Ultrafast Microwave Quasi‐Solid‐State Construction of Os‐OsP₂ with Enhanced Interfacial Spillover for Seawater‐Based Anion Exchange Membrane Electrolyzers

Abstract Developing cost‐effective hydrogen evolution reactions (HER) catalysts to replace Pt/C in alkaline seawater media remains a critical challenge. Therefore, the osmium‐osmium phosphide (Os‐OsP2) catalyst is reported with a heterogeneous junction through ultrafast (20 s) microwave quasi‐solid approach for seawater‐splitting under industrial‐grade current density. Experimental and theoretical analysis reveal that the Os‐OsP₂ interface optimizes electronic structure: osmium (Os) sites accelerate water dissociation by lowering the d‐band center, while OsP₂ promotes hydrogen desorption via interfacial spillover, collectively reducing the HER energy barrier. In addition, the catalyst requires only 1.74 V to reach 1 A cm−2 and owns high price activity in the anion exchange membrane water electrolyzer, surpassing commercial Pt/C by 23% in efficiency under identical conditions. Furthermore, it exhibits robust HER activity across a wide pH range and exceptional durability over 100 h in alkaline seawater. Economic evaluation highlights its superior cost activity (85.6 A dollar⁻¹), 90‐fold higher than Pt/C, with hydrogen production costs ($0.86 GGE⁻¹) undercutting the U.S. DOE target. This study provides feasible guidance for the development of high‐performance, cost‐effective catalysts for scalable hydrogen production from seawater.