Dual-ligand engineering of gradient-alloyed quantum dots: Optimizing of charge carrier separation and photocatalytic hydrogen evolution

The increasingly growing global demand for sustainable energy solutions has heightened emphasis on photocatalytic hydrogen production as a crucial technological advancement. This study represents a significant advancement in this field by creating gradient-alloyed quantum dots (QDs) composed of CdS@Zn x Cd 1-x S@ZnS structures, which demonstrates exceptional photocatalytic activity for hydrogen evolution. By using an innovative dual-ligand engineering approach that incorporates both mercaptopropionic acid (MPA) and thiocyanate (SCN) ligands, we have achieved a substantial enhancement in photocatalytic activity, demonstrating a 3.83-fold increase compared to MPA-QDs and an extraordinary 97.43-fold increase relative to SCN-QDs. This enhancement is attributed to the synergistic interactions between inorganic and organic ligands, which optimizes the dynamics of electron and hole transfer. The HOMO energy level from MPA, coupled with the strong electrostatic interactions of the inorganic ligands, markedly improves the redox properties of the QDs, leading to an impressive hydrogen evolution rate of approximately 1422.7 μmol/g h. Our findings elucidate the critical role of surface ligands in modulating redox reactions and demonstrate the potential of dual-ligand systems to substantially surpass the performance of single-ligand systems. This research provides a novel strategy for optimizing the photocatalytic performance of QDs, representing a significant advancement in the pursuit of efficient and sustainable hydrogen production methods, with broader implications for the fields of photocatalysis and optoelectronics.