Enhanced Proton Conduction with Low Oxygen Vacancy Concentration and Favorable Hydration for Protonic Ceramic Fuel Cells Cathode

Protonic ceramic fuel cells (PCFCs), as an efficient energy storage and conversion device, have great potential to solve the serious problems of energy shortage and environmental pollution. Improving the proton conductivity of the promising cathode materials is an effective solution to promote the widespread application of PCFCs at low temperatures (450–650 °C). Herein, considering the high oxygen reduction reaction (ORR) activity of BaCoO₃-based perovskite oxide and beneficial proton uptake capacity of Zn-doping, we construct BaCo_0.4Fe_0.4Zn_0.1Y_0.1O_3‑δ (BCFZnY) as the PCFCs cathode, and compare it with the classic triple-conducting cathode BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3‑δ (BCFZrY). Different from the general strategy of increasing the initial oxygen vacancy concentration of cathode materials, this work unveils that enhancing the hydration of perovskite oxide with low oxygen vacancy concentration is a more effective strategy to accelerate the proton diffusion in the electrode. Therefore, the BCFZnY cathode achieved excellent proton conductivities of 8.05 × 10^–3 and 6.38 × 10^–3 S cm^–1 as obtained by hydrogen permeation measurements and peak power densities of 982 and 320 mW cm^–2 in a BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3‑δ-based anode-supported fuel cell at 600 and 450 °C, respectively.