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

Abstract

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.