| Abstract
| - The surface chemistry of benzene and bromobenzene over Pt(111) has been studied by temperature-programmedXPS/MS and NEXAFS. Time-resolved XPS shows that benzene adopts a single chemically distinguishableenvironment 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 tosurface carbon. Bromobenzene likewise adsorbs molecularly at 90 K, giving rise to two C 1s environmentsat 284.4 and 285.3 eV corresponding to the C−H and C−Br functions, respectively. The saturation C6H5Brmonolayer coverage is 0.11 ML. NEXAFS reveals that bromobenzene adopts a tilted geometry, with the ringplane at 60 ± 5° to the surface. Bromobenzene multilayers desorb at ∼180 K, with higher temperaturespromoting 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 heatingresults in desorption of reactively formed H2, C6H6, and HBr; however, there was no evidence for eitherbiphenyl or Br2 formation. Pt(111) is an efficient surface for low-temperature bromobenzene hydrodebromination to benzene and HBr.
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