Capturing the Long-Lived Photogenerated Electronsin Au/TiO 2 upon UV or Visible Irradiation by Time-ResolvedInfrared Spectroscopy

Abstract

Gold nanoparticle modifications for TiO2 (Au/TiO2) can extend the absorption wavelength from UV to visible (Vis) and enhance the photocatalytic performance, thus fueling increasing attention as an emerging photocatalysis strategy. To explore the plasmon-enhanced photocatalytic mechanism and directly unveil the intrinsic properties of Au/TiO2, the decay kinetics of photoelectrons upon UV (355 nm) or Vis (532 nm) excitation are monitored by means of nanosecond time-resolved infrared spectroscopy, which is a unique tool offering observations without interference of the holes. Under UV irradiation, the longer lifetime of photoelectrons observed in Au/TiO2 compared to that in bare TiO2 provides unambiguous evidence for the enhanced charge separation by AuNPs. Under Vis irradiation, the long-lived (hundreds of microseconds) electrons produced by injection from AuNPs into TiO2 upon plasmon excitation are here detected for the first time. Moreover, the effects of TiO2 phase composition and the amount of AuNPs loa...