Controlled Synthesis of WO₃ Nanorods and Their Electrochromic Properties in H₂SO₄ Electrolyte

Uniform crystalline WO 3 nanorods were synthesized by a lithium- or sulfate-free hydrothermal process with NaCl as a capping agent. It is found that variations in the pH and amount of capping agent have critical influence on the morphologies of the resultant WO 3 nanostructures. The electrochromic film comprised of the as-synthesized crystalline WO 3 nanorods exhibits a fast coloration/bleaching switching, coloration efficiency comparable to that of conventional amorphous WO 3 films, and a high H + ion-insertion ability in 0.5 mol/L H 2 SO 4 solution without degradation.