Effect of oxidation conditions on the contrast ratio of a titanium electrochromic electrode

This study investigates the electrochromic properties of TiO₂ oxide films produced by the electrochemical oxidation of titanium in alkali metal nitrate melts with additives. The study focuses on the contrast ratio (K), a key parameter for evaluating the performance of electrochromic materials. It was found that the highest contrast ratio values of K = 7÷8 were achieved during anodic oxidation in melts containing potassium fluoride (KF) at a concentration of 0.01–0.04 mol/kg under the following conditions: temperature of 625 ± 10 K, voltage of 20 ± 5 V, and process duration of 5÷12 min in potentiostatic mode. The introduction of fluoride ions promotes the formation of a defect-rich oxide layer, thereby improving its electrochromic characteristics. The optimal synthesis conditions yield TiO₂ films with high corrosion resistance and reversible electrochromic behavior. Visual observations and quantitative measurements confirmed that these films exhibit intense dark-blue coloration under cathodic polarization and complete bleaching under anodic polarization. Long-term cycling tests in 1 M H₂SO₄ solution, equivalent to 2 N, demonstrated high stability of the electrochromic properties of the oxide layers, making them promising for use in indicator devices, such as displays and smart-window applications. The results also emphasize the importance of electrolyte composition and oxidation parameters for obtaining reproducible, high-quality electrochromic materials. The obtained data can be used for further optimization of synthesis processes and the development of TiO₂-based composite materials.

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