Levich equation channel electrode

Channel techniques employ rectangular ducts through which the electrolyte flows. The electrode is embedded into the wall [33]. Under suitable geometrical conditions [2] a parabolic velocity profile develops. Potential-controlled steady state (diffusion limiting conditions) and transient experiments are possible [34]. Similar to the Levich equation at the RDE, the diffusion limiting current is... 

We next consider the behaviour for DISP1 reactions at channel electrodes. The normalised steady-state convective-diffusion equations for this case, under the Levich approximation, are... 

The hydrodynamics of flow of solution past the electrode, which is essential to the cell design, was rigorously investigated. In the range of flow rates used (10 4to 10-1cm3s-1), the flow was laminar (Reynolds Number, Re < 10) and hence, beyond a lead-in section of length 0.1 Re b, a parabolic velocity profile developed across the narrow channel. Thus, the hydrodynamics of the coaxial cell were equivalent to those of the conventional channel electrode [59]. It was predicted that the diffusion-limited current would obey the Levich equation... 

The diffusion layer thickness also varies with, which from Eq. (9) means that the mass transport-limited flux across the CE varies with, so that the electrode is nonuniformly accessible. An analogous Levich equation to the TE has been derived analytically for the CE. This gives the mass transport-limited current for fast flow (where as with the TE, diffusion in the direction of convective flow can be considered to be negligible and where convection is so efficient that the concentration gradient of reactive species near the electrode can be linearized [53]) and for short electrodes (in which the diffusion layer can be considered to be thin compared to the height of the channel) as... 

Application Laminar flow was established using flow rates such that the Reynolds Number, Re < 10. Thus, after sufficient lead-in (specifically 0.1 x Re x h), which in this case is negligible, a parabolic velocity profile develops across the flow-path. In this manner, the hydrodynamics of this electrochemical setup are equivalent to that of the channel electrode flow system the mass transport-limiting current is therefore given by the Levich equation [86],... 

The Levich equation for the transport-limited current at a channel electrode predicts... 

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