Sunlight-Assisted Photocatalytic Degradation of Rhodamine B Dye by High-Entropy Fluorite Oxide

In the present work, a six-cation high-entropy fluorite-type oxide photocatalyst composition (Ce1/6Gd1/6Pr1/6Sm1/6Y1/6Zr1/6)O2−δ (HEFO) was prepared with the concept of “high entropy” using a glycine-assisted solution combustion method. Several characterization techniques, such as X-ray diffraction (XRD), UV–visible spectroscopy, and field emission scanning electron microscopy (FESEM), were employed to evaluate the physicochemical properties. Structural analysis by XRD confirmed the formation of a single-phase cubic fluorite structure supported by the Rietveld refinement analysis. The photocatalytic application was systematically evaluated using the prepared HEFO for the degradation of Rhodamine B dye with the help of natural sunlight and H2O2. Several parameters such as photocatalyst dose, dye concentration, and pH were investigated, and the results revealed that 25 mg of photocatalyst, 20 ppm dye concentration, and pH 11 achieved 99.25% of Rhodamine B degradation. Similarly, radical-scavenger tests suggested the involvement of more than one reactive pathway. In addition, the photocatalyst demonstrated excellent reusability, retaining 74.46% degradation efficiency after five cycles (83.6% activity retention), with XRD confirming the preserved cubic fluorite structure. The photocatalytic investigations demonstrate high-entropy oxides to be highly efficient and sustainable photocatalysts for the degradation of Rhodamine B dye.