STUDY OF THE ACTIVITY AND DEACTIVATION OF NI-YSZ CERMET IN DRY CH4 USING TEMPERATURE-PROGRAMMED TECHNIQUES

A combination of temperature-programed (TP) and isothermal experiments were performed on a conventional solid oxide fuel cell (SOFC) anode material, Ni-YSZ cermet (55 vol % (64.8 wt %) Ni on yttria-stabilized zirconia), to investigate its suitability for use with CH4 feeds. Reaction experiments were performed with and without added water. In the absence of water, CH4 appears to dissociate on the surface of the NI-YSZ cermet to give rise to surface carbon species and atomic hydrogen. Subsequent TP oxidation (TPO) and TP hydrogenation (TPH) experiments were used to determine the type and quantity of carbon deposition. Two types of carbon deposit were detected and identified as vermicular and pyrolytic species. The stability of both species increased with increasing temperature of formation. The extent of carbon deposition was significantly decreased when 3% H2O was added to the 5% CH4 feed.