Ce³⁺/Ce⁴⁺–TiO₂ Nano‐Octahedra as Active Photocatalysts for Ciprofloxacin Photodegradation Under Solar Light

Abstract Cerium‐containing titania nano‐octahedra (CeTNOh) are obtained by ultrasonication‐hydrothermal synthesis of Ce‐containing titanate nanowires (0.35, 0.46, and 0.70 Ce mol %) from commercial TiO2 (Degussa P25). CeTNOh are tested as photocatalysts to degrade a target pollutant (ciprofloxacin) under simulated solar light and at mild conditions. CeTNOh are anatase polymorphs with increasing crystallite size as Ce content increases. Hydrothermal treatments enhance the specific surface area (SSA) compared to P25, although Ce addition slightly reduces SSA while increasing crystallite size. Electron Microscopy confirms the morphology, although higher Ce levels hinder a full transformation. X‐ray photoemission spectroscopy (XPS) shows the presence of Ce 3+ /Ce 4+ redox pair, promoting electron mobility and Ti‐Ce interactions. Optical and electronic spectroscopy reveals that Ce loading reduces the bandgap from 3.20 to 2.74 eV, extending light absorption into the visible range, thus enhancing the photocatalytic activity. The best sample, CeTNOh0.35, achieved 83% degradation of ciprofloxacin after 360 minutes under solar irradiation, with poor adsorption in the dark period. Higher Ce loadings negatively affect photoactivity by partially covering titania active sites. Reusability tests confirm the stability and efficiency of CeTNOh0.35 over three cycles, highlighting the importance of octahedral morphology in Ce‐containing systems to boost the final photoactivity for water remediation.