Novel visible-light-responsive photo-catalysts based on palladium decorated nanotube films fabricated on titanium substrates

A novel visible-light-responsive photo-catalyst was synthesized for the photo-degradation of methylene blue. Highly ordered and uniformly distributed titanium dioxide-tungsten trioxide nanotubes on pure titanium substrates were successfully fabricated by one-step electrochemical anodizing and palladium deposited on these nanotubes by photo-reduction method. The resulting samples were characterized by X-ray diffraction, field emission scanning electron microscope, ultraviolet–visible spectroscopy and energy dispersive X-ray spectrometer methods. The degradation of methylene blue (MB) was used as a model reaction to evaluate the photo-catalytic activity of the obtained samples. After irradiated under visible light for 60 min, degradation ratio of Pd-deposited nanotubes was improved as compared with that of bare titanium dioxide-tungsten trioxide nanotubes. Under the same condition, no obvious photo-degradation of methylene blue was found for bare TiO2 nanotubes. Kinetic research showed that photo-degradation process followed the first-order reaction; the apparent reaction rate constant of Pd-based nanotubes was approximately 2.19 times higher than that on the unmodified nanotubes. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photo-catalytic activity.