Hydrodynamic Voltammetry at a Rocking Disc Electrode: Theory versus Experiment

Abstract

Rocking disc electrode voltammetry (RoDE) is introduced as an experimentally convenient and versatile alternative to rotating disc voltammetry. A 1.6 mm diameter disc electrode is employed with an overall rocking angle of Θ = 90 degree applied over a frequency range of 0.83 Hz to 25 Hz. For a set of known aqueous redox systems (the oxidation of Fe(CN)6 4in 1 M KCl, the reduction of Ru(NH3)6 3+ in 0.1 M KCl, the oxidation of hydroquinone in 0.1 M pH 7 phosphate buffer, the oxidation of Iin 0.125 M H2SO4, and the reduction of H + in 1 M KCl)

Control of stationary convective instabilities in the rotating disk boundary layer via time-periodic modulation

“…In electrochemistry, the rotating disk electrode is utilised to perform hydrodynamic voltammetry (Ahn et al. 2014, 2016). In part, it is the simplicity of the model that has made the von Kármán flow an attractive candidate for studies of some of these more general three-dimensional boundary layers.…”

Hydrodynamic Rocking Disc Electrode Study of the TEMPO‐mediated Catalytic Oxidation of Primary Alcohols

“…With increasing rocking rate, the shape changes and the mass transport limited current increases. A quantitative "Levich-type" expression for this type of process has been reported recently [12] (see equation 1) to link l lim the hydrodynamic mass transport limited current to experimental parameters. As shown in the plot in Figure 4B, the limiting current is indeed linearly dependent upon the square root of rocking frequency and in excellent agreement with the theory.…”

“…The non-uniform nature of diffusion at the leading edge and at the trailing edge of electrodes in these flow cells requires multi-dimensional computational algorithms to link the experimentally measured steady state limiting currents [9,10] (or transients [11]) with the microscopic details of the electrode process. For uniformly accessible hydrodynamic electrodes (such as those used in rotating disc or rocking disc voltammetry [12,13,14]) a one-dimensional simulation model based on the knowledge of the average diffusion layer thickness can be sufficient [15]. Even cases of turbulent mass transport with an in average uniformly accessible electrode (e.g.…”

“…The experimental conditions during "rocking" are very similar to those during "rotating" apart from the fact that the electrode is not completing a full 3608 rotation. Instead a "four-bar mechanism" [12] is employed to only rock 458 forward and 458 backward (to result in an overall rocking angle of V = 908; see Figure 2). Although the flow conditions at the electrode surface are more complex compared to those at the rotating disc electrode, an approximate quantitative expression for the resulting limiting currents and for the diffusion layer thickness (assuming laminar flow conditions) has recently been developed (equations 1 and 2, respectively [12]).…”

Modular Flow-Through Platform for Spectroelectrochemical Analysis

“…Automating the stages of liquid replacement and mixing increases the precision and accuracy of measurements. ,− Flow systems also provide much needed design flexibility. Choosing the right flow pattern (laminar ,, or turbulent, − ) and format (continuous, stop-flow, quench-flow, and bypass flow) is as critical as choosing the right electrochemical method to increase the collection efficiency and sensitivity. Overall, the majority of electrochemical flow systems rely on laminar flow patterns because they are stable, well characterized, and relatively easy to model. − …”