title: Facet-Dependent Photoreduction on Single ZnO Crystals.
abstract: Photocatalytic reactions occur at the crystal-solution interface, and hence specific crystal facet expression and surface defects can play an important role. Here we investigate the structure-related photoreduction at zinc oxide (ZnO) microparticles via integrated light and electron microscopy in combination with silver metal photodeposition. This enables a direct visualization of the photoreduction activity at specific crystallographic features. It is found that silver nanoparticle photodeposition on dumbbell-shaped crystals mainly takes place at the edges of O-terminated (0001̅) polar facets. In contrast, on ZnO microrods photodeposition is more homogeneously distributed with an increased activity at {101̅1̅} facets. Additional time-resolved measurements reveal a direct spatial link between the enhanced photoactivity and increased charge carrier lifetimes. These findings contradict previous observations based on indirect, bulk-scale experiments, assigning the highest photocatalytic activity to polar facets. The presented research demonstrates the need for advanced microscopy techniques to directly probe the location of photocatalytic activity.
authors.affiliation: Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, KU Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Debroye
authors.affiliation: Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Jordi
authors.initials: J
authors.lastname: Van Loon
authors.affiliation: Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, KU Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Haifeng
authors.identifier: http://orcid.org/0000-0001-6652-3670
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, KU Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Kris P F
authors.initials: KP
authors.lastname: Janssen
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Zaizhu
authors.initials: Z
authors.lastname: Lou
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Sooyeon
authors.initials: S
authors.lastname: Kim
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Tetsuro
authors.identifier: http://orcid.org/0000-0003-1805-1677
authors.initials: T
authors.lastname: Majima
authors.affiliation: Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems, KU Leuven , Celestijnenlaan 200F, 3001 Leuven, Belgium.
authors.forename: Maarten B J
authors.identifier: http://orcid.org/0000-0001-6582-6514
authors.initials: MB
authors.lastname: Roeffaers