A study on the potentiostatic current transient and linear sweep voltammogram simulated from fractal intercalation electrode: diffusion coupled with interfacial charge transfer

Abstract

Potentiostatic current transient and linear sweep voltammogram, theoretically calculated from the well-defined fractal profiles were analysed, with particular emphasis on hydrogen transport under the condition where hydrogen diffusion in the electrode is kinetically coupled with the charge-transfer reaction at the electrode/electrolyte interface. Under such a constraint of mixed control, the simulated current transient from the fractal electrode hardly exhibited the generalised Cottrell behaviour, and, especially, it displayed an inflexion point at the time that corresponds to the temporal outer cut-off of fractality (crossover time required for the fractal to flat transition). In the case of the linear sweep voltammogram computed from the fractal electrode, moreover, the power dependence of the peak current on the scan rate deviated negatively from the generalised Randles-Seveik behaviour, above the slow threshold scan rate (crossover scan rate needed for the fractal to flat transition). From the analyses of the current transients and the linear sweep voltammograms calculated with various values of the simulation parameters, it was further recognised that during the potential jump as well as the potential scan, the temporal cut-off ranges of fractality under the constraint of mixed control are crucially determined by the interfacial charge-transfer kinetics, even though the spatial cut-off range and the hydrogen diffusivity in the electrode are maintained constant. (C) 2004 Elsevier Ltd. All rights reserved.