Synergistic Self-Assembly and High-Entropy Dual Engineering of the Ruddlesden-Popper Air Electrode for High-performance and Stable Reversible Protonic Ceramic Cells

Overcoming sluggish oxygen reduction and evolution reaction kinetics remains a fundamental challenge in developing high-performance air electrodes for reversible protonic ceramic cells (RPCCs). Herein, we present an innovative approach combining high-entropy engineering with self-assembly processes to fabricate a thermally derived composite electrode Pr 0.4 Sr 0.4 Nd 0.4 La 0.4 Gd 0.4 Co 0.5 Ni 0.5 O 4+δ (PSNLGCN). This unique architecture consists of Pr-deficient Pr 0.4-x Sr 0.4 Nd 0.4 La 0.4 Gd 0.4 Co 0.5 Ni 0.5 O 4+δ matrix and exsolved Pr 6 O 11 nanoparticles. The high-entropy design ensures exceptional structural stability through configurational entropy stabilization, while the in-situ formed Pr 6 O 11nanoparticles significantly enhance electrocatalytic activity by providing abundant active sites for oxygen reactions. The RPCC with the PSNLGCN air electrode demonstrates remarkable performance, attaining a peak power density (PPD) of 1.1 W cm -2 in fuel cell (FC) mode and a current density of -2.9 A cm -2 at 1.3 V in electrolysis cell (EC) mode at 700 ℃. More importantly, the cells exhibit outstanding durability, maintaining stable operation for 200 h in FC mode, 130 h in EC mode, and 100 h under reversible cycling conditions at 600 ℃. This work establishes a novel materials design paradigm for developing RPCC air electrodes that simultaneously achieve superior electrocatalytic performance and operational stability.