Energy level tuning of CdSe colloidal quantum dots in ternary 0D-2D-2D CdSe QD/B-rGO/O-gC3N4 as photocatalysts for enhanced hydrogen generation

Abstract

Colloidal quantum dots (QD) electronic properties are tailorable via modifications of its quantum confinement environment. Herein, surface-chemistry-mediated approach through the application of unique surface thiol ligands (thioglycolic acid, glutathione, 3-mercaptopropioninc acid and N-Acetylcysteine) exhibited energy level and gap shifts in aqueous CdSe QDs. Trends in the photocatalytic performance employing ligand-specific CdSe QDs are consistent with their respective measured energy and gap level. Results underscore that a still underutilized mean of surface-chemistry-mediated modification of colloidal CdSe QDs can be employed as a versatile parameter in the performance optimizations of QD photocatalysts for photocatalytic hydrogen (H2) reactions. This optimized CdSe QD is further utilized as sensitizers to bolster and facilitate effective charge transfer across the ternary, multi-level heterointerfaces of 0D-2D-2D CdSe QD/B-rGO/O-gC3N4. Upon loading, the ternary composite achieved a maximum H2 evolution of 1435 μmol h−1 g−1 even without the help of precious metal co-catalyst which is otherwise required when used as individual unit. This augmented photoactivity is attributed to the synergetic effect of CdSe sensitization and p-n junction administered by the p-type B-rGO and n-type O-gC3N4.