Recent results on solid oxide fuel cells with Ni/YSZ and Ni/GDC anodes reveal a mechanism for permanent performance degradation due to hydrogen sulfide exposure. Our results confirm the temporary performance decline observed by others but also reveal a mechanism for the long term permanent degradation. we find that hydrogen sulfide leads to nickel migration and depletion in the anode, thereby compromising electrical conductivity and cell performance. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.