<p>Hydrogen bubble behavior strongly affects the performance of alkaline water electrolysis, particularly at high current densities. This study experimentally investigates the influence of electrode surface modification on hydrogen bubble dynamics using nickel wire cathodes. The electrode surfaces were modified via electrodeposition at different deposition current densities, resulting in distinct surface morphologies. The non-coated electrode exhibited bubble behavior that varied with electrolysis current density, whereas the surface-modified electrodes predominantly showed dispersed bubble generation over a wide operating range, indicating an increased density of active nucleation sites. The hydrogen bubble generation volume rate increased monotonically with current density for all electrodes, while bubble size and residence time were strongly dependent on the surface condition. Cell voltage and energy conversion efficiency were governed by bubble surface coverage and detachment characteristics. Moderate surface modification reduced voltage losses and mitigated efficiency degradation, whereas excessive modification led to increased electrical losses. These results demonstrate that optimizing electrode surface morphology is essential for enhancing the performance of alkaline water electrolysis systems.</p>