Nanoscopic carbon electrodes: Structure, electrical properties and application for electrochemistry

Abstract

For many electrochemical applications, glassy carbon is an important electrode material that acts as a catalyst support and carbon nanotubes are frequently exploited as a catalyst itself or as a support for other active materials. Here we demonstrate a carbon-based, nanostructured, and high surface area electrode that consist of individual, free standing and vertically aligned multi-wall carbon nanotubes (MWCNTs) directly grown on glassy carbon via direct current plasma enhanced chemical vapour deposition. The structure is characterized via electron microscopy techniques, and local current-voltage measurements on individual MWCNTs confirm a good Ohmic contact of the individual vertically aligned MWCNTs and the glassy carbon bulk electrode. The proposed electrode can be used as a model system to study the mass transport of vertically aligned one-dimensional nanomaterials in electrochemistry applications. Its electrochemical characteristics are investigated using aqueous Ru(NH3)63+/2+ as an outer sphere redox couple. Cyclic voltammetry measurements show a significant increase in double-layer capacitance of the textured electrodes with respect to pristine glassy carbon. Finally, we demonstrate that the morphology of textured electrodes results in altered mass transport properties and yields a mixed linear- and thin-layer diffusion response depending on the scan rate, which is illustrated through numerical simulations.