Effect of precious-metal dopants on SOFC anodes for direct utilization of hydrocarbons

The effect on cell performance of adding dopant levels of precious metals (PM: Pt, Rh, or Pd) into solid oxide fuel cell (SOFC) anodes based on carbon, ceria, and yttria-stabilized zirconia (YSZ) was examined. The PM-doped anodes remained stable in dry CH4 and n-butane over a period of at least 24 h. While maximum power densities for H-2 and n-butane increased by almost a factor of two upon addition of PM, the maximum power density for CH4 increased by a factor of almost 10 over that measured on a Cu-ceria-YSZ anode, to 280 mW/cm(2) at 973 K. The open-circuit voltages (OCVs) were also measured for CH4 and n-butane as a function of H2O and CO2 concentrations. The addition of PM dopants led to a significant increase in the OCV for CH4 and n-butane, although the OCV remained lower than the theoretical Nernst potentials. The differences between the theoretical and measured OCV are attributed to barriers to surface reaction, which in turn can be decreased through improved catalytic properties. (C) 2003 The Electrochemical Society.