Structure-Controlled Anatase TiO₂ Nanorods from P25: Synthesis and Optimization for Enhanced Artificial Sunlight Photocatalytic Activity

Bare TiO2 is an efficient photocatalyst, but it has the disadvantage of a wide bandgap, which limits its use in solar radiation. In this work, we present a strategy to improve the photocatalytic efficiency of TiO2 nanorods (TNRs) in the degradation of Rhodamine B (RhB). We investigate the effect of calcination temperature on the crystallographic, structural, and electronic properties of the synthesised photocatalysts. A series of TiO2 nanorodswereprepared by alkaline hydrothermal treatment of commercial TiO2 P25 catalyst. They were subsequentlycalcined at different temperatures (450–800 °C). The photocatalytic behaviour of these samples was evaluated in the photodegradation of Rhodamine B carried out under ultraviolet-visible light illumination at room temperature. Advanced characterization techniques, including N2 -adorption-desorption isotherm, X-ray diffraction (XRD), Raman spectroscopy and UV-Vis diffuse reflectance spectroscopy (DRS) analysis, revealed a progressive phase transition from TiO2-B to anatase as temperatures increased from 450 °C to 800 °C. Simultaneously, the material’s optical properties underwent significant changes, with the bandgap energy graduallydiminishing from 3.43 eV to 3.19 eV. This trend is directly correlated with enhanced crystallinity and anatase phase development. This red-shifted absorption together with improved textural properties, exhibit the catalyst calcined at 700 °C (TNRs). At this temperature, an optimal balance was achieved between crystalline structure and surface characteristics, maximizing photocatalytic efficiency. The findings highlight the importance of the catalyst calcination temperature on the phase composition, surface area, and crystallinity in TiO2 nanorods. This provides valuable insights for developing advanced environmental remediation technologies.