Improved performance of solid oxide fuel cell operating on biogas using tin anode-infiltration

This work presents a novel method of Sn-infiltration on SOFC anodes for SOFC operation in biogas dry reforming. Using commercially available NiYSZ-based anode supported half cells with hand-painted LSM/YSZ cathode layers, Sn-infiltrated NiYSZ SOFCs containing different amounts of Sn were manufactured. These SOFCs were tested for their electrochemical performance and quantity of deposited carbon during operation on simulated biogas of 1:2 volume ratio of CO2:CH4 without humidification but with 25% Helium added to the feed stream to enable measurements of the fuel cell outlet gas composition using a quadrupole mass spectrometer. Most of the SOFCs were tested in biogas for 1 day (22 hours), but several cells were tested for 6 days (150 hours) to evaluate performance degradation. The electrochemical performance tests at 750 oC showed that with H2 as fuel the non-infiltrated NiYSZ SOFCs were able to reliably generate a moderate level of current of 350 mA cm-2 at 0.7 V; however when simulated biogas was introduced, current dropped significantly to 90-200 mA cm-2. Contrary to non-infiltrated cells, a series of Sn-infiltrated cells under the same operating conditions performed equally well both on H2 and biogas producing 310 to 420 mA cm-2 at 0.7 V. Several cells showed stable electrochemical performance over 150 hours of operation both on H2 and biogas. Using Temperature Programmed Oxidation (TPO), both Sn-infiltrated and non-infiltrated SOFCs showed low quantities of carbon formed during 22 hours operation on biogas. Visual observation and SEM images of the anode surface after 150 hours operation on biogas showed no sign of deposited carbon. The conclusion is that Sn-infiltrated NiYSZ-based SOFC can be operated on simulated biogas with significantly higher electrochemical performance and low carbon deposition, given the anode is adequately modified