High-Performance Protonic Ceramic Fuel Cells Based on PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ Microstructure Optimization

Protonic ceramic fuel cells (PCFCs) are emerging as a promising technology for lower power generation temperature ranges using highly conductive protonic conducting oxides. However, the sluggish cathodic kinetics, the representative rate-determining step of ceramic fuel cells, remained a major challenge to overcome. To tackle the challenge, modifications of the cathode that optimize the key microstructural properties of porosity and cathode–electrolyte interface. Here, the microstructural properties were successfully controlled by varying the ethyl cellulose (EC) content of PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+δ (PBSCF) slurry using a simple and cost-effective spin coating process. As a result, PCFC containing PBSCF cathode with optimal microstructure significantly reduced the activation energy to ~ 0.85 eV and recorded a high peak power density of 477 mW cm⁻² at 500 °C. Electrochemical impedance spectroscopy (EIS) analysis demonstrated that porosity and cathode–electrolyte interface are the critical factors that enhance the mass transfer of the reaction gas and the bulk diffusion of protons, respectively. Our findings are meaningful in that demonstrating the effective approach to overcome the challenges of PCFCs by providing new insights for cathode design.