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Fenton chemistry at aqueous interfaces

Enami, Shinichi and Sakamoto, Yosuke and Colussi, Agustín J. (2014) Fenton chemistry at aqueous interfaces. Proceedings of the National Academy of Sciences of the United States of America, 111 (2). pp. 623-628. ISSN 0027-8424. PMCID PMC3896178. https://resolver.caltech.edu/CaltechAUTHORS:20140214-082356104

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Abstract

In a fundamental process throughout nature, reduced iron unleashes the oxidative power of hydrogen peroxide into reactive intermediates. However, notwithstanding much work, the mechanism by which Fe^(2+) catalyzes H_2O_2 oxidations and the identity of the participating intermediates remain controversial. Here we report the prompt formation of O=Fe^(IV)CI_3^− and chloride-bridged di-iron O=Fe^(IV)·CI·FeIICI_4^− and O=Fe^(IV)·CI·Fe^(III)CI_5^− ferryl species, in addition to Fe^(III)CI_4^−, on the surface of aqueous FeCI_2 microjets exposed to gaseous H_2O_2 or O_3 beams for <50 μs. The unambiguous identification of such species in situ via online electrospray mass spectrometry let us investigate their individual dependences on Fe^(2+), H_2O_2, O_3, and H^+ concentrations, and their responses to tert-butanol (an ·OH scavenger) and DMSO (an O-atom acceptor) cosolutes. We found that (i) mass spectra are not affected by excess tert-butanol, i.e., the detected species are primary products whose formation does not involve ·OH radicals, and (ii) the di-iron ferryls, but not O=Fe^(IV)CI_3^−, can be fully quenched by DMSO under present conditions. We infer that interfacial Fe(H_2O)_n^(2+) ions react with H_2O_2 and O_3 >10^3 times faster than Fe(H_2O)_6^(2+) in bulk water via a process that favors inner-sphere two-electron O-atom over outer-sphere one-electron transfers. The higher reactivity of di-iron ferryls vs. O=Fe^(IV)CI_3^− as O-atom donors implicates the electronic coupling of mixed-valence iron centers in the weakening of the Fe^(IV)–O bond in poly-iron ferryl species.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://www.pnas.org/content/111/2/623PublisherArticle
http://dx.doi.org/10.1073/pnas.1314885111DOIArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3896178/PubMed CentralArticle
ORCID:
AuthorORCID
Enami, Shinichi0000-0002-2790-7361
Colussi, Agustín J.0000-0002-3400-4101
Additional Information:© 2014 National Academy of Sciences. Edited by Richard J. Saykally, University of California, Berkeley, CA, and approved December 9, 2013 (received for review August 6, 2013). We are grateful to Dr. Himanshu Mishra and Profs. Michael Hoffmann, William Goddard, and Harry Gray of the California Institute of Technology for valuable discussions. S.E. thanks the Japan Science and Technology Agency PRESTO program, Grant for Environmental Research Projects from The Sumitomo Foundation, and Steel Foundation for Environmental Protection Technology. Y.S. thanks the Grant-in-Aid for Japan Society for the Promotion of Science Fellows for financial support. Author contributions: S.E. designed research; S.E. and Y.S. performed research; S.E. contributed new reagents/analytic tools; S.E., Y.S., and A.J.C. analyzed data; and S.E. and A.J.C. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. Freely available online through the PNAS open access option.
Funders:
Funding AgencyGrant Number
Japan Science and Technology Agency (JST) PRESTO programUNSPECIFIED
Sumitomo FoundationUNSPECIFIED
Steel Foundation for Environmental Protection TechnologyUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:metal ions; reactive oxygen species; aerosols; advanced oxidation processes; nanoparticles
Issue or Number:2
PubMed Central ID:PMC3896178
Record Number:CaltechAUTHORS:20140214-082356104
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140214-082356104
Official Citation:Fenton chemistry at aqueous interfaces PNAS 2014 111 (2) 623-628; published ahead of print December 30, 2013, doi:10.1073/pnas.1314885111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43827
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:18 Feb 2014 16:17
Last Modified:03 Oct 2019 06:11

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