Electrochemistry of bi-redox ionic liquid from solution to bi-functional carbon surface

In this work, bi-redox molecule based ionic liquid was synthesized. Ferrocene donor group and anthraquinone acceptor group were linked to imidazolium cation. Next, the electrochemistry of the as synthesized molecule was investigated demonstrating the presence of two reversible redox systems. Furthermore, the diffusion coefficient and electron transfer rate constant were measured using the ferrocene oxidation and the anthraquinone reduction. Besides that, the bi-redox molecule was immobilized onto carbon electrode using two steps procedure based on the oxidative grafting of primary layer bearing diazonium head group followed by Gomberg-Bachmann coupling surface reaction. The surface characterization confirms the attachment of the imidazolium bi-redox molecule as well as the presence of the labile anion within the layer. Interestingly, the electrochemical investigations confirm the bi-redox grafting with an equi-distribution of the electron donor and acceptor within the attached layer. Finally, the attached layer exhibits an enhancement of double-layer capacitance which is correlated to the increase of the charge density and ionic property of the layer. (C) 2020 Elsevier Ltd. All rights reserved.