A SmBaCo2O5+δ double perovskite with epitaxially grown Sm0.2Ce0.8O2−δ nanoparticles as a promising cathode for solid oxide fuel cells

Abstract

Modified by Sm_0.2Ce_0.8O_2−δ (SDC) nanoparticles (NPs), SmBaCo₂O_5+δ (SBCO) double perovskite oxide is evaluated as a promising cathode material for intermediate temperature solid oxide fuel cells. The SDC NPs are epitaxially grown on the surface of SBCO with (220) planes of SDC aligning smoothly to (020) or (100) planes of SBCO, forming a tight, coherent connection at the interface. The influence of this modification on thermal expansion, oxygen diffusion, electrical conductivity and electrochemical properties is investigated thoroughly in this work. The designed SBCO–SDC cathode material demonstrates a lower thermal expansion coefficient (TEC), ∼16.4 × 10⁻⁶ K⁻¹, than that of the unmodified SBCO, ∼20.9 × 10⁻⁶ K⁻¹. While SDC coating results in a decreased total electrical conductivity, it facilitates oxygen bulk diffusion and improves the surface exchange reaction kinetics. Coating with SDC NPs can accelerate the rate-determining process of dissociation of the absorbed molecular oxygen, especially at intermediate temperatures. Accordingly, the constructed symmetrical cell with the La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ (LSGM) electrolyte shows lower polarization resistance values, if the SBCO–SDC cathode is utilized. Also, the LSGM electrolyte-supported (300 μm) full cell is found to deliver a high power density of 800 mW cm⁻² at 800 °C. Owing to the strong and coherent interfacial connection, the developed cathode demonstrates a relatively steady electrochemical performance.