title: On the dynamical nature of the active center in a single-site photocatalyst visualized by 4D ultrafast electron microscopy.
abstract: Understanding the dynamical nature of the catalytic active site embedded in complex systems at the atomic level is critical to developing efficient photocatalytic materials. Here, we report, using 4D ultrafast electron microscopy, the spatiotemporal behaviors of titanium and oxygen in a titanosilicate catalytic material. The observed changes in Bragg diffraction intensity with time at the specific lattice planes, and with a tilted geometry, provide the relaxation pathway: the Ti(4+)=O(2-) double bond transformation to a Ti(3+)-O(1-) single bond via the individual atomic displacements of the titanium and the apical oxygen. The dilation of the double bond is up to 0.8 Å and occurs on the femtosecond time scale. These findings suggest the direct catalytic involvement of the Ti(3+)-O(1-) local structure, the significance of nonthermal processes at the reactive site, and the efficient photo-induced electron transfer that plays a pivotal role in many photocatalytic reactions.
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Byung-Kuk
authors.initials: BK
authors.lastname: Yoo
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Zixue
authors.initials: Z
authors.lastname: Su
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom.
authors.forename: John Meurig
authors.initials: JM
authors.lastname: Thomas
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125; zewail@caltech.edu.
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Zewail
keywords: single-site photocatalysis; time-resolved microscopy; titanium based photocatalyst; ulatrafast phenomena; ultrafast electron microscopy