Programming Intraparticle Ordering in Y6-Derived Organic Photocatalyst Nanoparticles for Efficient Solar Hydrogen...

Area of Science:

• Materials Science
• Photocatalysis
• Renewable Energy

Background:

• Organic photocatalyst nanoparticles (NPs) are promising for scalable solar hydrogen production.
• Controlling intraparticle molecular packing in NPs is a critical challenge for efficiency.
• Nonfullerene acceptors (NFAs) are key components in organic photocatalysts.

Purpose of the Study:

• To investigate the effect of removing core alkyl chains on the intraparticle ordering of Y6-derived NFAs.
• To enhance the solar hydrogen production efficiency of organic photocatalyst NPs.
• To establish a design principle for morphology-controlled NP photocatalysts.

Main Methods:

• Synthesis of YHD-2F by removing core alkyl chains from Y6.
• Characterization using absorption spectroscopy, powder X-ray diffraction, and cryo-transmission electron microscopy (cryo-TEM).
• Molecular dynamics simulations and transient/photoinduced absorption spectroscopy to analyze electronic properties and packing.
• Solar hydrogen evolution rate measurements under AM 1.5G irradiation.

Main Results:

• YHD-2F NPs showed reduced energetic disorder, indicated by pronounced vibronic features and a smaller Stokes shift compared to Y6 NPs.
• YHD-2F NPs maintained discernible lattice order during formation, unlike Y6 NPs, suggesting improved intermolecular packing.
• YHD-2F NPs achieved a hydrogen evolution rate of 116.4 mmol g^-1 h^-1, over three times higher than Y6 NPs, with an apparent quantum yield of 1.50% at 800 nm.

Conclusions:

• Core alkyl-chain engineering effectively programs intraparticle ordering in organic photocatalyst NPs.
• Improved molecular packing in YHD-2F NPs leads to a larger population of long-lived electrons and enhanced photocatalytic activity.
• This study presents a general design principle for developing efficient morphology-controlled NP photocatalysts for solar-to-hydrogen energy conversion.