Structural and electrochemical performance of (Sr1.8Ln0.2)FeMoO6 (Ln = Sr, La, Sm, Eu) anode for solid oxide fuel cell

Different electronic structure on 4 f shell endows rare earth with variable of catalytic activity. In order to explore the catalytic effect of rare earth on solid oxide fuel cell (SOFC) electrode, we prepare electrolyte-supported (Sr1.8Ln0.2)FeMoO6/SDC/LSGM/SBCO single cell with Ln = Sr, La, Sm and Eu, and investigate their electrochemical performance based on X-ray diffraction (XRD), DC four-point probe, I-V and electrochemical impedance spectra. XRD results show that (Sr1.8Ln0.2)FeMoO6 are of single phase and belong to I4/m space group. Owing to the increased density of states, electronic conductivity of (Sr1.8La0.2)FeMoO6 (SLFM), (Sr1.8Sm0.2)FeMoO6 (SSFM) and (Sr1.8Eu0.2)FeMoO6 (SEFM) increases significantly, where SEFM exhibits the highest value in the measuring range. The higher conductivity and the smaller activation energy favor the power output of the investigated cell. The maximum power density of Sr2FeMoO6 (SFMO)-based cell is 772 mW·cm−2 at 850 ℃, that of SLFM- and SSFM-based cell increases to 890.8 mW·cm−2 and 861.6 mW·cm−2, while SEFM-based cell exhibits the highest value of 964.6 mW·cm−2. Electrochemical Impedance Spectroscopy (EIS) finds that SEFM-based cell possesses the smallest electrode resistance, charge transfer resistance, the fastest surface exchange and oxygen diffusion process, which favors its highest power output. These results demonstrate that the synergistic reaction in catalytic activity between rare earth atoms and SFMO lattice is different to a large degree, and our innovative discovery is the good catalytic activity of SEFM anode, which is conducive to comprehensively understanding the catalytic properties of rare earth for SOFC electrodes.