Photocatalytic behaviors of TiO 2-SrTiO 3 composite thin film and nanostructure

To improve the efficiency of water splitting by photo-catalysis, a semiconductor heterojunction made of titanium dioxide (TiO2) and strontium titanate (SrTiO3) is constructed to promote the separation of photo-induced electron and hole (e-/h+) pairs. The photocatalytic behaviors of the TiO2-SrTiO3 composite film and nanostructure fabricated by the sol-gel and hydrothermal methods are studied. UV-visible and ultraviolet photoelectron spectroscopies (UV-Vis & UPS) are adopted to identify the band structure of the TiO2- SrTiO3 heterojunction. For the composite film system, an approximately 0.5 eV band shift at the heterojunction improves the separation of photo-induced e-/h+ pairs. The photocurrent density of the composite film is about 2-3 times larger than that of the TiO2 or SrTiO3 film alone. For the composite nanostructure system, it is composed of an array of TiO2 nanotubes coated with SrTiO3 nanoparticles. An approximately 0.2 eV band shift at the heterojunction is determined for the composite nanostructure. It is found that the size of the SrTiO3 nanoparticles, which can be controlled by the hydrothermal temperature and time, is a key factor in influencing the photocurrent density of the TiO2-SrTiO3 composite nanostructure. © 2011 by ASME.