Lattice‐Hydrogen Pumping in Ni 2 P@MoO 3 Enables Self‐Buffered and Scaling‐Resistant Hydrogen Evolution in Natural Seawater

ABSTRACT Cathodic hydrogen evolution in natural seawater offers green hydrogen production, but rapid proton consumption and hydroxyl‐ion accumulation cause local alkalinization and metal hydroxide precipitation. This study reports a reversible lattice hydrogen exchange strategy that suppresses Mg/Ca precipitation by regulating the local interfacial pH with a Ni 2 P@MoO 3 /CC heterostructure. During electrocatalysis, MoO 3 dynamically adopts an H x MoO 3 ‐like state, accelerating water dissociation and lattice‐hydrogen transfer to Ni 2 P while buffering OH − ‐ buildup and local pH rise. Electronic modulation at the heterointerface accelerates OH − diffusion and maintains the local pH below the precipitation limit of 9.5. As a result, the catalyst required an overpotential of only 49.3 mV at 10 mA cm −2 in simulated seawater and outperformed commercial Pt/C/CC at current densities above 200 mA cm −2 . Moreover, when used as the cathode in an asymmetric seawater/alkaline electrolyzer, with natural seawater in the cathode chamber and 1.0 M KOH in the anode chamber, the Ni 2 P@MoO 3 /CC cathode enables stable operation for over 1000 h at 100 mA cm −2 . This study demonstrates lattice hydrogen dynamics as a feasible strategy to construct efficient and scaling‐resistant cathodes for the natural seawater hydrogen evolution reaction (HER), which can be coupled with the alkaline oxygen evolution reaction (OER) in an asymmetric seawater/alkaline electrolyzer.