A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

Noah T. Plymale, Mita Dasog, Bruce S. Brunschwig, Nathan S. Lewis

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H-Si(111) surfaces have been reacted with liquid methanol (CH3OH) in the absence or presence of a series of oxidants and/or illumination. Oxidant-activated methoxylation of H-Si(111) surfaces was observed in the dark after exposure to CH3OH solutions that contained the one-electron oxidants acetylferrocenium, ferrocenium, or 1,1′-dimethylferrocenium. The oxidant-activated reactivity toward CH3OH of intrinsic and n-type H-Si(111) surfaces increased upon exposure to ambient light. The results suggest that oxidant-activated methoxylation requires that two conditions be met: (1) the position of the quasi-Fermi levels must energetically favor oxidation of the H-Si(111) surface and (2) the position of the quasi-Fermi levels must energetically favor reduction of an oxidant in solution. Consistently, illuminated n-type H-Si(111) surfaces underwent methoxylation under applied external bias more rapidly and at more negative potentials than p-type H-Si(111) surfaces. The results under potentiostatic control indicate that only conditions that favor oxidation of the H-Si(111) surface need be met, with charge balance at the surface maintained by current flow at the back of the electrode. The results are described by a mechanistic framework that analyzes the positions of the quasi-Fermi levels relative to the energy levels relevant for each system.

Original languageEnglish
Pages (from-to)4270-4282
Number of pages13
JournalJournal of Physical Chemistry C
Issue number8
Publication statusPublished - Mar 2 2017


ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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