Preparation and performance characterization of the Fe-Ni/ScSZ cermet anode for oxidation of ethanol fuel in SOFCs

摘要

An anodic cermet of Fe-Ni alloy and scandia stabilized zirconia (ScSZ) has been investigated for a solid oxide fuel cell (SOFC) running on ethanol fuel. Composite anodes having alloy compositions of 0, 12.5, 25, 37.5, 50 and 100 wt.% Ni were exposed to ethanol stream at 700℃ for 12 h to demonstrate that carbon formation is greatly suppressed on the Fe-Ni alloys compared to that of pure Ni. Then the short-term stability for the cells with the Ni/ScSZ and Fe_(0.5)Ni_(0.5)/ScSZ anodes in ethanol stream at 700℃ was checked over a relative long period of operation. Open circuit voltages (OCVs) increased from 1.03 to 1.1 V, and power densities increased from 120 to 460mW cm~2 as the operating temperature of a SOFC with Fe_(0.5)Ni_(0.5)/ScSZ anode was increased from 700 to 850℃ in ethanol stream. Electrochemical impedance spectra (EIS) illustrated that the cell with Ni/ScSZ anode exhibits slightly less total impedance than that observed for the cell with Fe_(0.5)Ni_(0.5)/ScSZ anode. The performance of a fuel cell made with the Ni/ScSZ and Fe_(0.5)Ni_(0.5)/ScSZ anodes was tested in ethanol stream for 48 h and showed a significant decrease in polarization resistance with time. Impedance spectra of similar fuel cells suggest that small carbon deposits are formed with time and that the decrease in polarization resistance is due to enhanced electronic conductivity in the anode.