Electrochimica Acta, Vol.56, No.6, 2754-2761, 2011
Investigation of interfacial reaction kinetics of I-(aq) with Ag2O(s) on Ag substrate: Determining mass transport and surface reaction rates
The reaction kinetics of Agl formation by reaction of Ag2O films with aqueous iodide were followed by monitoring the open-circuit potential (E-oc). Previous studies have shown that complete conversion of Ag2O to Agl is indicated by an abrupt transition in the Eoc from a value close to the equilibrium potential for the Ag vertical bar Ag2O vertical bar H2O system to one close to that for Ag vertical bar Agl vertical bar I-, allowing an easy determination of the total reaction time, tau(f). The solid-solution interfacial kinetic parameters can then be determined by measuring tau(f) as a function of the initial amount of Ag2O and the I- concentration. In this study, the application of the technique was extended to examine the effect of I-(aq) transport to an Ag2O surface by measuring tau(f) as a function of electrode rotation rate. By studying the chemical conversion as a function of electrode rotation rate we are able to separate mass transport effects from the reaction kinetics. The interfacial reaction follows kinetics typical of a sequential binary-reaction system consisting of mass transport to, followed by reaction at, the surface. The mass transport rate was proportional to the square root of the electrode rotation rate, consistent with the well-established diffusion-boundary layer model fora rotating disc. Varying the rotation rate allows a quantitative extrapolation of the data to the infinite rotation rate to determine the chemical reaction rate at the surface. (C) 2011 Elsevier Ltd. All rights reserved.
Keywords:Interfacial reaction kinetics;Silver oxide-iodide interaction;Mass-transfer limited;Surface-reaction limited