A Review of Proton-Conducting Electrolytes for Efficient Low-Temperature Solid Oxide Fuel Cells: Progress, Challenges, and Perspectives

Aiming to replace traditional energy sources such as coal and oil, researchers from around the world are working hard to develop green technologies that offer safer and more efficient ways to produce clean energy. In this regard, solid oxide fuel cells (SOFCs) have steadily grown in popularity because of their ability to produce electricity through electrochemical reactions. However, the notable drawback of typical solid oxide fuel cells is the high operating temperature, generally over 700–1000 °C. Low-temperature solid oxide fuel cells (LT-SOFCs) are a promising energy technology that offers several advantages for stationary and mobile power generation at low temperatures. LT-SOFCs are highly dependent on electrolyte materials characterized by proton-conducting oxides. This review discusses progress in the development of proton-conducting solid oxide electrolytes for LT-SOFCs, including advances from materials to devices. In detail, this work focuses on improving performance through various strategies, manipulating the composition and properties of proton-conductors, and addressing the opportunities and challenges associated with their development. Solid oxide materials containing proton-conducting components play a crucial role in the efficient functioning of hydrogen-based energy devices, such as electrolyzers, SOFCs, electronic systems, and hydrogen separation membranes. To enhance the performance of these devices, it is essential to identify materials that efficiently conduct protons and remain durable under hydrogen and water exposure. This study offers valuable insights and guidelines for designing oxide materials with rapid proton diffusion and strong durability, contributing to the continuous improvement of such devices.