Unveiling Entropy‐Driven Performance Enhancement in Double Perovskite Oxygen Electrodes for Protonic Ceramic Electrochemical Cells

The secure and efficient delivery of energy demands advanced solutions, such as protonic ceramic electrochemical cells (PCECs). Despite their promise, challenges including sluggish oxygen electrode kinetics and phase instability in humid or CO 2 ‐rich environments hinder their widespread adoption. Herein, a novel high‐entropy double perovskite oxide (HEDPO), Pr 0.2 La 0.2 Nd 0.2 Na 0.2 Ca 0.2 Ba 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PLNNCBSCF), engineered to leverage the stabilizing effects of high configurational entropy while delivering superior electrochemical performance is developed. Physicochemical characterization confirms the successful formation of a high‐entropy matrix, providing enhanced structural stability and a high density of catalytically active defects. Density functional theory calculations further reveal that the dynamic atomic configurations and heterogeneous electronic distributions within PLNNCBSCF facilitate improved electrochemical reaction kinetics. PCECs incorporating PLNNCBSCF oxygen electrodes demonstrate exceptional performance, achieving a peak power density of 1.77 W·cm −2 in fuel cell mode and a current density of 4.42 A·cm −2 at 1.3 V in electrolysis cell mode at 650 °C. These findings highlight the potential of HEDPOs as robust, high‐performance oxygen electrodes, paving the way for sustainable energy technologies in electrochemical energy conversion and storage.