Defect Formation Thermodynamics of (A,A′)(B,B′)O3 (A = Mg,Ca,Sr and B = Ti,Mn,Cr,Fe,Mo) Perovskites

In a previous theoretical study [B. Grimm and T. Bredow, Oxygen Defect Formation Thermodynamics of CaMnO3: A Closer Look. Phys. Status Solidi B 2022, https://doi.org/10.1002/pssb.202200427], the structural, thermodynamic, and electronic properties of CaMnO3 have been studied. The present study increases the range of compounds to ternary perovskites in a search for suitable anode materials for high-temperature water electrolysis. (A,A ')(B,B ')O3 compounds containing the abundant elements A = Mg,Ca,Sr and B = Ti,Mn,Cr,Fe,Mo are studied theoretically on hybrid density functional theory level. Criteria for a suitable electrode material are low-oxygen defect formation energy and high reaction energy for decomposition into other phases. Based on these criteria, the most suitable ABO3 perovskites are chosen as starting points to create stable mixed compounds. The compound Ca0.5Sr0.5Fe0.25Mn0.75O3-(delta) is found to be the optimal choice as electrode material, with an oxygen defect concentration of at least delta = 0.1875 present at 520 K and highly endothermic decomposition reactions.