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Small traces of H2S in natural gas can cause significant degradation in the performance of solid-oxide fuel cells (SOFCs) operating under direct internal reforming conditions. This study investigates the sulphur resistance of Au-doped Ni/GDC (gadolinia-doped ceria) powders to assess their potential use as anode materials during catalytic methane steam reforming in presence of H2S. It was found that both the presence of Au and annealing at high temperatures have promoting effects on the stability of the catalytic performances. This was attributed to limited sulphur diffusion from the GDC surface to the catalytically active Ni sites. Moreover, H2S chemisorption experiments indicated that Au can limit the formation of strongly bonded sulphur compounds due the formation of Au–Ni alloys, thus demonstrating that Au-modified Ni/GDC is a promising anode material for SOFCs using natural gas as a fuel.

This study shows that Yttria-Stabilized Zirconia (YSZ) is an effective catalyst for soot particles oxidation. Soot oxidation already occurs from 270°C. Temperature-Programmed Oxidation experiments with 18O2 demonstrate the key-role of bulk oxygen species in the oxidation process. To the best of our knowledge, this is the first time that such a result is reported for a purely O2- ionically conducting ceramic without any redox property. We assume that the soot oxidation takes place via a fuel-cell type electrochemical mechanism at the nanometric scale. Electrochemical oxidation of the soot takes place at the soot/YSZ interface while oxygen electrochemical reaction occurs at the triple phase boundary.