Investigation of B-site doped perovskites Sr₂Fe_1.4X_0.1Mo_0.5O_6-Δ (X=Bi, Al, Mg) as high-performance anodes for hybrid direct carbon fuel cell

B-site substituted Sr₂Fe_1.4X_0.1Mo_0.5O_6-δ (SFXM, X = Bi, Al and Mg) are evaluated as anode materials for hybrid direct carbon fuel cells (HDCFCs). The structure, morphology, conductivity and catalytic activity of the as-prepared SFXM anode are systematically investigated. Under a reducing atmosphere, the exsolution of metallic Fe from the SFXM perovskite lattice are demonstrated by the XRD, SEM and TEM observations. Further element valence analysis on reduced SFXM suggests the X doping significantly alters the Fe³⁺/Fe²⁺ and Mo⁶⁺/Mo⁵⁺ ratio, and thus beneficial to the intrinsic conductivity of SFXM. All these advantages are responsible for the good electrochemical performances of SFXM anodes. Meanwhile, among these SFXM anodes, the conductivity, catalytic activity and electrochemical performance all obey the order of SFBM > SFAM > SFMM. The maximum power densities of the La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte supported single cell with SFBM as the anode reaches 399, 287 and 141 mW cm⁻² at 800 °C, 750 °C and 700 °C, respectively. Such designed B-site substitution perovskites have great potential to be applied as HDCFC anode materials.