Advanced Materials for Thin‐Film Solid Oxide Fuel Cells: Recent Progress and Challenges in Boosting the Device Performance at Low Temperatures

Solid oxide fuel cells (SOFCs) are efficient and fuel flexible electrochemical energy conversion devices that can power the future green society with regards to homes, cars, and even down to portable electronics. They do have the potential to become low cost, since no noble metals are used. Their broad commercialization, however, is hampered by the high operating temperatures of 700–900 °C. Lowering the operating temperature of SOFCs is challenging as both the charge transport in the solid electrolyte and oxygen exchange reactions are thermally activated processes. Herein, the recent progress in the development of anode, electrolyte, and cathode materials to lower the operating temperature of SOFC below 600 °C is summarized and the new opportunities, as well as challenges that remain to be solved, are discussed. The focus of this review is addressed to thin film SOFCs, sub-micrometer SOFCs (μSOFCs) based on microelectromechanical systems, as well as devices based on proton-conducting oxide electrolyte (protonic ceramic fuel cells), which are especially promising for powering portable devices.