Functional Oxides for Oxygen Scavenging Applications

Abstract

The aim of this experimental study is to develop oxide-based materials for oxygen enrichment/separation from air through pressure/temperature swing sorption. Production of commercial oxygen is conventionally achieved through cryogenic distillation of air into its components, which requires large capital investment and energy consumption. Other methods like polymeric membrane separation and pressure swing adsorption are used for small to medium size (1-400 Nm3/h) demand of oxygen. As an alternative, membrane separation with the use of mixed ionic/electronic conducting oxide ceramics offer infinitely high perm-selectivity compared to other separation processes. Certain non-stoichiometric transition metal oxides can reversibly incorporate or release oxygen from their lattice by changing the ambient conditions. A change in oxygen partial pressure or temperature of the surrounding can influence the oxygen content in their lattice. Thus, switching of ambient partial pressure of oxygen from low to high can incorporate oxygen selectively into the lattice and vice versa, achieving an efficient separation of oxygen from air. Transition metal Perovskite oxides (general formula ABO3) and related structures are notable candidates in this regard. They have a relatively open structure of corner shared octahedra with variable oxide ion vacancies that can be tuned by synthesis methods and chemistry. Perovskite and double perovskite oxides such as SrCoO3ð€€€d and (RE)BaCo2O5+d (RE = Dy, Y) respectively have been explored for oxygen separation applications in this thesis