Abstract
SOFCs fed with dry H2 and CH4 fuels were examined using 20 wt% Ni/SDC and 0.2 wt% BaO-added 20 wt% Ni/SDC [Ni(BaO)/SDC] anodes. The i–v characteristics of the cells in H2 and CH4 resulted in a higher output produced by CH4 fuel compared to that produced by H2 fuel in both anodes. In both fuels, better anode characteristics were obtained for Ni(BaO)/SDC. Consequently, the anodic performance was in the order of Ni(BaO)/SDC in CH4 > Ni/SDC in CH4 > Ni(BaO)/SDC in H2 > Ni/SDC in H2. A significant carbon deposition was observed in the Ni/SDC anode in CH4, but the carbon deposition observed in Ni(BaO)/SDC was less. From the DC electrical resistance measurement of the anode films, a remarkable decrease in resistance was observed in Ni/SDC due to the carbon deposition after CH4 exposure. The resistance of Ni(BaO)/SDC was higher than that of Ni/SDC and did not change even after CH4 exposure because of the less carbon deposit. The high dispersibility of Ni particles was confirmed in both anodes and was particularly remarkable in Ni(BaO)/SDC. The highest anodic performance in Ni(BaO)/SDC was attributed to the high Ni dispersibility which might promote CH4 decomposition by producing less carbon deposit. It was speculated that the higher cell output in CH4 than that in H2 is due to the locally high concentration of H2 and/or CO gas on the anode surface by the promotion of CH4 decomposition.
Highlights
As solid oxide fuel cells (SOFCs) operate at high temperatures, they have the advantage of having higher power generation efficiency than the other fuel cells and can directly use different fuels other than hydrogen fuel (H2)
We evaluated anode characteristics in dry H2 and CH4 fuels using 20 wt% Ni/Sm-doped ceria (SDC) with the addition of 0.2 wt% BaO, the effect of BaO addition on the anode structure and catalytic activity and the influence of carbon deposition under CH4 fuel on the cell performance
20 wt% Ni/SDC and 0.2 wt% BaO-doped 20 wt% Ni/SDC [Ni(BaO)/SDC] were examined as anodes of SOFCs fed with dry H2 and CH4 fuels
Summary
As solid oxide fuel cells (SOFCs) operate at high temperatures, they have the advantage of having higher power generation efficiency than the other fuel cells and can directly use different fuels other than hydrogen fuel (H2). We evaluated anode characteristics in dry H2 and CH4 fuels using 20 wt% Ni/SDC with the addition of 0.2 wt% BaO, the effect of BaO addition on the anode structure and catalytic activity and the influence of carbon deposition under CH4 fuel on the cell performance. To analyze the deposited carbon, the Ni/SDC powder after the reaction was further examined with the temperatureprogrammed oxidation with H2O (H2O-TPO) In this measurement, helium gas after passing through a H2O bubbler was fed in the carbon-deposited sample with a flow rate of 50 ml·min−1. To observe the deposited carbon directly, the anode powders pressed into disks treated with methane similar to the aforementioned catalytic examination and cross section of the disks after the CH4 treatment were observed by SEM-EDS. The resistance of the elements, R, was determined by the following equation: R (10-E’)R’/E’
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