A Key for Achieving Higher Open-Circuit Voltage in Protonic Ceramic Fuel Cells: Lowering Interfacial Electrode Polarization

Although protonic ceramic fuel cells (PCFCs) have a great potential to realize higher energy-conversion efficiency compared with all other conventional devices, actual PCFCs have shown current leakage loss due to their intrinsic transport property with electron-hole conduction of proton-conducting electrolytes, resulting in a decrease in efficiency. The present study shows a new finding that open-circuit voltage (OCV), which is an indicator of current leakage loss, depends on the ratio of the electrode polarization resistance to the electrolyte ohmic resistance within a PCFC and experimentally demonstrates improvement in OCV by developing high-performance cathode and anode. Results show that our anode-supported PCFC with BaZr0.1Ce0.7Y0.1Yb0.1O3−δ electrolyte and high-performance electrodes achieves extremely high OCV, e.g., 1.112 V at 600 °C (≈ 98% of the theoretical OCV) and 1.132 V at 550 °C (≈ 99% of the theoretical OCV). Compared with recently reported OCVs for PCFCs, these measured OCVs are remarkably high. These results indicate that high-performance electrodes lead to suppression of current leakage loss in PCFCs and thus enable PCFCs to operate with higher energy-conversion efficiency.