Feasibility of liquid hydrocarbon fuels for SOFC with Ni-ScSZ anode

Solid oxide fuel cell (SOFC) operation with a nickel-scandia stabilized zirconia (Ni-ScSZ) cermet anode was carried out with liquid hydrocarbon of n-dodecane (C₁₂H₂₆), used as a model fuel of kerosene, without fuel dilution by inert carrier gas. Continuous operation was achieved for more than 120 h at S/C = 2.0 and at 800 °C. The obtained open circuit voltage was about -0.97 V and the average current density was about 140 mA cm^-2 under the constant anode potential of -0.75 V versus air. This current density corresponded to fuel utilization of 55%. In the impedance spectra for the anode, two semicircles were observed not only for hydrogen but also for C1 to C12 paraffin. Electrode conductivity for each semicircle, σ_H for high frequency part and σ_L for low frequency part, were calculated by following equation:σ (S c m^{- 2}) = frac(1, A R)where A (cm²) is electrode area and R (Ω) is electrode resistance determined from each semicircle. Electrode conductivities for hydrocarbon fuels showed the same water partial pressure dependence as that for hydrogen whether fuel is diluted or not. Hydrogen produced by reforming reaction was the most active element for electrochemical oxidation at the anode even for hydrocarbon fuels.