Regulating defect chemistry and oxygen reduction kinetics of high-entropy perovskite oxygen electrodes through A-site Pr deficiency engineering

A-site non-stoichiometry provides an effective strategy for regulating the defect chemistry and oxygen reduction reaction (ORR) kinetics of high-entropy perovskites for high-performance solid oxide fuel cell (SOFC) oxygen electrodes. Herein, Pr-deficient high-entropy perovskites Pr 0.5-x Ba 0.5 Fe 0.2 Co 0.2 Ni 0.2 Cu 0.2 Mn 0.2 O 3-δ (HEPBM-x, x = 0.05, 0.1) were synthesized to investigate the effects of Pr deficiency on their properties and electrochemical performance as SOFC oxygen electrodes. Both materials exhibited good high-temperature phase stability. Furthermore, increasing the Pr deficiency induced lattice contraction and regulated the valence states of B-site transition metals and surface oxygen species, thereby increasing the proportion of active oxygen species and charge transport capability. HEPBM-0.1 exhibited a polarization resistance of 1.38 Ω·cm 2 at 700 °C, lower than that of HEPBM-0.05 (1.61 Ω·cm 2 ), and demonstrated outstanding long-term stability. A single cell using HEPBM-0.1 as the oxygen electrode achieved a peak power density of 735 mW·cm −2 at 800 °C, representing an ∼39% increase compared to HEPBM-0.05. The results indicate that Pr-deficiency can promote ORR kinetics by regulating defect chemistry, surface oxygen activity and charge transport, providing an effective strategy for the defect design of high-performance SOFC oxygen electrodes.