Type-I CdS/ZnS Core/Shell Quantum Dot-Gold Heterostructural Nanocrystals for Enhanced Photocatalytic Hydrogen Generation

The rapid industrialization has led to serious problems of environmental pollution and energy shortages, necessitating the need for exploring renewable energy sources that can be produced ecologically without further releasing pollutants, such as molecular hydrogen (H₂). Type-I core/shell quantum dot (QD) systems have been long recognized and utilized as efficient, stable, and sustainable light harvesting and emitting materials. Nevertheless, the application of Type-I core/shell QDs in photocatalysis has been restricted due to the strongly confined photogenerated charges within the core, making them catalytically “inert”. In this project, we found that through the decoration of Au satellite-type domains on the surface of Type-I CdS/ZnS core/shell quantum dots, the energy barrier introduced by the wide-bandgap shell material can be effectively overcome and an over-four-hundred-fold enhancement of the photocatalytic H₂ evolution rate was achieved compared to bare CdS/ZnS quantum dots. Transient absorption spectroscopic studies indicated that the charges can be effectively extracted and subsequently transferred to surrounding molecular substrates in a sub-picosecond timescale in such hybrid nanocrystals. Based on density functional theory calculations, the ultrafast charge separation rates were ascribed to the formation of an intermediate Au₂S layer at the semiconductor-metal interface, which can successfully offset the energy confinement introduced by the ZnS shell. Our findings not only provide insightful understandings of charge carrier dynamics in semiconductor-metal heterostructural materials but also pave the way for the future design of quantum dot-based hybrid photocatalytic systems.