Synthesis of Self-Ordered Tantalum-Niobium Mixed Oxide Nanotubes and Their Use for Clean Hydrogen Production

We report on the first fabrication of vertically-oriented tantalum-niobium mixed oxide nanotube arrays (Ta-Nb-O NTs) via one-step anodization of Ta-Nb alloy sheet in NH4F-containing electrolytes. The synthesized Ta-Nb-O NTs were fully characterized via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The prepared nanotubes have an average diameter of similar to 35 nm with a wall thickness similar to 15 nm and a length similar to 1.0 mu m. The photoactivity of the fabricated Ta-Nb-O NTs was tested toward the photocatalytic hydrogen production, revealing a steady rate with no indication of activity poisoning. The amount of hydrogen produced can be as high as 150 mu L/cm(2)after 5 h of illumination, which is much higher than that reported for most metal oxides. Therefore, the demonstrated platform of Ta-Nb-O nanotube arrays holds promise for a variety of solar energy applications.