Tuning Sr2Fe1.5Mo0.5O6-δ perovskites with Ni as an active and durable air electrode for reversible proton ceramic electrochemical cells

Reversible proton ceramic electrochemical cells (R-PCECs) hold strong promise for effective energy storage and conversion, yet their practical utilization is restricted by the insufficient reaction kinetics and hydration ability of air electrodes. In this work, we introduce a Ni doping strategy to optimize Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) perovskite, with emphasis on the impact of different Ni doping ratios on phase structure, oxygen vacancy, and electrochemical performance. Among them, Sr 2 Fe 1.5 Mo 0.3 Ni 0.2 O 6-δ (SFMN0.2) demonstrates the highest activity and hydration capacity, with a 38 % decrease in polarization impedance compared to the undoped SFM at 700 °C. The SFMN0.2 air electrode-based R-PCEC reached a peak power density of 768 mW cm −2 in fuel cell mode and 1053 mA cm −2 under 1.3 V in electrolysis mode at 700 °C. Besides, the cell manifests robust cycling stability in both modes over nearly 100 h of operation. These findings indicate that appropriate Ni doping is a feasible approach for designing high-performance air electrodes in R-PCECs.