Hydrodynamically modulated rotating disc electrode

HMRDE hydrodynamically modulated rotating disc electrode... 

Miller and Bruckenstein [27,28] introduced the hydrodynamically modulated rotating disc electrode (HMRDE) in 1974. The steady-state current density at a rotating disc electrode is well-defined, given by the Levich equation (equation (10.15)) ... 

The hydrodynamically modulated rotating disc electrode The idea of this technique [15-17] is to allow the separation of kinetic and mass transport controlled components of a measured current (either in the region of mixed electron transfer/mass transport control or in situations where there are two competing electrode reactions, one mass transport controlled and the other kinetically controlled, (e.g. solvent decomposition) by using a sinusoidal modulation of the rotation rate and employing a phase sensitive detection method to measure the perturbation of the current. Only the mass transport limited component of the current will respond to the modulation. 

Hydrodynamic modulation has been performed almost exclusively at the rotating disc electrode. It has found use for analytical purposes at rotating and tubular electrodes owing to the fact that non-convectively dependent electrode processes are unaffected by the modulation [236]. 

Hydrodynamic electrodes permit the control of the diffusion layer thickness by imposing convection. This thickess can also be modulated. Implicit functions link the current, potential and convection modulation. For the rotating disc electrode... 

Both qualitative and quantitative insight can be garnered from transient X -i, i-t and r -t measurements in quiescent or stirred solutions, while measurements of steady-state behavior are best performed under well-defined hydrodynamic conditions. Typically, a rotating disc electrode (RDE), or a related method, is used to specify and/or modulate the hydrodynamic boundary layer thickness, 8. With an RDE the boundary layer is specified by... 

Fig. 9. Polarization curve of an Fe-disc Pt-split-ring electrode with hydrodynamic square wave modulation. In 1 M NaOH with anodic and cathodic scan including capacity of the Fe disc (dashed curve), modulation frequency of rotation co = 0.05 Hz (insert), simultaneous detection of Fe(II) and Fe(III) ions at Pt half rings [12].

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