Cobalt doped LaSrTiO3-δ as an anode catalyst: effect of Co nanoparticle precipitation on SOFCs operating on H2S-containing hydrogen

This article compares the effects of Co doping on phase structures and stability of lanthanum strontium titanate (LST) anodes and electrochemical measurements in solid oxide fuel cells (SOFCs) employing H2S-containing H-2 as fuel. The Co-doped LST (LSCT) with a perovskite structure was synthesized via a solid state approach, achieving excellent phase purity and refined particle size. The catalytic activity and electrochemical performance are significantly improved by introducing Co. A maximum power density of 300 mW cm(-2) was achieved at 900 degrees C with 5000 ppm H2S-H-2 in a fuel cell having a 300 mu m thick YSZ electrolyte. Trace amounts of metallic Co nanoparticles with sizes typically no larger than 10 nm in diameter were detected on the LSCT surface after reduction in H-2 at 900 degrees C. The nano-sized Co clusters could reduce the anode polarization resistance, as well as improve the cell performance, compared with undoped LST anodes. The LSCT anode catalyst was electrochemically stable in 5000 ppm H2S-H-2 during the test time at high operating temperature. The LSCT anode catalyst also had relatively high redox stability in reversible oxidation-reduction cycles.