Boosting electrochemical performance of single-walled carbon nanotube three-dimensional architectures through appropriate selection of organic dispersant

Abstract

The choice of organic dispersant in the fabrication of 3D carbon nanotube architectures affects their macroscopic properties. Binder-free papers (referred to as buckypapers, BPs) consisting of single-walled nanotubes (SWCNTs) fabricated by vacuum filtration of nanotube suspensions in isopropanol, ethanol, benzoic acid dissolved in ethanol and lemon oil show a work of adhesion of water that varies from 25.7 to 112.2 mJ·m−2. Bulk electrical resistivity also changes significantly from 145 to 1010 mΩ cm. Raman and FTIR spectra of pristine SWCNTs and BPs show evidence of permanent adsorption of organic molecules on SWCNTs. Heterogeneous electron transfer (HET) standard rate constants, k0, for ferro/ferricyanide and hexaammineruthenium(II)/(III) redox probes estimated from cyclic voltammetry measurements on BP electrodes vary from 12.6×10−4cms−1 to 32.7×10−4cms−1 and 12.8×10−4cms−1 to 26.0×10−4cms−1, respectively, depending on the dispersant used. Calculations using the Gerischer-Marcus model show that molecules adsorbed act as electron donors that boost HET kinetics and cause a shift in the reaction half-wave potential. The level of doping of nanotubes depends on the dipole moment of the dispersant molecules and proton affinity. Thus, the electrocatalytic activity of three-dimensional architectures composed of nanotubes can be adjusted by selecting an appropriate dispersant.