Boosting the electrochemical performance of cobalt-free Fe-based cathodes by calcium-doping for solid oxide fuel cells

A key obstacle to commercialization of solid oxide fuel cells is the sluggish oxygen reduction on the cathodes. In this work, a series of calcium-doped La0.5-xCaxBa0.5FeO3-δ (x = 0–0.2) are developed as highly active cathode materials and systematically evaluated their physicochemical properties. Among all the components, the La0.35Ca0.15Ba0.5FeO3-δ cathode delivers the minimal polarization resistance (0.059 Ω cm2) and maximum power densities (452 mW cm−2) at 800 °C, and possesses better stability after long-term operation. Based on the analysis results of electrochemical impedance spectra and distribution of relaxation time, the adsorption process of oxygen on the La0.35Ca0.15Ba0.5FeO3-δ cathode surface is proved to be the major rate-limiting step. These results suggest that La0.35Ca0.15Ba0.5FeO3-δ can be used as a candidate cathode material for solid oxide fuel cells.