Design of Speed Bump Flow Field for Reducing Bubble Overpotential in Proton Exchange Membrane Water Electrolysis

The design of the bipolar plates is essential to ensure a uniform distribution of reactants in the active area. This study designed a flow field that can quickly discharge oxygen. The designed improved performance by up to 12.13% at over 0.15 A cm⁻². With increasing voltage, the reactants supplied to the catalyst-coated membrane (CCM) increased in both flow fields. There was no significant difference in performance between the two flow fields at 2.25 V. This is because the oxygen residence time is long when the current density is low, blocking the water supply. As current density increased, oxygen residence time decreased. The performance of the designed flow field, where many reactants are supplied, was improved. This is because bubble overpotential decreased as more water was supplied to the CCM. However, a continuous increase in current density did not result in a further increase in performance. This is because oxygen coalescence occurs more frequently. Furthermore, it was observed that when the radius of the speed bumps is increased to 0.5 mm, water becomes trapped between them at 3.15 V, where the oxygen generation rate is high. This is because oxygen pushes water between the speed bumps.