Berlin 2005 – scientific programme
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O: Oberflächenphysik
O 55: Epitaxie und Oberfl
ächenreaktionen
O 55.5: Talk
Wednesday, March 9, 2005, 11:45–12:00, TU EB107
Water Formation from H2 ad O2 on Pt(111) — •Timo Jacob1,2 and William A. Goddard III.1 — 1MSC, Caltech, Pasadena, USA — 2Fritz-Haber-Institut der MPG, Berlin, Germany
Using density functional theory (DFT) with the B3LYP gradient-corrected exchange-correlation functional, the reaction of H2+1/2O2—→ H2O was studied on Pt(111), which was represented by a 35 atom cluster. In order to study possible reaction pathways, first binding structures and energetics of each possible intermediate were calculated separately (O, H, O2, H2, OH, OOH, H2O) and afterwards combined with the corresponding dissociation barriers.
Between the two dominant reaction pathways the rate-determining step of the O2-Dissociation is Oad+Had—→ OHad with a barrier of 31.66 kcal/mol. Along the OOH-Formation pathway OOHad—→ OHad+ Oad dissociation has the highest barrier with 17.13 kcal/mol. Although the OOH-Formation is preferred, the oxygen atom, which remains after this reaction without further use, would lead to surface termination. Thus, it also has to use the other reaction channel, or recombine to O2, which then can be used within the OOH-Formation process.