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 La _0.5-xCa _xBa _0.5FeO _3-δ ( x = 0–0.2) are developed as highly active cathode materials and systematically evaluated their physicochemical properties. Among all the components, the La _0.35Ca _0.15Ba _0.5FeO _3-δ cathode delivers the minimal polarization resistance (0.059 Ω cm ²) 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 La _0.35Ca _0.15Ba _0.5FeO _3-δ cathode surface is proved to be the major rate-limiting step. These results suggest that La _0.35Ca _0.15Ba _0.5FeO _3-δ can be used as a candidate cathode material for solid oxide fuel cells.