Designing an air electrode for dual ceramic cells using an ionic Lewis acid strength polarization distribution strategy

Ceramic cells promise ideal energy conversion and storage devices, making the development of efficient and robust air electrodes crucial for their application. In this study, a Ba0.4Sr0.5Cs0.1Co0.7Fe0.2Nb0.1O3−δ (BSCCFN) air electrode, based on Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), is designed using a perovskite A-B-site ionic Lewis acid strength (ISA) polarization distribution strategy and is successfully applied in both oxygen-ion conducting solid oxide fuel cells (O-SOFCs) and proton-conducting reversible protonic ceramic cells (R-PCCs). When BSCCFN is used as the air electrode in O-SOFCs, a peak power density (PPD) of 1.45 W cm−2 is achieved at 650 °C, whereas in R-PCCs, a PPD of 1.13 W cm−2 and a current density of −1.8 A cm−2 at 1.3 V are achieved at the same temperature and show stable reversibility over 100 h. Experimental measurements and theoretical calculations demonstrate that low-ISA Cs+ doping accelerates the reaction kinetics of both oxygen ions and protons, while high-ISA Nb5+ doping enhances electrode stability. The synergistic effect of Cs+ and Nb5+ co-doping in the BSCCFN electrode lies in the ISA polarization distribution, which weakens the Co/Fe–O bond covalency, thereby promoting oxygen vacancy formation and facilitating the conduction of oxygen ions and protons.