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• rGO exhibits excellent performance for enhancing PM oxidation. • Oxygen containing groups can provide electrons for activating PM. • Structural defects can mediate electron transfer between organics and PM. • Changeover between electron donor and mediator can be controlled by regulating active sites. Reports that the exploitation of metal-free carbon materials to enhance permanganate (PM) oxidation to abate organic pollution in water have emerged in recent publications. However, the activation mechanism and active sites involved are ambiguous because of the intricate physicochemical properties of carbon. In this study, reduced graphene oxide (rGO) as a typical carbon material exhibits excellent capability to boost permanganate oxidation for removing a wide array of organic contaminants. The simultaneous two reaction pathways in the rGO/PM system were justified: i) rGO donates to electrons to decompose PM and produce highly reactive intermediate Mn species for oxidizing organic contaminants; ii) rGO mediates electron transfer from organics to PM. Oxygen-containing groups (hydroxyl, carboxyl, and carbonyl) were justified as electron-donating groups, while structural defects (vacancy and edge defects) were shown to be critical for rGO-mediated electron transfer. Therefore, the oxidation pathway of the rGO/PM system can be controlled by regulating oxygen functional groups and structural defects. The changeover from electron donor to electron mediator by decorating surface active sites of carbon materials will be of great help to the design and application of carbocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Scandium oxide functionalized carbon nitride (5-ScO-CN) is successfully prepared. • A new approach to boost PMS based oxidation is proposed. • 5-ScO-CN mediate the photoexcited electron transfer between PMS and organic contaminants. • Sc 2 O 3 causes fast oxidation of organic contaminants and activation of PMS to produce radicals. • 5-ScO-CN exhibits high stability for multiple usage and the potential of practical application. Generation of reactive radicals via photocatalytic peroxymonosulfate (PMS) is restricted by the sluggish kinetics of PMS decomposition and lack of electron transfer channel. Herein, we firstly prepared rare earth oxide functionalized carbon nitride (5-ScO-CN) by simple in-situ one-step calcination method, and surprisingly found it mediated photoexcited electron transfer between PMS and organic contaminants to boost PMS based oxidation decontamination. Rare earth oxide proceeds as active sites to mediate electron transfer from organic contaminants and PMS under visible light irradiation, it concurrently elevates fast oxidation of organic contaminant and activation of PMS to produce reactive radicals to further oxidize organic contaminants. We conducted density functional theory (DFT) calculation and galvanic oxidation process (GOP) to further unveil the role of 5-ScO-CN for mediating photoexcited electron transfer and generation of reactive radicals. This work proposes a novel mechanism for visible light boosted PMS based oxidation and provides a novel strategy for application of photocatalytic oxidation in environmental remediation field. [ABSTRACT FROM AUTHOR]

• cMnO 2 can significantly promote Fe(VI) to oxidize various micropollutants. • High-valent Fe species were the primary active oxidants in the cMnO 2 −Fe(VI) system. • A novel surface-promoted mechanism was fully verified in the cMnO 2 −Fe(VI) system. • cMnO 2 showed outstanding catalytic stability in actual water. Current research focuses on introducing additional energy or reducing agents to directly accelerate the formation of Fe(IV) and Fe(V) from ferrate (Fe(VI)), thereby ameliorating the oxidation activity of Fe(VI). Interestingly, this study discovers that colloid manganese dioxide (cMnO 2) can remarkably promote Fe(VI) to remove various contaminants via a novel surface-promoted pathway. Many lines of evidence suggest that high-valent Fe species are the primary active oxidants in the cMnO 2 −Fe(VI) system, however, the underlying activation mechanism for the direct reduction of Fe(VI) by cMnO 2 to generate Fe(IV)/Fe(V) is eliminated. Further analysis found that Fe(VI) can combine with the vacancies in cMnO 2 to form precursor complex (cMnO 2 −Fe(VI)*), which possesses a higher oxidation potential than Fe(VI). This makes cMnO 2 −Fe(VI)* is more vigorous to oxidize pollutants with electron-rich moieties through the electron transfer step than alone Fe(VI), resulting in producing Fe(V) and Fe(IV). The products of Fe(VI) decay (i.e., Fe(II), Fe(III), and H 2 O 2) are revealed to play vital roles in further boosting the formation of Fe(IV) and Fe(V). Most importantly, the catalytic stability of cMnO 2 in complicated waters is superior to popular reductants, suggesting its outstanding application potential. Taken together, this work provides a full-scale insight into the surface-promoted mechanism in Fe(VI) oxidation process, thus providing an efficient and green strategy for Fe(VI) activation. [Display omitted] [ABSTRACT FROM AUTHOR]

