An examination of carbonaceous deposits in direct-utilization SOFC anodes

The deposition, stability, and function of carbonaceous films formed by exposing porous yttria-stabilized zirconia (YSZ) anodes in YSZ-based solid oxide fuel cells (SOFCs) to n-butane at elevated temperatures was studied using a combination of four-probe conductivity, impedance spectroscopy, and cell polarization measurements. The carbonaceous deposits were found to have high electronic conductivity and to be relatively stable for steam-to-carbon ratios as high as 3.75. Comparison of the performance of cells in which carbon films were used as the sole current collector in the anode with anodes containing both Cu and carbon films indicated that in the latter case, the carbon layer plays an important role in providing electronic conductivity near the three-phase boundary. (C) 2004 The Electrochemical Society.