Solution combustion synthesis and physico-chemical properties of ultrafine CeO2 nanoparticles and their photocatalytic activity

Abstract

Ultrafine cerium oxide (CeO₂) nanoparticles have been confirmed to be capable photocatalysts for environmental remediation because of their strong redox ability, long-term stability, nontoxicity, and cost effectiveness. CeO₂ nanoparticles were successfully synthesized by a solution combustion method using cerium nitrate and urea. The physical, chemical, thermal and optical properties of the as-prepared samples were characterized using various analytical techniques. X-ray diffraction data confirm that the synthesized nanocrystalline CeO₂ samples have cubic structure with an average grain size of 10, 8 and 19 nm corresponding to as-prepared, 300 and 600 °C annealed samples, respectively. The HRTEM results confirmed that the synthesized nanoparticles exhibit good polycrystalline nature with spherical ultrafine nanoparticles having size in the range of ∼9 nm. The UV/vis spectrum shows a maximum absorption at 294 nm and the band gap of CeO₂ was tuned by adjusting the annealing temperature. In the PL spectra, a strong and broad emission band was observed at 425 nm due to the presence of a blue shift in the visible region. The photocatalytic activities of annealed CeO₂ nanoparticles were investigated by photodegradation of methylene blue (MB) under UV light irradiation. It was found that the ultra-fine CeO₂ nanoparticles exhibited better photocatalytic activity than that of already available commercial photocatalysts. Based on the investigation, these ultra-fine CeO₂ nanoparticles possess adaptable potential applications for wastewater purification.