Modulating Unidirectional Charge Transfer via in Situ Etching-Accompanied Layer-By-Layer Self-Assembly toward Multifarious Photoredox Catalysis

Metal–semiconductor heterostructures have been arousing enduring interest on account of the pivotal roles of metal nanocrystals (NCs) as interfacial Schottky junction-induced charge flow mediators and surface plasmon resonance-triggered photosensitizers. Tungsten oxide (WO 3 ) stands out among fruitful semiconductors by virtue of favorable energy-level alignment and light absorption capability, but slow charge transfer rate, especially the sluggish hole transport kinetics and short life span of charge carriers, retards its widespread photocatalytic applications. In this work, an efficient and unidirectional charge-transfer channel was constructed in the in situ-formed gold nanoparticle (Au NP)-decorated WO 3 [Au/WO 3 nanorods (NRs)] heterostructures which were constructed by a facile, green, easily accessible, and efficacious layer-by-layer (LbL) self-assembly strategy at ambient conditions, wherein the in situ generation of Au NPs and the morphology transformation of WO 3 NRs to a mesoporous ensemble occur simultaneously. Moreover, the deposition amount of Au NCs on the WO 3 matrix can be finely tuned by the assembly cycle. Intriguingly, the unique integration mode of Au NPs with the WO 3 matrix at the nanoscale level endowed by the LbL self-assembly benefits the high-efficiency extraction, separation, and migration of energetic charge carriers photoinduced over WO 3 NRs. It was found that self-assembled Au/WO 3 heterostructures demonstrate highly efficient and versatile photoredox performances toward mineralization of organic pollutants and photoreduction of heavy metal ions under both simulated solar and visible light irradiation, substantially outperforming the single WO 3 counterpart. This is predominantly ascribed to the crucial role of Au NPs as electron traps rather than the plasmonic photosensitizers to accelerate the interfacial electron transfer, thereby considerably enhancing the separation and prolonging the lifetime of photoinduced electron–hole pairs. In addition, predominant active species in the photoredox catalysis were unambiguously determined, and the photocatalytic mechanism was clearly elucidated. Our work would open up new frontiers to rationally design a large variety of metal–semiconductor heterostructures for promising solar energy conversion.