Surface Modulation, Optics, and Electrochemical Hydrogen Evolution Studies on CdS-Ag₂S Superlattice Heterostructures

Area of Science:

• Materials Science
• Nanotechnology
• Catalysis

Background:

• Semiconductor superlattice heterostructures with periodic electronic states are promising for catalysis, photodetectors, and electronic devices.
• CdS-based superlattice quantum dots are attractive due to exciton dynamics enhancing electron transport across heterogeneous energy states.

Purpose of the Study:

• To synthesize and characterize CdS-Ag2S random superlattices quantum dots and ordered nanorod superlattices.
• To investigate the photoluminescence properties and electrochemical hydrogen evolution activity of these superlattices.

Main Methods:

• Ligand-mediated decomposition of metal-organic precursors to form CdS-Ag2S@octadecyl amine (ODA) and CdS-Ag2S@dodecane thiol (DDT) superlattices.
• High-resolution scanning transmission electron microscopy (HR-STEM) and energy-dispersive X-ray spectroscopy (EDX) for structural and compositional analysis.
• Photoluminescence (PL) spectroscopy and electrochemical hydrogen evolution reaction (HER) measurements.

Main Results:

• CdS-Ag2S@ODA superlattices exhibited dual-band PL emissions with fast band-edge recombination and delayed non-radiative decay from surface trap states.
• CdS-Ag2S@DDT nanorods showed majority charge carrier recombination with band-edge emission lifetimes.
• CdS-Ag2S@DDT nanorod superlattices demonstrated enhanced electrochemical hydrogen evolution in neutral media, outperforming ODA-capped structures.

Conclusions:

• Ordered CdS-Ag2S@DDT nanorod superlattices exhibit superior electrochemical hydrogen evolution activity compared to random CdS-Ag2S@ODA superlattices.
• The metallic character of Ag2S and interfacial charge accumulation contribute to enhanced HER activity.
• Atomic packing and interfacial coupling influenced by capping ligands (DDT vs. ODA) are critical factors for catalytic performance.