Method of Separation and Determination of the Characteristics of the Adsorbed and Nonadsorbed States of Electroactive Substances on Electrodes

• Published in: Langmuir Vol. 18; no. 7; pp. 2765 - 2770
• Main Authors: Łobacz, M, Orlik, M, Stroka, J, Galus, Z
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02-04-2002
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la011046o

The electrochemical analysis of the properties of the adsorbed reactant state for the case when it is energetically close to the nonadsorbed state of the electroactive species is presented. The method of separation of the corresponding adsorption and adsorption-free contributions to the overall faradaic response, which may also supply the voltammetric properties of adsorbed state, is given. It is based on recording, for a given solution, two normal pulse, charge−potential (voltocoulometric) curves. The first curve is obtained by integration of the faradaic current over the entire duration of the potential pulse t (Q t − E curve). For the second curve the charge is measured with the exclusion of the first millisecond after the application of the potential pulse (Q t -1 vs E curve). The numerical model of such dependencies proves that the shape of their difference ΔQ = Q t − Q t - 1 as a function of the electrode potential satisfactorily approximates the electrochemical properties of the adsorption state. Such an approach is recommended as a simple way of analysis of the properties of the adsorption state of electroactive substances which do not yield a distinct separate faradaic response from the adsorption state.