Abstract
We present a mechanistic study of a PTCDA2-/TiO2 dye-sensitized photocatalytic system, in which the stable radical dianion PTCDA2- is formed via a two-step consecutive photoinduced electron transfer from its neutral precursor PTCDA (i.e., perylenetetracarboxylic dianhydride). Photoexcitation of PTCDA2- brings forth an interesting behavior known as vibrationally excited-state-selective, visible-light photocatalytic hydrogen evolution reaction (HER). In conjunction with the information gleaned from optical spectroscopy and ultrafast dynamics, we reveal that an intermediate complex (IC) state with a lifetime of ∼12 ps exists in the vicinity of a certain vibrationally excited state of PTCDA2-. Such a unique IC state mediates the interfacial electron transfer (IET) channel from the specific excited state of PTCDA2- to the conduction band continuum of TiO2. As an outcome, the effective IC-mediated IET process in this photocatalytic system leads to a remarkable HER rate that reaches ∼4660 μmol g-1 h-1.
Published Version
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