Braxton, Emily, Fox, David J., Breeze, Ben, Tully, Joshua J., Levey, Katherine J., Newton, Mark E. and Macpherson, Julie V. (2022) Data for Electron paramagnetic resonance for the detection of electrochemically generated hydroxyl radicals : issues associated with electrochemical oxidation of the spin trap. [Dataset]

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Abstract

For the detection of electrochemically produced hydroxyl radicals (HO·) from the oxidation of water on a boron-doped diamond (BDD) electrode, electron paramagnetic resonance spectroscopy (EPR) in combination with spin trap labels is a popular technique. Here, we show that quantification of the concentration of HO· from water oxidation via spin trap electrochemical (EC)-EPR is problematic. This is primarily due to the spin trap oxidizing at potentials less positive than water, resulting in the same spin trap-OH· adduct as formed from the solution reaction of OH· with the spin trap. We illustrate this through consideration of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap for OH·. DMPO oxidation on a BDD electrode in an acidic aqueous solution occurs at a peak current potential of +1.90 V vs SCE; the current for water oxidation starts to rise rapidly at ca. +2.3 V vs SCE. EC-EPR spectra show signatures due to the spin trap adduct (DMPO-OH·) at potentials lower than that predicted thermodynamically (for water/HO·) and in the region for DMPO oxidation. Increasing the potential into the water oxidation region, surprisingly, shows a lower DMPO-OH· concentration than when the potential is in the DMPO oxidation region. This behavior is attributed to further oxidation of DMPO-OH·, production of fouling products on the electrode surface, and bubble formation. Radical scavengers (ethanol) and other spin traps, here N-tert-butyl-α-phenylnitrone, α-(4-pyridyl N-oxide)-N-tert-butylnitrone, and 2-methyl-2-nitrosopropane dimer, also show electrochemical oxidation signals less positive than that of water on a BDD electrode. Such behavior also complicates their use for the intended application.

Item Type:	Dataset
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Library of Congress Subject Headings (LCSH):	Electron paramagnetic resonance, Electrochemistry, Hydroxyl group
Publisher:	University of Warwick, Department of Chemistry
Official Date:	7 October 2022
Dates:	Date Event 7 October 2022 Published 3 October 2022 Available 3 October 2022 Created
Status:	Not Peer Reviewed
Publication Status:	Published
Media of Output (format):	.txt, .opd
Access rights to Published version:	Open Access (Creative Commons)
Copyright Holders:	University of Warwick
Description:	he file has been divided into two sections: 1 - Main Article Data Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6 2 - Supporting Information Data Figure S1, Figure S2, Figure S3, Figure S4, Figure S5, Figure S6, Figure S8 and Figure S9
Date of first compliant deposit:	3 October 2022
Date of first compliant Open Access:	7 October 2022
RIOXX Funder/Project Grant:	Project/Grant ID RIOXX Funder Name Funder ID EP/L015307/1 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266 EP/V056778/1 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266 INF/PHD/180016 Royal Society http://dx.doi.org/10.13039/501100000288 EP/L015315/1 Centre for Doctoral Training in Diamond Science and Technology UNSPECIFIED EP/L015315/1 [EPSRC] Engineering and Physical Sciences Research Council http://dx.doi.org/10.13039/501100000266
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