Reconstruction of Interfacial Charge Topology in S-Scheme Heterojunction for Enhanced CO₂ Photoreduction

The S-scheme heterojunction enables efficient spatial charge separation while preserving strong redox capabilities in photocatalysis. Yet its interfacial charge dynamics remain inherently constrained by fixed band alignment and a built-in electric field, limiting further performance gains. Here, we demonstrate that plasmonic Au nanoparticles can fundamentally reconstruct, not merely enhance, the interfacial charge topology of an S-scheme system. By integrating Cs₃Bi₂Br₉ quantum dots (CBBQD) with porous BiOCl and decorating with Au, we fabricate a ternary Au/CBBQD/BiOCl heterojunction that achieves a CO evolution rate of 115.4 µmol g^-1 h^-1, 57.7 times higher than pristine BiOCl and 2.3 times beyond the binary CBBQD/BiOCl S-scheme counterpart. Combined experimental and density functional theory studies reveal that Au not only serves as a localized surface plasmon resonance (LSPR) hot-electron injector that redirects photogenerated electrons from CBBQD to the conduction band of BiOCl, thereby shifting the primary CO₂ reduction site and enabling multi-site hole utilization, but also lowers the Gibbs free energy barrier of the rate-limiting ^*CO₂ → ^*COOH step by 0.36 eV. Our work moves beyond conventional S-scheme design by establishing plasmonic metals as active architects of interfacial charge flow, offering a general strategy to unlock high-efficiency CO₂ photoreduction through deliberate manipulation of electron delivery pathways.