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.