Faradaic rectification studies of two electron charge transfer redox couples at the metal (solid) interface

Abstract

The Faradaic rectification studies of the two electron charge transfer processes, cationic and anionic redox couples, have been carried out. The mechanism of the iodide—iodine reaction through single charge transfer comprises the following steps, of which reaction (b) is the slowest and controls the rate of overall reactions. ▪ The values of the transfer coefficient and rate constant are obtained for the second step, which is rate determining in both the directions. The values of the parameters obtained when the concentration of the electrochemical species (I 2) is much less in comparison to that of iodide, are α c = α a = 0·5 and k O a of the order of 5 × 10 −5 cm/s. The parameters for the iodide—iodine reaction, using 1·0 M KNO 3 as supporting electrolyte, are α c = 0·49, α a = 0·51 and k O a of the order of 5 × 10 −3 cm/s. For the stannous-stannic reaction either of the two steps appears to be rate determining in both directions and the values of the parameters obtained are α c = 0·48, α a = 0·52 and k 0 a = 2·1 × 10 −3 cm/s.