Vapor growth of binary and ternary phosphorus-based semiconductors into TiO(2) nanotube arrays and application in visible light driven water splitting

We report successful synthesis of low band gap inorganic polyphosphide and TiO(2) heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP(7), SnIP, and (CuI)(3)P(12)) were successfully reacted and deposited into electrochemically fabricated TiO(2) nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO(2) nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP(7). Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO(2) hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO(2) emerged to be the most active among the polyphosphide@TiO(2) materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO(2).