Infrared Study of Ozone Adsorption on CeO2

Abstract

Ozone (O3) adsorption on CeO2 pretreated under different conditions and characterized by low-temperature CO adsorption was studied by Fourier transform infrared (FTIR) spectroscopy at 77−300 K. Preliminary exposure to CO2, pyridine, acetonitrile, or methanol at 293 K or to CO at 77 K, as well as adsorption of 18O substituted O3 were used to clarify the nature of adsorption sites and the structure of the surface species. In addition to physisorption and weak H-bonding with the most acidic OH groups of the ceria surface, O3 forms coordinate complexes with two kinds of Lewis acid sites. These complexes have the bands of the ν1 and ν3 modes of O3 at 1096 and 1018−1015 cm-1, or 1104 and 1012−1008 cm-1, respectively. The coordinated O3 molecule is no longer symmetric but is bound to a surface Ce4+ ion via one of its terminal oxygen atoms. Basic surface sites of the samples pretreated at 773 K account for O3 decomposition, which occurs almost explosively at 77 K but could be inhibited if O3 adsorption is perform...