Selective Pt–S Anchoring at Interfacial Defects for Atom‐Economical Solar Hydrogen Production

ABSTRACT Defects in photocatalysts strongly influence charge transfer behavior, and selectively exploiting defect‐rich interfacial sites as chemically addressable anchors provides a new pathway for atom‐economical hydrogen production. Here, we report a defect anchoring strategy that selectively exploits sulfur‐defect‐rich interfacial sites as chemically specific docking sites for Pt–S coordination, enabling stable Pt deployment at an ultralow loading of only 0.084 wt%. In situ spectroscopy and first‐principles calculations reveal that these defect‐anchored Pt–S motifs efficiently extract electrons from interfacial sulfur sites and optimize hydrogen adsorption thermodynamics for accelerated HER kinetics. The optimized photocatalyst delivers hydrogen evolution rates of 22.43 mmol g −1 h −1 under visible light and 91.35 mmol g −1 h −1 under full‐spectrum irradiation, exhibiting excellent long‐term stability. When immobilized as a scalable catalyst film via an immersion process, it achieves an areal H 2 flux of 331.34 mmol m −2 h −1 . More broadly, we show that the same defect‐guided Pt‐anchoring rule operates across multiple ZnIn 2 S 4 ‐based heterojunctions, highlighting a transferable site‐definition strategy for atom‐economical noble‐metal deployment. Ultimately, this approach redefines interfacial defects in heterojunction photocatalysts as programmable chemical sockets for noble‐metal placement, establishing a general blueprint for atom‐economical and scalable solar hydrogen generation.