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HERO ID
3981307
Reference Type
Journal Article
Title
Fluorination of Boron-Doped Diamond Film Electrodes for Minimization of Perchlorate Formation
Author(s)
Gayen, P; Chaplin, BP
Year
2017
Is Peer Reviewed?
1
Journal
ACS Applied Materials & Interfaces
ISSN:
1944-8244
EISSN:
1944-8252
Volume
9
Issue
33
Page Numbers
27638-27648
Language
English
PMID
28749130
DOI
10.1021/acsami.7b06028
Web of Science Id
WOS:000408518800033
Abstract
This research investigated the effects of surface fluorination on both rates of organic compound oxidation (phenol and terephthalic acid (TA)) and ClO4(-) formation at boron-doped diamond (BDD) film anodes at 22 °C. Different fluorination methods (i.e., electrochemical oxidation with perfluorooctanoic acid (PFOA), radio frequency plasma, and silanization) were used to incorporate fluorinated moieties on the BDD surface, which was confirmed by X-ray photoelectron spectroscopy (XPS). The silanization method was found to be the most effective fluorination method using a 1H,1H,2H,2H-perfluorodecyltrichlorosilane precursor to form a self-assembled monolayer (SAM) on the oxygenated BDD surface. The ClO4(-) formation decreased from rates of 0.45 ± 0.03 mmol m(-2) min(-1) during 1 mM NaClO3 oxidation and 0.28 ± 0.01 mmol m(-2) min(-1) during 10 mM NaCl oxidation on the BDD electrode to below detectable levels (<0.12 μmoles m(-2) min(-1)) for the BDD electrode functionalized by a 1H,1H,2H,2H-perfluorodecyltrichlorosilane SAM. These decreases in rates corresponded to 99.94 and 99.85% decreases in selectivity for ClO4(-) formation during the electrolysis of 10 mM NaCl and 1 mM NaClO3 electrolytes, respectively. By contrast, the oxidation rates of phenol were reduced by only 16.3% in the NaCl electrolyte and 61% in a nonreactive 0.1 M KH2PO4 electrolyte. Cyclic voltammetry with Fe(CN)6(3-/4-) and Fe(3+/2+) redox couples indicated that the long fluorinated chains created a blocking layer on the BDD surface that inhibited charge transfer via steric hindrance and hydrophobic effects. The surface coverages and thicknesses of the fluorinated films controlled the charge transfer rates, which was confirmed by estimates of film thicknesses using XPS and density functional theory simulations. The aliphatic silanized electrode also showed very high stability during OH(•) production. Perchlorate formation rates were below the detection limit (<0.12 μmoles m(-2) min(-1)) for up to 10 consecutive NaClO3 oxidation experiments.
Keywords
electrochemical oxidation; boron-doped diamond; perchlorate; blocking film; fluorination
Tags
PFAS
•
Additional PFAS (formerly XAgency)
•
^Per- and Polyfluoroalkyl Substances (PFAS)
PFOA (335-67-1) and PFOS (1763-23-1)
Literature Search – Adverse outcome pathway (2015-present)
Pubmed
•
PFAS 150
Literature Search August 2019
PubMed
Not prioritized for screening
Ammonium perfluorooctanoate
Perfluorooctanoic acid
•
PFNA
Litsearch Update 2017-2018
Pubmed
Literature Search
Pubmed
•
PFOA (335-67-1) and PFOS (1763-23-1)
Literature Search – Adverse outcome pathway (2015-present)
Pubmed
Screening Results
Excluded/Not on Topic
Literature Search Update (2013-2019)
PubMed
WOS
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