Synthesis and characterization of new ternary transition metal sulfide anodes for H2S-powered solid oxide fuel cell

A number of ternary transition metal sulfides with general composition AB2S4 (where A and B are different transition metal atoms) have been prepared and investigated as potential anode catalysts for use in H2S-powered solid oxide fuel cells (SOFCs). For the initial screening, polarization resistance of the materials was measured in a two electrode symmetrical cell at 700–850 °C. Vanadium-based materials showed the lowest polarization resistance, and so were chosen for subsequent full cell tests using the configuration [H2S, AV2S4/YSZ/Pt, air] (where A = Ni, Cr, Mo). MoV2S4 anode had superior activity and performance in the full cell setup, consistent with results from symmetrical cell tests. Polarization curves showed MoV2S4 had the lowest potential drop, with up to a 200 mA cm−2 current density at 800 °C. The highest power density of ca. 275 mW cm−2 at 800 °C was obtained with a pure H2S stream. Polarization resistance of materials was a strong function of current density, and showed a sharp change of slope attributable to a change in the rate-limiting step of the anode reaction mechanism. MoV2S4 was chemically stable during prolonged (10 days) exposure to H2S at 850 °C, and fuel cell performance was stable during continuous 3-day operation at 370 mA cm−2 current density.