Probing the Charge Separation Process on In2S3/Pt-TiO2 Nanocomposites for Boosted Visible-light Photocatalytic Hydrogen Production

摘要

A simple refluxing wet-chemical approach is employed for fabricatingIn2S3/Pt-TiO2 heterogeneous catalysts for hydrogen generation under visiblelight irradiation. When the mass ratio between Pt-TiO2 and cubic-phased In2S3(denoted as In2S3/Pt-TiO2) is two, the composite catalyst shows the highesthydrogen production, which exhibits an 82-fold enhancement over in-situdeposited Pt-In2S3. UV-vis diffuse reflectance and valence band X-rayphotoelectron spectra elucidate that the conduction band of In2S3 is 0.3 eVmore negative compared to that of TiO2, favoring charge separation in thenanocomposites. Photoelectrochemical transient photo-current measurements andoptical pump - terahertz probe spectroscopic studies further corroborate thecharge separation in In2S3/Pt-TiO2. The migration of photo-induced electronsfrom the In2S3 conduction band to the TiO2 conduction band and subsequentlyinto the Pt nanoparticles is found to occur within 5 picoseconds. Based on theexperimental evidence, a charge separation process is proposed which accountsfor the enhanced activity exhibited by the In2S3/Pt-TiO2 composite catalysts.