Electrochromic properties of nitrogen doped titanium dioxide films

Nitrogen doping is an effective way to improve the electrochromic performance of inorganic materials. However, there is still a lack of systematic studies on the electrochromic properties of nitrogen-doped TiO2 materials. In this work, the N-doped titanium dioxide films (N-TiO2) with different N content were prepared by an ion exchange method combined with hydrothermal approach. The effects of different N doping concentrations on the morphology and electrochromic properties of samples were studied by XRD, XPS, FESEM, HR-TEM and electrochemical methods. It was found that the nitrogen doping has a great influence on the crystal structure of the TiO2, leading to an obvious light transmittance difference in bleaching/coloring states for all the films. The N1-TiO2 film (nitrogen doping concentration was 1 mol/L) shows the best electrochromic performance. The ion diffusion coefficient of N1-TiO2 composite film was 2.28 × 10−9 cm2/s, and the coloring efficiency is 10.61 cm2/C, the coloring and bleaching switching time was 31.13 s and 3.79 s, and the optical modulation amplitude retention rate after 100 cycles can reach 65.43 %, indicating that nitrogen doping with proper amount is indeed an effective method to tune electrochromic properties of TiO2.