Interfacial OH − Dynamic Modulation by Alternating Current Enables Precipitation‐Suppressed Direct Seawater Electrolysis for Hydrogen Production

ABSTRACT Direct seawater electrolysis (DSE) for H 2 production suffers from severe performance degradation caused by the precipitation of Mg/Ca hydroxides, where OH − generated from the hydrogen evolution reaction (HER) reacts with Mg 2+ /Ca 2+ in seawater. To address this issue, we propose an innovative alternating current‐driven DSE (AC‐DSE) instead of conventional direct current‐driven DSE (DC‐DSE). Periodic polarity reversal under AC enables the same electrode to alternately function as cathode and anode, ensuring OH − from HER is promptly consumed by subsequent anodic OH − ‐consuming reaction. This dynamic interfacial OH − modulation prevents local alkalization and precipitation. Proof‐of‐concept experiments using PtRh electrodes validated that AC‐DSE effectively prevents precipitation and maintains a stable current, in contrast to the rapid precipitation and performance decay observed in DC‐DSE. FEM simulations and experimental established the optimal AC waveform and period for effective precipitation‐suppressed and high Faradaic efficiency. Furthermore, by replacing the oxygen evolution reaction with ethylene glycol oxidation (EGOR), a reaction typically requiring strong alkali, the AC‑driven local microenvironment enables efficient HER‑EGOR coupling in neutral seawater. Importantly, this HER‑EGOR coupling system eliminates H 2 /O 2 mixing risks, lowers energy consumption and co‐produces value‑added chemicals. This work establishes AC‐DSE as an effective and promising route for sustainable H 2 production from seawater.