Immobilizing CdS quantum dots and dendritic Pt nanocrystals on thiolated graphene nanosheets toward highly efficient photocatalytic H₂ evolution

We report the development of a highly efficient photocatalytic system by immobilizing high-quality CdS quantum dots and dendritic Pt nanocrystals on thiol-functionalized graphene substrates. We have demonstrated that the use of QDs with compact sizes leads to a dramatically enhanced performance in comparison with their bulk counterparts. Our design allows for systematic examination of the impact of QD sizes and the loading, morphology, and surface coating of the Pt nanocrystal cocatalyst on the H₂ evolution activity. It was found that the CdS-Pt binary system has a high photocatalytic efficiency of 1.37 mmol h^-1 for visible light driven H₂ evolution, and there was a 30% improvement by introducing the thiolated reduced graphene oxide to form the three-component CdS-Pt-G_cys nanocomposites. The highest H₂ evolution rate of 2.15 mmol h ^-1 (λ ≥ 420 nm) with a QE of 50.7% was achieved by further photo-annealing of the CdS-Pt-G_cys nanocomposites prior to the photocatalytic reaction.