Hydrogen bubble growth on platinum microelectrode: Effects of electrode diameter, electrolyte concentration, and surface texturing

Hydrogen bubble dynamics on microelectrodes strongly influence the performance and durability of electrochemical devices, yet the combined effects of electrode diameter, electrolyte concentration, and surface texturing remain insufficiently understood. In this study, we systematically investigate the growth, detachment, and regime transitions of electrolytically generated hydrogen bubbles on untextured (polished) and laser-textured platinum microelectrodes with diameters of 50, 100, and 200 μm in sulfuric acid solutions with concentrations between 0.05 and 1.00 mol L −1 . Synchronized high-speed imaging and potentiostatic measurements are used to identify four reproducible regimes: (I) isolated bubble growth without coalescence, (II) limited lateral coalescence, (III) a single coalesced bubble, and (IV) a pinned single coalesced bubble. A regime map constructed in the parameter space of applied potential, electrolyte concentration, and electrode diameter reveals that increasing H 2 SO 4 concentration and decreasing electrode diameter promote earlier onset of coalescence and pinning. The detachment diameter increases with applied potential under most conditions, while the current–density response reflects a balance between increasing driving force and bubble-induced surface shielding. For the 200 μm electrode, an optimal operating window is identified at intermediate electrolyte concentration (∼0.5 mol L −1 ), where high current density can be sustained to higher potentials before the onset of persistent pinning. In addition, an empirical, diffusion-inspired correlation is proposed for the detachment diameter on the untextured 200 μm electrode, providing a compact description of its dependence on potential and electrolyte concentration within the monotonic regime. Surface texturing significantly modifies bubble dynamics by reducing nucleation overpotential and delaying the onset of persistent pinning by ∼ 2.3 V, resulting in higher current densities at high applied potentials. Overall, the results establish a unified framework linking bubble dynamics, operating conditions, and electrochemical performance, and provide practical guidance for the design of efficient microstructured electrochemical systems.