Capturing the Long-Lived Photogenerated Electrons in Au/TiO2 upon UV or Visible Irradiation by Time-Resolved Infrared Spectroscopy

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 here detected for the first time. Moreover, the effects of TiO2 phase composition decay kinetics of long-lived photoelectrons are examined. AuNPs into TiO2 upon plasmon excitation are and the amount of AuNPs loading on the decay kinetics of long-lived photoelectrons are examined.