Ceria coatings effect on H₂S poisoning of Ni/YSZ anodes for solid oxide fuel cells

Ceria is a good sulfur sorbent under reducing atmospheres because of its high affinity for sulfide at high temperatures. In this study, to enhance the sulfur tolerances of anodes for solid oxide fuel cells, we have used a dip-coating method to modify the pore wall surfaces of conventional nickel/yttria-stabilized zirconia (Ni/YSZ) anodes by coating them with ceria nanoparticles (10-20 nm). We have monitored the sulfur poisoning process in various H₂ S concentrations at 700°C. Because the ceria reacted with H₂ S to form Ce₂ O₂ S, which acted as a sulfur sorbent, Ni₃ S₂ was hardly formed in the ceria-coated Ni/YSZ anode; therefore, its performance dropped to a lesser degree relative to that of the conventional Ni/YSZ anode. Furthermore, impedance spectroscopy revealed that the polarization resistance increased upon increasing the H₂ S concentration. Our results suggest that ceria nanocoatings on Ni-YSZ anodes provide greater sulfur tolerance at higher H₂ S concentrations (200 ppm) and lower operating temperatures (700°C).