Study of the Change of Electrical Conductivity of Ni-YSZ Cermet Caused by Carbon Formation

The change in electrical conductivity of Ni-YSZ cermet used for the solid oxide fuel cell (SOFC) anode was investigated under methane, ethylene and n-butane feeding. Rectangular-shaped pellets have been prepared and exposed to gaseous mixtures including hydrocarbons and nitrogen with or without steam at 750 °C. In the absence of steam, carbon deposition occurred in the Ni-YSZ pellets and consequently the electrical conductivity decreased exponentially. When steam was fed (steam to carbon ratio = 2) to make carbon formation thermodynamically unfavorable, the electrical conductivity was kept constant, except for supplying butane. The effect of the mole fraction of methane on the change of electrical conductivity was also investigated in the CH₄-N₂ system. When the molar concentration was increased, the rate of decrease of electrical conductivity was increased. The present study helps to understand the effect of carbon deposition on the electrical conductivity of Ni-YSZ anode.