Grafting of Quinones on Carbons as Active Electrode Materials in Electrochemical Capacitors

The electrochemical performance of electrochemical capacitors can be improved with electroactive quinone molecules. Systems based on redox active electrolyte as well as physisorbed and chemically grafted molecules have been investigated. In all these cases, carbon materials were used as substrate and electrode material. This short review will mainly describe work related to these systems and materials from the authors’ laboratories. Nonetheless, some important studies from other research groups will be discussed

Anthraquinone modification of microporous carbide derived carbon films for on-chip micro-supercapacitors applications

The modification of carbide derived carbon (CDC) thin film electrodes with anthraquinone (AQ) molecules was demonstrated by using pulsed chronoamperometry, in 0.1 M NEt4BF4/ACN solution of AQ diazonium derivative. The functionalization of CDC electrodes was only possible when a critical pore size is reached: only 2 nm pore diameter CDC can be grafted with AQ moieties, smaller pore size leading to a poorly functionalized electrode. High AQ surface coverage of 0.88 × 10−10 mol.cm−2 was determined using 2 nm pore size CDC. Despite a decrease in double layer capacitance value of about 10%, the total capacitance of the AQ-modified on-chip CDC electrodes was twice larger than that of pristine CDC film, leading to high total capacitance value of 44 mF.cm−2 (338 F.cm−3). The cyclability of the AQ-modified on-chip CDC electrode was also investigated. The faradic contribution of AQ grafted molecules progressively decreased during cycling and only 39% of the normalized capacity remained after 500 cycles; this decrease has been assigned to electrostatic repulsion of dianionic AQ confined in narrow micropores in the alkaline media

Conception et caractérisation d’une batterie organique obtenue par greffage direct de molécules électroactives sur carbone activé

Date du colloque : 07/2013</p

Nouvelles stratégies de production in situ de sels de diazonium pour la modification éléctrochimique de surfaces

Date du colloque : 07/2011</p

Toward fully organic rechargeable charge storage devices based on carbon electrodes grafted with redox molecules

Activated carbon powders modified with naphthalimide and 2,2,6,6-tetramethylpiperidine-N-oxyl were assembled into a hybrid electrochemical capacitor containing an organic electrolyte. The fully organic rechargeable system demonstrated an increase in specific capacitance up to 51%, an extended operating voltage of 2.9 V in propylene carbonate, compared to 1.9 V for the unmodified system, and a power 2.5 times higher

Effect of the porous texture of activated carbons on the electrochemical properties of molecule-grafted carbon products in organic media

Two commercial activated carbons, different from their texture, were grafted with electroactive molecules and tested for determining what texture is well-suited for the grafting. Microporous and mesoporous carbons, having approximately the same BET surface area, were selected. The electroactive molecule consists in a naphthalimide compound having an amine as surface attachment group. The present work was divided in two parts. In a first part, the modified carbons were characterized by thermal gravimetric analysis, X-ray photoelectron spectroscopy, elemental chemical analysis and nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the textural properties of carbons. In a second part, the electrochemical properties of the modified carbons were studied in propylene carbonate +1 M Bu4NBF4. Results show that the grafting ruins the performances of the microporous carbon, while the mesoporous carbon appears well-suited for the grafting, showing a good compromise between electrolyte-accessibility and ionic transportation

Direct introduction of redox centers at activated carbon substrate based on acid-substituent-assisted diazotization

Redox properties have been imparted to activated carbon with a high degree of functionalization by chemical grafting of 2-amino-4,5-dimethoxybenzoic add in situ diazotized. The diazotization reaction was accomplished in the presence or in the absence of HCl for estimating the positive or negative effect of the carboxylic acid substituent on the grafting yield. Thermal gravimetric analysis, X-ray photoelectron spectroscopy and cyclic voltammetry experiments show that when the carboxylic acid group participates to the diazotization reaction. the grafting yield is improved and becomes even better than when the carboxylic group is not present, increasing the capacitance of pristine carbon electrode from 120 to 200 F/g

Supercapacitor behaviour of nanosized α-LiFeO2 in neutral sulphate electrolytes

II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC

Covalent vs. non-covalent redox functionalization of C-LiFePO4 based electrodes

During high rate utilization of porous Li battery, Li+ refuelling from the electrolyte limits the discharge kinetics of positive electrodes. In the case of thick electrodes a strategy to buffer the resulting sharp drop of Li+ concentration gradient would be to functionalize the electrode with anionic based redox molecules (RMR) that would be therefore able to relay intercalation process. The occurrence of these RMR in the electrode should not however, induce adverse effect on Li intercalation processes. In this respect, this work studies the effect of functionalizing LFPC based electrodes by either covalent or non-covalent chemistry, on Li intercalation kinetics. To do so, model molecules containing a nitro group were introduced at the surface of both carbon conducting additives and active material (C-LiFePO4). It is shown that presumably due to formation of sp(3) defects, covalent anchoring using diazonium chemistry inhibits the intercalation kinetics in C-FePO4. On the contrary, if molecules such as pyrene derivatives are immobilized by pi-staking interactions, Li intercalation is not impeded. Therefore non-covalent functionalization of pyrene based RMR appears as a promising route to relay Li intercalation reaction during high power demand. The framework for future development of this strategy is discussed. (C) 2013 Elsevier B.V. All rights reserved