Efficient Photoelectrochemical Hydrogen Generation Based on Core Size Effect of Heterostructured Quantum Dots

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Colloidal quantum dots (QDs) are effective light-harvesting sensitizers for metal oxide semiconductor (MOS) photoelectrodes.
• CdSe/CdS core/shell QDs offer tunable absorption and band alignment for efficient carrier separation.
• Understanding the impact of core size on QD photoelectrochemical (PEC) performance is crucial.

Purpose of the Study:

• To investigate the effect of CdSe core size on the PEC performance of CdSe/CdS core/shell QDs.
• To tailor the band alignment of core/shell QDs for improved hydrogen generation.
• To optimize QD-sensitized MOS photoelectrodes for efficient PEC water splitting.

Main Methods:

• Synthesized CdSe/CdS core/shell QDs with varying CdSe core diameters (2.8–4.8 nm) while maintaining a constant CdS shell thickness.
• Fabricated CdSe/CdS/TiO2 photoelectrodes using the synthesized QDs.
• Characterized the PEC performance, including photocurrent density (Jph), under simulated solar irradiation.
• Investigated different core/shell architectures (Type II, Quasi-Type II, Type I).

Main Results:

• Successfully formed Type II, Quasi-Type II, and Type I CdSe/CdS core/shell architectures by varying core size.
• The optimized CdSe/CdS/TiO2 photoelectrode with a 3.5 nm CdSe core achieved a saturated photocurrent density (Jph) of 17.4 mA cm⁻².
• Further optimization with alloyed shells boosted Jph to 22 mA cm⁻², demonstrating state-of-the-art performance for colloidal QD-based electrodes.

Conclusions:

• CdSe core size significantly influences the band alignment and PEC performance of CdSe/CdS core/shell QDs.
• Optimized core size and shell composition are critical for maximizing hydrogen generation efficiency.
• These findings pave the way for advanced QD-sensitized photoelectrodes for solar fuel production.