Nanoscale surface chemistry

Theodore E. Madey, Kalman Pelhos, Qifei Wu, Robin Barnes, Ivan Ermanoski, Wenhua Chen, Jacek J. Kolodziej, John E. Rowe

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

We report evidence in several experiments for nanometer-size effects in surface chemistry. The evidence concerns bimetallic systems, monolayer films of Pt or Pd on W(111) surfaces. Pyramidal facets with {211} faces are formed on annealing on physical monolayer of Pt, Pd on a W(111) substrate, and facet sizes increase with annealing temperature. We used synchrotron radiation-based soft x-ray photoemission to show that monolayer films of Pt, Pd, on W "float" on the outer surface, whereas multilayer films form alloys on annealing. Acetylene reactions over bimetallic planar and faceted Pd/W surfaces exhibit size effects on the nanometer scale, that is, thermal desorption spectra of reactively formed benzene and ethylene (after acetylene adsorption) change systematically with facet size. In the second case, the decomposition of C2H2 over planar and faceted Ir(210) surfaces also exhibits structure sensitivity; temperature programmed desorption of H2 from C2H2 dissociation depends on the nanoscale surface structure. Finally, we have characterized interactions of Cu with the highly ordered S(4 × 4)/W(111) surface. The substrate is a sulfur-induced nanoscale reconstruction of W(111) with (4 × 4) periodicity, having broad planar terraces (≈30 nm in width). Fractional monolayers of vapor-deposited Cu grow as threedimensional clusters on the S(4 × 4) surface over a wide coverage range. At low Cu coverage (≤0.1 ML), Cu nanoclusters nucleate preferentially at characteristic 3-fold hollow sites; we find a clear energetic preference for one type of site over others, and evidence for self-limiting growth of nanoclusters.

Original languageEnglish (US)
Pages (from-to)6503-6508
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume99
Issue numberSUPPL. 2
DOIs
StatePublished - Apr 30 2002

ASJC Scopus subject areas

  • General

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    Madey, T. E., Pelhos, K., Wu, Q., Barnes, R., Ermanoski, I., Chen, W., Kolodziej, J. J., & Rowe, J. E. (2002). Nanoscale surface chemistry. Proceedings of the National Academy of Sciences of the United States of America, 99(SUPPL. 2), 6503-6508. https://doi.org/10.1073/pnas.062536499