Interface structure plays an extremely
important role in the charge-transfer
and photocatalytic performances in plasmonic metal/semiconductor systems.
Defect engineering by introducing an oxygen vacancy (Ovac) is an effective way to modulate the interface structure. Here,
a representative photocatalyst system including TiO2, TiO2–x
, Au-TiO2 and Au-TiO2–x
as designed delicately to reveal
the detailed mechanism of the plasmon-resonance-induced charge separation
in interfacial defect structure from the nanoscale. The local charge
transfer via a conducting amorphous-like interface layer is visualized
as the arched valence change from Ti3+ to Ti4+ at the Au-TiO2–x
interface after
Schottky contact. This phenomenon eventually leads to the enhancement
of localized surface plasmon resonance (LSPR) at 2.3 eV, and the introduction
of Ovac reduces the Schottky barrier height of Au-TiO2–x
by 5 mV compared with that of Au-TiO2. Under visible light, Au-TiO2–x
excites the most photogenerated carriers to the surface, which
is larger than that of TiO2–x
and
Au-TiO2. It can be concluded that the changes in electronic
structure eventually promote charge transfer in visible light and
explain the original reason that the coupling of Ovac and
Au could improve the photocatalytic performance.
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