Photocatalytic degradation of aqueous Congo red dye pollutants by rare-earth metal oxide (CeO₂) nanorods

Existing nano powder-based photocatalysts face challenges in degradation performance, particularly for the degradation of complex dyes like Congo red (CR). In this work, cerium dioxide (CeO₂) nanorods are successfully fabricated combining hydrothermal synthesis with calcination for the photocatalytic degradation of CR dyes. The synthesized CeO₂ nanorods possess a diameter of ∼ 100 nm based on field emission scanning electron microscopy (FE-SEM) investigation. The atomic percentages of Ce and O elements are measured to be 44.2 at% and 39.2 at%, respectively, by the energy dispersive X-ray spectroscopy (EDS). By means of X-Ray diffraction (XRD) analysis, all the prepared samples show cubic CeO₂ with a small amount of Ce₂O₃. To validate their photocatalytic function, the CeO₂ nanorods are tested towards CR dyes, where the degradation of CR solution under UV irradiation is faster than that in dark condition. A high CR degradation efficiency of up to 97.7% is revealed within 130 min photocatalytic activity. From the scavenger test, superoxide radical (^•O₂^–) and hole (h⁺) are discovered to be the most reactive oxygen species generated during photodegradation process. This finding provides a simple yet effective method to fabricate highly effective photocatalytic materials for dye pollutant degradation in wastewater treatment. Future work will focus on optimizing the material properties and degradation mechanisms further, opening avenues for the scaled application of these materials. © 2023 Elsevier B.V.