Use of anode barrier layers in tubular solid-oxide fuel cells for robust operation on hydrocarbon fuels

This paper presents a unique demonstration of anode barrier-layer technology in a tubular solid-oxide fuel cell (SOFC) architecture. The anode barrier layer is a chemically inert, porous ceramic tube that is positioned within the inside diameter of the tubular SOFC, separating the catalytically active anode from the hydrocarbon-carrying fuel stream. This porous tube reduces the respective diffusion rates of reactants and products into and out of the anode. This increases the local concentration of electrochemically produced steam and carbon dioxide throughout the anode, resulting in higher local steam-to-carbon ratios that enhance the selectivity of internal-reforming reactions toward hydrogen and carbon monoxide over the formation of deleterious carbon deposits. In this study, stable electrochemical performance is demonstrated under a simulated biogas fuel stream (63% CH4/34% CO2/3% H2O) over 12 days of continuous operation. The performance of the barrier layer-equipped SOFC is characterized under biogas and hydrogen fuels, and compared to the performance of an SOFC without a barrier layer. While some decrease in power density is evident with the presence of a barrier layer, the performance decrease at 0.7V is modest. Morphological characterization after performance testing reveals no evidence of carbon deposition within the anode or barrier layer. These results demonstrate the potential of barrier-layer technology in tubular solid-oxide fuel cell architectures. (C) 2012 Elsevier B.V. All rights reserved.