Titanium dioxide/tungsten trioxide nanoarrays film for high electrochromic performance

A novel type of TiO₂/WO₃ core/shell nanoarrays film as a good electrode material with superior performance has been successfully synthesized by hydrothermal and sol-gel method. The advantage of core/shell structure and the electrochromic behavior of the film have been discussed. The effects of annealing temperature and dipping times on the structure, optical modulation, electrochromic property and cycle stability of the film were also investigated in detail. The results indicate that the TiO₂/WO₃ core/shell nanoarrays with two dipping times under 250 °C have significant optical modulation (vary between 16–73% in 400–700 nm range) and fast Li¹⁺ diffusion rate (with 1.4 × 10⁻¹⁰ cm²/s Li¹⁺ diffusion coefficients). The improved electrochromic properties are mainly attributed to the core/shell structure and the optimization function of TiO₂, which have high surface area, good contact with the electrolyte solution and fewer defects, leading to faster Li¹⁺ diffusion rate and better electrochemical cycling stability. The new structure of TiO₂/WO₃, producing the best possible advantage of WO₃ and TiO₂, can be regarded as an ideal electrochromic material with high practical value