Electrochromic properties of cobalt-doped titanium dioxide films

Abstract

Titanium dioxide (TiO₂) has been widely studied as an inexpensive and efficient electrochromic material. However, slow response speed and poor cycling performance still constrain the further application of TiO₂ electrochromic materials. In this work, a series of cobalt-doped TiO₂ electrochromic films were fabricated via hydrothermal method combined with a spin-coated approach. The effects of doped cobalt ions on the electrochemical and electrochromic performance of TiO₂ were explored. The cobalt-doping concentrations on the morphology and electrochromic performance of the samples were investigated by means of XRD, XPS, FESEM, HR-TEM, and electrochemical techniques. It is found that the ionic diffusion coefficient of the 0.5% Co-TiO₂ composite film is 6.44 × 10⁻¹⁰ cm²/s, the coloring efficiency is 34.11 cm²/C, and the coloring and bleaching switching time are 1.92 s and 10.71 s, respectively. Moreover, the 0.5% and 1% Co-TiO₂ composite films showed superior cyclic performance than pristine TiO₂. This indicates that the appropriate amount of Co doping can significantly enhance the electrochromic properties of titanium dioxide films.