Anchoring Ni Sites on “Giant” Reverse Type-I CdS/CdSe Core/Shell Quantum Dots for Visible-Light-Induced Hydrogen Evolution

Semiconductor quantum dots (QDs) are attractive building blocks for photocatalytic hydrogen evolution because their optical and electronic properties can be tailored through nanoscale structural design. However, in many QD-based hybrid systems, limited interfacial coupling between the QDs and cocatalyst hinders charge transfer and obscures the relationship between the interfacial structure and function. Herein, we report a Ni-modified giant reverse type-I CdS/CdSe core/shell QD system prepared by photodeposition, in which the Ni loading can be quantitatively tuned from 1 to 7 atoms per QD. Structural and spectroscopic characterizations indicate that the deposited Ni species are intimately associated with the CdS/CdSe QDs, while the giant core/shell architecture is retained. This interfacial modification leads to systematic changes in charge-carrier behavior, as evidenced by photoluminescence, photocurrent, electrochemical impedance, transient photovoltage, and transient absorption measurements. Among the series, CdS/CdSe-Ni₄ exhibits the most efficient visible-light-driven hydrogen evolution, with a rate of 4492 μmol g⁻¹ h⁻¹ and a turnover frequency of 2.6 s⁻¹ per Ni site. The results show that the regulation of the QD/Ni interface plays an important role in promoting electron extraction and interfacial charge transfer. This study provides a useful model for understanding how surface metal-site modification influences the photophysical and photocatalytic properties of colloidal semiconductor core/shell nanostructures.