Fenton oxidation technology is a widely-used advanced oxidation technology. However, the generation of hydroxyl radicals is restrained by the sluggish recovery of Fe(II), thus affecting its long-lasting performance for water decontamination. Here, a novel niobium carbide (Nb 2 C) MXene material was applied as a green co-catalyst. Nb 2 C MXene can significantly promote Fenton reactions to produce hydroxyl radicals for degrading dimethyl phthalate (DMP) with high efficiency and high stability for long-term operation, which outperforms than various reported co-catalysts. Meanwhile, the Nb 2 C/Fe(III)/H 2 O 2 system is capable of non-selectively degrading a wide spectrum of refractory pollutants. Mechanism investigation reveals that Nb 2 C MXene as an electron donor can straight reduce Fe(III), meanwhile mediate electron shuttle from Fe(II) to H 2 O 2 to strongly expedite the generation of hydroxyl radicals. In addition, four main degradation routes of DMP were proposed. Therefore, this study offers an updated and valid strategy for the refractory organic pollutants elimination by coupling Nb 2 C MXene and Fenton oxidation. [Display omitted] • Nb 2 C MXene outperformed than a variety of co-catalysts of enhanced Fenton system. • The Nb 2 C/Fe(III)/H 2 O 2 can non-selectively degrade a wide spectrum of organic contaminants. • Nb 2 C MXene can provide electrons for direct Fe(III) reduction by cleaving Nb-C bonds. • Nb 2 C MXene can mediate electron transfer between Fe(II) and H 2 O 2 to promote Fenton reaction. [ABSTRACT FROM AUTHOR]

In this study, the effects of ferric ion (Fe3+) on the degradation of atrazine (ATZ) in Bi 2 MoO 6 /peroxymonosulfate (PMS) system under visible light irradiation was investigated. With the addition of Fe3+, ATZ in the visible light/Bi 2 MoO 6 /PMS system degraded rapidly after 20 min treatment (removal rate > 99%). The enhancement of ATZ removal can be attributed to the role of Fe3+. As an electron transfer mediator, Fe3+ not only inhibits the recombination of photo-charges and prolongs the life of photogenerated carriers, but also promotes the activation of PMS by accelerating the electron transfer from Bi 2 MoO 6 to PMS. The generation of •OH and SO 4 •− in the system was determined via electron paramagnetic resonance (EPR) technology and quenching experiments. Furthermore, the characterization of Bi 2 MoO 6 before and after reaction, influence of the reaction parameters (i.e., catalyst and PMS dosages, Fe3+ and ATZ concentration, initial pH), influence of inorganic anions and humic acid, and the recyclability of catalyst in the vis/Bi 2 MoO 6 /PMS/Fe3+ system was also investigated. Additionally, the existence of Fe3+ also exhibits a wide selectivity for the degradation of different pollutants and high treatment efficiency. In general, the vis/Bi 2 MoO 6 /PMS/Fe3+ system demonstrated the potential as an efficient, economical, and environment-friendly water treatment process. [Display omitted] • Fe3+addition not only inhibits the recombination of the photo-charges, but also promotes PMS activation. • Fe3+ can activate PMS and capture photo-electron to enhance the photo-synergy for ATZ degradation. • •OH and SO 4 •− were the dominant species in the degradation of atrazine. • Bi 2 MoO 6 nanosheet showed excellent reusability and wide degradation selectivity in vis/Bi 2 MoO 6 /PMS/Fe3+ system. [ABSTRACT FROM AUTHOR]

Periodate (PI) has recently been studied as an excellent oxidant in advanced oxidation processes, and its reported mechanism is mainly the formation of reactive oxygen species (ROS). This work presents an efficient approach using N-doped iron-based porous carbon (Fe@N-C) to activate periodate for the degradation of sulfisoxazole (SIZ). Characterization results indicated the catalyst has high catalytic activity, stable structure, and high electron transfer activity. In terms of degradation mechanism, it is pointed out that the non-radical pathway is the dominant mechanism. In order to prove this mechanism, we have carried out scavenging experiments, electron paramagnetic resonance (EPR) analysis, salt bridge experiments and electrochemical experiments, which demonstrate the occurrence of mediated electron transfer mechanism. Fe@N-C could mediate the electron transfer from organic contaminant molecules to PI, thus improving the efficiency of PI utilization, rather than simply inducing the activation of PI through Fe@N-C. The overall results of this study provided a new understanding into the application of Fe@N-C activated PI in wastewater treatment. [Display omitted] • The activation of PI was successfully promoted with Fe@N-C. • The reaction mechanism of Fe@N-C/PI system is electron transfer mechanism. • The degradation pathway of pollutants in Fe@N-C/PI system was proposed. • No iodate and other harmful byproducts were produced during the reaction. [ABSTRACT FROM AUTHOR]

