Direct Seawater Hydrogen Evolution via Atomically Precise Regulation of Interfacial pH and Ion‐Water Interactions

Direct seawater electrolysis offers a sustainable route to green hydrogen production from abundant saline water resources, yet industrial applications are limited by sluggish kinetics and catalyst deactivation caused by Mg(OH) 2 /Ca(OH) 2 precipitation or Cl − corrosion. Here, we report a pH‐gradient‐mediated interfacial engineering strategy that simultaneously enhances activity and stability of metal nanocatalysts for the hydrogen evolution reaction (HER) in natural seawater. By using atomically precise Pt 6 (TPP) 4 Cl 5 nanoclusters (NCs) (Pt 6 ‐TPP, TPP = triphenylphosphine) as paradigm catalysts, we demonstrate self‐organized TPP ligands on cluster surface tether Na + /K + via cation–π interactions. The locally concentrated Na + /K + cations disrupt the hydrogen‐bond network of water molecules for accelerating HER kinetics, and electrostatically attract OH − to establish an alkaline interfacial pH, which can propagate into a diffuse pH gradient toward the bulk of the solution. This pH gradient drives Mg 2+ /Ca 2+ precipitation away from the catalytic surface, preventing site blockage. The enriched OH − can also resist Cl − corrosion of Pt 6 ‐TPP NCs. Consequently, Pt 6 ‐TPP achieves 10 mA cm −2 at an overpotential of 292 mV and retains exceptional stability (> 500 h) under intermittent renewable‐energy operation, with one‐tenth the Pt loading of commercial Pt/C. This work establishes a pH gradient‐mediated interfacial chemistry framework enabled by atomically precise engineering, providing guidance for sustainable and efficient direct seawater hydrogen evolution.