Role of oxygen and superoxide radicals in promoting H2O2 production during VUV/UV radiation of water

Du, Jinying; Wang, Chuang; Zhao, Zhiwei; Cui, Fuyi; Ou, Qin; Liu, Jie

doi:10.1016/j.ces.2021.116683

Cited by 22 publications

(5 citation statements)

References 48 publications

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“…The OH• species with high oxidation potential adsorbed on the photoanode surface would influence the Fermi level. The generated OH• can induce a series of chain reactions [44,45], forming a stable peroxide complex that prevents the transport of holes, leading to a performance drop. The formation of OH• and the OER should be competing reactions [46][47][48][49], and the addition of Co 2+ ions into the solution can remove OH• (Fig.…”

Section: Tracking Oh• Radicals By Epr During Water Oxidationmentioning

confidence: 99%

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Shi

Cui

2022

Sci. China Mater.

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Photoelectrochemical (PEC) water splitting in acid is promising, but its development has been hindered by the lack of stable photoanodes and effective nonprecious cocatalysts. WO 3 is one of the few acid-stable semiconductors, but its fast performance decay under illumination remains elusive and unsolved. Herein, we present that the fast photocurrent decreases of both WO 3 and WO 3 /SnO 2 photoanodes were caused by the hydroxyl radicals (OH•) generated at the electrode/electrolyte interfaces, and we solved this issue by introducing cobalt (Co 2+ ) ions into the electrolyte at pH 0.3, allowing for the efficient oxidation of H 2 O to O 2 rather than to detrimental OH• radicals, with the Faradaic efficiency toward oxygen evolution increasing from 40% to 95% and the photocurrent density increasing from 0.6 to 0.8 mA cm −2 and being stable for 25 h at 1.2 V (reversible hydrogen electrode). Importantly, the scavenging of OH• radicals by vitamin C demonstrated the same photocurrent stability as the introduction of Co 2+ ions, further implying the crucial inhibiting role of Co 2+ ions. In-situ ultraviolet-visible and Raman spectroscopy indicated the trapping of surface holes by the oxidation of Co 2+ to Co 3+ , and electron paramagnetic resonance revealed the role of Co 2+ ions in the inhibition of OH• radicals. This study provides an ideal model for combining a homogeneous redox-active Co 2+ /Co 3+ couple with a photoanode for water oxidation in strong acid.

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Section: Tracking Oh• Radicals By Epr During Water Oxidationmentioning

confidence: 99%

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Shi

Cui

2022

Sci. China Mater.

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“…However, none of the studies have looked at the generation and potential degradation of PFAS related to ozone produced during VUV process. Furthermore, it has been previously demonstrated that the generation of H 2 O 2 is enhanced during UV/VUV process in the presence of oxygen but was negatively impacted under alkaline conditions and in the presence of anions [25]. The addition of chemicals could therefore be avoided during VUV process due to in-situ generation H 2 O 2 [26,27].…”

Section: Introductionmentioning

confidence: 99%

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Umar

2021

Water

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Perfluoroalkyl and polyfluoroalkyl substances (PFASs) consist of a group of environmentally persistent, toxic and bio-accumulative organic compounds of industrial origin that are widely present in water and wastewater. Despite restricted use due to current regulations on their use, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) remain the most commonly detected long-chain PFAS. This article reviews UV-based oxidative and reductive studies for the degradation of PFAS. Most of the UV-based processes studied at lab-scale include low pressure mercury lamps (emitting at 254 and 185 nm) with some studies using medium pressure mercury lamps (200–400 nm). A critical evaluation of the findings is made considering the degradation of PFAS, the impact of water quality conditions (pH, background ions, organics), types of oxidizing/reducing species, and source of irradiation with emphasis given to mechanisms of degradation and reaction by-products. Research gaps related to understanding of the factors influencing oxidative and reductive defluorination, impact of co-existing ions from the perspective of complexation with PFAS, and post-treatment toxicity are highlighted. The review also provides an overview of future perspectives regarding the challenges in relation to the current knowledge gaps, and future needs.

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“…It has been reported that •OH can be generated in the presence of DOM mainly through two pathways: − (1) DOM compounds containing hydroxy groups and carboxyl groups (e.g., −OH, −COOH, −CO, etc.) may be stimulated to a triplet state such as quinoid enol tautomer under irradiation, which subsequently oxidized the water by abstracting the H atom and formed •OH; (2) the oxygen accepted electrons from DOM to form superoxide radicals (•O 2 – ), which further combined with proton (H + ) to form •HO 2 – and H 2 O 2 , decomposing ultimately into •OH . However, the signal of •O 2 – of all DOM samples in EPR was hard to be observed (Figure S10).…”

Section: Resultsmentioning

confidence: 99%

Hydrophilic Fraction of Dissolved Organic Matter Largely Facilitated Microplastics Photoaging: Insights from Redox Properties and Reactive Oxygen Species

Ma,

He,

Han

et al. 2024

Environ. Sci. Technol.

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Dissolved organic matter (DOM) exists widely in natural water, which inevitably influences microplastic (MP) photoaging. Nevertheless, the impacts of DOM fractions with diverse molecular structures on MP photoaging remain to be elucidated. This study explored the photoaging mechanisms of polylactic acid (PLA)-MPs and polystyrene (PS)-MPs in the presence of DOM and its subfractions (hydrophobic acid (HPOA), hydrophobic neutral (HPON), and hydrophilic (HPI)). Across DOM fractions, HPI exhibited the highest electron accepting capacity (23 μmol e − (mg C) −1 ) due to its abundant tannin-like species (36.8%) with carboxylic groups, which facilitated more reactive oxygen species generation (particularly hydroxyl radical), leading to the strongest photoaging rate of two MPs by HPI. However, the sequences of bond cleavage during photoaging of each MPs were not clearly shifted as revealed by two-dimensional infrared correlation spectra. Inconspicuous effects on the extent of PS-and PLA-MPs photoaging were observed for HPOA and HPON, respectively. This was mainly ascribed to the occurrence of inhibitory mechanisms (e.g., light-shielding and quenching effect) counteracting the reactive oxygen speciespromoting effects. The findings identified the HPI fraction of DOM for promoting PS-and PLA-MPs photoaging rate and first constructed a link among DOM molecular structures, redox properties, and effects on MP photoaging.

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Role of oxygen and superoxide radicals in promoting H2O2 production during VUV/UV radiation of water

Cited by 22 publications

References 48 publications

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Improving WO3/SnO2 photoanode stability by inhibiting hydroxyl radicals with cobalt ions in strong acid

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Hydrophilic Fraction of Dissolved Organic Matter Largely Facilitated Microplastics Photoaging: Insights from Redox Properties and Reactive Oxygen Species

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