The low cost and high performance via a simple way of fabrication are considerable challenges for Si-based anode in the application of lithium-ion batteries. In this study, we synthesize a novel free-standing Si/C anode, consisting of yolk (Si)-shell (amorphous carbon) nanoparticles and carbon nanofibers (denoted as Si@void@C/CNFs), via a facile route of template removal and electrospun. The designed yolk-shell structure help buffer the volume expansion of silicon during the discharge/charge cycles, and the intertwined CNFs are conducive to electron fast transmission and guarantee structural integrity. As expected, with a low Si content (∼23 wt%), the self-supporting electrode of Si@void@C/CNFs exhibits a high specific capacity of ∼627.5 mAh g−1 as well as 69.3% capacity retention at 0.1 A g−1 after 100 cycles, better than Si@C/CNFs (20%) and Si/CNFs (9.5%) electrodes. The superior performance of Si@void@C/CNFs indicates that it is an attractive anode material for the practical application of Lithium-ion batteries. [Display omitted] • A facile strategy is designed to prepare free-standing Si@void@C/CNFs composite. • This structure consists of the yolk-shell structure and a 3D conducting network. • The structure can buffer the volume expansion of Si and accelerate electron transfer. • The composite demonstrates ideal cycle stability as lithium-ion batteries anode. [ABSTRACT FROM AUTHOR]

Herein, an electrochemical (EC) system was applied as "co-catalyst" to enhance the activation of peroxymonosulfate (EC/Fe(III)/PMS) for efficient Sulfamethoxazole (SMX) degradation. The cathodic reduction reaction can facilitate electron transfer to Fe(III) and trigger the sustainable Fe(III)/Fe(II) redox cycle. Unexpectedly, in addition to hydroxyl radical (•OH) and sulfate radical (SO 4 •−), non-radicals mechanism including singlet oxygen (1O 2) and Fe(IV) were also found involved in EC/Fe(III)/PMS system. The degradation of SMX in EC/Fe(III)/PMS system was accomplished by the collaboration of radicals and non-radicals oxidation. The generation routes and mechanisms of involved reactive oxygen species (ROS) were explored. The relative contributions of •OH, SO 4 •−, and nonradical species for the degradation of SMX were calculated to 4.75 %, 25.31 %, and 69.94 %, respectively. Besides, multiple degradation pathways of SMX were proposed by identifying the formed byproducts. The EC/Fe(III)/PMS process could efficiently degrade SMX under the influence of co-existing ions and inactivate pathogens in the wastewater. [Display omitted] • Electrochemical system was used as a "co-catalyst" to promote the Fe(III)/Fe(II) redox cycle. • SMX is effectively degraded with a weak electrical current consumption in EC/Fe(III)/PMS system. • EC/Fe(III)/PMS system is mainly a non-radical pathway dominated by 1O 2 and Fe(IV). • EC/Fe(III)/PMS system demonstrated the ability to simultaneously eliminate contaminants and pathogens. [ABSTRACT FROM AUTHOR]

In this study, N and O co-doping carbon materials with porous structure (NOPC-x) were applied to activate peroxymonosulfate (PMS) for bisphenol (BPA) degradation and the underlying effects in affecting NOPC-x activity were revealed. Electrochemical characterization, electron paramagnetic resonance (EPR) tests, quenching and PMS adsorption experiments were applied to clarify the mechanism of BPA degradation. It's found that BPA can be completely removed within 20 min (k obs = 0.30 min−1) in the NOPC/PMS system depending on the electron transfer path with the necessity of moderate surfaced unpaired electrons for electrons delivery, which could be regulated by the modifier dosage. However, excessive surfaced unpaired electrons were unfavorable to PMS adsorption, resulting in deterioration of BPA degradation. This study indicates that controlling the amount of surfaced unpaired electrons in an appropriate range is essential to ensure the carbonaceous materials activity in PMS activation to obtain a satisfactory BPA degradation. [Display omitted] ● NOPC exhibited superior activity for BPA degradation by PMS activation. ● Increasing heteroatomic doping enhanced the amount of surfaced unpaired electrons. ● Degradation of BPA was proposed to follow a nonradical electron transfer pathway. ● The role of surfaced unpaired electrons of NOPC in PMS activation was clarified. [ABSTRACT FROM AUTHOR]

