Self-hydrogenated shell promoting photocatalytic H₂ evolution on anatase TiO₂

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Titanium dioxide (TiO2) is a crucial photocatalyst with extensive research.
• Understanding interfacial reactions between water and TiO2 is key to photocatalysis mechanisms.
• Current methods for studying anatase TiO2 photocatalysis are limited to water vapor or single molecules.

Purpose of the Study:

• To investigate the photocatalytic reaction of anatase TiO2 nanoparticles in liquid water.
• To characterize the interfacial processes at the nanoscale.
• To elucidate the mechanism of hydrogen evolution enhancement.

Main Methods:

• Liquid environmental transmission electron microscopy (LETEM) was employed.
• First-principles calculations were used to model reaction mechanisms.
• Experimental validation confirmed theoretical predictions.

Main Results:

• A self-hydrogenated shell formed on the TiO2 surface prior to hydrogen bubble generation.
• This shell is composed of subsurface-diffused photo-reduced water protons.
• The shell contains reduced titanium ions and its thickness increases with UV illuminance.

Conclusions:

• The self-hydrogenated shell promotes photocatalytic hydrogen evolution.
• Subsurface proton diffusion lowers the activation barrier for H2 formation.
• This finding offers new insights into optimizing TiO2-based photocatalytic systems.