High Cationic Dispersity Boosted Oxygen Reduction Reactivity in Multi‐Element Doped Perovskites

Oxygen‐ion conducting perovskite oxides are important functional materials for solid oxide fuel cells and oxygen‐permeable membranes operating at high temperatures (>500 °C). Co‐doped perovskites have recently shown their potential to boost oxygen‐related kinetics, but challenges remain in understanding the underlying mechanisms. This study unveils the local cation arrangement as a new key factor controlling oxygen kinetics in perovskite oxides. By single‐ and co‐doping Nb5+ and Ta5+ into SrCoO3‐δ, dominant factors affecting oxygen kinetics, such as lattice geometry, cobalt states, and oxygen vacancies, which are confirmed by neutron and synchrotron X‐ray diffraction as well as high‐temperature X‐ray absorption spectroscopy, are controlled. The combined experimental and theoretical study unveils that co‐doping likely leads to higher cation dispersion at the B‐site compared to single‐doping. Consequently, a high‐entropy configuration enhances oxygen ion migration in the lattice, translating to improved oxygen reduction activity. The underlying mechanism for enhanced oxygen reduction reaction (ORR) activity of co‐doped SrCo0.8Nb0.105Ta0.095O2.562 (SCNT) compared to single‐doped SrCo0.846Nb0.154O2.565 (SCN) and SrCo0.805Ta0.195O2.589 (SCT) materials is presented. Combined X‐ray absorption and computational results show that the SCNT has a similar cobalt state but higher cation dispersion. The studies reveal that high dopant dispersion enhances oxygen vacancy migration and, therefore, ORR activity, achieved through increased configuration entropy.