Surface modification of Ni-YSZ using niobium oxide for sulfur-tolerant anodes in solid oxide fuel cells

The surface of a dense Ni-yttria-stabilized zirconia (YSZ) anode for solid oxide fuel cells (SOFCs) was modified with niobium oxide (Nb2 O5) in order to achieve sulfur tolerance. Results suggest that Nb2 O5 was reduced to NbO2 under SOFC operating conditions, which has high electrical conductivity and catalytic activity toward hydrogen oxidation. The NbOx -coated dense Ni-YSZ cermet anode showed sulfur tolerance when exposed to 50 ppm H2 S at 700°C over 12 h. Raman spectroscopy and X-ray diffraction analysis suggest that different phases of niobium sulfides (NbSx) were formed on the surfaces of niobium oxides. Furthermore, density of state (DOS) analysis of NbO2, NbS, and NbS2 indicates that the electronic structure of niobium sulfides are similar to that of NbO2; they are electrically conductive and catalytically active for hydrogen oxidation in H2 S containing fuels under the conditions studied.