Résumé
Grafting redox active moieties, including anthraquinone, on large surface area carbons has been for long considered has a good opportunity to increase the energy density of electrochemical capacitors. From the CVs, usually looking like the merging of redox and capacitive signals, the storage capability obviously takes benefit from both contributions. Unfortunately, performances are not fully met: when increasing the anthraquinone loading above 10-15 w%, the double layer contribution decreases because of pore clogging. Cyclability is also poor: during the first few hundreds of cycles (often less), the capacity is progressively fading down because of either physisorb anthraquinone molecules being washed away from the carbon surface and molecule degradation.
Various approaches have been considered to address these limits. This paper is an introduction to two of those we have explored. The first one consists in the covalent grafting of an anthraquinone propargyl molecule by a Diels Alders reaction using carbon surfaces as dienophyl. For the second, anthraquinone molecules are first simply adsorbed at the carbon surface. In a second step, flakes from exfoliated MXene are deposited on top of the anthraquinone film by dip-coating. This carbide shell provides the resulting composite some extra electronic conductivity while allowing the electrolytic species to reach both anthraquinone and carbon thanks to its open structure. Attractive electrochemical characteristics have been obtained from electrodes based on these two different materials. These are discussed based on the compositions and morphologies of the prepared composite materials.
References
Brousse, T.; Cougnon, C.; Bélanger, D., Grafting of Quinones on Carbons as Active Electrode Materials in Electrochemical Capacitors.
Journal of the Brazilian Chemical Society
2018,
29
, 989-997.
Pognon, G.; Brousse, T.; Demarconnay, L.; Bélanger, D., Performance and stability of electrochemical capacitor based on anthraquinone modified activated carbon.
Journal of Power Sources
2011,
196
(8), 4117-4122.