Reduced graphene oxide – CeO2 nanocomposites for photocatalytic dye degradation

Abstract

Over the past few decades, the widespread use of dyes has led to considerable environmental pollution, posing serious threats to human health and ecosystems. In this context, here focus on a tailored nanocomposite comprising reduced graphene oxide (rGO) and cerium oxide (CeO2) to eradicate methylene blue (MB) dye. The fabrication process involves a facile synthesis wherein CeO2 nanoparticles are anchored onto rGO sheets through co-precipitation treatment by mixing a precursor salt of cerium with graphene oxide (GO) in presence of reducing agent. The resulting nanocomposites were characterized using X-ray diffraction (XRD) analysis which confirms the crystallite size of CeO2 and rGO-CeO2 determined to be 21.61 nm and 10.74 nm respectively. Further FE-SEM analysis vividly illustrates the relatively spherical form of CeO2, which is dispersed on the rGO surface and energy dispersive X-ray spectroscopy (EDX) results provide clear evidence of the presence of carbon, cerium and oxygen in the composite. Additionally, Fourier-transform infrared spectroscopy (FTIR) confirms the composition of the rGO-CeO2 nanocomposites demonstrating the existence of various oxygen-containing groups, including O–H, C=O and Ce–O bonds. Thermogravimetric analysis (TGA) highlights that the rGO-CeO2 nanocomposites exhibits higher thermal stability with only 21.88 % weight loss up to 400 °C. Moreover, the photocatalytic activity of rGO-CeO2 nanocomposite exhibits a remarkable 94.92 % degradation of MB dye within 80 min under optimal conditions of UV light irradiation (λ = 254 nm), with a catalyst dosage of 7 mg in a 20 ppm of MB dye solution at pH 9. In contrast, pristine rGO and CeO2 achieved only 32.27 % and 38.48 % in 100 and 90 min respectively. The kinetics of photocatalysis process were meticulously studied and revealed that they followed pseudo-second order kinetic model suggesting chemisorption of MB dye onto nanocomposites prior to degradation. The stability of the nanocomposite was assessed under optimal conditions, demonstrating robust MB degradation (78 %) even up to the 4th cycle. Overall, the successful outcomes of this study show significant potential for degrading MB dye in wastewater by using the rGO-CeO2 nanocomposite.