Tunable Oxygen Vacancy Formation Energetics in the Complex Perovskite Oxide SrxLa1-xMnyAl1-yO3

The composition dependence of oxygen vacancy formation energies (E-V) in the complex perovskite SrxLa1-xMnyAl1yO3, a material system demonstrated to significantly outperform ceria for solar thermochemical (STC) fuel production, was investigated using a combination of ab initio and experimental techniques. Density functional theory calculations predict that E-V as a function of composition spans a large range from near 0 to over 3 E-V under standard conditions and exhibits trends consistent with equilibrium oxygen nonstoichiometries we determined using thermogravimetric analysis. Our findings show that the strong sensitivity of E-V to composition arises from the composition dependence of the Fermi energy relative to the O 2p band center. From these results, we identify the range of E-V particularly suited for STC cycles for a given set of reduction and oxidation reaction conditions and present a materials design strategy for the optimization of E-V through compositional tuning.