Insights into hydrogen bubble dynamics and electrochemical performance on flat and electrochemically etched stainless steel electrodes using high-speed imaging

Gas bubbles formed on electrodes during electrochemical processes increase overpotential and ohmic voltage drop, leading to higher energy consumption in water electrolysis. This study investigates the effect of surface roughness on hydrogen bubble dynamics and hydrogen evolution reaction (HER) performance using flat and electrochemically etched SS-316L working electrodes. Electrochemical experiments were conducted at room temperature in a three-compartment acrylic cell using a potentiostat. The SS-316L electrodes served as the working electrode (WE), with platinum and Ag/AgCl wires functioning as the counter and reference electrodes in 0.5 M KOH electrolyte. The etched electrode was prepared through electrochemical etching in a freshly prepared dilute Aqua Regia solution, followed by ultrasonic cleaning and drying. Bubble evolution was recorded using a high-speed visualization system. Results reveal that the etched electrode exhibits smaller bubble detachment radii (average 162 μm vs. 248 μm), shorter growth time (5.8 s vs. 9.2 s), and lower voltage fluctuations than the flat electrode, indicating improved bubble release dynamics. Enhanced surface roughness promotes higher HER activity, with the etched electrode showing a reduced onset potential of 0.43 V (0.11 V lower than flat WE), decreased overpotential from 331.4 to 247.8 mV at 10 mA cm-2, and a lower charge transfer resistance (67.2 Ω vs. 234.3 Ω). The double-layer capacitance increases from 0.38 to 0.91 mF cm-2, confirming a larger electrochemically active surface area. The etched electrode also demonstrates superior stability, maintaining consistent polarization behaviour after 500 CV cycles at 100 mV s-1.