Alkyl-group grafting onto glassy carbon cathodes by reduction of primary monohaloalkanes: electrochemistry and X-ray photoelectron spectroscopy studies

Autor: Benjamin H. R. Gerroll, Joshua A. Beeler, Allen R. Siedle, Ana G. Couto Petro, Steven L. Tait, Kent J. Griffith, Dennis G. Peters, Christopher G. Williams, J. Tyler Barnes
Rok vydání: 2020
Předmět:
Zdroj: Journal of Electroanalytical Chemistry. 856:113531
ISSN: 1572-6657
DOI: 10.1016/j.jelechem.2019.113531
Popis: Surface alkylation of glassy carbon (GC) and reticulated vitreous carbon (RVC) cathodes can occur when a primary alkyl monohalide is present in solution and when the electrode is polarized at potentials more negative than those required for reductive cleavage of the carbon–halogen bond, leading to the grafting of alkyl moieties onto the surface of the carbon cathode. Examination of electrode surfaces by means of X-ray photoelectron spectroscopy (XPS) has revealed that surface sp2:sp3 carbon ratios are approximately 4:1 for both pristine GC and RVC electrode materials that are commercially available. Further XPS analysis of these electrodes before and after reduction of perfluorobutyl iodide (C4F9I) provides substantial supporting evidence for a previously proposed mechanism for the grafting process that involves an SN2-like reaction between sp2-hybridized carbon (nucleophile) of the cathode and primary alkyl halides (electrophile) leading to conversion of sp2 sites to sp3 sites, with final surface sp2:sp3 carbon ratios that fall below 1:1. At the end of this paper, we discuss (mainly in qualitative terms) the ramifications of this surface modification of GC and RVC electrodes with respect to (a) bulk reduction of primary alkyl halides and (b) use and behavior of a well-known catalyst precursor (1,2,4,5-tetracyanobenzene).
Databáze: OpenAIRE
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