| 초록 |
Ceria has been known as sulfur sorbent under reducing atmosphere due to its good affinity with sulfide in high temperature.In this paper, to enhance sulfur tolerance of the anodes in solid oxide fuel cells (SOFCs), we have modified pore wall surface of conventional nickel yttria-stabilized-zirconia (Ni/YSZ) anode by coating ceria nano-particles (10~20 nm) through dip coating method. The sulfur poisoning process has been analyzed under 0.2 A cm-2 of constant current for 24 h varying H2S concentrations.The cell voltages decreased rapidly after introducing the H2S in the first several hours in both the unmodified and the ceria-modified anodes and then reached a relatively stable state.Both the modified and unmodified anode was poisoned under H2S exposure.Ni3S2 was hardly formed in the ceria-coated Ni/YSZ anode, which led to less performance drop comparing to the conventional Ni/YSZ anode because the ceria reacted with H2S to form Ce2O2S which acts as a sulfur sorbent. Furthermore, impedance spectroscopy showed that the polarization resistance increased with increasing the H2S concentrations.Our results suggest the ceria nano-coating on Ni-YSZ anode has more tolerance effects in higher level of H2S concentration ( 200 ppm) and low operating temperature (700 oC). |
