Multi-interfacial plasmon coupling in multigap (Au/AgAu)@CdS core–shell hybrids for efficient photocatalytic hydrogen generation

Abstract

Plasmon coupling induced intense light absorption and near-field enhancement have vast potential for high-efficiency photocatalytic applications. Herein, (Au/AgAu)@CdS core–shell hybrids with strong multi-interfacial plasmon coupling were prepared through a convenient strategy for efficient photocatalytic hydrogen generation. Bimetallic Au/AgAu cores with an adjustable number of nanogaps (from one to four) were primarily synthesized by well-controlled multi-cycle galvanic replacement and overgrowth processes. Extinction tests and numerical simulations synergistically revealed that the multigap Au/AgAu hybrids possess a gap-dependent light absorption region and a local electric field owing to the multigap-induced multi-interfacial plasmon coupling. With these characteristics, hetero-photocatalysts prepared by further coating of CdS shells on multigap Au/AgAu cores exhibited a prominent gap-dependent photocatalytic hydrogen production activity from water splitting under light irradiation (λ > 420 nm). It is found that the hydrogen generation rates of multigap (Au/AgAu)@CdS have an exponential improvement compared with that of pure CdS as the number of nanogaps increases. In particular, four-gap (Au/AgAu)@CdS core–shell catalysts displayed the highest hydrogen generation rate, that is 96.1 and 47.2 times those of pure CdS and gapless Au@CdS core–shell hybrids. These improvements can be ascribed to the strong plasmon absorption and near-field enhancement induced by the multi-interfacial plasmon coupling, which can greatly improve the light-harvesting efficiency, offer more plasmonic energy, and boost the generation and separation of electron–hole pairs in the multigap catalysts.