Short‐Pulse Techniques: I . Kinetics of the Triiodide/Iodide Reaction on a Platinum Electrode in Neutral Solution

Abstract

The subject application permits observation of polarization changes on an electrode surface in times as short as 25 nanosec. The required miniaturization of the electrolytic cell is achieved by the use of a solion. Short pulses limit electrochemical processes so that only those reactants already present at the metal/solution interface are available for reaction. The perturbation time of iodide ions in the compact double layer was estimated to be . Kinetic relations for polarization build‐up and decay are derived and applied to this redox system for both anodic and cathodic polarization. The variability of the transfer coefficient, α, found by Newson and Riddiford, is confirmed over a wide range in both the anodic and cathodic directions. Kinetic parameters are determined, and the equations based on the Vetter electron transfer step, with some modifications, are verified. Surface coverage determinations indicate that the fraction of available platinum surface covered with adsorbed iodine atoms at zero overvoltage for adsorbed iodine atoms is 0.09. Parameters are also determined for the hydrogen formation reaction at potentials where all of the iodine is reduced. A model for the adsorption of iodine species on the electrode surface is given in order to explain the relationship between surface coverage of these species and the exchange current density.