Au Single-Atom Interlayer Bridge Promotes Cross-Layer Charge Transport and Intrinsic Catalytic Dual-Sites Activation for Efficient CO2 Photoreduction.

Layered photocatalysts are attractive for artificial photosynthesis, but their performance is often limited by inefficient charge transport across interlayer gaps and sluggish surface reaction kinetics. Herein, we propose a single-atom interlayer bridge strategy by introducing Au single atoms into layered Bi4O5Br2 (AuIB-BOB) to address the above limitations. The incorporated Au atoms substitute Bi sites and are stabilized by a mixed O/Br coordination environment with an average local structure of Au1O3Br2, forming a covalent bridge between the Br- and [Bi4O5]2+ layers to provide an excellent pathway for cross-layer charge transport. Thus, holes that would otherwise remain confined in the Br- layer are extracted and delivered to the surface O-oxidation sites, while photogenerated electrons are retained and utilized at the surface Bi-reduction sites. This directional charge redistribution considerably suppresses charge recombination, prolonging the average carrier lifetime from 19.5 to 109.7 ps. Meanwhile, the bridge-mediated charge transport activates the intrinsic Bi reduction sites and O oxidation sites synchronously, promoting CO2 adsorption/activation and H2O oxidation-related processes. Without sacrificial agents or photosensitizers, AuIB-BOB achieves a CO2-to-CO evolution rate of 58.21 µmol g-1 h-1 in pure water. This work provides an atomic-level paradigm for regulating cross-layer charge transfer and unlocking intrinsic redox sites in layered photocatalysts.