An intermediate-temperature solid oxide fuel cell providing higher performance with hydrocarbons than with hydrogen

The promotion of direct electrochemical oxidation of hydrocarbons in a solid oxide fuel cell was investigated using a ceria-based electrolyte with different noble metals-containing anode at 600degreesC. The objective was to avoid interference from a large amount of steam and CO2 being produced by discharging the cell, because these gases degrade the anode performance, especially at a high fuel utilization. Ru was an effective catalyst for removing these gases from the anode surface due to its high catalytic activity for the steam and CO2 reforming of hydrocarbons. The resulting peak power densities reached 750 mW cm(-2) with dry methane, which was comparable to the peak power density of 769 mW cm(-2) with wet (2.9 vol %H2O) hydrogen. The cell performance was maintained at a high level regardless of the change in methane utilization from 12 to 46% but was significantly reduced by increasing hydrogen utilization from 13 to 42%. The anodic reaction of hydrogen was controlled by the slow surface diffusion of hydrogen, while the anodic reaction of methane was not subject to the onset of such a gas-diffusion process. (C) 2002 The Electrochemical Society.