Synergistic Modulation of Oxygen Vacancies and Proton Hydration in Iron-Based Perovskites for Protonic Ceramic Fuel Cells

Proton-conducting ceramics have emerged as a transformative solution for next-generation solid oxide fuel cells for their superior protonic conductivity and high fuel efficiency at intermediate-to-low temperatures. Cobalt-based perovskite oxides stand out as the dominant cathode materials for proton-conducting ceramic fuel cells (PCFCs) due to their unparalleled oxygen reduction reaction activity. However, their implementation is constrained by limited natural reserves and high production costs. To address these challenges, we developed a series of cobalt-free BaFe0.8Zr0.2–xGdxO3−δ (BFZGx, x = 0–0.20) cathodes for low-cost PCFCs. Gd doping simultaneously enhanced the oxygen vacancy concentration and proton hydration capacity while also boosting the total conductivity, with an optimal doping amount of 0.1. Electrochemical evaluations demonstrate the outstanding performance of the BFZGx electrodes, with BaFe0.8Zr0.1Gd0.1O3−δ achieving a 1.93-fold power density compared to the undoped counterpart. This work establishes Gd-doped BaFe0.8Zr0.2O3−δ perovskites as promising high-performance and cost-effective cathode materials for PCFCs.