Increasing visible-light photoactivity of TiO₂ by bio-inspired cerium incorporation into the crystal lattice

Abstract

Ce-doped TiO₂ nanophotocatalysts were successfully synthesized via a green route using Leucaena leucocephala leaf extract to enhance visible-light photocatalytic activity. XRD analysis confirmed the anatase phase of TiO₂, while peak shifts toward higher 2θ values and peak broadening after Ce incorporation indicated lattice distortion, microstrain, and suppressed crystallite growth. Crystallite size calculated using the Scherrer and Williamson–Hall methods showed a significant reduction for Ce-doped TiO₂, confirming dopant-induced lattice perturbation. FTIR spectra revealed characteristic Ti–O–Ti vibrations along with Ce–O-related bands, broad O–H stretching, and phytochemical-derived functional groups, demonstrating the role of the leaf extract as a natural capping and stabilizing agent. UV–Vis studies showed enhanced visible-light absorption and band-gap narrowing from 3.32 eV for pristine TiO₂ to 3.17 eV for Ce-doped TiO₂ due to Ce-induced defect states and improved charge separation. Under visible-light irradiation, Ce-doped TiO₂ exhibited superior photocatalytic performance, achieving 93.42% degradation of methylene blue within 160 min, compared to 40.82% for pure TiO₂. The pseudo-first-order rate constant increased to 0.01579 min⁻¹ . These findings demonstrate that green-synthesized Ce-doped TiO₂ possesses enhanced light-harvesting ability, efficient charge separation, and improved surface reactivity, making it a sustainable and efficient photocatalyst for visible-light-driven dye degradation.