Effect of Fe content on physical properties of BaO-CeOx-FeOy catalysts for direct NO decomposition

摘要

The physical properties of the Ba-loaded Ce-Fe mixed oxide catalysts, which exhibited high activity for NO decomposition to N2, were investigated. The optimum Fe/(Ce + Fe) molar ratio was 0.02. The X-ray absorption near edge structure, electron spin resonance, and diffuse reflectance UV-vis spectra indicated that the optimum catalyst had the highest proportion of isolated tetrahedral Fe~(3+) ions in all the Fe species. Raman spectra suggested that incorporation of Fe~(3+) in the fluorite structure of CeO2 caused an increase in the concentration of oxygen vacancies, which play an important role in the NO decomposition activity of the catalysts. Temperature-programmed desorption (TPD) of O2 showed that the addition of the Fe component to BaO/CeO2 enhanced O2 uptakes and facilitated oxygen desorption. NO-TPD profiles showed that NO desorption was associated with the desorption of O2, indicating that these two species are formed by decomposition of surface nitrate species.