Adsorption of NO and NO2 on ceria-zirconia of composition Ce0.69Zr0.31O2 : A DRIFTS study

Abstract In this study, the nature of surface intermediates generated by adsorption of NO and NO 2 on a commercial ceria–zirconia powder of composition Ce 0.69 Zr 0.31 O 2 was investigated using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The conditions of occurrence of the main adsorbed species, i.e. nitrites and nitrates, are studied semi-quantitatively as a function of catalyst pre-treatment and/or type of adsorbed NO x molecule. On the partially reduced ceria–zirconia, the primary role of NO x is to re-oxidize the surface via adsorption/decomposition on reduced sites. By contrast, the formation of nitrites and nitrates readily occurs on oxidized surfaces, the latter kind of species being strongly promoted in the case of NO 2 adsorption only.