Steering Surface Reaction at Specific Sites with Self-Assembly Strategy.
basic_science · Level V
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- Record sourced from PubMed, PMID 28809530.
- Also identified by DOI 10.1021/acsnano.7b04900.
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Abstract
To discern the catalytic activity of different active sites, a self-assembly strategy is applied to confine the involved species that are "attached" to specific surface sites. The employed probe reaction system is the Ullmann coupling of 4-bromobiphenyl, C<sub>6</sub>H<sub>5</sub>C<sub>6</sub>H<sub>4</sub>Br, on an atomically flat Ag(111) surface, which is explored by combined scanning tunneling microscopy, synchrotron X-ray photoelectron spectroscopy, and density functional theory calculations. The catalytic cycle involves the detachment of the Br atom from the initial reactant to form an organometallic intermediate, C<sub>6</sub>H<sub>5</sub>C<sub>6</sub>H<sub>4</sub>AgC<sub>6</sub>H<sub>4</sub>C<sub>6</sub>H<sub>5</sub>, which subsequently self-assembles with its central Ag atom residing either on 2-fold bridge or 3-fold hollow sites at full coverage. The hollow site turns out to be catalytically more active than the bridge one, allowing us to achieve site-steered reaction control from the intermediate to the final coupling product, p-quaterphenyl, at 390 and 410 K, respectively.