Direct collisionally activated and trapping-mediated dissociative chemisorption of neopentane on clean Pt(111): the activity of surface defect sites

• Published in: Surface science 1997-12, Vol.393 (1), p.150-161
• Main Authors: Weaver, Jason F., Krzyzowski, Michael A., Madix, Robert J.
• Format: Article
• Language: English
• Subjects: Adsorption kinetics; Alkanes; Applied sciences; Chemistry; Exact sciences and technology; General and physical chemistry; Low index single crystal surfaces; Metals. Metallurgy; Models of surface kinetics; Molecule-solid reactions; Platinum; Single crystal surfaces; Solid-gas interface; Surface physical chemistry
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(97)00580-3

Molecular beam results indicate that the dissociative chemisorption of neopentane on Pt(111) occurs by both direct collisionally activated and trapping-mediated mechanisms. Direct dissociation dominates at translational energies greater than about 110 kJ mol −1, exhibits normal energy scaling and is nearly independent of the surface temperature. The trapping-mediated pathway, which displays a significant temperature dependence, is the controlling dissociative adsorption mechanism at gas-molecule translational energies less than 110 kJ mol −1. Experiments performed on Pt(111) surfaces with differing defect-site densities indicate that trapping-mediated dissociation is facilitated by surface defects. The measured surface-temperature dependence of the trapping-mediated dissociation probability was accurately reproduced by a model which assumes that the rate of migration to defects is rapid compared to the dissociation and desorption rates.