Structural and Optical Properties of Mesoporous Sm3+:CeO2 and its Environmental Applications

Abstract

Cerium oxide (CeO2) is one of the most interesting oxides industrially because it has been widely used as a catalyst, three-way automotive catalytic converters for purification of exhaust gases, oxygen sensors, and so forth for long periods of time. Recently, CeO2 nanoparticles has also emerged as a fascinating and lucrative material for environmental remediation applications. The key for most of the above mentioned applications of CeO2 based materials is its extraordinary ability to release or uptake oxygen by shifting some Ce4+ to Ce3+ ions. Better catalytic performances of CeO2 have been reported in the presence of Ce3+ and oxygen vacancy defects, which are potentially potent surface sites for catalysis. Here, we present the effect of Sm3+ doping on structural and optical properties of mesoporous CeO2 and its environmental applications. The XRD results showed that even as-prepared material has cubic fluorite structure of CeO2 with no crystalline impurity phase. All the nanopowders exhibited strong absorption in the UV region and good transmittance in the visible region. Mesoporous Sm3+ doped CeO2 sample could effectively photodegrade all types of cationic, anionic and nonionic dyes under natural sunlight irradiation. These high surface area mesoporous materials exhibited notable adsorption and effective removal of Cr(VI) from aqueous solutions. Further Sm3+ doping was found to cause unusual emissions with a dominant 4G5/2 → 6H5/2 transition cantered at 573 nm. Additionally, the luminescence intensities enhanced with increasing Sm3+ concentration from 0.5 mol% to 1 mol% with further increasing Sm3+ concentration leads to the decrease in luminescence intensities. The presence of increased surface hydroxyl group, mesoporosity, and surface defects have contributed towards an improved activity of mesoporous CeO2, which appears to be potential candidates for optical, and environmental applications.