Reviving Air Electrodes in Protonic Ceramic Cells by Unlocking Subsurface

Protonic ceramic electrochemical cells (PCECs) show promise for efficient hydrogen production and power generation, yet surface degradation of perovskite air electrodes caused by A-site cation segregation poses a challenge. Rather than suppressing surface segregation, this work leverages the opportunity, unlocking the latent potential of the catalytically active, B-site-enriched subsurface beneath the segregated surface layers. Using PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) as a model electrode, we expose a subsurface enriched with oxygen vacancies through an alkaline treatment. As a result, the electrolysis current density increases by 28% at 1.3 V and the peak power density improves by 24% at 650 °C in reversible PCEC operation, while maintaining stability. These improvements arise from enhanced H2O/O2 adsorption and dissociation, and facilitated charge transfer, supported by experimental and theoretical analysis. This surface activation strategy is further validated across multiple perovskite air electrodes, demonstrating a general approach to revive segregated electrodes by harnessing the self-reconstructed subsurface.