Porous microsphere LiNi_0.8Co_0.15Al_0.05O₂ electrode modified by Na₂CO₃: Enhanced performance of low temperature solid oxide fuel cells

LiNi_0.8Co_0.15Al_0.05O₂ (NCAL) has been extensively adopted as symmetric electrode for low temperature solid oxide fuel cells (SOFCs) based on oxide semiconductor electrolytes. However, the performance of NCAL electrode depend on material source, morphology and operating conditions. In this study, commercial microsphere NCAL is successfully modified with Na₂CO₃ by a wet chemical method. The crystal structure, surface morphology, elemental analysis, surface chemistry and electrochemical properties of NCAL modified by Na₂CO₃ (NCALN) are characterized by various techniques. When Na₂CO₃ content in NCALN is 5 wt% and 10 wt%, the CeO₂ electrolyte SOFCs with NCALN symmetric electrode show significantly superior performance to that with NCAL symmetric electrode. The optimal heterostructure electrode NCALN5 exhibits a peak power density of 805 mW cm⁻² and a polarization resistance of 0.237 Ω cm² at 550 °C, which is 17 % higher and 21 % lower than those of NCAL electrode. Compared with NCAL electrode, NCALN5 electrode enhances the catalytic activities to both hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) but contributes more to ORR than HOR, especially at low temperatures. These results clearly demonstrate NCALN heterostructure composites are promising electrode materials for low temperature SOFCs.