Boosting Electrochemical Performance of Sm 0.5 Sr 0.5 CoO 3‐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 0.5 Sr 0.5 CoO 3‐δ (SSC) electrodes. A series of Sm 0.5 Sr 0.5 Co 1+x O 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 0.5 Sr 0.5 Co 1.1 O 3‐δ (SSC1.1) composition demonstrates a polarization resistance of 0.517 Ω cm 2 at 550 °C, outperforming the standard SSC cathode (0.711 Ω cm 2 ). 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.