La-Doped Ba0.5Sr0.5Co0.8Fe0.2O3-delta Air Electrodes with Enhanced Performance and Stability for Reversible Protonic Ceramic Cells

Reversible protonic ceramic cells (R-PCCs) have attracted intensive attention, as they can operate efficiently for both power generation and fuel production. The practical application of R-PCCs is, however, limited by the poor catalytic activity and stability of the air electrode. Here, we report a novel electrochemical catalyst of 10 mol% La substituted Ba0.5Sr0.5Co0.8Fe0.2O3-delta , showing improved stability under typical R-PCCs working conditions. XRD patterns confirm that La0.1Ba0.4Sr0.5Co0.8Fe0.2O3-delta maintains the cubic structure after heat treatment in humid air (3% H2O) at 700 degrees C for 100 h. In addition, the assembled full cells using this novel material as air electrode catalyst present outstanding performance. At 700 degrees C, the peak power density reaches 650 mW cm(-2) (fuel cell mode); and in electrolysis mode the maximum current density reaches 1840 mA cm(-2) at 1.5 V. We speculate that the much-improved stability and electrochemical performance of the La0.1Ba0.4Sr0.5Co0.8Fe0.2O3-delta air electrode may result from the higher electronegativity of La, which is beneficial for reducing the basicity and improving the chemical stability in acidic atmospheres; from the smaller ionic radius of La, which can alleviate the lattice distortion of BSCF; and from the stronger interaction between La and lattice oxygen inhibiting the structural degradation caused by Sr segregation.