A comprehensive review of recent progresses in cathode materials for Proton-conducting SOFCs

Solid oxide fuel cells (SOFCs) are widely recognized as efficient energy sources that have the potential to shape the future of energy development. Among various types of SOFCs, the low-temperature operation of proton-conducting SOFCs (H–SOFCs) offers distinct advantages for wide commercialization compared to oxygen-ion conducting SOFCs (O–SOFCs). However, the commercialization of H–SOFCs is hindered by several challenges, including slow oxygen reduction kinetics and long-term instability of cathode materials. The electrochemical performance of the cathode system in H–SOFCs is limited by the poor proton conductivity of the cathode material and the scarcity of surface reaction sites. Additionally, the presence of undesirable phases induced by elements such as Cr and CO₂ adversely affects the chemical stability and catalytic activity of the cathode. Thermal stress arising from the mismatch in coefficient of thermal expansion between the cathode and electrolyte further adds to the challenges. Therefore, this comprehensive review presents underlying mechanisms and potential solutions to overcome the challenges in H–SOFCs, leading to higher efficiency and wider commercialization of H–SOFCs.