Solid oxide fuel cells (SOFC) are an attractive energy resource in part because of their fuel flexibility. In addition to operating with pure hydrogen, SOFCs are capable of direct hydrocarbon fuel use. Natural gas is of interest because it is cheap, widely available on an existing distribution system and can be transported more easily than hydrogen for off-grid applications. Natural gas can be internally reforming on SOFC anodes to produce hydrogen that is then consumed electrochemically. However, Ni-based anodes are highly sensitive to the low concentrations (&lt;1 ppm) of hydrogen sulfide (H2S) and sulfur dioxide (~1 ppm SO2) present in natural gas even after processing. Though the relationship between adsorbed sulfur and methane steam reforming activity has been researched extensively, most Ni/YSZ studies probing interactions of sulfur with the anode are done using voltammetric measurements making it difficult to directly relate deactivation measurements with conventional nickel-based reforming catalysts. The present study demonstrates that Ni/YSZ has a higher sulfur uptake capacity for both H2S and SO2 than a much higher active surface area commercially available reforming catalyst (Süd Chemie C11-NK, Ni/K2O-CaAl2O4). The bare support materials have also been investigated for sulfur uptake and show very little H­2S uptake, but YSZ has some SO2 uptake which supports recent DFT studies that show diffusion of sulfur into the lattice to replace oxygen vacancies. Conclusions from this work indicate that further examination of the mechanism for sulfur poisoning on Ni/YSZ is needed due to potential complications from diffusion of sulfur into the lattice and exchange with the support material.

Impact of SO2 and Hss adsorption on methane steam reforming on Ni-YSZ compared to Ni-alumina

249th National Meeting (2015)

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