Gas bubble evolution on transparent electrode during water electrolysis in a magnetic field

Abstract Alkaline water electrolysis was operated in a magnetic field and oxygen gas evolution was observed form the back side of a transparent glass electrode. The projection images clearly demonstrated the nucleation sites, bubble growth and motion on the electrode. Gas bubbles evolved in no magnetic field could stay at the nucleation site without any detachments until natural convection (pumping effect) was developed. On the other hand in a magnetic field, they were flushed away by the magnetohydrodynamics (MHD) convection as soon as they were nucleated at more than 1 T and their nucleation number decreased with increasing in the magnetic field intensity. The bubble motion in a magnetic field reflected the rising velocity accelerated by MHD convection. These results suggested that a magnetic field caused remarkable improvement of the surface coverage of the electrode.