Solid oxide cell (SOC) can convert chemical energy of fuel into electrical energy in fuel cell mode or convert electrical energy into chemical energy in electrolysis cell mode. It has advantages of high conversion efficiency, fuel flexibility, etc., which is very attractive for the storage and conversion of renewable energy. The electrode, where the electrochemical reaction takes place, plays a key role in SOC performance. Compared with the traditional composite electrode materials, perovskite materials have attracted extensive attention because of their simple structure, strong structural tolerance and adjustable electrochemical properties. The Mn-based A-site layered double perovskite (LnBaMn₂O_5+δ, Ln = lanthanide) has fast oxygen ion migration channel and good catalytic activity for both fuel oxidation and oxygen reduction processes and shows good structural stability under a wide oxygen partial pressure. Therefore, it is widely used as an SOC electrode. The structural characteristics and the formation reasons of the Mn-based A-site double perovskites are introduced, and the modification strategies and the progress are summarized in this work. The prospects of the Mn-based A-site double perovskites are also prospected.

In this work, the long-term stability and degradation mechanism of a direct internal-reforming solid oxide fuel cell stack (IR-SOFC stack) using hydrogen-blended methane steam reforming were investigated. An overall degradation rate of 2.3%·kh^–1 was found after the stack was operated for 3000 hours, indicating a good long-term stability. However, the voltages of the two cells in the stack were increased at the rates of 3.38 mV·kh^–1 and 3.78 mV·kh^–1, while the area specific resistances of the three metal interconnects in the stack were increased to 0.276 Ω·cm², 0.254 Ω·cm² and 0.249 Ω·cm². The degradation of the stack might be caused by segregation of chromium on the surface of metal interconnects and the formation of SrCrO₄ insulating phase in the current collecting layer of the cathode, which result in an increase in the interfacial resistance and a decrease in the stack performance. The long-term performance of a flat-tube IR-SOFC stack could be further improved by suitably coating the metal interconnect surface. This work provides theoretical and experimental guideline for the application of hydrogen-blended methane steam reforming in flat-tube IR-SOFC stacks.