Performance and stability of composite nickel and molybdenum sulfide-based anodes for SOFC utilizing H2S

Performances of four anode compositions with different weight ratios of Ni3±xS2 to MoS2 (2:1, 1:1, 1:2 and 1:4) were compared for H2S oxidation in SOFC at 700–850 °C. Their thermal and chemical stability were determined using DSC/TGA, XRD, SEM and NAA. Electrochemical stability was investigated in fuel cell mode under OCV and constant overpotential conditions. It was shown that MoS2 disappearance previously attributed to its volatility at temperature above 450 °C was instead related to its preliminary oxidation to MoO3 in fuel cell mode as MoO3 is highly volatile at temperatures above 600 °C. Suppression of volatility of MoO3 by addition of Ni3±xS2 was shown by DSC/TGA analysis. Highest power density ca. 300 mW cm2 at 850 °C was achieved with 1:1 weight ratio anode composition. All four compositions had unstable electrochemical performance which was more pronounced under polarization conditions than at OCV.