Modeling and experimental approach of membrane and diaphragm sono-electrolytic production of hydrogen

This study evaluates the performance of three anion-exchange membranes (FAS-50, AMX, Fujifilm-AEM) and a diaphragm separator (Zirfon® UTP 500) in alkaline water sono-electrolysis using a 25 % KOH electrolyte at ambient temperature. Energy efficiency, hydrogen production kinetics, and membrane stability were assessed experimentally and through modeling. Among the tested separators, Zirfon achieved the highest energy efficiency, outperforming AEM, AMX, and FAS-50. Hydrogen production rates under silent conditions ranged from 2.55 µg/s (AEM) to 2.92 µg/s (FAS-50), while sonication (40 kHz, 60 W) increased rates by 0.03-0.12 µg/s, with the strongest relative effect observed for FAS-50 (≈4.0 % increase). By contrast, Zirfon and AEM showed slight efficiency reductions (0.5-2 %) under ultrasound due to their higher structural resistance. Ion-exchange capacity tests confirmed significant degradation of polymeric membranes (IEC losses of 60-90 %), while Zirfon maintained stability in 25 % KOH. Modeling results showed that the diaphragm resistance was dominated by the ohmic losses (55-86 %), with ultrasound reducing bubble coverage and associated resistance only marginally (<0.02 V). Overall, Zirfon demonstrated superior stability and efficiency for long-term operation, while ultrasound primarily enhanced hydrogen evolution kinetics in mechanically weaker polymeric membranes.