Key Roles of Initial Calcination Temperature in Accelerating the Performance in Proton Ceramic Fuel Cells via Regulating 3D Microstructure and Electronic Structure

Developing cathode materials with high performance in oxygen reduction reaction (ORR) is desirable for proton ceramic fuel cells (PCFCs) for energy conversion technology. BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3–δ (BCFZY) is widely investigated as a cathode. Herein, BCFZY cathode is used as a paradigmatic example to study the impact of calcination temperature on microstructure, electronic structure, and ORR performance. Ion beam-scanning electron microscopy indicates BCFZY prepared at 800 °C (BCFZY800) exhibits the largest specific surface area and cathode/electrolyte contact area. BCFZY800 exhibits a peak power density of 1.32 W cm⁻² at 650 °C, which is 37% and 193% higher than that of BCFZY prepared at 700 °C (BCFZY700) and 1100 °C (BCFZY1100), respectively. Furthermore, BCFZY800 demonstrates high long-term stability over 500 h. Soft X-Ray absorption spectra indicate that the oxidation state of BCFZY800 is reduced, suggesting more catalytically active sites than those of BCFZY700 and BCFZY1100 after the ORR. This work provides a new understanding for enhanced PCFCs performance by proper porosity structure via fine-tuning the calcination temperature.