Accurate Prediction of Oxygen Vacancy Concentration with Disordered A-Site Cations in High-Entropy Perovskite Oxides: Article No. 29

Entropic stabilized ABO3 perovskite oxides promise many applications, including the two-step solar thermochemical hydrogen (STCH) production. Using binary and quaternary A-site mixed {A}FeO3 as a model system, we reveal that as more cation types, especially above four, are mixed on the A-site, the cell lattice becomes more cubic-like but the local Fe-O octahedrons are more distorted. By comparing four different Density Functional Theory-informed statistical models with experiments, we show that the oxygen vacancy formation energies (EfV) distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry (..delta..) accurately. For STCH applications, the EfV distribution, including both the average and the spread, can be optimized jointly to improve ..Delta..delta.. (difference of ..delta.. between the two-step conditions) in some hydrogen production levels. This model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in {A}FeO3 perovskites.