Synthesis and electrochromic properties of crystalline 3d urchin-like nanostructures

Novel 3D (three-dimensional) urchin-like WO_2.72 nanostructures were prepared by a template-free hydrothermal synthetic route using W(CO)₆ and ethyl alcohol reagents. The detailed morphology and crystallinity were dependant on the synthesis temperature and synthesis time. The potential use of WO_2.72 nanourchins as a cathode electrode for electrochromic devices was assessed. The WO_2.72 electrochromic films exhibited a rapid switching response time (coloring time ~5 s, bleaching time ~1.6 s), outstanding high coloration efficiency (~116 cm²/C), and durability in an acidic electrolyte. This performance was attributed to the high diffusion coefficient [~6.43×10-9 cm²/s (in the intercalation)] of the urchin-likeWO_2.72 with a high surface area to volume ratio and high crystallinity.