(165c) Photocatalytic Water-Splitting by Ru-Doped Titania Nanotubes

Titania nanotubes are a well-known photocatalytically active material that offers a wide band gap and high surface to volume ratio. The purpose of this study is to explore the use of titania nanotubes for simultaneous water-splitting and hydrocarbon formation. Thin films of titania were first deposited on a silicon substrate by E-beam evaporator in a clean room environment. Titania nanotubes were then synthesized by anodic oxidation in a fluoride-containing electrolyte to form aligned arrays of titania nanotubes perpendicular to the silicon substrate surface. Doping of the titania nanotubes was accomplished by incipient wetness impregnating and subsequent annealing in air. Characterization of the titania nanotubes was accomplished by scanning electron microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. Low fluoride concentration in the electrolyte has been shown to result in oxygen to titanium ratios of greater than 2:1 in the titania nanotubes. Titania nanotubes with this surplus of oxygen exhibit increased photocatalytic activity compared to stoichiometric TiO₂ nanotubes and Titania P25 as demonstrated by photocatalytic methylene blue decomposition. Also, titania nanotubes have been shown to be stable in temperatures up to 800°C. In this study, we show that titania nanotubes with excess oxygen can be used to photocatalytically decompose water vapor in a quartz plate reactor at elevated temperatures under ultraviolet (UV) light from a 100W Hg lamp.