Enhancement of oxygen evolution reaction in alkaline water electrolysis by Lorentz forces generated by an external magnetic field

The effects of vertical Lorentz forces generated by an external magnetic field applied perpendicular to the inherent electric field on the oxygen evolution reaction conducted on a Ni wire are investigated using cyclic voltammetry, impedance measurements, and particle image velocimetry (PIV). Both downward and upward Lorentz forces provide smaller overpotentials than that generated in their absence. Based on a dual-bubble layer model for reactant transfer, we find that the diffusion resistance of the hydroxide ions and increased ohmic resistance (after iR correction) induced by the layer of bubbles attached to the electrode surface are most effectively alleviated by the downward Lorentz force, while the charge-transfer resistance is retained. Furthermore, the generated bubbles have smaller average diameters. By using PIV measurements, we find that stronger shear stresses induced by the faster flow of the electrolyte in the vicinity of the working electrode facilitate the detachment of bubbles from the electrode surface.