Boosting Electrochemical Performance of Sm0.5Sr0.5CoO3-δ Cathodes in Low-Temperature Solid Oxide Fuel Cells via B-Site Excess.

High-performance solid oxide fuel cells (SOFCs) operating at intermediate to low temperatures require cathode materials with enhanced activity and stability. This study investigates the effect of excess B-site cations on the electrochemical performance of Sm_0.5Sr_0.5CoO_3-δ (SSC) electrodes. A series of Sm_0.5Sr_0.5Co_1+xO_3-δ (SSC1 + x, X = 0, 0.05, 0.1, 0.15, and 0.3) perovskite cathodes with varying Co excess are synthesized to investigate their effect on electrical conductivity, oxygen vacancy formation, and overall cathode properties. The Sm_0.5Sr_0.5Co_1.1O_3-δ (SSC1.1) composition demonstrates a polarization resistance of 0.517 Ω cm² at 550 °C, outperforming the standard SSC cathode (0.711 Ω cm²). Moreover, single cells with SSC1.1 cathodes achieve a peak power density of 1.054 W cm^-2 at 700 °C, marking a 25% improvement over standard SSC cathodes (0.842 W cm^-2). These results highlight the potential of SSC1.1 as an advanced cathode material for enhancing SOFC performance at reduced temperatures.