Hydrodebromination of bromobenzene over Pt(111)

Adam F. Lee, Zhipeng Chang, Simon F.J. Hackett, Andrew D. Newman, Karen Wilson

Research output: Contribution to journalArticle

Abstract

The surface chemistry of benzene and bromobenzene over Pt(111) has been studied by temperature-programmed XPS/MS and NEXAFS. Time-resolved XPS shows that benzene adopts a single chemically distinguishable environment during low-temperature adsorption within the monolayer, with a saturation coverage at θC6H6 = 0.2 ML. Around 20% of a benzene monolayer desorbs molecularly, while the remainder dehydrogenates to surface carbon. Bromobenzene likewise adsorbs molecularly at 90 K, giving rise to two C 1s environments at 284.4 and 285.3 eV corresponding to the C−H and C−Br functions, respectively. The saturation C6H5Br monolayer coverage is 0.11 ML. NEXAFS reveals that bromobenzene adopts a tilted geometry, with the ring plane at 60 ± 5° to the surface. Bromobenzene multilayers desorb at ∼180 K, with higher temperatures promoting competitive molecular desorption versus C−Br scission within the monolayer. Approximately 30% of a saturated bromobenzene monolayer either desorbs reversibly or as reactively formed hydrocarbons. Debromination yields a stable (phenyl) surface intermediate and atomic bromine at 300 K. Further heating results in desorption of reactively formed H2, C6H6, and HBr; however, there was no evidence for either biphenyl or Br2 formation. Pt(111) is an efficient surface for low-temperature bromobenzene hydrodebromination to benzene and HBr.
Original languageEnglish
Pages (from-to)10455-10460
Number of pages6
JournalJournal of Physical Chemistry: Part C
Volume111
Issue number28
Early online date20 Jun 2007
DOIs
Publication statusPublished - 19 Jul 2007

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    Lee, A. F., Chang, Z., Hackett, SF. J., Newman, A. D., & Wilson, K. (2007). Hydrodebromination of bromobenzene over Pt(111). Journal of Physical Chemistry: Part C, 111(28), 10455-10460. https://doi.org/10.1021/jp070488r