Green-Synthesized rGO-CeO₂ Nanocomposites for Enhanced Visible-Light Photodegradation of Eosin Y

Green-synthesized rGO-CeO₂ nanocomposites (NCs) were fabricated using an eco-friendly approach, in which the leaf extract of Saraca asoca (Sa) served as a natural reducing and stabilizing agent. Reduced graphene oxide (rGO) was obtained through the chemical reduction of graphene oxide (GO) and combined with CeO₂ nanoparticles (NPs) via a simple physical grinding method to produce uniform nanocomposites. Comprehensive characterization using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-DRS), field emission scanning electron microscopy (FE-SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), energy-dispersive x-ray (EDX), thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS), zeta potential, and Brunauer-Emmett-Teller (BET) analyses confirmed the formation of face-centered cubic CeO₂, with spherical and hexagonal nanoparticles uniformly anchored onto rGO sheets and an average particle size of 16.82 nm. Optical analysis revealed a reduced band gap of 2.73 eV, while XPS results confirmed the coexistence of mixed cerium oxidation states (Ce³⁺/Ce⁴⁺). Under visible light irradiation (500 W), the rGO-CeO₂ NCs demonstrated excellent photocatalytic performance, achieving 93.78% degradation of Eosin Y (EY), a reddish-pink fluorescent dye, following a first-order kinetic model. Radical scavenging experiments indicated that hydroxyl (•OH) and superoxide (•O₂ ^-) radicals were the primary reactive species involved in the degradation process. Moreover, the NCs exhibited good structural stability and retained high photocatalytic efficiency over multiple reuse cycles, highlighting their potential as cost-effective photocatalysts for the treatment of dye-contaminated textile wastewater.