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 .