Effect of hydrothermal conditions on microstructures of pure and doped CeO 2 nanoparticles and their photo-catalytic activity: degradation mechanism and pathway of methylene blue dye

CeO2, Sm and Gd doped CeO2 were synthesized using the hydrothermal route. The influence of synthesis conditions on the crystal structure, particle size and microstructure was investigated. The prepared nanoparticles were characterized using X-ray powder diffraction, FT-Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. The photo-catalytic degradation of methylene blue was examined under UV light using the prepared nanoparticles at different conditions (pH, dye concentration, catalyst dosage). The photo-catalytic activity of CeO2 was kinetically enhanced by trivalent cations (Gd+3 and Sm+3) doping. The results displayed the excellent catalytic activity of the Gd doped CeO2 as compared to that Sm doped CeO2 and the undoped one. The degradation pathways of MB were followed using liquid chromatography/mass spectroscopy (LC/MS), it was found that MB was degraded completely into safe byproducts. The total organic carbon content measurements confirmed the results obtained by LC/MS.