Temperature-modulated high-entropy perovskite cathodes with superior electrocatalytic activity for reversible solid oxide cells

Abstract Solid oxide cells (SOCs) hold great promise for clean energy conversion, yet conventional cathodes such as La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) suffer from insufficient electrocatalytic activity and poor CO2 tolerance. This study designed a high-entropy perovskite, La0.2Sr0.2Pr0.2Nd0.2Ba0.2Co0.2Fe0.8O3–δ (HELSCF), via A-site high-entropy modification of LSCF. By regulating the synthesis temperature, two distinct crystal structures were achieved: an asymmetric tetragonal phase (HELSCF-Pbnm) with enhanced lattice distortion obtained at 1000 °C and a symmetric cubic phase (HELSCF-Pm3m) obtained at 1100 °C. Comprehensive characterizations confirmed that HELSCF-Pbnm exhibits superior properties, including a higher specific surface area, increased oxygen vacancy concentration, and optimized electronic structure. At 750 °C, the HELSCF-Pbnm-based symmetric cell delivers the lowest area-specific resistance of 0.040 Ω·cm2, along with excellent bifunctional activity toward both the oxygen reduction reaction and oxygen evolution reaction, as well as outstanding tolerance under CO2-containing atmospheres. When employed as the cathode in a single cell, it achieves a maximum power density of up to 1.38 W·cm−2, approximately 1.7 times that of LSCF. Furthermore, it demonstrates exceptional operational stability for over 260 h at 600 °C. Density functional theory calculations further reveal that the orthorhombic structure enhances O2 adsorption and d–p orbital hybridization, synergistically boosting catalytic performance. A temperature-modulated high-entropy strategy offers a facile and effective route for developing high-performance, CO2-tolerant cathodes for reversible SOCs.