La-doped Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ as cathode for protonic-conducting solid oxide fuel cells with enhanced structure stability

As a highly efficient energy conversion device, proton-conducting solid oxide fuel cells (PCFCs) have attracted intensive attention. Unfortunately, its practical application is limited by the catalytic activity and stability of the cathode. Here, we report a novel electrochemical catalyst of 10 mol.% La modified Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-d cathode, showing much improved stability under typical PCFCs working conditions. XRD patterns confirm that La_0.1Ba_0.4Sr_0.5Co_0.8Fe_0.2O_3-d maintains cubic structure after treated in humid air or 10% H₂O - 90% N₂. In addition, La_0.1Ba_0.4Sr_0.5Co_0.8Fe_0.2O_3-d also demonstrates outstanding oxygen transport properties with a chemical surface exchange coefficient of 2.3^∗10^-3 cm s^-1 at 700 °C, and the assembled single cells using this novel material present a minimal polarization resistance of 0.05 W cm² at 700 °C. The high stability and great electrochemical performance of La_0.1Ba_0.4Sr_0.5Co_0.8Fe_0.2O_3-d may result from the stronger interaction in the La-O bond than in Ba-O. This work provides a strategy to modify materials properties via optimizing the interaction between metal and oxygen ions in the oxide lattice.