Experimental investigation of hydrogen bubble dynamics and electrochemical performance on flat and surface modified stainless-steel electrodes using shadowgraphy imaging

This study examined the influence of surface roughness on hydrogen bubble dynamics and electrochemical performance utilizing shadowgraphy imaging to analyze a flat surface and various sandblasted SS-316L working electrodes (WEs). This study investigates the effect of surface roughness on hydrogen bubble dynamics and hydrogen evolution reaction (HER) performance using shadowgraphy imaging and electrochemical analysis on flat and sandblasted SS-316L working electrodes (WEs). Results show that increasing surface roughness markedly improves bubble detachment and HER activity. Compared with the flat WE, sandblasted electrodes exhibit smaller bubble detachment radii, shorter growth times, and reduced voltage fluctuations, indicating enhanced bubble release. The SB6 WE demonstrates the best performance, producing smaller and more numerous bubbles due to increased active sites and micro-cavities. Electrochemically, SB6 shows a reduced onset potential (0.43 V) compared with the flat WE (0.58 V). The overpotential decreases from 340.7 to 201.5 mV at 10 mA cm−2, and reaches 301.3 mV at 50 mA cm−2, lower than all other electrodes. Electrochemical impedance spectroscopy reveals a significantly lower charge-transfer resistance for SB6 (32.4 Ω) compared with the flat WE (248.3 Ω), while its higher double-layer capacitance (1.53 mF cm−2) indicates a larger electrochemically active surface area. Current–voltage measurements show enhanced performance, with current density increasing from 135 to 330 mA cm−2 at 2.5 V SB6 also exhibits excellent durability, maintaining stable polarization behavior after 1000 CV cycles. However, immersion corrosion tests reveal increased corrosion rates with higher roughness, rising from 0.00217 mm yr−1 (flat) to 0.02464 mm yr−1 (SB6). Overall, controlled sandblasting significantly enhances HER performance by improving bubble dynamics, though long-term corrosion resistance must be carefully balanced for practical applications.