Synthesis and characterization of facile industrially scalable and cost effective WO3 micro-nanostructures for electrochromic devices and photocatalyst

A novel strategy for the synthesis of tungsten trioxide (WO3) micro-nanostructures by thermal annealing of tungsten powder under ambient conditions is reported. The as-synthesized WO3 samples are thoroughly characterized using powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) measurement. The TEM results show that the size of highly crystalline WO3 particles can be tuned from micro to nano by simply varying the annealing temperatures. The BET results demonstrate that the surface area and pore size of the synthesized WO3 decreases with increasing annealing temperatures. Furthermore, the WO3 synthesized at 550 °C (WO-550) exhibits not only higher surface area and pore size, but also excellent photocatalytic activity as well as super hydrophilicity compared to the other prepared and commercially available WO3. However, among the synthesized WO3 particles, only WO-550 exhibits moderate electrochromic properties. Our strategy is facile, cheap, rapid, and highly reproducible for large-scale production, and the use of toxic precursors or additional capping agents is also eliminated. We believe that the synthesis of WO3 by our method could have various practical industrial applications, and yield an excellent alternative to commercial WO3.