Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes

Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (HBC and CQD) onto conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrodes states at different potentials and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than –0.5 V vs Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This ...