Cobalt-free high-entropy perovskite La_0.2Pr_0.2Nd_0.2Sm_0.2Sr_0.2FeO_3-δ solid oxide cell air electrode with enhanced performance

This study investigates the novel cobalt-free high-entropy perovskite, La _0.2Pr _0.2Nd _0.2Sm _0.2Sr _0.2FeO _3–δ (LPNSSF), as an air electrode material for solid oxide cells (SOCs). When testing a button cell with a single-phase LPNSSF electrode, a current density of 0.55 A cm ⁻² is obtained at 0.7 V in fuel cell mode at 800°C. In order to mitigate the moderate electronic conductivity of LPNSSF, two approaches are explored. Incorporating a Co-free highly conductive perovskite, LaNi _0.6Fe _0.4O _3–δ (LNF), either as an LPNSSF–LNF composite electrode or as a current collector layer (CCL), enhances the performance to 0.61 and 0.66 A cm ⁻², respectively, under the same conditions. Microstructural features are studied by electron microscopy and show a rather dense structure of the CCL. Optimization of the current collector increases the current density further to 0.96 A cm ⁻² at 0.7 V in a 5 × 5 cm ² anode-supported cell at 800°C. This cell exhibits good long-term stability in electrolysis mode in H ₂-H ₂O with 80% humidification. Continuous polarization of −0.69 A cm ⁻² is sustained for 1000 h, with an average degradation rate of 10 mV kh ⁻¹ after an initial run-in phase. These findings demonstrate the promising performance and durability of LPNSSF as cobalt-free SOC air electrode.