Nonradical oxidation in persulfate activation by graphene-like nanosheets (GNS): Differentiating the contributions of singlet oxygen (1O2) and sorption-dependent electron transfer

Zhu, Shishu; Jin, Chao; Duan, Xiaoguang; Wang, Shaobin; Ho, Shih‐Hsin

doi:10.1016/j.cej.2020.124725

Cited by 100 publications

(26 citation statements)

References 61 publications

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“…34,60 The results in this study (Figures S4c, 1b, and S11) suggested typical nonradical oxidation in an NHCS/PMS system, depending on the electron transfer on the surface of NHCS. 13,31,54 Crucial metastable intermediates on N-doped CMs, such as outer-sphere complexes with PMS, have been regarded as redox sites of triggering this electron transfer. 27,32,53,54,61,62 However, it is difficult to explain the observed phenomenon when only using the nonradical mechanism reported in the previous studies.…”

Section: •−mentioning

confidence: 99%

“…Peroxymonosulfate (PMS) is a promising oxidizer for advanced oxidation processes (AOPs) due to its low cost, high reactivity, and good stability during transportation . By activating PMS, sulfate and hydroxyl radicals (SO 4 •– 2.5–3.1 V vs • OH 2.7 V) are largely produced and serve as highly reactive oxygen species (ROS) for contaminant degradation (e.g., phenolics and anilines). , Benchmark carbonaceous materials (CMs), such as graphene oxide (GO), carbon nanotubes (CNTs), or nanodiamond (ND), exhibit considerable ability to activate PMS due to their porosity, defective edges, and distorted π-delocalized electrons. − Moreover, natural or artificial pyrogenic CMs can activate PMS by their inherent redox sites (e.g., persistent free radicals, PFRs) and graphene nanosheets. , When appropriate heterocyclic N dopants were involved, the reactivity of CMs toward PMS activation could be further promoted. ,− Beneficial from the specific electron configuration, the N dopants in CMs enhanced the interactions with PMS or ability of electron transfer within a π-delocalized system. ,,− Thus, the N-doped CMs possess high potential for practical application and have attracted much attention from researchers. However, the mechanisms of PMS activation on N-doped CMs are still controversial, owing to the concurrence of radical and nonradical pathways .…”

Section: Introductionmentioning

confidence: 99%

“…4−11 Moreover, natural or artificial pyrogenic CMs can activate PMS by their inherent redox sites (e.g., persistent free radicals, PFRs) and graphene nanosheets. 12,13 When appropriate heterocyclic N dopants were involved, the reactivity of CMs toward PMS activation could be further promoted. 11,14−23 Beneficial from the specific electron configuration, the N dopants in CMs enhanced the interactions with PMS or ability of electron transfer within a πdelocalized system.…”

Section: ■ Introductionmentioning

confidence: 99%

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Identifying the Persistent Free Radicals (PFRs) Formed as Crucial Metastable Intermediates during Peroxymonosulfate (PMS) Activation by N-Doped Carbonaceous Materials

Zhen

Zhu

Sun

et al. 2021

Environ. Sci. Technol.

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A nonradical mechanism involved in peroxymonosulfate (PMS) activation in carbonaceous materials (CMs) is still controversial. In this study, we prepared N-doped CMs, including hollow carbon spheres (NHCSs) and carbon nanotubes (N-CNTs), to probe the crucial intermediates during PMS activation. The results suggested that the higher efficiency and lower activation energy (13.72 kJ mol–1) toward phenol (PN) degradation in an NHCS/PMS system than PMS alone (∼24.07 kJ mol–1) depended on a typical nonradical reaction. Persistent free radicals (PFRs) with a g factor of 2.0033–2.0045, formed as crucial metastable intermediates on NHCS or N-CNT in the presence of PMS, contribute largely to the organic degradation (∼73.4%). Solid evidence suggested that the formation of PFRs relied on the attack of surface-bonded •OH and SO4 •– or peroxides in PMS, among which surface-bonded SO4 •– was most thermodynamically favorable based on theoretical calculations. Electron holes within PFRs on NHCSs shifted the Fermi level to the positive energy with the valance band increasing from 1.18 to 1.98 eV, promoting the reactivity toward nucleophilic substances. The degradation intermediates of aromatic compounds (e.g., PN) and electron rearrangement triggered the evolution of PFRs from oxygen-centered to carbon-centered radicals. Moreover, due to the specific electron configuration, graphitic N on NHCS was critical for stabilizing the PFRs. This study provides insightful understanding of the fate of organic contaminants and the structure–activity relationship of reactivity of CMs toward PMS activation.

