Surfactant Assisted Synthesis and Characterization of High Surface Area Mesoporous Nanocrystalline Pure, Eu3+ and Sm3+ doped Ceria for Selected Applications

Abstract

CeO2 is one of the most interesting oxides industrially because it has been widely used as a catalyst, metal polishing agent, three-way automotive catalytic converters for purification of exhaust gases, oxygen ion conductor in solid oxide fuel cells, oxidative coupling of methane and water-gas shift reaction, 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 application as photocatalyst for degradation of toxic pollutants. 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. The present work is undertaken on multigram synthesis of high content of Ce3+, high surface area and high quality mesoporous pure CeO2 as well as Sm3+, and Eu3+ doped CeO2 using cheaper metal inorganic precursor. The XRD results showed that even as-prepared material has cubic fluorite structure of CeO2 with no crystalline impurity phase. Thereby, confirming the ability of the present aqueous based synthetic approach to prepare mesoporous crystalline CeO2 nanoparticles at a lower temperature of 100°C. All the nanopowder exhibited strong absorption in the UV region and good transmittance in the visible region. Sm3+ and Eu3+ doped CeO2 nanopowder showed enhanced photoluminescence in the red and orange 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 at room temperature and without any adjustment of pH. Mesoporous Sm3+ doped CeO2 samples also exhibited excellent autocatalytical properties. 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, environmental and biomedical applications.