Scalable Magnetohydrodynamic Bubble Removal for Electrolytic Hydrogen Production

Abstract

Water electrolysis is an essential electrochemical process for both oxygen production in space as well as green hydrogen production on Earth. The presence of bubbles on electrodes increases the resistivity of the electrolytic cell and hinders mass-transport of the liquid electrolyte to the electrode surface. On Earth, efficiency losses due to the presence of bubbles can be as high as 30%, and potentiostatic parabolic plane experiments have shown a further decrease by 11% at current densities up to 100 mA/cm 2 . Among a variety of methods for accelerating bubble evacuation from the electrode surface, magnetohydrodynamic (MHD) pumping via a magnetically-induced Lorentz force has shown promise in controlled lab trials. The MHD effect reduced bubble coverage by 50% under a 1 T field and increased hydrogen-evolution current density by 25% at 700 mA/cm 2 under a 5 T field. Experiments employing permanent magnets have shown a 5% decrease in cell overpotential from B-fields of 0.2 T at 150 mA/cm 2 . In this work, we describe the modeling and testing of alkaline water electrolysis conducted in the presence of a magnetic field produced by a scalable Halbach array of permanent magnets. Unlike many prior efforts, the field is produced by off-the-shelf rare-Earth N52 magnets of various sizes. These arrays are located just behind the electrodes in a “Halbach” sinusoidal pattern which serves to amplify the magnetic field strength. Bench-top tests of a pair of 1.6 cm 2 electrodes show an 18.4% efficiency increase at current densities between 25-300 mA/cm 2 . Since the magnets are permanent, there is no additional power required for generating the MHD swirling, aside from a trivial overpotential of ~0.05% of cell power. This architecture presents a promising solution for scalability for industrial electrolyzers. Figure 1

Identifiers

DOI

10.1149/ma2025-02673217mtgabs

Journal

ECS Meeting Abstracts

Year

2025