Collection Efficiency of a Rotating Ring-Disk Electrode

This Demonstration shows how the geometry of a ring disk electrode determines the maximum theoretical collection number (left figure). It also shows that the collection factor can be measured on voltammetric curves, using the ratio between the mass transport–limited current of the ring and that of the disk. The collection factor is equal to the absolute value of the mass transport–limited ring dimensionless current (right figure).

SNAPSHOTS

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DETAILS

The rotating ring-disk electrode (RRDE) was first developed by Frumkin et al. in 1958 [1], following the work by Levich on the rotating disk electrode (RDE) [2, 3]. Performing voltammetry experiments on an RDE with controlled hydrodynamics and using the results of the work by Levich and Koutecký–Levich [4] allowed the researchers to determine important mass-transport and kinetic parameters such as the diffusion coefficient, the kinetic standard constant and the symmetry factor. Adding a concentric ring allows the user to collect species that are produced on the disk in steady-state mass transport–limited conditions. The maximum collection efficiency factor only depends on the geometry of the electrode. Albery and Bruckenstein [5] were the first to propose a theoretical expression to calculate . can be written
,
with
.
Studying the experimental deviations from the theoretical relationships at various rotation rates provides a way to measure homogeneous bulk reactions of intermediate species produced at the disk [6–8]. The range of applications is very broad. It was, for example, used to study corrosion in selective dissolution of intermetallic particles in Al alloys [9]. This Demonstration shows the dependence of with the geometry of the ring disk electrode, following the expressions first derived by Albery and Bruckenstein [5]. On the right side, the corresponding dimensionless steady-state mass transport–limited voltammetric curves are shown as well as the graphical definition: , where and are the mass transport–limited current on the ring and the disk, respectively. The disk is held at a potential , such that the reaction produces an anodic current while the ring is maintained at a sufficiently negative constant potential . The reaction produces a cathodic current . The currents and are plotted as functions of [10]. The left side shows the geometry of the ring disk electrode corresponding to the curves on the right side. You can see the effect of changing the diameters of the ring and the disk or the space between the two electrodes. The maximum theoretical collection coefficient is calculated.
References
[1] A. Frumkin, L. Nekrasov, B. Levich and JU. Ivanov, "Die anwendung der rotierenden scheibenelektrode mit einem ringe zur untersuchung von zwischenprodukten elektrochemischer reaktionen," Journal of Electroanalytical Chemistry, 1(1), 1959 pp. 84–90. doi:10.1016/0022-0728(59)80012-7.
[2] В. Г. Левич, Физико-химическая гидродинамика, Издательство АН СССР, Москва, 1952.
[3] V. G. Levich, Physicochemical Hydrodynamics (Scripta Technica, Inc., trans.), Englewood Cliffs, NJ: Prentice-Hall, 1962.
[4] Й. Кутецкий, В. Г. Левич, ЖУРНАЛ ФИЗИЧЕСКОЙ ХИМИИ, 32, 1958 p. 1565.
[5] W. J. Albery and S. Bruckenstein, Transactions of the Faraday Society, 62, 1966 pp. 1920–1931. doi:10.1039/TF9666201920.
[6] W. J. Albery and S. Bruckenstein, Transactions of the Faraday Society, 62, 1966 pp. 1946–1954. doi:10.1039/TF9666201946.
[7] W. J. Albery and S. Bruckenstein, "Ring-Disc Electrodes. Part 6.—Second-Order Reactions," Transactions of the Faraday Society, 62, 1966 pp. 2584–2595. doi:10.1039/TF9666202584.
[8] W. J. Albery and S. Bruckenstein, "Ring-Disc Electrodes. Part 7.—Homogeneous and Heterogeneous Kinetics," Transactions of the Faraday Society, 62, 1966 pp. 2596–2606. doi:10.1039/TF9666202596.
[9] R. G. Buchheit, M. A. Martinez and L. P. Montes, "Evidence for Cu Ion Formation by Dissolution and Dealloying the Intermetallic Compound in Rotating Ring-Disk Collection Experiments," Journal of the Electrochemical Society, 147(1), 2000 p. 119. doi:10.1149%2F1.1393164.
[10] A. J. Bard and L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd ed., New York: Wiley, 2001.
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