Enhancement of photocatalytic activity of CeO₂ nanorods through lanthanum doping (La–CeO₂) for the degradation of Congo red dyes

The discharge of synthetic dyes into water bodies poses severe environmental risks due to their toxic and recalcitrant nature. This study explores the enhancement of photocatalytic properties of cerium dioxide (CeO₂) nanorods by doping with lanthanum (La) to improve their efficacy in degrading aqueous solutions of Congo red dye. The CeO₂ nanorods were synthesized via a hydrothermal method and subsequently doped with varying concentrations of La. The scanning electron microscopy (SEM) images confirmed the rod-like structures (nanorods) were observed for all samples, while the energy-dispersive X-ray spectroscopy (EDX) confirmed the homogeneous incorporation of La into the CeO₂ matrix. The X-ray diffraction (XRD) spectra demonstrate lattice distortion due to substitutional defect. Photocatalytic experiments revealed that La-doped CeO₂ nanorods exhibited significantly enhanced degradation capabilities compared to undoped counterparts, achieving up to a 3-fold photocatalytic kinetics ((30 ± 2) × 10⁻³ min⁻¹) compared to the undoped counterparts ((11.5 ± 0.4) × 10⁻³ min⁻¹). Influence of various parameters that affect the photocatalysis performance (i.e., contact time, initial dye concentration, catalyst dosage, and dye solution pH value) were also investigated. Radical scavenger experiments reveal that superoxide radicals play a dominant role in the photocatalytic process. Collectively, these findings confirm that the strategic incorporation of lanthanum into CeO₂ nanorods not only enhances their overall photocatalytic efficiency but also tailors their activity towards specific pollutants through radical-mediated pathways.