Dual S-scheme MoS2/ZnIn2S4/Graphene quantum dots ternary heterojunctions for highly efficient photocatalytic hydrogen evolution

Abstract

The layered chalcogenide ZnIn2S4 (ZIS) exhibits photo-stability and a tunable band gap but is limited in photocatalytic applications, such as hydrogen (H2) production, due to rapid carrier recombination and slow charge separation. To overcome these limitations, we have synthesized a ternary MoS2/ZIS/graphene quantum dots (GQDs) heterojunction, wherein MoS2 and GQDs are strategically attached to ZIS interlaced nanoflakes, enhancing light absorption across the 500–1500 nm range. This heterojunction benefits from dual S-scheme interfaces between MoS2-ZIS and ZIS-GQDs, establishing directed internal electric fields (IEFs). These IEFs accelerate the transfer of photoinduced electrons from the conduction bands of MoS2 and GQDs to the valence band of ZIS, promoting rapid recombination with holes and facilitating efficient catalytic reactions with plentiful photoinduced electrons stemmed from the conduction band of ZIS. As a result, the photocatalytic H2 production rate of the MoS2/ZIS/GQDs heterojunction is measured at 21.63 mmol h−1 g−1, marking an increase of 36.7 times over pure ZIS. This research provides valuable insights into designing novel heterojunctions for improved charge separation and transfer for solar energy conversion applications.