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

Abstract

Protonic ceramic fuel cells (PCFCs), as efficient energy storage and conversion devices, 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 BaZr_0.88−xFe_xY_0.12O_3−δ (BZFY) were investigated by optimizing the iron content (x = 0.6, 0.7 and 0.8) to achieve superior catalytic activity. It was demonstrated that adjusting the iron ratio to 0.7 yielded 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 an oxygen electrode, the enhanced proton reaction step in BZFY0.7 exhibited the lowest polarization resistance and exceptional long-term stability. The full cell with the BZFY0.7 oxygen electrode showed power density of 0.4 W cm⁻² at 600 °C, and in the electrolysis mode, the BZFY0.7 oxygen electrode showed good catalytic activity for water electrolysis with a current density of 0.45 A cm⁻² at 1.3 V.