Glassy carbon electrodes doped by surface graphite nano-flakes: Multi-step redox transitions functionalization

A simple mechanical deposition of soft graphite (natural from Ceylon or highly oriented pyrolytic graphite, HOPG) onto properly polished glassy carbon surfaces permits, after sonication, their profound and stable modification by coverage with graphite nano-particles (NP size ≤ 100 nm). Those electrode surfaces (tested in organic polar solvents containing tetraalkylammonium salts, TAA+X−) disclosed unsuspected features in cyclic voltammetry: the appearance of several redox steps whose potentials as well as shape and relative size are reproducible and stable. These features were found to be specific of each TAA+ cation. The stability of those layers was studied as a function of the cation bulkiness (from tetramethyl- to tetraoctylammonium) and the expected consequences of the exfoliation of the deposited material. Redox doping of NPs at these versatile surfaces permits redox catalysis of the reduction of alkyl halides RX via the concomitant generation of free alkyl radicals allowing chemical functionalization of these NPs.

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► Formation of graphite nano-particles (NPs) at glassy carbon surface
► Cathodic charge of those NPs by tetraalkylammonium (TAAX) salts
► Specificity of the charge with each TAA+
► Use of those charged surfaces for evidencing redox catalysis processes