Study of oxygen reduction mechanism on Ag modified Sm_(1.8)Ge_(0.2)CuO_4 cathode for solid oxide fuel cell

摘要

Different amount of metal silver particles are infiltrated into porous Sm_(1.8)Ce_(0.2)CuO_4 (SCC) scaffold to form SCC-Ag composite cathodes. The chemical stability, microstructure evolution and electrochemical performance of the composite cathode are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and AC impedance spectroscopy respectively. The composite cathode exhibits enhanced chemical stability. The metal Ag remains un-reacted with SCC and Ce_(0.9)Gd_(0.1)O_(1.95) (CGO) at 800 ℃ for 72 h. The polarization resistance of the composite cathode decreases with the addition of metal Ag. The optimum cathode SCC-AgOS exhibits the lowest area specific resistance (ASR, 0.43 Ω cm~2) at 700 ℃ in air. Investigation shows that metal Ag accelerates the charge transfer process in the composite cathode, and the rate limiting step for electrochemical oxveen reduction reaction (ORR) changes to oxveen dissociation and diffusion process.