Mass Transport Limitations in Plasmonic Photocatalysis

Area of Science:

• Materials Science
• Photochemistry
• Nanotechnology

Background:

• Understanding hot carrier dynamics in metallic nanostructures is crucial for advancing plasmonic photocatalysis.
• The solid-liquid interface plays a key role in hot carrier extraction for photodevice efficiency.
• Current interpretations of hot carrier reactivity often overlook mass transport limitations.

Purpose of the Study:

• To investigate the influence of molecular diffusion on hot carrier extraction rates at the solid-liquid interface.
• To identify regimes where mass transport hinders plasmon-driven photochemical activity.
• To elucidate the impact of molecular availability on the quantum efficiency of plasmonic photocatalysts.

Main Methods:

• Spatially defined scanning photoelectrochemical microscopy.
• Low-power monochromatic illumination (<2 W cm^-2).
• Investigation of gold (Au) nanoislands on ultrathin titanium dioxide (TiO₂) substrates.

Main Results:

• A diffusion-controlled regime was identified, hindering photochemical activity.
• Mass transport was shown to significantly influence quantum efficiency.
• The availability of molecules at the interface was found to directly limit hot hole extraction.

Conclusions:

• Molecular diffusion is a critical, often overlooked, factor in plasmonic photocatalysis.
• Mass transport limitations can hinder the efficiency of photodevices utilizing metallic nanostructures.
• Further research is needed to understand if thermal effects from mass transport can enhance nonthermal carrier reactivity.