Aspect Ratio-Dependent Charge Carrier Dynamics in Matchstick-like Ag₂S-ZnS Nanorods for Solar Hydrogen Generation

Matchstick-like Ag₂S-ZnS nanorods (NRs) with a tunable aspect ratio (AR) were synthesized using one-pot thermal decomposition. The ultraviolet photoelectron spectra and time-resolved photoluminescence spectra of the Ag₂S-ZnS NRs were collected to study their electronic band structures and charge carrier dynamics. The energy difference (ΔE) at the interface between the ZnS stem and Ag₂S tip was altered as the AR of Ag₂S-ZnS NRs increased from 11.9 to 18.4, resulting in an enlarged driving force for the delocalized electrons along the conduction band of ZnS being injected into that of Ag₂S. The interfacial electron transfer rate constant (k_et) from ZnS to Ag₂S could be enhanced by ∼2 orders of magnitude from 5.27 × 10⁶ to 3.24 × 10⁸ s^-1, leading to a significant improvement in the efficiency of solar hydrogen generation. This investigation provides new physical insights into the manipulation of charge carrier dynamics by means of AR adjustment in semiconductor nanoheterostructures for photoelectric conversions.