Ceria Coatings Effect on H2S Poisoning of Ni/YSZ Anodes for Solid Oxide Fuel Cells

Abstract

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 H2S concentrations at 700 degrees C. Because the ceria reacted with H2S to form Ce2O2S, which acted as a sulfur sorbent, Ni3S2 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 H2S concentration. Our results suggest that ceria nanocoatings on Ni-YSZ anodes provide greater sulfur tolerance at higher H2S concentrations (>= 200 ppm) and lower operating temperatures (700 degrees C). (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3499215] All rights reserved.