Achieving Long-Lived Charge Separated State through Ultrafast Interfacial Hole Transfer in Redox Sites-Isolated CdS Nanorods for Enhanced Photocatalysis.

As opposed to natural photosynthesis, a significant challenge in a semiconductor-based photocatalyst is the limited hole extraction efficiency, which adversely affects solar-to-fuel efficiency. Recent studies have demonstrated that photocatalysts featuring spatially isolated dual catalytic oxidation/reduction sites can yield enhanced hole extraction efficiencies. However, the decay dynamics of excited states in such photocatalysts have not been explored. Here a ternary barbell-shaped CdS/MoS 2 /Cu 2 S heterostructure is prepared, comprising CdS nanorods (NRs) interfaced with MoS 2 nanosheets at both ends and Cu 2 S nanoparticles on the sidewall. By using transient absorption (TA) spectra, highly efficient charge separation within the CdS/MoS 2 /Cu 2 S heterostructure are identified. This is achieved through directed electron transfer to the MoS 2 tips at a rate constant of >8.3 × 10 9 s -1 and rapid hole transfer to the Cu 2 S nanoparticles on the sidewall at a rate of >6.1 × 10 10 s -1 , leading to an exceptional overall charge transfer constant of 2.3 × 10 11 s -1 in CdS/MoS 2 /Cu 2 S. The enhanced hole transfer efficiency results in a remarkably prolonged charge-separated state, facilitating efficient electron accumulation within the MoS 2 tips. Consequently, the ternary CdS/MoS 2 /Cu 2 S heterostructure demonstrates a 22-fold enhancement in visible-light-driven H 2 generation compare to pure CdS nanorods. This work highlights the significance of efficient hole extraction in enhancing the solar-to-H 2 performance of semiconductor-based heterostructure.