title: Effect of Water Adsorption on Carrier Trapping Dynamics at the Surface of Anatase TiO2 Nanoparticles.
abstract: Charge carrier trapping plays a vital role in heterogeneous photocatalytic water splitting because it strongly affects the dynamics of photogenerated charges and hence the photoconversion efficiency. Although hole trapping by water at water/photocatalyst interface is the first step of oxygen evolution in water splitting, little has been known on how water adsorbate itself is involved in hole trapping dynamics. To clarify this point, we have performed infrared transient and steady-state absorption spectroscopy of anatase TiO2 nanoparticles as a function of the number of water adsorbate layers. Here, we demonstrate that water molecules reversibly adsorbed in the first layer on TiO2 nanoparticles are capable to trap photogenerated holes, while water in the second layer hydrogen bonding to the first-layer water makes hole trapping less effective.
authors.affiliation: Graduate School of Science, Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Shirai
authors.affiliation: Graduate School of Science, Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Sugimoto
authors.affiliation: Graduate School of Science, Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Institute for Chemical Research, Kyoto University, Uji , Kyoto 611-0011, Japan.
authors.forename: Mitsutaka
authors.initials: M
authors.lastname: Haruta
authors.affiliation: Institute for Chemical Research, Kyoto University, Uji , Kyoto 611-0011, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kurata
authors.affiliation: Graduate School of Science, Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan.
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Matsumoto
keywords: Photocatalysis; TiO2 nanoparticles; charge dynamics; water adsorption; water splitting