Analysis of ramped square-wave voltammetry in the frequency domain

We present a new approach to the analysis of square-wave voltammetry in the frequency domain. By extending our earlier work (J. Electroanal. Chem. 480 (2000) 133) on the numerical simulation of ac sine wave voltammetry, we ar e able to solve the governing equations when a square waveform of any ampli tude is superimposed onto a linearly varying dc potential which is swept at a finite scan rate. By considering the numerical results in the frequency domain by using the fast Fourier transform (FFT) method, we are able to dev elop a very simple and general form of analysis which will theoretically al low consideration of reaction phenomena over a very wide range of timescale s using a single potential sweep. We go on to develop some novel theoretica l analyses, which support our numerical results, using an assumption that t he applied square-wave signal is superimposed on top of a fixed (or very sl owly varying) dc signal. This allows us to give exact and surprisingly simp le analytical results relating the amplitude and phase of the output signal at the half-wave potential (at odd multiples of the fundamental frequency) , to the amplitude of the applied square-wave signal, for any amplitude of the applied signal. Finally, we give brief experimental results showing qua litative agreement with our simulation results. (C) 2001 Elsevier Science B .V. All rights reserved.