Sc-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathodes for protonic ceramic fuel cells

Sc is used as a dopant to tailor the traditional Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathode for protonic ceramic fuel cells (PCFCs). Experiments and first-principles calculations are used in this study to explore the influence of Sc-doping on the performance of BSCF cathodes for PCFCs. Sc can only occupy the Co or Fe sites, and doping Sc at the Ba or Sr sites results in the formation of secondary phases. The use of Sc dopant reduces the high thermal expansion of traditional BSCF. More importantly, doping Sc into BSCF reduces the formation of oxygen vacancies while improving hydration and decreasing the proton migration barrier. Doping Sc at the Fe site outperforms doping at the Co site in terms of oxygen vacancy content, hydration capability, and proton migration ability. The new Ba0.5Sr0.5Co0.8Fe0.1Sc0.1O3-δ (Sc doped at Fe site) has a high fuel cell performance of 1666 mW cm−2 at 700 °C and a low polarization resistance of 0.033 Ω cm2. The fuel cell performance is superior to that of most BSCF-based PCFCs reported, indicating the efficacy of using the Sc-doping strategy to tailor BSCF and the importance of selecting the appropriate doping site.