Y and Zn co-doped Ba(Fe,Zr)O3−δ perovskite: A cobalt-free oxygen electrode material for the high-stable proton ceramic electrochemical cells

The TEC of BFZYZ is lower to 13.8 × 10 −6 1/K, matching well with the electrolyte. • Y and Zn co-doping enhances hydration ability and surface oxygen vacancies. • BFZYZ yields an R p of 0.26 Ω cm 2 at 600 °C, 50% lower than that of BFZ. • PCFC with BFZYZ electrode achieved peak power density of 0.8 W/cm 2 at 600 °C. • The cell with BFZYZ electrode operates stably for 500 h. Developing active and durable oxygen electrodes for both oxygen reduction and oxygen evolution reactions at low temperatures remains a major challenge for proton ceramic electrochemical cells (PCECs). Herein, a cobalt-free Y and Zn co-doped Ba(Fe,Zr)O 3−δ perovskite (BFZYZ) is developed as a PCEC oxygen electrode, integrating excellent electrochemical performance and durability. At 600 °C, Y and Zn co-doping reduces the polarization resistance by 50%, mainly owing to enhanced hydration capability and surface oxygen exchange, which accelerate ORR/OER kinetics. Meanwhile, BFZYZ shows a lower average thermal expansion coefficient of 13.8 × 10 −6 1/K over 30–600 °C, improving its thermal compatibility with the electrolyte. The PCEC with BFZYZ electrode achieves a peak power density of 0.8 W/cm 2 in fuel cell mode and a current density of 0.82 A/cm 2 at 1.3 V in steam electrolysis mode at 600 °C, with stable operation, demonstrating the potential of BFZYZ for high-performance and durable PCECs.