Effect of Mn content on physical properties of CeOx–MnOy support and BaO–CeOx–MnOy catalysts for direct NO decomposition

A series of manganese–cerium mixed oxides were prepared by a glycothermal method, and the NO decomposition activities of the Ba-loaded Ce–Mn oxides were examined. Among the catalysts examined, the highest NO conversion was obtained on the BaO/Ce–Mn oxide catalyst with a Mn/(Ce+Mn) ratio of 0.25. The X-ray diffraction and Raman analyses indicated the formation of Ce–Mn oxide solid solutions with a cubic fluorite structure. The electron spin resonance analysis indicated the presence of paramagnetic Mn2+ species in the composite catalysts. Incorporation of Mn2+ in the fluorite structure of CeO2 causes an increase in the concentration of oxygen vacancies, which play an important role in the NO decomposition activity of the catalysts. The catalysts were also characterized by X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Based on the results obtained, the relationship between the physical properties of the catalysts and their NO decomposition activities was discussed.