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 (\({E}_{V}^{f}\)) distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry (δ) accurately. For STCH applications, the \({E}_{V}^{f}\) distribution, including both the average and the spread, can be optimized jointly to improve Δδ (difference of δ 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.

熵稳定的 ABO ₃钙钛矿氧化物有望用于许多应用，包括两步太阳能热化学制氢 (STCH) 生产。使用二元和四元 A 位混合 {A}FeO ₃作为模型系统，我们发现随着更多阳离子类型（尤其是超过四种）在 A 位上混合，晶胞晶格变得更像立方体，但局部 Fe –O 八面体更扭曲。通过将四种不同的密度泛函理论统计模型与实验进行比较，我们表明必须考虑氧空位形成能 ( \({E}_{V}^{f}\) )分布和空位相互作用来预测氧非化学计量 ( δ ) 准确。对于 STCH 应用，\({E}_{V}^{f}\)分布，包括平均值和分布，可以联合优化以改善某些氢气生产水平的Δδ （两步条件之间的δ差异）。该模型可用于预测通过在 {A}FeO ₃钙钛矿中混合阳离子可以热力学改善的水分解范围。