Computational study of sulfur-nickel interactions: A new S-Ni phase diagram

Prediction of the interactions between H2S-contaminated hydrogen fuel and Ni surfaces under conditions similar to those for solid oxide fuel cell (SOFC) operation using DFT (density function theory) calculations (with thermodynamic corrections) has resulted in a new S-Ni phase diagram, which suggests the existence of an intermediate state between clean Ni surfaces and nickel sulfides - sulfur atoms adsorbed on Ni surfaces. This prediction is consistent with many experimental observations relevant to sulfur poisoning of Ni-based anodes in SOFCs, which cannot be explained using the existing S-Ni bulk phase diagram from classical thermodynamics. The accurate prediction of the adsorption phase is vital to a fundamental understanding of the sulfur poisoning mechanism of Ni-based anodes under SOFC operating conditions. (c) 2007 Elsevier B.V. All rights reserved.