Double Perovskite Materials for Applications in Chemical Looping and Oxygen Storage

Chemical looping combustion is a process currently being studied for its potential to reduce the energy penalty associated with carbon capture. To reduce this energy penalty, chemical looping makes use of metal oxides as the source of oxygen for combustion of a fuel. The resulting waste stream consists only of CO₂ and water. The water can then be condensed resulting in a pure CO₂ stream ready for sequestration. One interesting class of materials for chemical looping applications are double perovskite oxides due to their ability to rapidly store and release oxygen. Previously, the double perovskite BaYMn₂O_5+x was shown to rapidly and reversibly store and release oxygen with unprecedented kinetics. The ability of these materials to store and release oxygen is derived from the fact that the cations in these materials can vary in oxidation state which allows the oxygen stoichiometry to vary. Altering the cation composition in these materials will allow for the optimization of both the amount of oxygen stored and the storage/release kinetics. Four double perovskite materials were synthesized and studied for this work, BaLaFe₂O_5+x, BaLaCo₂O_5+x, BaYCo₂O_5+x and BaYFe₂O_5+x. Characterization of the materials using X-ray diffraction and X-ray photoelectron spectroscopy will be presented. We will also present adsorption/desorption studies and basic kinetic data as well as initial results of testing with methane as a model fuel. The Fe-containing compounds have proven to be the most interesting as they are stable for multiple adsorption/desorption cycles with both nitrogen/air and hydrogen/air at multiple temperatures.