Hydrogen-free exsolution of Ir–Fe nanoalloys on the surface of solid oxide cell perovskite air electrodes

Abstract

Metal nanoparticle decoration via exsolution in a hydrogen reducing environment has emerged as a powerful strategy to enhance the performance of solid oxide cell (SOC) perovskite air electrodes. The exsolution process is fundamentally constrained by its reliance on a reducing atmosphere (H₂), which is inherently incompatible with oxidizing conditions of air electrodes, thereby constraining the range of elements and systems that can be practically implemented. Here, we report a hydrogen-free exsolution pathway that directly forms stable, socketed nanoalloys in air. By harnessing the intrinsic chemical affinity and broad miscibility between iridium and iron, we demonstrate that atomic-layer-deposited Ir nanoparticles act as thermodynamic sinks, selectively redistributing Fe from Sr₂Fe_1.5Mo_0.5O_6−δ (SFMO) perovskites during annealing in air. This process directly yields anchored Ir–Fe nanoalloys without the need for reducing gas. The Ir–Fe anchored SFMO electrodes exhibit improved activity and stability at 800 °C. The resulting socketed architecture not only resists coarsening but also mitigates surface strain, suppresses Sr segregation, and enhances oxygen exchange kinetics. This work establishes affinity-driven socketed nanoparticle formation as a distinct hydrogen-free exsolution pathway for SOC air electrodes.