Tuning the proton concentration and uptake kinetics of BaFeO3 based oxygen electrode for reversible protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs), as efficient energy storage and conversion device, have great potential to address the critical challenges of energy shortage and environmental pollution. Improving the proton concentration and uptake kinetics of promising oxygen electrode materials is an effective solution to promote the widespread application of PCFCs. The proton uptake capability and electrochemical performance of BaZr0.88-xFexY0.12O3-δ (BZFY) were investigated by optimizing the iron content (x=0.6, 0.7 and 0.8) to achieve superior catalytic activity. It is demonstrated that adjusting the iron ratio to 0.7 yields a proton concentration of 0.36 mol% and proton surface exchange kinetics of 1.99×10-6 cm s-1 at 600 °C. When applied as oxygen electrode, the enhanced proton reaction step in BZFY0.7 exhibits the lowest polarization resistance and exceptional long-term stability. The full cell with BZFY0.7 oxygen electrode shows 0.4 Wcm-2 at 600 °C, and in electrolysis mode, the BZFY0.7 oxygen electrode shows good catalytic activity for water electrolysis with 0.45 A/cm² current density at 1.3V.