Investigation of perfluoroperoxy radicals self-coupling reactions by kinetic EPR spectroscopy

Buttafava, A.; Guarda, Pier Antonio; Marchionni, G.; Ronconi, R.; Faucitano, A.

doi:10.1016/s0022-1139(01)00541-3

Cited by 7 publications

(5 citation statements)

References 27 publications

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“…A number of previous studies attributed enhanced PFCA degradation putatively associated with OH to radical combination with the perfluoroalkyl radical intermediate (pathway C, Figure 3) (Wang et al, 2019;Wu et al, 2019). However, it is generally accepted-primarily based on the reactivity of hydrocarbon analogues and known perfluoroalkane reactivity (Dolbier, 1997;Chawla and Fessenden, 1975;Conway and Dzieciuch, 1963;Wallington et al, 1993;Paul et al, 1978; Barr et al, 1956;Buttafava et al, 2002)-that PFCA oxidation occurs at the carboxylic acid/carboxylate headgroup, which initiates a series of reactions occurring through unstable intermediates eventually leading to a shorter-chain length PFCA. These intermediates have been computationally investigated (Zhang et al, 2019;Niu et al, 2013) but are not directly observed in PFCA degradation studies.…”

Section: The Reactivity Of Hydroxyl Radical With Pfca Transformation ...mentioning

confidence: 99%

Aqueous PFCA Destruction by Hydroxyl Radical at Low pH: A Putative H-atom Abstraction Mechanism

Carre-Burritt

Amador

Vyas

2022

Preprint

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Hydroxyl radical is a potent oxidant invoked in numerous advanced oxidation processes as a species responsible for destroying recalcitrant organic contaminants. However, there has been little direct evidence for the reaction between hydroxyl radical and perfluoroalkyl carboxylic acids in the aqueous phase. Nevertheless, we discovered that at low pH, perfluoroalkyl carboxylic acids are degraded by hydroxyl radical. When perfluorobutanoic acid was treated with H2O2 under steady-state 254 nm irradiation in 1 M HClO4, it was transformed to shorter-chain perfluoroalkyl carboxylic acid homologues and F–/HF. Empirical and computational mechanistic studies suggested an H-atom abstraction mechanism. Namely, more perfluorobutanoic acid was removed as the pH was decreased, which corresponds to a larger fraction of protonated perfluorobutanoic acid vs. conjugate base. Meanwhile, density functional theory calculations indicated that single electron transfer oxidation of protonated perfluoroalkyl carboxylic acids has a much larger free energy of activation relative to single electron transfer oxidation of the conjugate base anion, suggesting that single electron transfer is unfavorable at low pH. This is the first clear description of aqueous perfluoroalkyl carboxylic acid destruction by hydroxyl radical under simple reaction conditions.

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Section: The Reactivity Of Hydroxyl Radical With Pfca Transformation ...mentioning

confidence: 99%

Aqueous PFCA Destruction by Hydroxyl Radical at Low pH: A Putative H-atom Abstraction Mechanism

Carre-Burritt

Amador

Vyas

2022

Preprint

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“…For example, the degradation of hydrocarbon fuel cell membrane containing aromatic rings can be initiated by OH radicals and propagated by O 2 molecules. 17 The investigation of perfluoroperoxy radical reaction by kinetic electron paramagnetic resonance spectroscopy shows the existence of the following reactions under low temperature 18 Rf − CF…”

Section: B1221mentioning

confidence: 99%

XPS Analysis of Polymer Membrane Degradation in PEMFCs

Chen¹,

Fuller

2009

J. Electrochem. Soc.

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An important challenge for proton exchange membrane fuel cells (PEMFCs) is the stability and durability of the membrane separator. In this study, fluoride ion emission rates were determined from fuel cell durability tests at different temperatures. Degraded membranes were removed after each test, and both the anode and cathode sides of degraded membranes were analyzed by X-ray photoelectron spectroscopy (XPS). The results show that degradation was accelerated by high temperature and that the decomposition of both sulfonic acid side chains and the poly(tetrafluoroethylene) backbone occurred. The degradation was more severe on the anode side, showing that at least half of the side groups were decomposed there. A multilayer membrane electrode assembly was also used to study degradation at different locations especially in the bulk membrane, which illustrates that the degradation also occurs there but is slower than that at the anode side. This result also indicates that the rate of membrane degradation slows with thicker membrane. Finally, an improved kinetic model of membrane degradation was proposed to explain the experimental results.

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“…In these conditions, the peroxidic links of (I), here indicated as RCF 2 -O-OCF 2 R where R is a PFPE moiety, homolitically decompose and generate two alkoxy radicals [10][11][12][13]:…”

Section: Synthesis Of Pfpe-ttd Block Copolymersmentioning

confidence: 99%

Novel perfluoropolyethers containing 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole blocks: synthesis and characterization

Avataneo

Navarrini

Patto

et al. 2009

Journal of Fluorine Chemistry

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Investigation of perfluoroperoxy radicals self-coupling reactions by kinetic EPR spectroscopy

Cited by 7 publications

References 27 publications

Aqueous PFCA Destruction by Hydroxyl Radical at Low pH: A Putative H-atom Abstraction Mechanism

Aqueous PFCA Destruction by Hydroxyl Radical at Low pH: A Putative H-atom Abstraction Mechanism

XPS Analysis of Polymer Membrane Degradation in PEMFCs

Novel perfluoropolyethers containing 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole blocks: synthesis and characterization

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