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Section: •−mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Identifying the Persistent Free Radicals (PFRs) Formed as Crucial Metastable Intermediates during Peroxymonosulfate (PMS) Activation by N-Doped Carbonaceous Materials

Zhen

Zhu

Sun

et al. 2021

Environ. Sci. Technol.

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“…Similarly, graphene-based materials are also capable of activating PDS for catalytic oxidation, whereas most of the systems are based on nonradical reactions. For instance, singlet oxygen was discovered in the PDS/rGO systems, generated at the ketonic groups and edging defects [87,88]. Over the intact graphitic carbon network, the electron-transfer regime typically dominates the oxidation, where PDS is activated and confined on the highly-conjugated basal plane of carbocatalysts as a metastable intermediate [89,90].…”

Section: Advanced Oxidation Processesmentioning

confidence: 99%

Sustainable Catalytic Processes Driven by Graphene-Based Materials

2020

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In the recent two decades, graphene-based materials have achieved great successes in catalytic processes towards sustainable production of chemicals, fuels and protection of the environment. In graphene, the carbon atoms are packed into a well-defined sp2-hybridized honeycomb lattice, and can be further constructed into other dimensional allotropes such as fullerene, carbon nanotubes, and aerogels. Graphene-based materials possess appealing optical, thermal, and electronic properties, and the graphitic structure is resistant to extreme conditions. Therefore, the green nature and robust framework make the graphene-based materials highly favourable for chemical reactions. More importantly, the open structure of graphene affords a platform to host a diversity of functional groups, dopants, and structural defects, which have been demonstrated to play crucial roles in catalytic processes. In this perspective, we introduced the potential active sites of graphene in green catalysis and showcased the marriage of metal-free carbon materials in chemical synthesis, catalytic oxidation, and environmental remediation. Future research directions are also highlighted in mechanistic investigation and applications of graphene-based materials in other promising catalytic systems.

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“…Generally, nitrogen-modified carbon materials can be divided into two kinds: N-doped materials (graphitic, pyridinic, and pyrrolic N) and N-functionalized materials (oxynitride and aminated groups) . Most of the reported studies have focused on N-doped or aminated carbons because oxynitride groups (-NO x ) in passivated carbocatalysts are inert for peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation. , For instance, Wang et al − and Peng et al − have designed and synthesized many nitrogen-modified carbon materials as highly efficient catalysts for organic pollutant degradation with PMS/PDS as oxidants.…”

Section: Introductionmentioning

confidence: 99%

Protective Strategy to Boost the Stability of Aminated Graphene in Fenton-like Reactions

Dai

et al. 2021

Environ. Sci. Technol.

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Improving the stability of aminated metal-free catalysts is a big challenge in Fenton-like reactions. Herein, trinuclear iron cluster (Fe3 cluster)-protected aminated graphene (Fe3-NH2-GR) is designed by a protective strategy. By protecting with the Fe3 cluster, the lone pair electrons of amino groups are protected and the N content of Fe3-NH2-GR can be fixed steadily. In peroxymonosulfate (PMS)-based Fenton-like reactions with a fixed-bed reactor, the lifetime of Fe3-NH2-GR is two times longer than that of aminated graphene (NH2-GR) under the same conditions. The deactivation kinetics shows that both Fe3-NH2-GR and NH2-GR follow zero-order kinetics and the deactivation rate constants of Fe3-NH2-GR are lower than that of NH2-GR at every period. Moreover, Fe3-NH2-GR still maintains 50% phenol degradation after 40 h rather than being constantly deactivated as NH2-GR. This stable activity is attributed to the formation of -O-NO2, while the N content will be lost in NH2-GR. This protective strategy by the Fe3 cluster provides a reliable method to enhance the efficiency and stability of carbon catalysts in Fenton-like reactions.

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Nonradical oxidation in persulfate activation by graphene-like nanosheets (GNS): Differentiating the contributions of singlet oxygen (1O2) and sorption-dependent electron transfer

Cited by 100 publications

References 61 publications

Identifying the Persistent Free Radicals (PFRs) Formed as Crucial Metastable Intermediates during Peroxymonosulfate (PMS) Activation by N-Doped Carbonaceous Materials

Identifying the Persistent Free Radicals (PFRs) Formed as Crucial Metastable Intermediates during Peroxymonosulfate (PMS) Activation by N-Doped Carbonaceous Materials

Sustainable Catalytic Processes Driven by Graphene-Based Materials

Protective Strategy to Boost the Stability of Aminated Graphene in Fenton-like Reactions

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