DFT insights on iron-based layered perovskites as oxygen catalysts

Density Functional Theory (DFT)-derived electronic descriptors are key to accelerating the design of effective ORR/OER catalysts. The O 2p-band center, in particular, is a robust descriptor of catalytic activity in perovskite oxides. This study examines the O 2p-band center in Fe 4+ perovskite-type layered oxides, focusing on the Ruddlesden Popper (RP) phases Sr 2 FeO 4 and Sr 3 Fe 2 O 7, as well as the high-Tc superconductor YSr 2 Cu 2 FeO 8. The analysis emphasizes trends driven by compositional modifications. The O 2p-band centers of Sr 2–2 x La 2 x FeO 4 and Sr 3–3 x La 3 x Fe 2 O 7 (0 < x < 1) correlate linearly with the Fe oxidation state, and span a wide energy range (−1.2 eV to −4.7 eV with PBE+ U; −1.9 eV to −4.7 eV with SCAN). Partial substitution of Fe with 3d transition metals (TM) in Sr 2 Fe 7/8 x M 1/8 O 4 shifts the O 2p band center, with the more electronegative TMs bringing it closer to the Fermi level. RP–Sr 2 FeO 4 exhibits remarkable tunability of the O 2p-band center, enabling the compositionally driven design of oxygen catalysts with potentially improved activity–stability balance. In contrast, YSr 2 Cu 2 FeO 7+ δ (0 < δ < 1) shows no correlation between the O 2p-band center and Fe oxidation states, likely due to a change in Fe coordination from octahedral ( δ = 1) to tetrahedral ( δ = 0). The O 2p-center values (−0.9 eV to −1.3 eV with PBE+ U; −1.5 eV to −2 eV with SCAN) suggest that YSr 2 Cu 2 FeO 7+ δ could potentially catalyze the ORR/OER, though stability over operation time remains a challenge. • Fe 4+ perovskite-type layered oxides as high-performance oxygen electrocatalysts. • DFT-guided O 2p-band center tuning in RP–Sr 2 FeO 4 , RP–Sr 3 Fe 2 O 7 , and YSr 2 Cu 2 FeO 7+ δ . • RP systems follow perovskite O 2p-band trends; YSr 2 Cu 2 FeO 7+ δ notably deviates. • Dual substitution in RP enables precise O 2p-band center tuning for enhanced OER. • YSr 2 Cu 2 FeO 7+ δ shows ORR potential across all δ values, but stability is a concern.