In this review article, the basic principles of Fourier transformed large amplitude ac voltammetry (FTACV), as developed by the Monash Electrochemistry Group, are surveyed. Special attention is paid to the key features associated with the higher order harmonic components of FTACV that are not available in dc transient voltammetry, including (1) enhanced kinetic sensitivity; (2) rejection of background charging current and (3) insensitivity to homogenous catalysis coupled to electron transfer. Examples are then given to demonstrate the high sensitivity offered by FTACV in studies of surface-confined processes and electrode kinetic determinations, and the ability to extract thermodynamic information relevant to the electron transfer step and kinetic data for the coupled catalytic process separately under catalytic turnover conditions.
IntroductionIn December 2014, I (Dr. Zhang) was invited to visit Japanese electrochemistry groups at Polarography, Vol.61, No.1, (2015) from our group. Earlier works that employed small amplitude ac voltammetry also are not
Basic principles and key features of FTACVFTACV was developed to overcome some major drawbacks associated with dc voltammetry. To appreciate the basic principles of the technique, it is informative to survey the origins of these major drawbacks, and understand how they are overcome by FTACV.In dc cyclic voltammetry, a ramped (or staircase) potential waveform is applied to the working electrode, and the resulting current is recorded as a function of applied potential (Fig. 1). Dc voltammetry is understandably the most popular voltammetric method because it is both simple and very informative. 6) For example, from simple inspection of the dc voltammogram shown in Fig. 1, one can recognize that a redox active species present in solution in the reduced state can be oxidized to a stable product on the relevant timescale since the ratio of the oxidation and reduction peak currents is close to
22Review of Polarography, Vol.61, No.1, (2015) 1 : In dc cyclic voltammetry, a decrease in the rate of an electrode process leads to the increase of the separation between oxidation and reduction peak potentials. Therefore, the peak-to-peak separation or ΔE p value is commonly used to quantify the electrode kinetics. 7) However, ΔE p is also influenced by R u . 7) Thus, only when the effect of R u is negligible, can the electrode kinetics be determined directly from the ΔE p value. When the effect of R u is significant, the electrode kinetics may be determined using numerical simulations that take the effect of this term into account. In principle, to measure the kinetics of fast electrode processes using dc cyclic voltammetry, one can increase the scan rate to shorten the timescale of the measurement to achieve an outcome where the electrode process becomes relatively slow with respect to the measurement timescale. However, when the scan rate is very high, the contribution from the background double layer charging current to the