Oxidation and Steam Reforming of CH 4 on Ni and Fe Anodes under Low Humidity Conditions in Solid Oxide Fuel Cells

Abstract

Oxidation and steam reforming of on Ni/YSZ and Fe/YSZ cermet anodes were examined, primarily under the condition of . In the fuel system, steam reforming occurs on anodes, generating CO and . The steam reforming activity of on Ni/YSZ was much higher than on Fe/YSZ at open circuit. The anodic polarization curves of an Ni/YSZ cermet electrode, both in dry and fuel systems, could be divided into two parts; one due to direct oxidation of C in the low overvoltage region, the other due to oxidation of and/or CO at higher overvoltages. On the other hand, the anodic polarization curves of an Fe/YSZ cermet electrode in fuel showed behavior different from that for Ni/YSZ in the dry or the fuel systems. The polarization curve in the dry fuel system showed multiple reaction slopes, while that in the fuel system showed only one slope. A thermochemical calculation was made to estimate the anode surface state and the equilibrium oxygen partial pressure between the anode/YSZ interface and the gas phase.