Localized surface plasmon resonance enhanced photocatalysis: an experimental and theoretical mechanistic investigation

Titanium dioxide (TiO₂) is an advantageous material in catalytic photodegradation due to its low cost, high stability, and considerably higher efficiency when compared to other semiconductors. However, the need for artificial radiation sources in the UV range is a limitation to its use in wastewater remediation. In this context, Localized Surface Plasmon Resonance (LSPR) has been shown to enhance the photoexcitation of charge carriers in the semiconductor. In the present work, the investigation of catalytic photodegradation of phenol solution under distinct excitation by UV-visible or just visible radiation, employing three TiO₂ based plasmonic catalysts, was conducted. Spherical silver nanoparticles which present LSPR along the TiO₂ bandgap energy and electrically insulated silver nanoparticles were employed. Gold nanoparticles, which present low energy LSPR, were also employed in order to compare the excitation efficiency. Discrete dipole approximation simulations were carried out in order to verify the electric field enhancement and penetration at the semiconductor surface of each plasmonic catalyst. The results presented here may help to shed some light with respect to the contribution of plasmonic photocatalysts and the charge transfer mechanism in catalysts containing plasmonic structures.

A theoretical (DDA simulation) and experimental (phenol degradation) study has shown the LSPR from Ag and Ag@SiO₂ NPs to contribute to better TiO₂ photocatalytic performances. Au NPs has shown very low contribution, due to its low energy LSPR.