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

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 ℃, and a symmetric cubic phase (HELSCF-Pm3m) obtained at 1100 ℃. 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 ℃, the HELSCF-Pbnm-based symmetric cell delivers an 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 cm², approximately 1.7 times that of LSCF. Furthermore, it demonstrates exceptional operational stability for over 260 hours at 600 ℃. Density functional theory calculations further reveal that the orthorhombic structure enhances O₂ adsorption and d-p orbital hybridization, synergistically boosting catalytic performance. Temperature-modulated high-entropy strategy offers a facile and effective route for developing high-performance, CO₂-tolerant cathodes for reversible solid oxide cells.