Characterization of Cu–impregnated Sr2–xMgMoO6–δ composite ceramic anode for SOFCs

Abstract

Sr–deficient Sr2–xMgMoO6–δ (SMMx) (x = 0.00–0.25) double perovskites were prepared using the sol–gel process. XRD results indicate that the x = 0.00–0.15 samples are pure phases with good redox stability, while trace SrMoO4 impurity was detected for the samples with x ≥ 0.20. XPS analysis demonstrates that Mo5+ content increases monotonously with Sr–deficiency, and the increasing number of Mo5+/Mo6+ redox pairs enhances electrical conductivity with increasing x. Among the SMMx compositions, the SMM0.15 anode exhibits optimal electrochemical performance, with polarization resistance attaining a minimum of 0.36 and 0.59 Ω cm2 in H2 and CO, respectively, at 850 °C. Using SMM0.15 as the anode skeleton, Cu nanoparticles were loaded onto the skeleton surface via nitrate impregnation. The resulting Cu–impregnated SMM0.15 composite anodes exhibited significantly improved electrical and electrochemical properties. Peak power densities of a single cell supported by a 300–μm–thick La0.9Sr0.1Ga0.8Mg0.2O3–δ electrolyte and a twice Cu–impregnated SMM0.15 composite anode achieve 933 mW cm−2 in H2 and 415 mW cm−2 in CO at 850 °C. The electrochemical reactions at the anode were mainly dominated by fuel diffusion and adsorption/disassociation, particularly for CO. The good cell stability in both H2 and CO further demonstrates that Cu–impregnated SMM0.15 has great potential as an anode candidate for SOFCs.