Feasibility of direct-biogas SOFC

Direct feeding of real biogas generated in a methane fermentation reactor to SOFC was tested by using Ni-ScSZ cermet as an anode material. At the operating temperature of 1000 degrees C, cell voltage above 0.9 V (at 200 mA cm(-2)) was stably obtained over 50 h without carbon deposition showing direct-biogas SOFC is feasible. This system is environmental-friendly, compact and cost-effective energy conversion system in which internal dry reforming of CH4 proceeds on Ni-based anode using CO2 included in biogas without external reformer and precious metal catalyst. H2S poisoning test was performed simulating H2S contamination of biogas. Electrochemical and catalytic properties of Ni-ScSZ anode in feeding simulated biogas mixture (CH4/CO2 = 1.5) and their changes by H2S supply were measured at 1000 degrees C under 200 mA cm(-2). 1 ppm H2S poisoning caused about 9% voltage drop and about 40% decrease in reaction rate of internal reforming, however, stable operation was achieved and complete recovery of cell voltage and reaction rate after stopping the H2S supply was confirmed, indicating that direct-biogas SOFC operated at 1000 degrees C is tolerant to 1 ppm level H2S contamination. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.