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A Surface Grafting of Carbon Allotropes with in‐situ Generated 3‐aryl Diazonium Chlorides: Electrochemical Kinetic Studies
Author(s) -
Radtke Mariusz,
Ignaszak Anna
Publication year - 2016
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.201600324
Subject(s) - electrochemistry , aryl , in situ , grafting , diazonium compounds , kinetic energy , carbon fibers , chemistry , materials science , polymer chemistry , inorganic chemistry , electrode , organic chemistry , alkyl , physics , quantum mechanics , composite number , composite material , polymer
In this work three different carbon allotropes: multi‐walled carbon nanotubes (MWCNT), graphene and carbon nanohorns (CNH) were covalently bound with in‐situ generated 3‐diazonium aryl chlorides. These species were attached to the carbon surface using an electrochemically‐initiated radical coupling, similar to the Gomberg‐Bachman type reaction. An electrochemical grafting of the extended π‐systems at the carbon surface was performed in aqueous media in a simple 3‐electrode system and its kinetics was investigated by a modified Butler‐Volmer approach. The analysis of Hammett constants demonstrated a strong influence of the type of electron donating‐/withdrawing substituents on the reduction potential peak position and the peak current. Moderately or strong electron withdrawing groups like ‐carboxy or ‐nitro tend to shift reduction potential towards more positive values, which facilitates an electron uptake. The deposition time varies for different carbon allotropes and depends on the carbon graphitization and the surface area. The best surface coverage was obtained at 90–150 sec of the deposition. Although, the surface functionalities are less conductive than the carbon, the electrodes showed a low internal resistance and thus a high rate of electron transfer (high exchange current density and the electron transfer rate constant), with the most promising observed for carbon nanohorns. The best performing carbon revealed also superior mass transport of the redox active species toward the electrode surface, owing to their unique particle shapes and its very porous structure. The Tafel analysis complemented by an impedance spectroscopy allowed selecting the best carbon substrate for the functionalization with a 3‐aminobenzoic acid.