Composite cathodes for protonic ceramic fuel cells: Rationales and materials

Abstract

Protonic ceramic fuel cells (PCFCs) or proton-conducting solid oxide fuel cells (SOFCs) are a class of electrochemical devices with high proton conductivity at the intermediate, even low operating temperatures (450–750 °C), which directly convert the chemical energy of hydrogen or hydrogen-containing fuels into electricity in a clean and efficient manner. In comparison to oxygen-ion conducting SOFCs , the operation at lower operating temperature overcomes the incompatibility and cathode delamination issues in high-temperature operated SOFCs. More attractively, the fuel is not diluted owing to the production of water at the cathode side . However, lowing working temperature weakens the electrode reaction kinetics and the ion migration, therefore the rational design of high-performance cathode materials is highly desired for PCFCs. Herein, we provide a review on the design criteria and state-of-art materials of PCFC composite cathodes including proton-conducting composite, proton-blocking composite and other types of composite cathodes, and discuss the underlying rationales and mechanisms. In particular, we discuss the feasibility of self-assembled composite cathodes used in PCFCs, and point out the future development directions of composite cathodes.