Emerging semiconductor ionic materials tailored by mixed ionic-electronic conductors for advanced fuel cells

Mixed ionic-electronic conductors (MIECs) play a crucial role in the landscape of energy conversion and storage technologies, with a pronounced focus on electrode materials’ application in solid oxide fuel cells (SOFCs) and proton-conducting ceramic fuel cells (PCFCs). In parallel, the emergence of semiconductor ionic materials (SIMs) has introduced a new paradigm in the field of functional materials, particularly for both electrode and electrolyte development for low-temperature, 300–550 ​°C, SOFCs, and PCFCs. This review article critically delves into the intricate mechanisms underpinning the synergistic relationship between MIECs and SIMs, with a particular emphasis on elucidating the fundamental working principles of semiconductor ionic membrane fuel cells (SIMFCs). By exploring critical facets such as ion-coupled electron transfer/transport, junction effect, energy bands alignment, and theoretical computations, it casts an illuminating spotlight on the transformative potential of MIECs, also involving triple charge conducting oxides (TCOs) in the context of SIMs and advanced fuel cells (FCs). The insights and findings articulated herein contribute substantially to the advancement of SIMs and SIMFCs by tailoring MIECs (TCOs) as promising avenues toward the emergence of high-performance SIMFCs. This scientific quest not only addresses the insistent challenges surrounding efficient charge transfer, ionic transport and power output but also unlocks the profound potential for the widespread commercialization of FC technology.