Comparison of the electrochemical behaviour of buckypaper and polymer-intercalated buckypaper electrodes

The performances of freestanding carbon nanotube (buckypaper) and polymer-intercalated buckypaper electrodes in an electroanalytical chemistry context were evaluated via analysis of direct current and Fourier Transform large-amplitude alternating current voltammograms derived from the ferrocenemonocarboxylic acid (FMCA0/+), ruthenium hexamine ([Ru(NH3)6]3+/2+) and ferricyanide ([Fe(CN)6]3−/4−) redox couples. The composite polymer-intercalated buckypaper electrodes exhibit substantially superior Faradaic-to-capacitive background charging current ratios under both dc and ac conditions compared and display close to ideal voltammetry for all three processes. A significant difference was detected in mid-point potentials determined by cyclic voltammetry at buckypaper and polymer-intercalated buckypaper electrodes, commensurate with different mass transport mechanisms. It is proposed that the porosity of the buckypaper gives rise to a restricted diffusion model of mass transport within the pores and a large electrode over that generates a large capacitance current. Thus, polymer intercalation is required to achieve high quality electroanalytical performance. Simulations of voltammograms obtained at porous polymer-intercalated buckypaper electrodes are consistent with the composite electrodes consisting of a randomly arranged array of nano-/micro-electrode domains, implying that significant surface heterogeneity is present. However, under slow scan rate conditions, when significant overlap of diffusion layers occurs, voltammograms may be approximately interpreted in terms of a linear diffusion based mass transport model.