Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 53, Issue 17, Pages 10197-10207Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.9b02946
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- U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Chemical Sciences, Geosciences, and Biosciences (CSGB) Division through its Geosciences program at Pacific Northwest National Laboratory
- DOE Office of Biological and Environmental Research
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Hematite nanoparticles are abundant in the photic zone of aquatic environments, where they play a prominent role in photocatalytic transformations of bound organics. Here, we examine the photocatalytic degradation of rhodamine B by visible light using two different structurally well-defined hematite nanoparticle morphologies. In addition to detailed solid characterization and aqueous kinetics measurements, we also exploit species-selective scavengers in electron paramagnetic resonance spectroscopy to sequester specific reaction channels and thereby assess their impact. The photodegradation rates for nanoplates dominated by {001} facets and nanocubes dominated by {012} facets were 0.13 and 0.7 h(-1), respectively, and the turnover frequencies for the active sites on {001} and {012} were 7.89 X 10(-3) and 3.07X 10(-3) s(-1), yielding apparent activation energies of 17.13 and 24.94 kcal/mol within the energetic span model, respectively. Facet-specific differences appear to be directly not linked with the simple aerial cation site density but instead with their extent of undercoordination. By establishing this linkage, the findings lay a foundation for predicting the photocatalytic degradation efficiency for the myriad of possible hematite nanoparticle morphologies and more broadly help unveil key reactions at the interface that may govern photocatalytic organic transformations in natural and engineered aquatic environments.
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