Title

Formation of Environmentally Persistent Free Radicals (EPFRs) on the Phenol-Dosed -FeO(0001) Surface

Authors

N I. Sakr, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Orhan Kizilkaya, Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States.
Sierra F. Carlson, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States.
Simon Chan, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States.
Reuben A. Oumnov, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States.
Jaqueline Catano, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States.
Richard L. Kurtz, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States; Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States.
Randall W. Hall, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, California 94901, United States; Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
E D. Poliakoff, Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Phillip T. Sprunger, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States; Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, Louisiana 70806, United States.

Document Type

Article

Publication Date

10-14-2021

Abstract

Environmentally persistent free radicals (EPFRs) are a class of toxic air pollutants that are found to form by the chemisorption of substituted aromatic molecules on the surface of metal oxides. In this study, we employ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) to perform a temperature-dependent study of phenol adsorption on -FeO(0001) to probe the radical formation mechanism by monitoring changes in the electronic structure of both the adsorbed phenol and metal oxide substrate. Upon dosing at room temperature, new phenol-derived electronic states have been clearly observed in the UPS spectrum at saturation coverage. However, upon dosing at high temperature (>200 °C), both photoemission techniques have shown distinctive features that strongly suggest electron transfer from adsorbed phenol to FeO surface atoms and consequent formation of a surface radical. Consistent with the experiment, DFT calculations show that phenoxyl adsorption on the iron oxide surface at RT leads to a minor charge transfer to the adsorbed molecule. The experimental findings at high temperatures agree well with the EPFRs' proposed formation mechanism and can guide future experimental and computational studies.

Publication Source (Journal or Book title)

The journal of physical chemistry. C, Nanomaterials and interfaces

First Page

21882

Last Page

21890

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