Controllable Jahn‐Teller Distortion Engineering Enables in‐situ Self‐assembly Phase‐Reconstruction for High‐Performance Protonic Ceramic Cell Air Electrodes

ABSTRACT In situ phase reconstruction presents a promising method to improve the electrocatalytic performance of air electrodes in proton ceramic cells, yet its kinetic and thermodynamic mechanisms are not fully clarified. Herein, we realize controllable phase reconstruction approach for Pr 1.6 Sr 0.4 CuO 4+ δ (PSC) perovskite materials, driven by thermodynamic immiscibility that induces phase separation through modulation of an atomic‐level descriptor—the Jahn‐Teller (J‐T) distortion activity. Through systematic Ni doping (5% to 40%), we trigger the formation of secondary (Pr,Sr) 2 Ni 1− x Cu x O 4+ δ phase, characterized by suppressed J‐T effect, which interfaces heterogeneously with the J‐T active PSC matrix. At 40%Ni doping (PSNC‐0.4), a complete phase transition to the J‐T‐inactive phase is realized. Remarkably, fine‐tuning the J‐T distortion at 10% Ni doping (PSNC‐0.1) results in outstanding electrochemical performance, including an ultra‐low area‐specific resistance of 0.06 Ω cm 2 , alongside record‐breaking peak power density and electrolysis current density reaching 1.74 W cm −2 and 2828 mA cm −2 (at 1.3 V) at 700°C, respectively. Comprehensive experiments and calculations confirm the optimal synergy between catalytically active PSC and proton‐conductive secondary phase in PSNC‐0.1. This work highlights the pivotal role of J‐T distortion modulation in guiding phase reconstruction and establishes a generalizable principle for designing high‐performance hetero‐structured electrodes via thermodynamic‐driven J‐T effect engineering.