Electrochromic properties of cobalt-doped titanium dioxide films

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 x 10(-10) cm(2)/s, the coloring efficiency is 34.11 cm(2)/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.