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

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 H₂ flux of 331.34 mmol m^-2 h^-1. More broadly, we show that the same defect-guided Pt-anchoring rule operates across multiple ZnIn₂S₄-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.