Facet-Dependent Photodegradation of Methylene Blue by Hematite Nanoplates in Visible Light

The expression of specific crystal facets in different nanostructures is known to play a vital role in determining the sensitivity toward the photodegradation of organics, which can generally be ascribed to differences in surface structure and energy. Herein, we report the synthesis of hematite nano...

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Bibliographic Details
Published in:Environmental science & technology 2021-01, Vol.55 (1), p.677-688
Main Authors: Zong, Meirong, Song, Duo, Zhang, Xin, Huang, Xiaopeng, Lu, Xiancai, Rosso, Kevin M
Format: Article
Language:English
Subjects:
Adsorption
Density functional theory
Design optimization
Environmental cleanup
Ferric Compounds
Free radicals
Hematite
Hydrogen peroxide
Hydroxyl radicals
Iron
Light
Methylene Blue
Nanostructure
Oxidation
Photocatalysis
Photodegradation
Photoelectrons
Photolysis
Surface chemistry
Surface structure
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Summary:The expression of specific crystal facets in different nanostructures is known to play a vital role in determining the sensitivity toward the photodegradation of organics, which can generally be ascribed to differences in surface structure and energy. Herein, we report the synthesis of hematite nanoplates with controlled relative exposure of basal (001) and edge (012) facets, enabling us to establish direct correlation between the surface structure and the photocatalytic degradation efficiency of methylene blue (MB) in the presence of hydrogen peroxide. MB adsorption experiments showed that the capacity on (001) is about three times larger than on (012). Density functional theory calculations suggest the adsorption energy on the (001) surface is 6.28 kcal/mol lower than that on the (012) surface. However, the MB photodegradation rate on the (001) surface is around 14.5 times faster than on the (012) surface. We attribute this to a higher availability of the photoelectron accepting surface Fe sites on the (001) facet. This facilitates more efficient iron valence cycling and the heterogeneous photo-Fenton reaction yielding MB-oxidizing hydroxyl radicals at the surface. Our findings help establish a rational basis for the design and optimization of hematite nanostructures as photocatalysts for environmental remediation.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.0c05592