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

Abstract Performances of four anode compositions with different weight ratios of Ni 3± x S 2 to MoS 2 (2:1, 1:1, 1:2 and 1:4) were compared for H 2 S 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 MoS 2 disappearance previously attributed to its volatility at temperature above 450 °C was instead related to its preliminary oxidation to MoO 3 in fuel cell mode as MoO 3 is highly volatile at temperatures above 600 °C. Suppression of volatility of MoO 3 by addition of Ni 3± x S 2 was shown by DSC/TGA analysis. Highest power density ca. 300 mW cm 2 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.