In-situ MRI velocimetry of the magnetohydrodynamic effect in electrochemical cells.

Electrochemical reactions have become increasingly important in a large number of processes and applications. The use of NMR (Nuclear Magnetic Resonance) techniques to follow in situ electrochemistry processes has been gaining increasing attention from the scientific community because they allow the identification and quantification of the products and reagents, whereas electrochemistry measurements alone are not able to do so. However, when an electrochemical reaction is performed in situ the reaction rate can be increased by action of the Lorentz force, which is equal to the cross product between the current density and the magnetic field applied. This phenomenon is called the magnetohydrodynamic (MHD) effect. Although this process is beneficial because it accelerates the reaction, it needs to be well understood and taken into account during the in situ electrochemical measurements. The MHD effect is based on increased mass transfer, which is shown by in situ MRI velocimetry here. Images had to be acquired in a rapid manner since current was not pulsed. Significant velocities in a plane parallel to the electrodes alongside with complex flow patterns were detected.