Single-site tin-grafted anatase TiO2 for photocatalytic hydrogen production: Toward understanding the nature of interfacial molecular junctions formed in semiconducting composite photocatalysts

This work focuses on the nature of enhanced H-2 production over SnO2/TiO2 composite photocatalysts. Three kinds of Sn-modified TiO2 materials were prepared by different methods. Photocatalytic H-2 production from methanol/water solution as a model reaction was used to evaluate the photocatalytic properties of the materials. The chemical states of Sn were characterized in detail by transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption fine structure spectroscopy. The results reveal a Sn nuclearity-dependent enhancement of H-2 production over Sn/TiO2 photocatalysts. According to the characterization results, it was well established that the number of Ti-IV-O-Sn-IV linkages formed at the TiO2-SnO2 interface determines the enhancement amplitude of H-2 production. The photo-generated electrons of TiO2 across the interfacial linkages are transferred into the mononuclear Sn moieties grafted on the (101) and (001) planes, where H-2 is presumably released. An interatomic electron transfer pathway for accelerating photocatalytic H-2 production over Sn/TiO2 catalysts was proposed based on this work. (C) 2012 Elsevier Inc. All rights reserved.