Understanding the effect of electrode thicknesses on bubble detachment and Hydrogen Evolution Reaction (HER) in water electrolysis using bare nickel foam

Nickel foam (NF) is extensively used as a supporting material for electrodes in alkaline water electrolysis due to its ability to optimize catalyst usage and enhance cell efficiency. In this study, we investigate the influence of bare NF electrode thicknesses on the hydrogen evolution reaction (HER). The behavior of bubbles on the NF during the HER was also observed using high-speed imaging. Results show that the NF thickness significantly affects both the current density and bubble behavior on the gas -evolving electrode, and increasing the NF thickness enhances the electrochemical surface area (ECSA). The current density normalized with ECSA shows that thicker electrodes exhibit higher electrochemical performance. As the thickness of NF increases from 0.3 mm to 2.0 mm, the current density increases by 70.72 %, respectively, at -1.0 V vs the reversible hydrogen electrode (RHE). This suggests that the improvement is not only caused by an increased surface area but also by factors influenced by the electrode thickness. Furthermore, we found that the NF thickness affects the bubble dynamics and is closely correlated to the HER performance. Thicker electrodes increase ECSA and bubble detachment, improving HER performance. With an increase in thickness, the number of bubbles generated from the NF surface increases due to more active sites, and smaller hydrogen (H 2 ) bubbles are produced, resulting in an increased total number of H 2 bubbles. Furthermore, both the critical diameter and residence time of bubbles tend to decrease as the thickness of NF increases. Therefore, it enables rapid detachment of bubbles from the electrode and helps to increase the HER efficiency.