Exploration of Mn incorporated CeO2 nanoflakes with meso- and macropores for the effective simultaneous catalytic oxidation of carbon monoxide and propane

Abstract

Highly porous ceria nanoflakes are prepared by a facile citric acid assisted sol–gel method. A Mn incorporated solid solution of CeO2 was also efficiently developed without disturbing the nanoflake morphology of pure CeO2. The formation of fluorite CeO2 with crystallite size ranging from 5–8 nm is evidently revealed from XRD analysis. The introduction of Mn to CeO2 resulted in the formation of smaller crystallites of CeO2 with reduced particle size and lattice parameters. SEM images displayed the flake like nature of CeO2 and Mn/CeO2 with meso and macro pores. TEM images confirm the pore size reduction of CeO2 with Mn doping which is already indicated from BET-BJH-surface area and pore-volume analysis. The presence of a large amount of oxygen vacancies in CeO2 upon Mn introduction is indicated from the drastic reduction in the peak intensities in the Raman spectrum. XPS results revealed that Ce exists in its +4 oxidation state whereas Mn exists in its +3 oxidation state, both of which are favorable for oxidation reactions. The catalytic performance of the prepared nanoflakes is investigated in the simultaneous oxidation of CO and C3H8. Mn incorporated CeO2 showed 100% oxidation of CO from 300 °C onwards and 84% hydrocarbon oxidation is observed even at a high gas flow rate of 500 ml/min at 400 °C over 0.5 g of the catalyst.