A single-step low-cost synthesis of tungsten oxide nanostructures by resistive hot wire oxidation

Abstract

The synthesis of metal oxide nanostructures commonly requires sophisticated scientific apparatus, complex synthesis processes, and time-inefficient processes, or produces undesirable by-products. We have overcome these challenges by developing a low-cost and time-effective synthesis technique that allows considerable control of growth energetics enabling exploration of crystal phases that occupy small regions of phase space. Here, we report on nanostructures of tungsten oxide WO_2.76 (W₁₇O₄₇) synthesized in a single-step process, which takes roughly one minute to grow WO_2.76 and an additional roughly 30 min for preparation. The nanostructures were synthesized directly onto tungsten filaments by resistive heating of tungsten wire in an oxygen environment. The nanostructures are rod-shaped with an average diameter of 25 ± 9 nm. Their physical properties were investigated through an arsenal of experimental probes including scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The improved electrochemical performance in comparison to WO₃ along with its large dielectric constant suggests that despite WO_2.76 being somewhat elusive to researchers, it demonstrates the potential of this compound for functional applications such as supercapacitors and photocatalytic water splitting.