Electrochemical, UV–Vis, and microscopical characteristics of sol–gel CeO2:V2O5 thin film

Cerium dioxide (CeO2) and cerium dioxide doped with vanadium pentoxide (CeO2:V2O5) were synthesized from sol–gel precursors and deposited by spin coating on a conductive glass substrate (FTO). The films with different concentration of dopant and number of deposited layers were studied throughout cyclic voltammetry (CV), chronoamperometry/chronocoulometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV–Vis spectroscopy. The best value of charge density of 18.9 mC cm−2 was obtained for CeO2 doped with 15 mol% of V2O5 film. The chemical diffusion coefficient of lithium ions into CeO2 was 1.73 × 10−12 and CeO2:V2O5 15 mol% 6.75 × 10−13 cm2 s−1. This film presented 79% of transparency in UV–Vis and 5% color change under ± 1.3 V of applied potentials. Structural analyses revealed its homogeneous surface and the root mean-squared roughness (RMS) value of 9.42 nm. Based on the obtained results, CeO2 doped with 15 mol% V2O5 film is a promising thin coating for the use in electrochromic devices as a passive counter-electrode.