Ti-Doped WO₃ synthesized by a facile wet bath method for improved electrochromism

Electrochromic materials could modulate the optical transmittance reversibly by the application of electric potential and the increase in the surface area for fast ionic diffusion is an efficient way to improve their electrochromism. In this work, WO₃ based nanomaterials with a size as small as 5 nm were synthesized via a facile wet bath method that leads to Ti doping of WO₃ based on the heterovalency of W(vi) and Ti(iv). Ti doping improved the WO₃ electrochromism effectiveness in transmittance contrast and coloration efficiency due to the reduced crystallite size and therefore an increase in the surface area, the Ti doping also enhanced the cycling stability benefiting from the stable Ti-O bonding. However, the coloring/bleaching kinetics were deteriorated due to the reduced proton diffusion coefficient after the Ti ion substitution into the WO₃ lattice. A high coloration efficiency of 106.6 cm² C^-1 and a good optical contrast of ∼67.6% can be obtained for the optimized Ti-doped WO₃ at a wavelength of 633 nm.