T. Horita et al., OXIDATION AND STEAM DEFORMING OF CH4 ON NI AND FE ANODES UNDER LOW HUMIDITY CONDITIONS IN SOLID OXIDE FUEL-CELLS, Journal of the Electrochemical Society, 143(4), 1996, pp. 1161-1168
Oxidation and steam reforming of CH4 on Ni/YSZ and Fe/YSZ cermet anode
s were examined, primarily under the condition of 0 less than or equal
to H2O/CH4 less than or equal to 1. In the CH4 + H2O fuel system, ste
am reforming occurs on anodes, generating CO and H-2. The steam reform
ing activity of CH4 on Ni/YSZ was much higher than on Fe/YSZ at open c
ircuit. The anodic polarization curves of an Ni/YSZ cermet electrode,
both in dry CH4 and CH4 + H2O 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 H-2 and/or CO at higher overvoltages. O
n the other hand, the anodic polarization curves of an Fe/YSZ cermet e
lectrode in CH4 fuel showed behavior different from that for Ni/YSZ in
the dry CH4 or the CH4-H2O fuel systems. The polarization curve in th
e dry CH4 fuel system showed multiple reaction slopes, while that in t
he CH4-H2O fuel system showed only one slope. A thermochemical calcula
tion was made to estimate the anode surface state and the equilibrium
oxygen partial pressure between the anode/YSZ interface and the gas ph
ase.