BaCo_0.4Fe_0.4Ti_0.1Ta_0.1O_3-δ as an efficient, stable and low-thermal-expansion cathode for solid oxide fuel cells operating at reduced temperatures

Solid oxide fuel cells (SOFCs) have gained increasing interests owing to the all-solid structure, superb fuel flexibility and high efficiency. Nevertheless, the commercialization of SOFCs is still restricted by several bottlenecks including poor lifetime and high material costs induced by the high operational temperatures. The effective reduction in the operational temperatures of SOFCs can be realized by the design of new cathodes with superb electrocatalytic activity for oxygen reduction reaction (ORR) at intermediate-temperature range (IT, 400–650 °C). In this study, a new BaCo_0.4Fe_0.4Ti_0.1Ta_0.1O_3-δ (BCFTT) perovskite oxide is designed by fully utilizing the unique features of Fe doped BaCoO_3-δ parent oxide and synergetic effect of titanium/tantalum co-doping as efficient and stable cathode for IT-SOFCs. BCFTT exhibits superior ORR activity with a low area-specific resistance of 0.043 Ω cm² at 600 °C because of the high surface exchange/bulk diffusion rate and large oxygen vacancy amount. More specifically, the single cell with such BCFTT cathode exhibits an excellent peak power density of 0.80 W cm⁻² and a superior stability for 240 h at 500 °C due to the low thermal expansion coefficient of 18.00 × 10⁻⁶ K⁻¹. This study reports a high-performance cathode for IT-SOFCs, promoting the large-scale application of this technology.