期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 22, 期 35, 页码 12548-12556出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201602173
关键词
cuprous oxide; EPR spectroscopy; facet-dependent properties; nanocrystals; photocatalysis
资金
- Ministry of Science and Technology of Taiwan [MOST 101-2113M-007-018-MY3, MOST 103-2633M-007-001]
This work confirms the presence of a large facet-dependent photocatalytic activity of Cu2O crystals through sparse deposition of gold particles on Cu2O cubes, octahedra, and rhombic dodecahedra. Au-decorated Cu2O 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-Cu2O core-shell rhombic dodecahedra also displayed a better photocatalytic activity than pristine rhombic dodecahedra. However, Au-deposited Cu2O 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 Cu2O rhombic dodecahedra than for the octahedra, but no radicals were produced from photoirradiated Cu2O cubes. The Cu2O {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.
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