Oxygen uptake, selectivity and reversibility of Tb–CeO₂ mixed oxides for air separation

A series of Tb–CeO₂ mixed oxides were investigated as novel oxygen sorbents. The relationship between %Tb content-oxygen uptake, alongside the selectivity and reversibility of these materials, was determined via chemisorption (400, 500 and 600 °C) and supporting thermogravimetric studies at 500 and 600 °C. Oxygen chemisorption experiments conducted at 600 °C showed higher uptakes were achieved by incorporating more Tb into the CeO₂ crystal lattice. The uptake of 40 mol% Tb–CeO₂ was 121 μmol g⁻¹ and for 10 mol% Tb–CeO₂ the uptake was 34 μmol g⁻¹. Increasing the analysis temperature for each material resulted in an increase in uptake as more oxygen was able to be removed. All materials exhibited good reversibility and cyclic stability during alternating N₂ and air atmospheres at 600 °C. High O₂/N₂ selectivity was also demonstrated as no detectible uptake was observed at 600 °C using N₂ as the adsorbate. The data suggests that these materials may have applications in air trace gas removal or as membranes for air separation applications.