Activating the cathode for solid oxide fuel cells by selective removal of surface strontium

Abstract

Sr segregation in perovskite cathodes depletes active sites for the oxygen reduction reaction (ORR) and accelerates performance degradation in solid oxide fuel cells (SOFCs). La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF), a representative cathode material for intermediate-temperature SOFCs, suffers from surface Sr segregation, leading to electrochemical deterioration. Here, we present a surface engineering strategy based on alkaline treatment to selectively remove Sr-rich surface species while preserving the bulk perovskite structure. Structural and electrochemical analyses using LSCF as a model cathode reveal that this treatment exposes catalytically active B-site (Co/Fe) cations and eliminates Sr-derived surface species, thereby optimizing ORR kinetics. The treated LSCF cathode exhibits a 27–40% reduction in area-specific resistance (ASR_p) over the temperature range of 700–550 °C and maintains stable performance during 150 h of operation. A single fuel cell with the modified cathode achieves a peak power density of 1.07 W cm⁻² at 650 °C, a 23% improvement over pristine LSCF. This approach is applicable to the commercial LSCF cathode and offers a promising route for developing high-performance cathode materials for intermediate-temperature SOFCs.