abstract
NO dissociation with and without the presence of hydrogen on the Au(321) surface was investigated using density functional theory and a periodic supercell approach. The role of hydrogen in the reaction of NO dissociation is studied by comparing four different routes (i.e. direct dissociation of NO on the clean surface and paths involving reaction with hydrogen adatoms prior to N-O bond cleavage). In the latter situation, two routes via a NOH intermediate were considered, producing N* + OH* or N* + H(2)O*, and another route via a NHOH intermediate was also considered, yielding NH* and OH* species. The calculations predict that the kinetically most favorable route is that producing nitrogen adatoms and water, i.e., NO* + 2H* -> N* + H(2)O* via the NOH* intermediate. This reaction is exothermic (1.1 eV) and the energy barriers for the separate NO* + H* -> NOH* and NOH* + H* -> N* + H(2)O* reactions are similar to 0.5 eV. An identical energy barrier was calculated for the reaction of the dissociation of molecular hydrogen on the stepped surface studied here, which is one-half of the barrier calculated in the case of the planar Au(111) surface. The reaction thermodynamically more favorable is that via the NHOH intermediate (1.5 eV). The kinetically least favorable path for NO dissociation on Au(321) is that occurring on the clean surface with an energy barrier of 3.5 eV; this reaction is also highly endothermic (> 2.2 eV). The present work shows that the presence of hydrogen is a necessary condition for NO dissociation on this stepped surface.
keywords
SELECTIVE CATALYTIC-REDUCTION; TOTAL-ENERGY CALCULATIONS; OXYGEN-RICH CONDITIONS; AUGMENTED-WAVE METHOD; NITRIC-OXIDE; LOW-TEMPERATURE; CARBON-MONOXIDE; DIRECT DECOMPOSITION; STORAGE-REDUCTION; AU(321) SURFACE
subject category
Chemistry; Science & Technology - Other Topics; Materials Science
authors
Fajin, JLC; Cordeiro, MNDS; Gomes, JRB
our authors
José R. B. Gomes
Principal Researcheracknowledgements
Thanks are due to Fundacao para a Ciencia e Tecnologia (FCT), Lisbon, Portugal and to FEDER for financial support to CIQUP, to REQUIMTE, and to CICECO. J.L.C.F. acknowledges FCT for the Grant SFRH/BPD/27167/2006.