Anodic Deposition of Vanadium Oxides for Thermal-Induced Growth of Vanadium Oxide Nanowires

Hydrous vanadium oxides (denoted hereafter as VOx center dot yH(2)O) were prepared by anodic deposition from an aqueous solution containing VOSO4 and H2O2. X-ray photoelectron spectroscopic analyses demonstrated that the valence of vanadium in the deposits was mixed pentavalent and tetravalent. Growth of vanadium oxide nanowires to unique sea-urchin-like structure from the as-deposited oxides can be induced by postdeposition annealing in air at 400 degrees C with time >= 4 h. The success in growing one-dimensional (1D) vanadium oxide nanowires strongly depends on the deposition variables such as the V5+/V4+ ratio (adjusted by H2O2 addition) in the VOSO4 solution and the applied current density during anodic deposition. From the transmission electron microscopic and selected area electron diffraction analyses, nanowires show single-crystalline structures of V2O5, alpha-V2O5, and V6O13. This thermal-induced growth of 1D vanadium oxide nanowires is attributable to the extrusion of V2O5, alpha-V2O5, and V6O13 single crystals originating from the thermal expansion of VOx center dot yH(2)O. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3216030] All rights reserved.