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

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.