Thermal Cycles of Perovskite Manganese Oxides for Syngas Production

When certain metal oxides are heated up in an intert atmosphere, they expel molecular oxygen from their lattice. When cooled and exposed to an oxidant such as CO2, these reduced metal oxides will re-oxidize and yield CO. The same process can be used to transform H2O to H2. This was demonstrated to be technologically feasible in a landmark 2011 Science paper, using cerium (IV) oxide, otherwise known as ceria, as the catalytic metal oxide. There have been many subsequent efforts to dope ceria so that the whole process can take place at temperatures lower than the ~1500C typically required, but the fluorite structure of ceria is not particularly amenable to extensive doping. Perovksite structures (ABO3), on the other hand, are easily doped and come in many different combinations, representing a vast scientific research space that is only now beginning to be explored in depth. In particular, perovskites featuring manganese on the B-site have proven to be particularly interesting, in some cases displaying catalytic activity at temperatures much lower than ceria, and at improved rates. This project described here features a systematic investigation of a wide variety of mangese-based perovskite structures and their utility in the CO2-to-CO thermocyclic conversion. The identification of chemical trends in this series may prove useful for future studies of thermocyclic carbon conversion.