Synergistic self-assembly and high-entropy dual engineering of the Ruddlesden–Popper air electrode for high-performance and stable reversible protonic ceramic cells

Abstract

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_0.4Sr_0.4Nd_0.4La_0.4Gd_0.4Co_0.5Ni_0.5O_4+δ (PSNLGCN). This unique architecture consists of a Pr-deficient Pr_0.4−xSr_0.4Nd_0.4La_0.4Gd_0.4Co_0.5Ni_0.5O_4+δ matrix and exsolved Pr₆O₁₁ nanoparticles. The high-entropy design ensures exceptional structural stability through configurational entropy stabilization, while the in situ formed Pr₆O₁₁ nanoparticles significantly enhance electrocatalytic activity by providing abundant active sites for oxygen reactions. The RPCCs with the PSNLGCN air electrode demonstrate 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 °C. 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 °C. This work establishes a novel materials design paradigm for developing RPCC air electrodes that simultaneously achieve superior electrocatalytic performance and operational stability.