Improvement of electrochemical performances of catechol-based supercapacitor electrodes by tuning the redox potential via different-sized O-protected catechol diazonium salts

Two different O-protected catechol diazonium salts were synthetized and reacted with microporous Norit-S50 carbon to investigate the impact of the protecting group on the electrochemical performances of supercapacitor electrodes in 1 M H2SO4. Carbon products were characterized by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) experiments and nitrogen gas adsorption-desorption measurements to investigate the film composition, as well as the impact of the grafting on the textural properties of the Norit-S50. Supercapacitor electrodes, prepared from carbon products, were studied by cyclic voltammetry at different scan rates and by galvanostatic charge/discharge experiments after deprotection of catechol-attached groups. It was found that the specific charge was improved by introducing catechol groups under protected forms and that the potential at which the redox reaction occurred depends on the protecting group used. With bulky triisopropylsilyl protecting groups, the formal potential of catechol-attached moieties shifted in the positive direction by about 300 mV, yielding an energy gain significantly increased, compared to the same charge stored in the level of catechol groups introduced with methyl protecting groups. 1100 repetitive charge/discharge curves at 1 A g−1 were achieved to study the stability of supercapacitors electrodes. Results obtained were tentatively explained in terms of the porous structure of the carbon

Preparation of a tetrahydroxyphenazine-modified carbon as cathode material for supercapacitor in aqueous acid electrolyte

A procedure for the grafting of oxocarbon compounds is proposed by condensation reaction with a benzenediamine to obtain an attached-phenazine moieties. A technical proof of concept is given by the covalent capture of rhodizonic acid on the Norit activated carbon and potentiality for supercapacitors is evidenced. The composite material obtained was tested as positive electrode for aqueous supercapacitors in 1 M H2SO4. The redox activity covering a wide range of potential gives an unprecedented increase in specific charge of 350% and a specific energy at the discharge 3.4 times higher than the unmodified carbon. Keywords: Supercapacitor, Activated carbon, Diazonium salt, Oxocarbons, Graftin

Toward fully organic rechargeable charge storage devices based on grafting of redox molecules

Date du colloque : 06/2013</p

Spontaneous arylation of activated carbon from aminobenzene organic acids as source of diazonium ions in mild conditions

International audienceActivated carbon products modified with benzoic, benzenesulfonic and benzylphosphonic acid groups were prepared by spontaneous reduction of aryldiazonium ions in situ generated in water from the corresponding aminobenzene organic acids without addition of an external acid. Electrochemistry and NMR studies show that the advancement of the diazotization reaction depends both on the acidity and the electronic effect of the organic acid substituent, giving a mixture of diazonium, amine and triazene functionalities. Carbon products prepared by reaction of activated carbon Norit with 4-aminobenzenecarboxylic acid, 4-aminobenzenesulfonic acid and (4-aminobenzyl)phosphonic acid were analyzed by chemical elemental analysis and X-ray photoelectron spectroscopy experiments. Results show that this strategy is well suited for the chemical functionalization, giving a maximized grafting yield due to a chemical cooperation of amine and diazonium functionalities

Modification chimique spontanée de carbones activés par réduction de sels de diazonium générés in situ par auto-diazotation. Préparation et études de matériaux pseudo-capacitifs appliqués au stockage de l’énergie

Date du colloque : 07/2011</p

Electrode grafting by oxidation of an amine catalyzed by a ferrocenyl “antenna” through intramolecular electron transfer

Two aminoferrocene complexes were studied by electrochemical techniques. Molecules retain the redox properties of both ferrocene and amine groups, but fundamentally different behaviours were observed depending on whether the linker between the two redox end groups was saturated (ethyl bridge) or not (ethynyl bridge). The possibility of an intramolecular electron transfer from the amine to the ferricenium moiety through the π-conjugated linker was demonstrated and the ethynyl bridge is expected to have a dual effect by facilitating both the oxidation of the amine into the cation radical and the production of aminyl radical, due to its strong electron withdrawing effect. Because of this synergy of properties, grafting of the conjugated aminoferrocene complex can occur just by oxidizing the ferrocene group without the presence of a base in solution. Keywords: Modified electrode, Ferrocene, Amine, Intramolecular electron transfer, Radical aminy

Base‐Assisted Electrografting of Aromatic Amines

International audienc