An active and durable perovskite electrode with reversibly phase transition-induced exsolution for protonic ceramic cells

Abstract

Protonic ceramic cells (PCCs) possess great application potential, attributed to their cleanliness and high energy conversion efficiency. However, designing active air electrodes with both high stability is challenging. Herein, we report a nanospinel-modified perovskite oxide, Nd_0.5Ba_0.5Mn_0.7Co_0.15Ni_0.15O_3−δ-(Co_xNi_y)₃O₄ (CNO@NBMCN), obtained by a reversibly phase transition-induced exsolution process, as a highly active and durable air electrode for PCCs. Phase-field simulations reveal the intrinsic mechanism of nanoparticles strongly pinning to the substrate in a high-temperature oxidizing environment. The CNO@NBMCN electrode exhibits remarkable low area specific resistance (0.38 Ω cm² at 600 °C) and exceptional stability (degradation rate 0.01 % h⁻¹). It is confirmed by soft X-ray absorption spectroscopy that the construction of the heterostructure leads to more distortion in Mn–O octahedra and weaker metal–oxygen bonds, thereby contributing to the formation of oxygen vacancies. And the exceptionally high durability supported by both fast ion surface exchange and charge transfer at triple-phase boundaries. A single cell with the CNO@NBMCN air electrode achieves outstanding performances in the fuel cell (peak power density of 1.28 W cm⁻²) and electrolysis modes (current density of 2.14 A cm⁻² at 1.3 V), recorded at 700 °C. This work inspires innovative design concepts for robust heterogeneous electrocatalysts.