Removal of bubbles from eletrodes in a planar cyclonic electrolyzer

Abstract

Alkaline water electrolysis is the most mature and most extensive in-scale hydrogen production technology. For scaled-up electrolyzers, the negative effect of the bubbles formed on the electrodes contributes to high energy consumption and hinders the further expansion of this technology. This study developed a planar cyclonic electrolyzer to improve bubble detachment. The effects of the hydrodynamics on the bubble detachment diameter and current density were studied. According to a proof-of-concept experiment, an increase in the electrolyte velocity led to a gradual decrease in the bubble detachment diameter and a significant increase in the current density. At an applied voltage of 5 V, the detached bubble size decreased from 160 to 82 microns when the electrolyte velocity increased from 0.33 to 2.33 m/s. Meanwhile, a marked rising in the current density from 0.43 to 1.71 A/cm2 was observed. The significance of bubble detachment from an electrode on electrolysis efficiency was discussed. Furthermore, the diaphragm-free separation of hydrogen and oxygen bubbles can be possibly achieved with this novel design.