Influence of crystalline phase structure of rare earth oxides on active oxygen and basic sites

Abstract

Herein, the effects of crystalline phase structures of rare earth oxides on active oxygen and basic sites were investigated. The fluorite structure shows the best lattice oxygen mobility and redox properties due to its open structure and weakest Ln-O bond strength. For Pr₆O₁₁ and Tb₄O₇, the presence of polyvalent cation states further enhances these properties. Based on the basicity and number of basic sites, the surfaces of A-type, B-type, and C-type lanthanide sesquioxides facilitate the generation of chemisorbed oxygen species in the following order: A-type > B-type > C-type. Furthermore, the basicity and amount of chemisorbed oxygen species are dependent on the electronegativity of rare earth elements, which decreases gradually from La to Lu. This is because from La₂O₃ to Lu₂O₃, electrons are less biased toward oxygen, the basicity of lattice oxygen decreases, and fewer electrons are produced for gaseous oxygen activation and chemisorbed oxygen generation.