Minimized thermal expansion mismatch of cobalt-based perovskite air electrode for solid oxide cells

The mismatch of thermal expansion coefficients (TECs) between cobalt-containing perovskite air electrode and electrolyte is a great challenge for the development of thermo-mechanically durable solid oxide cell (SOC). In this work, we proposed a facile design principle to directly grow highly dispersed Co reactive site onto ionic conducting scaffold and confine the dimension of active centre within nanoscale. As a representative, the Co socketed BaCe0.7Zr0.2Y0.1O3-δ perovskite (R-BCZY-Co) were constructed by a consecutive sol-gel and in-situ exsolution approach. Combined XRD, H2-TPR, SEM and TEM results confirm the emergence of Co nanoparticle on BCZY matrix without segregation of secondary Co-rich phase. The symmetric half-cell measurement suggests that the R-BCZY-Co air electrode with optimal Co content of 10 mol% exhibits a 7-fold promoted oxygen activation performance with a polarization resistance of ~0.17 Ω cm2 at 750 °C. The TEC mismatch between fabricated R-BCZY-Co electrode and BCZY electrolyte is minimized down to only ~11.4%, which is significantly lower than other representative counterparts. Moreover, the detailed XPS result proves that the architecture of exsolved Co on BCZY possesses higher concentration of surface oxygen vacancy, which further benefits the kinetics of ion diffusion and oxygen absorption.