Mass Transfer Intensification via Intra-Diaphragm Gap Feeding in Alkaline Water Electrolysis

Abstract Alkaline water electrolysis (AWE) coupled with fluctuating photovoltaic power confronts severe operational limitations stemming from intrinsic near-electrode mass transfer barriers. These transport defects exacerbate both ohmic polarization and trans-diaphragm H2/O2 crossover, significantly restricting the flexible operating window of electrolyzer stacks. Targeting these inherent limitations, this work proposes an innovative intradiaphragm gap (IDG) inside-to-out feeding configuration equipped with decoupled gas–liquid efflux channels. The IDG configuration achieves uniform close-range electrolyte supply across the entire electrode surfaces and mitigates two-phase buildup within the cell compartment via separate dual outlets. The hydrogen impurity level in oxygen streams remains below the 2 vol % safety threshold even at an ultralow current density of 10 mA cm–2. The IDG scheme lowers ohmic resistance by 25.3% and hydrogen-specific energy consumption by 1.15 kWh Nm–3 at 1000 mA cm–2. Under dynamic photovoltaic load fluctuations, the IDG electrolyzer maintains stable operation and compliant gas purity, yielding 14.3% higher annual hydrogen yield than conventional bottom-fed setups. Synergistically optimized electrolyte distribution and interfacial gas removal reinforce near-electrode mass transfer, improving overall cell efficiency and dynamic load adaptability. This feeding configuration provides a feasible retrofitting strategy for commercial alkaline electrolysis facilities.