.
