title: Highly Facet-Dependent Photocatalytic Properties of Cu2 O Crystals Established through the Formation of Au-Decorated Cu2 O Heterostructures.
abstract: This work confirms the presence of a large facet-dependent photocatalytic activity of Cu2 O crystals through sparse deposition of gold particles on Cu2 O cubes, octahedra, and rhombic dodecahedra. Au-decorated Cu2 O rhombic dodecahedra and octahedra showed greatly enhanced photodegradation rates of methyl orange resulting from a better separation of the photogenerated electrons and holes, with the rhombic dodecahedra giving the best efficiency. Au-Cu2 O core-shell rhombic dodecahedra also displayed a better photocatalytic activity than pristine rhombic dodecahedra. However, Au-deposited Cu2 O cubes, pristine cubes, and Au-deposited small nanocubes bound by entirely {100} facets are all photocatalytically inactive. X-ray photoelectron spectra (XPS) showed identical copper peak positions for these Au-decorated crystals. Remarkably, electron paramagnetic resonance (EPR) measurements indicated a higher production of hydroxyl radicals for the photoirradiated Cu2 O rhombic dodecahedra than for the octahedra, but no radicals were produced from photoirradiated Cu2 O cubes. The Cu2 O {100} face may present a high energy barrier through its large band edge bending and/or electrostatic repulsion, preventing charge carriers from reaching to this surface. The conventional photocatalysis model fails in this case. The facet-dependent photocatalytic differences should be observable in other semiconductor systems whenever a photoinduced charge-transfer process occurs across an interface.
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Guo-Zhi
authors.initials: GZ
authors.lastname: Yuan
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Chi-Fu
authors.initials: CF
authors.lastname: Hsia
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Zhen-Wen
authors.initials: ZW
authors.lastname: Lin
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Chieh
authors.initials: C
authors.lastname: Chiang
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan.
authors.forename: Yun-Wei
authors.initials: YW
authors.lastname: Chiang
authors.affiliation: Department of Chemistry and Frontier Research Center on Fundamental and, Applied Science of Matter, National Tsing Hua University, Hsinchu, 30013, Taiwan. hyhuang@mx.nthu.edu.tw.
authors.forename: Michael H
authors.identifier: http://orcid.org/0000-0002-5648-4345
authors.initials: MH
authors.lastname: Huang
keywords: EPR spectroscopy; cuprous oxide; facet-dependent properties; nanocrystals; photocatalysis