Study the contribution of surface defects on the structural, electronic structural, magnetic, and photocatalyst properties of Fe: CeO2 nanoparticles

摘要

In this work, the structural, ferromagnetic (FM) and photocatalytic properties of Ce1-xFexO2-delta (0 <= x <= 0. 20) nanoparticles (NPs) synthesized through simple co-precipitation technique have been explored. X-ray diffraction (XRD) spectra revealed that all the samples possess single-phase fluorite structure. The crystallites size measured using XRD pattern found to decrease (8.9-6.5 nm) as the Fe content increased. The decrease in the crystallite size, further illustrated by TEM micrographs is also related to increase in the oxygen deficiency (delta) over the surfaces of Fe: CeO2-delta NPs. The Ov has been traced from the Raman spectra, in which the F-2g Raman phonon mode at 462 cm(-1) showed a broadening and red shift indicating that the Fe dopant further induces Ov. The NEXAFS spectral feature at Fe L-3,L-2 edges signified that the Fe ions partially occupy the sites of Ce ions in the CeO2 matrix with Fe3+ and Fe2+ mixed valence state. Hence, the surface Ov is believed to activate the FM response based on bound magnetic polarons (BMP) mechanism, and the observed negative magnetic susceptibility at high applied magnetic field has been interpreted by simple approach dependent on coexistence of CeO2/Ce2O3 (core/shell) structures. The photo-catalyst activity of the samples were examined through decomposition of methylene blue (MB) dye under the sunlight. The catalyst efficiency and dissociation of adsorbed water molecules at the surfaces of NPs enhanced as the Fe doping content increased. This is related to Fe2+/Fe3+ redox cycles and creation of Ce3+/Fe2+ profound bands induced via Ov, which causes a suppression of the recombination of photo-generated electron-hole pairs.