Shape and Size of Cobalt Nanoislands Formed Spontaneously on Cobalt Terraces during Fischer-Tropsch Synthesis

Arghya Banerjee, Violeta Navarro, Joost W.M. Frenken, Alexander P. Van Bavel, Herman P.C.E. Kuipers, Mark Saeys*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Cobalt-based catalysts undergo a massive and spontaneous reconstruction to form uniform triangular nanoislands under Fischer-Tropsch (FT) conditions. This reconstruction is driven by the unusual and synergistic adsorption of square-planar carbon and CO at the 4-fold edge sites of the nanoislands, driving the formation of triangular islands. The size of the nanoislands is determined by the balance between energy gain from creating C/CO-covered edges and energy penalty to create C/CO-covered corners. For carbon chemical potentials corresponding to FT conditions, triangular Co islands with 45 Co atoms (about 2 nm) are the most stable surface structure. Decreasing the carbon chemical potential and hence the stability of square-planar carbon favors the formation of larger islands, until reconstruction becomes unfavorable and CO-covered terraces are thermodynamically the most stable. The predicted structure of the islands is consistent with in situ scanning tunneling microscopy images obtained for the first time under realistic FT reaction conditions on a Co(0001) surface.

Original languageEnglish
Pages (from-to)1996-2001
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume7
Issue number11
DOIs
Publication statusPublished - 2 Jun 2016
Externally publishedYes

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