Double-Perovskite Anode Materials For Solid Oxide Fuel Cells

Double-perovskite Ba₂MMoO₆（M=Fe, Co, Mn, Ni） and A₂FeMoO₆（A=Ba, Sr, Ca）have been systematically investigated as anode materials for intermediate temperaturesolid oxide fuel cells （IT-SOFCs）. Ba₂MMoO₆and A₂FeMoO₆were synthesized viasol-gel method. The phase and the structure were ananlyzed. The conductivity, thermalexpansion coefficient and thermogravimetric curve of the studied anode materials weretested. Iodometric titration method was used to measure the valence of the M ions in theas-prepared Ba₂MMoO₆and hence the formation of crystal oxygen vacancies. SingleSOFC cells were fabricated based on electrolyte-supported mode with300μm thickLa_0.8Sr_0.2Ga_0.83Mg₍0.17_O3-δ（LSGM） as the electrolyte. The power output was tested withArbin tester, and the anodic overpotential and impedance spectroscopy of the cells weremeasured with electrochemical workstation.Among the Ba₂MMoO₆materials, Ba₂FeMoO₆shows the best electrochemicalperformance with maximum power density of605mW cm2and electronic conductivityof196S cm1at850°C in H₂. Thermal expansion coefficient of Ba₂MMoO₆is distributedwithin the range of （10¹8）×10^-6K-1, which match well with theintermediate-temperature LSGM electrolyte. Thermogravimetric analysis clearly indicatesthe formation of oxygen vacancies for all the Ba₂MMoO₆materials. The power output forthe Ba₂MMoO₆anodes decreases in the order of M=Fe> M=Co> M=Mn> M=Ni;the overpotential increases in the order of M=Fe <M=Co <M=Mn <M=Ni; and theimpedance varies in the order of M=Co<M=Fe <M=Mn <M=Ni. The differentperformance in this family is ascribed to the difference in conductivity and oxygenvacancy. Our experimental results indicate that the double-perovskites Ba₂MMoO₆（M=Fe, Co, Mn, Ni） are potential alternative anode materials for SOFCs.A₂FeMoO₆（A=Ba, Sr, Ca） materials show excellent conductivities in H₂, the highestconductivity of Ba₂FeMoO₆, Sr₂FeMoO₆and Ca₂FeMoO₆could reach243,302and561Scm^-1. Thermogravimetric analysis clearly indicates the formation of oxygen vacancies forall the A₂FeMoO₆materials and Sr₂FeMoO₆shows the hightest weigh loss. The poweroutput for the A₂FeMoO₆anodes decreases in the order of A=Sr﹥A=Ba﹥A=Ca, at the same time, BFMO and SFMO show favorable cycle performance; The overpotentialdecreases in the order of A=Ca﹥A=Sr﹥A=Ba; and the impedance varies in the orderof A=Ba﹥A=Sr. Sr₂FeMoO₆material indicative of outstanding performance and thecomprehensive performance of Ca₂FeMoO₆is not very good.