Facile cathodic surfacial carboxylation of glassy carbon by means of immobilized alkanoic acids chains

The reduction of ω-bromoalkanoic acids Br(CH2)nCOOH at glassy carbon cathodes in aprotic polar solvents (acetonitrile, N,N-dimethylformamide or propylene carbonate) in the presence of tetraalkylammonium salts at E < − 1.7 V vs. Ag/AgCl results in a dense organic layer, covalently attached to carbon, which progressively covers the electrode surface. It was evidenced that the immobilization of alkyl chains occurs via the scission of C-Br bonds permitting an efficient coverage of the carbon surface with the layers built of alkyl links [CH2]n (3 ≤ n ≤ 11) terminated with COOH groups. The carboxyls immobilized this way were easily transformed into electroactive esters or into amides by reacting with phenols or amines, respectively. Thus grafted π-acceptor groups allowed estimating the carboxylation level as very high, ca. (1–5) × 10− 9 mol/cm2 when taking into account the starting surface area. In aqueous media, the immobilized films with long alkyl linkers visibly behave as hydrophobic layers.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Efficient grafting of ω-bromoalkanoic acids at carbon surfaces ► Immobilization of long chain alkanoic acids forming compact layers ► Carbon carboxylation permitting surfaces functionalization ► Extension to macro-modification of industrial coke powders for catalysis.