화학공학소재연구정보센터
Energy Conversion and Management, Vol.43, No.3, 365-371, 2002
MHD-control on limiting Faradaic currents
Magnetically induced phenomena in electrochemistry are illustrated by the well-known convective effect that can be readily observed on diffusion limiting currents due to a magnetohydrodynamic control. Yet, a point still needs to be analysed to shed light on that controversial problem: the magnitude of the forces then involved cannot account for the measured increase of the current when the superimposed homogeneous magnetic field B is parallel to the plane surface of the working electrode. If the natural convection is also taken into account, a classical hydrodynamic treatment allows us to obtain laws that can be perfectly demonstrated and are in good agreement with every experimental result. Moreover, the supporting electrolyte exerts an effect on the current-B relationship that can be explained neither by classical migration phenomena nor classical hydrodynamic equations. We must then assume that a transverse electric field component in the close vicinity of the electrode/electrolyte interface generates the fluid motion and therefrom the convective MHD effect, hence an increase of diffusion limiting currents. Such a hypothesis has been confirmed by a new experimental device in which the same effects could be detected, although with no magnetic field, by simply creating an electric field component along the surface of the electrode.