Finite kinetics, scanning electrochemical

Bard AJ, Mirkin MV, Unwin PR, Wipf DO (1992) Scanning electrochemical microscopy. 12. Theory and experiment of the feedback mode with finite heterogeneous electron-transfer kinetics and arbitrary substrate size. J Phys Chem 96 1861-1868... 

FIGURE 5.2 Simulated feedback SECM transients with various rate constants for an irreversible heterogeneous process at the substrate. The upper and lower dashed curves correspond, respectively, to the limits A ijs ° and A [,s=0. The solid curves (from top to bottom) represent log A s=3.0, 1.5, 1.0, 0.5, 0, -0.5, and -1.0. RG=10. (Reprinted with permission from Bard, A.J., Mirkin, M.V., Unwin, P.R., and Wipf, D.O., Scanning electrochemical microscopy. 12. Theory and experiment of the feedback mode with finite heterogeneous electron-transfer kinetics and arbitrary substrate size, J. Phys. Chem., 96, 1861-1868, 1992. Copyright 1992 American Chemical Society.)... 

The diffusion of the electroactive ions is both physical and due to electron transfer reactions.45 The occurrence of either or both mechanisms is a function of the electroactive species present. It has been observed that the detailed electrochemical behaviour of the electroactive species often deviates from the ideal thin film behaviour. For example, for an ideal nemstian reaction under Langmuir isotherm conditions there should be no splitting between the anodic and cathodic peaks in the cyclic voltammogram further, for a one-electron charge at 25 °C the width at half peak height should be 90.6 mV.4 In practice a difference between anodic and cathodic potentials may be finite even at slow scan rates. This arises from kinetic effects of phase formation and of interconversion between different forms of the polymer-confined electroactive molecules with different standard potentials.46... 

---