Nanocrystalline Mn-doped and Mn/Fe co-doped Ceria Solid Solutions for Low Temperature CO Oxidation

Background: In recent years, development of noble-metal-free catalysts for CO oxidation at lower temperatures has attracted both the scientific and industrial community. Nanosized dopedceria (CeO2) catalyst found huge application in this process because of its unique facile redox ability, oxygen storage/release capacity, cost-effectiveness, and less toxicity. Objective: The aim of the present work is to comparatively study the effect of doping Mn alone and Fe together with Mn in CeO2 on the physicochemical properties and correlate the findings with their respective catalytic activity. Method: A simple and facile co-precipitation method was employed to synthesize the un-doped, Mndoped as well as Mn/Fe co-doped ceria nanocomposites. Results: XRD and Raman results indicated the formation of solid solution with a cubic phase, and TEM-HREM studies disclosed the nanosized nature of the particles. The co-doping of Mn and Fe into ceria lattice leads to enhance the structural defects, such as the concentration of surface Ce3+ ions, oxygen vacancies, etc., as validated by XPS, Raman, and O2-TPD techniques. Conclusion: The catalytic CO oxidation activity of Mn/Fe co-doped CeO2 is significantly higher as compared to the un-doped and Mn-doped CeO2. This improved activity of Mn/Fe co-doped CeO2 is ascribed to the collective properties such as larger surface area, smaller particle size, a higher amount of surface Ce3+ species (oxygen vacancies), and enhanced reducibility. Further, this catalyst showed an excellent stability towards CO oxidation in the time-on-stream experiment of 40 h.