Unlocking the Scalability of Overlapping Electric Double Layers for Water Splitting

Membrane-less pure water electrolysis with earth-abundant catalysts promises minimum-cost green hydrogen (H 2 ) production, yet it faces kinetic and scalability barriers. Here, we present a scalable architecture that exploits overlapping electrical double layers (EDLs) within nanospaced electrodes. This nanoconfinement generates intense electric fields that facilitate in situ water ionization and create a bipolar acid–base reaction environment, bypassing the kinetic barriers of pure water splitting. We identify structural trade-offs that govern efficiency and scalability of the overlapping EDLs and develop an interdigitated reactor that balances voltage efficiency, mass transport, and current purity. This design suppresses pseudo-current and preserves overlapping EDL effects during geometric scaling. When integrated into a modular multi-chip system, this design yields a projected power density of 11.42 kW·kg –1, exceeding that of conventional electrolyzers by three orders of magnitude. This work bridges nanoconfinement physics and macroscopic engineering, enabling scalable green H 2 production without membranes, supporting electrolytes, or precious metal catalysts.