Advancing Plasmon-Induced Selectivity in Chemical Transformations with Optically Coupled Transmission Electron...

Area of Science:

• Materials Science and Nanotechnology
• Physical Chemistry
• Catalysis

Background:

• Nanoparticle photocatalysts are crucial for chemical production, water purification, and sterilization.
• Understanding and controlling photochemistry at the atomic scale is vital for improving catalyst efficiency and selectivity.
• Traditional transmission electron microscopy (TEM) requires high vacuum, limiting in-situ studies of reactions.

Purpose of the Study:

• To demonstrate how advances in plasmonics and optically coupled transmission electron microscopy (OTEM) can image and control nanoscale light-induced chemical transformations.
• To investigate the interaction between hydrogen gas and palladium (Pd) nanoparticles as a model system for hydrogenation catalysis and hydrogen storage.
• To explore the role of plasmonic effects in site-selective photocatalysis.

Main Methods:

• Utilized an environmental transmission electron microscope equipped with optical sources and detectors for in-situ studies.
• Employed electron energy loss spectroscopy (EELS) to monitor bulk plasmon resonance and phase transformations in Pd nanoparticles.
• Applied contrast imaging techniques like phase contrast STEM and displaced-aperture dark field for real-time imaging of phase transformations.

Main Results:

• Observed coherent phase transformations (α-phase to β-phase) in Pd nanoparticles (<100 nm) during hydrogen loading, monitored via plasmon resonance.
• Demonstrated real-time imaging of phase transformations with 100 ms temporal resolution.
• Showed that internal strain and grain boundaries in Pd nanoparticles influence hydrogenation.
• Revealed that in plasmonic heterostructures (Au-Pd), light-induced α-phase nucleation occurs near electromagnetic 'hot spots' on the gold nanoparticle antenna, not necessarily at preferred catalytic sites.
• Highlighted the importance of nonthermal plasmonic effects (electromagnetic field enhancement, hot carriers) in explaining site selectivity.

Conclusions:

• OTEM provides a powerful tool to image and control light-induced chemical reactions at the nanoscale.
• Plasmonic effects, particularly electromagnetic field enhancement and hot carriers, play a critical role in directing site selectivity in photocatalysis.
• This approach paves the way for developing sustainable, solar-driven chemical production using engineered plasmonic heterostructures.