Ba-deficiency in BaCoO3 cathode allows high performance for proton-conducting solid oxide fuel cells

A slight deficiency of Ba in BaCoO 3 boosts its performance as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). The Ba-deficiency compound Ba 0.95 CoO 3 is successfully prepared, and the Ba-deficiency is found to be beneficial for the improvement in chemical stability. Theoretical calculations at the atomic level reveal that the Ba-deficiency in BaCoO 3 improves the protonation of the material and also lowers the energy barriers in the proton migration procedure. Furthermore, surface catalytic activity towards O 2 is enhanced with the Ba-deficiency, allowing a weakened O–O bond. The theoretical predictions have been proved with experimental studies. The cell using the traditional BaCoO 3 cathode shows a peak power density of 720 mW cm -2 at 700 °C, while the peak power density of the Ba 0.95 CoO 3 cell is 1155 mW cm -2 at the same testing condition. Impedance analysis indicates that the much-reduced polarization resistance contributes to the enhanced fuel cell performance. The current Ba 0.95 CoO 3 cell shows not only improved performance compared with the stoichiometric BaCoO 3 cell but also exhibits comparable or even better performance than some of the recently reported high-performance H–SOFCs, suggesting the Ba-deficiency strategy provides a facile and interesting way to tailor the traditional cathode materials with high performance.