Redox behaviour of boron subphthalocyanine carbon nanotube composites

Abstract

Organic redox-active carbon composites can be used as sustainable electrode materials in electrochemical energy storage systems. Among numerous redox active species, peripherally dodecafluorinated boron subphthalocyanines (F12BsubPcs) have shown electrochemical redox activities in the solution phase. Nonetheless, the electrochemical properties of solid F12BsubPcs when compositing with nano carbon warrants further investigation for potential applications in energy storage. In this work, nanometer scale axially brominated F12BsubPcs (Br-F12BsubPcs) were coated onto bare graphitized multiwalled carbon nanotubes (GCNT) and COOH-functionalized GCNT (COOH-GCNT) by a facile dip coating method to produce two composites and to compare the effects of the surface functional group interactions with Br-F12BsubPcs. While the surface chemical and morphological characterizations confirmed the presence of Br-F12BsubPc coating on both bare and COOH-GCNTs, the coverage on the latter was higher. Cyclic voltammetric studies in acidic electrolyte revealed a highly reversible redox couple on both composites with Br-F12BsubPc coated COOH-GCNT demonstrating up to c.a. 70% higher redox peak currents than with Br-F12BsubPc coated GCNT. Further analyses of the coated COOH-GCNT suggested a 2-electron transfer process. The charge transfer has fast-kinetics and a strong dependence on the proton concentration. The composites produced in this work demonstrate potential for future application in energy storage and can provide a strategy for developing BsubPc-based carbon composites.