title: Hot-Electron-Induced Highly Efficient O2 Activation by Pt Nanoparticles Supported on Ta2O5 Driven by Visible Light.
abstract: Aerobic oxidation on a heterogeneous catalyst driven by visible light (λ >400 nm) at ambient temperature is a very important reaction for green organic synthesis. A metal particles/semiconductor system, driven by charge separation via an injection of "hot electrons (e(hot)(-))" from photoactivated metal particles to semiconductor, is one of the promising systems. These systems, however, suffer from low quantum yields for the reaction (<5% at 550 nm) because the Schottky barrier created at the metal/semiconductor interface suppresses the e(hot)(-) injection. Some metal particle systems promote aerobic oxidation via a non-e(hot)(-)-injection mechanism, but require high reaction temperatures (>373 K). Here we report that Pt nanoparticles (∼5 nm diameter), when supported on semiconductor Ta2O5, promote the reaction without e(hot)(-) injection at room temperature with significantly high quantum yields (∼25%). Strong Pt-Ta2O5 interaction increases the electron density of the Pt particles and enhances interband transition of Pt electrons by absorbing visible light. A large number of photogenerated e(hot)(-) directly activate O2 on the Pt surface and produce active oxygen species, thus promoting highly efficient aerobic oxidation at room temperature.
authors.affiliation: †Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
authors.forename: Hirokatsu
authors.initials: H
authors.lastname: Sakamoto
authors.affiliation: †Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ohara
authors.affiliation: †Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yasumoto
authors.affiliation: †Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.|‡PRESTO, JST, Saitama 332-0012, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shiraishi
authors.affiliation: ∥Institute for NanoScience Design, Osaka University, Toyonaka 560-8531, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ichikawa
authors.affiliation: §Department of Chemical, Energy and Environmental Engineering, Kansai University, Suita 564-8680, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: †Research Center for Solar Energy Chemistry, and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hirai