Diagnostics of Anodic Stripping Mechanisms under Square-Wave Voltammetry Conditions Using Bismuth Film Substrates

Abstract

A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface.

Measuring the Electrode Kinetics of Surface Confined Electrode Reactions at a Constant Scan Rate

“…The application of square-wave voltammetry (SWV) [1] for mechanistic and kinetic studies [2][3][4][5][6][7][8] of electrode processes increases permanently in the last decade, due to the intensive development of the theory of the technique for a variety of electrode mechanisms and electrode geometries [9][10][11][12][13][14][15][16][17]. A plethora of intriguing studies has been conducted in relation to the kinetics of charge transfer processes at liquid/liquid interfaces [18][19][20][21][22][23], electrochemistry of immobilized proteins [24,25], and catalytic mechanisms [26][27][28], revealing that SWV is highly suited for both mechanistic and kinetic characterization of electrode reactions, besides its excellent analytical performances [29][30][31][32][33][34] and its appropriateness for bioanalytical applications [35][36][37][38][39][40][41].…”

Mechanisms and kinetics of electrode processes at bismuth and antimony film and bare glassy carbon surfaces under square-wave anodic stripping voltammetry conditions

“…At BiFEs the accumulation potential of −1.4 V was applied without stirring, in order to obtain the metal deposit morphology as uniform as possible, being in accordance with the theoretical assumptions upon which the theoretical model is based [23]. The anodic stripping voltammogram was recorded by applying a positive-going square-wave potential scan with a potential step of usually 2 mV and with a frequency and an amplitude as denoted in each experiment.…”

“…The recent theoretical treatment of anodic stripping voltammetric processes at BiFEs [23] under conditions of SWV encompassed three different mechanisms: (i) simple anodic stripping mechanism in which the metal analyte ions are the subject of diffusion mass transport following the stripping step, (ii) adsorption mechanism, in which the diffusion mass transport is coupled with a partial adsorption of the analyte ions on the Bi-film surface, and (iii) adsorption-interaction mechanism in which, besides adsorption and diffusion, the role of interactions (attractive or repulsive) between accumulated metal particles have been taken into account. The latter mechanism is the most general one, providing a basis for detail qualitative description of the majority of the experimental data.…”

“…The −10 mol/cm 2 , step potential E = 5 mV, and SW amplitude Esw = 25 mV (A) and 50 mV (B). The ordinate displays the dimensionless net SW peak current « p [23].…”

“…Recently, an attempt was made to develop a phenomenological theoretical background to rationalize some of possible electrode mechanisms [23] under conditions of square-wave voltammetry (SWV) [24,25]. In the present communication we apply the recent theory [23] to characterize the anodic stripping electrode mechanisms of Pb(II), Cd(II) and Zn(II) from mechanistic and kinetic point at both BiFEs and SbFEs, while the mechanism of Pb(II) was studied at bare GCE as well.…”