Density functional theory studies of methane dissociation on anode catalysts in solid-oxide fuel cells: Suggestions for coke reduction

We studied the dissociation of methane into adsorbed carbon and hydrogen atoms on various surfaces to gain insight into carbon coke formation on solid-oxide fuel cell anodes. Preferred adsorption sites and energies were calculated for CHx (x = 0,..., 3) and H on Ni and Cu (111) planar and (211) stepped surfaces, on Cu-Ni and Cu-Co surface alloys, and on Ni(211) surfaces with step edge sites blocked by Au- and S-promoter atoms. Transition states and kinetic barriers were calculated on Cu(111) and Cu(211) and on the S-Ni(211) surface. Our results are in excellent agreement with existing experimental and theoretical studies, suggesting that copper anodes have very low activity and high resistance to coking, and that step-blocking on the nickel surface can increase the tolerance of nickel-based anodes to carbon coke formation. (c) 2007 Elsevier Inc. All rights reserved.