Effective Atomic N Doping on CeO2 Nanoparticles by Environmentally Benign Urea Thermolysis and Its Significant Effects on the Scavenging of Reactive Oxygen Radicals.

ABSTRACT

Atomic nitrogen doping on CeO2 nanoparticles (NPs) by an efficient and environmentally benign urea thermolysis approach is first studied, and its effects on the intrinsic scavenging activity of the CeO2 NPs for reactive oxygen radicals are investigated. The N-doped CeO2 (N-CeO2) NPs, characterized by X-ray photoelectron and Raman spectroscopy analyses, showed considerably high levels of N atomic doping (2.3-11.6%), accompanying with an order of magnitude increase of the lattice oxygen vacancies on the CeO2 crystal surface. The radical scavenging properties of the N-CeO2 NPs are characterized by applying Fenton's reaction with collective and quantitative kinetic analysis. The results revealed that the significant increase of surface oxygen vacancies is the leading cause for the enhancements of radical scavenging properties by the N doping of CeO2 NPs. Enriched with abundant surface oxygen vacancies, the N-CeO2 NPs prepared by urea thermolysis provided about 1.4-2.5 times greater radical scavenging properties than the pristine CeO2. The collective kinetic analysis revealed that the surface-area-normalized intrinsic radical scavenging activity of the N-CeO2 NPs is about 6- to 8-fold greater than that of the pristine CeO2 NPs. The results suggest the high effectiveness of the N doping of CeO2 by the environmentally benign urea thermolysis approach to enhance the radical scavenging activity of CeO2 NPs for extensive applications such as that in polymer electrolyte membrane fuel cells.