Effect of vanadium (V) doping on the physical characteristics of novel n-type TiO2 for sustainable energy storage

Abstract

The design of high-performance advanced materials for green energy nanotechnology is vital for progress in cutting-edge domains such as environmental sustainability and energy conversion technologies. In this study, we report the synthesis and characterization of undoped and vanadium-doped titanium dioxide (TiO₂) in both pellet and thin film forms. The influence of vanadium doping levels on the material's physical and electrical properties was systematically investigated. Structural, morphological, compositional, electrical, and optical analyses were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), impedance spectroscopy (IS) (for pellets) and UV-visible spectroscopy (for films). XRD results confirmed that all samples were polycrystalline in the anatase phase, while increasing vanadium content reduced crystallite size and enhanced density. While the elemental composition remained relatively stable, XPS data showed the formation of Ti³⁺ states and oxygen vacancies, which play a pivotal role in modifying electronic behavior. Impedance spectroscopy indicated semiconducting behavior, with resistance decreasing as temperature increased, reflecting enhanced conductivity. Optical studies (UV-vis spectroscopy) showed a redshift in the absorption edge toward the visible region, with a reduction in bandgap energy from 3.20 eV (undoped) to 2.85 eV (6% V-doped), attributed to localized states and the formation of impurity bands. Electrical measurements showed enhanced conductivity with temperature and a clear transition to non-Debye behavior, reflecting a distribution of relaxation times likely due to grain boundaries and defect states. Notably, the dielectric constant was significantly elevated, supporting potential use in energy storage or solar energy applications. This work provides key insights into tailoring TiO₂-based materials through metal doping for sustainable energy storage.