Mediator-free Z-scheme photocatalytic system based on ultrathin CdS nanosheets for efficient hydrogen evolution

The development of a facile and scalable method to synthesize ultrathin CdS nanosheets and fabricate a mediator-free Z-scheme photocatalytic (PC) system based on ultrathin CdS nanosheets are highly challenging. Herein, we present a one-pot diethylenetriamine-assisted method for synthesizing ultrathin CdS nanosheets (CdS NSs) and their composites with reduced graphene oxide (CdS-NSs/RGO), and then we rationally design a mediator-free Z-scheme PC system composed of electrostatically interacting CdS NSs or CdS-NSs/RGO and WO3 nanosheets (WO3 NSs) for efficient PC H-2 evolution. The results of PC tests show that in the presence of an optimized amount of RGO, the photocatalytic hydrogen evolution activity of CdS-NSs/RGO is higher than that of pure ultrathin CdS NSs. Furthermore, when combined with WO3 NSs to fabricate Z-scheme PC systems, the composite photocatalysts exhibit higher photocatalytic activity for hydrogen evolution in water-ethanol mixtures compared with their pure components. Special ultrathin and 2D sheet-like structure, electrostatic interaction, suitable energy band structure and assistance of RGO as a supporting matrix and an electron collector contribute to the effortless transfer of electrons, resulting in enhanced PC performance. Impressively, the as-fabricated mediator-free Z-scheme PC system can also be used as a photocathode for photoelectrochemical (PEC) H-2 evolution. Our present work may provide a promising strategy to fabricate efficient PC and PEC systems for solar-to-fuel energy conversion.