Probing Long‐Lived Plasmonic‐Generated Charges in TiO₂/Au by High‐Resolution X‐ray Absorption Spectroscopy

Abstract

Exploiting plasmonic Au nanoparticles to sensitize TiO2 to visible light is a widely employed route to produce efficient photocatalysts. However, a description of the atomic and electronic structure of the semiconductor sites in which charges are injected is still not available. Such a description is of great importance in understanding the underlying physical mechanisms and to improve the design of catalysts with enhanced photoactivity. We investigated changes in the local electronic structure of Ti in pure and N-doped nanostructured TiO2 loaded with Au nanoparticles during continuous selective excitation of the Au localized surface plasmon resonance with X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). Spectral variations strongly support the presence of long-lived charges localized on Ti states at the semiconductor surface, giving rise to new laser-induced low-coordinated Ti sites.

Charge carrier dynamics and visible light photocatalysis in vanadium-doped TiO2 nanoparticles

“…By means of a quantitative analysis, a long electron lifetime in the defective sites of 0.8 ms was estimated. This work followed our previous study of plasmon-induced hot electron transfer in Au-TiO2 nanostructures [46]. In the context of X-ray spectroscopic investigations we note that electron transfer to defective Ti sites in undoped or dye-sensitized TiO2 NPs has been demonstrated by time resolved methods on the 100 ps time scale by Rittmann Frank et al [47] and more recently on the 100 fs time scale by Obara et al [48].…”

Photo-electrochemical hydrogen production from neutral phosphate buffer and seawater using micro-structured p-Si photo-electrodes functionalized by solution-based methods

“…A schematic view of the optics and the experimental set up is presented elsewhere. 63,64 The pre-edge region of the XAS spectra (4967 to 4976 eV) is particularly sensitive to the symmetry at the Ti sites. 65,66 The pre-edge of crystalline TiO 2 has three characteristic peaks, denoted as A1, A2 and A3.…”

H2 production by photocatalytic reforming of oxygenated compounds using TiO2-based materials

“…Various energy-transfer processes have been proposed to explain the improved activity of photocatalysts comprising co-catalysts with SPR effect. Direct Electron Transfer (DET) is realized when of "hot" electrons produced by irradiation of plasmonic metal nanoparticles possess enough energy to overcome the Schottky barrier at the metal/TiO 2 interface and are injected into the conduction band of the semiconductor [88,89]. An increase of electron-hole generation rate in the Au/TiO 2 composites has been related with Local ElectroMagnetic Field (LEMF) enhancement near the surface of TiO 2 [90] or Plasmonic Resonant Energy Transfer (PRET) from metal to semiconductor [91].…”