Morphological effect of CeO₂-MnO_x catalyst on their catalytic performance in lean methane combustion

Ship-like, oblate spheroid and nano sheet CeO₂-MnO_x mixed oxides were prepared by hydrothermal method and characterized by N₂ sorption, XRD, SEM, TEM, H₂-TPR, Raman spectra and XPS. The relationship between the structure of CeO₂-MnO_x and their catalytic performance in lean methane combustion were then investigated. The results reveal that the catalytic performance of the mixed CeO₂-MnO_x oxide was greatly depended on its morphology. Among all of the samples, the mixed oblate spheroid CeO₂-MnO_x oxides with most oxygen vacancies, Ce³⁺ content and surface active oxygen exhibited the highest activity in lean methane combustion, with a complete CH₄ conversion at 540℃. Following it, the mixed ship-like CeO₂-MnO_x oxides catalyst had 94.05% of the CH₄ conversion at 540℃. On the contrast, the mixed nano sheet CeO₂-MnO_x oxides catalyst presented the lowest catalytic activity with only 89.68% CH₄ conversion at the same reaction temprature owing to its lower oxygen vacancies and surface active oxygen.