Abstract
Photocatalytic water splitting for hydrogen production represents an ideal pathway for solar energy harvesting and conversion, for which narrow bandgap multinary sulfides play an important role. Here, series of Zn-AgIn5S8/g-C3N4 0D/2D nanocomposites were prepared by in-situ growth of the Zn AgIn5S8 quantum dots (QDs) on g-C3N4 nanosheets for improved charge separation. To our surprise, rather than a photoactive component, here g-C3N4 nanosheets act as a charge transfer mediator, where only a relatively low ratio is required. The as-fabricated Zn-AgIn5S8/g-C3N4 nanocomposites were systematically studied. When the mass ratio of g-C3N4 was 10%, the hydrogen production rate was maximized, which was 1.39 times higher than pure Zn-AgIn5S8 QDs and 138.6 times higher than g-C3N4. The enhanced photocatalytic activity of the Zn-AgIn5S8/g-C3N4 nanocomposites is attributed to the intimate interface contact, which results in the effective separation and transfer of the photogenerated charge carriers as proved by the PL lifetime, transient photocurrent and electrochemical impedance spectra measurements. The Zn-AgIn5S8/g-C3N4 nano-composites also exhibit excellent cycle stability. A plausible mechanism was proposed for the 0D/2D Zn-AgIn5S8/g-C3N4 composite photocatalysts. This work provides a relatively simple method for constructing high-quality 0D/2D heterostructure of QDs/nanosheets, as well as new insight for the efficiency improvement of narrow-bandgap sulfide photocatalysts. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.