• Satisfactory degradation efficiency of pollutants was achieved by FeS/PAA system. • S(-II) and H 2 S (aq) played a significant role in Fe(II) regeneration. • •OH played a dominant role in pharmaceuticals degradation. • The R-O• generated was supposed to be quickly consumed by sulfur specie. • Degradation products of three pharmaceuticals were successfully detoxified. As peracetic acid (PAA) is being increasingly used as an alternative disinfectant, efficient activation of PAA by low-cost and environmentally friendly catalysts over a wide pH range is potentially useful for simultaneous sterilization and pharmaceutical degradation in wastewater, such as hospital wastewater. In this study, peracetic acid (PAA) was successfully activated by low-cost and environmental-friendly FeS (25 mg/L) for efficient oxidative removal of three pharmaceuticals over a wide pH range (3.0∼9.0) as indicated by 80∼100% removal rate within 5 min. As expected, Fe(II) rather than sulfur species was the primary reactive site for PAA activation, while unlike the homogeneous Fe2+/PAA system with organic radicals (R-O·) and ·OH as the dominant reactive oxidized species (ROS), ·OH is the key reactive species in the FeS/PAA system. Interestingly and surprisingly, in-depth investigation revealed the dual role of sulfur species in regulating the reactive oxidized species: (1) S(-II) and its conversion product H 2 S (aq) played a significant role in Fe(II) regeneration with a result of accelerated PAA activation; (2) however, the R-O· generated in the initial seconds of the FeS/PAA process was supposed to be quickly consumed by sulfur species, resulting in ·OH as the dominant ROS over the whole process. The selective reaction of sulfur species with R-O· instead of ·OH was supported by the obviously lower Gibbs free energy of CH 3 COO· and sulfur species than ·OH, suggesting the preference of CH 3 COO· to react with sulfur species with electron transfer. After treatment with the FeS/PAA system, the products obtained from the three pharmaceuticals were detoxified and even facilitated the growth of E. coli probably due to the supply of numerous carbon sources by activated PAA. This study significantly advances the understanding of the reaction between PAA and sulfur-containing catalysts and suggests the practical application potential of the FeS/PAA process combined with biotreatment processes. [Display omitted] [ABSTRACT FROM AUTHOR]

Photoreforming of plastic waste is a novel approach, which can not only degrade plastic waste into valuable chemicals, but also produce high-energy-density hydrogen fuels. Here, we developed an in-situ derived carbon nitride-carbon nanotubes-NiMo hybrids via NiMo-assisted catalysis route, which works as an efficient and stable photocatalyst for plastics photoreforming. The strong π-π interaction between in-situ derived CNTs and CN promotes electron transfer, increases carrier lifetime and improves photocatalytic activity. The DFT calculations and single-particle PL quenching phenomenon confirmed the strong interface effect and charge transport for CN-CNTs-NM. In addition, the strong interaction between photocatalyst and ethylene glycol in plastics was observed in situ by single-particle PL. This work provides a smart strategy of utilizing in-situ derived π-π interaction as well as direct evidence of the charge transfer from the photocatalysts to ethylene glycol, which provides guidance for the rational design of highly efficient photocatalysts for plastics photoreforming. Photoreforming of plastics is a novel approach, which can not only degrade plastic waste into valuable chemicals, but also produce high-energy-density hydrogen fuels. Here, we developed an in-situ derived carbon nitride-carbon nanotubes-NiMo hybrids (CN-CNTs-NiMo) via NiMo self-catalytic route, which works as an efficient and stable photocatalyst for photoreforming of plastics under alkaline conditions. [Display omitted] • PET photoreforming can convert plastics into value-added chemicals and hydrogen using sunlight. • In situ-derived CN-CNTs-NM hybrids were synthesized NiMo-assisted catalysis route for photoreforming of PET. • Single-particle PL and DFT calculations confirm the existence of π-π interactions between CN and CNTs. • The real-world applicability of plastics photoreforming was confirmed by photoreforming of PET bottle. • The mechanism of plastics photoreforming was investigated in situ using single-particle PL. [ABSTRACT FROM AUTHOR]

[Display omitted] • A heterogeneous catalytic system of NaBiO 3 for PMS without light irradiation was investigated. • Both radical (SO 4 −• and •OH) and non-radical (1O 2) were contributed to BPAF degradation. • The contribution rate of 1O 2 , · SO- 4, and · OH was calculated as 80.4%, 8.7%, and 9.9%, respectively. It has been shown previously that the NaBiO 3 (NBO) could efficiently photocatalytically degrade organic contaminants because of its excellent photocatalytic property. In this study, we proposed a heterogeneous catalytic system of NBO for peroxymonosulfate (PMS) without light irradiation. The results showed that NBO/PMS exhibited excellent performance toward bisphenol AF (BPAF) degradation and mineralization. The effectiveness of the NBO/PMS system was also investigated in different multicomponent systems. The effects of initial pH, NBO dosages, and PMS concentration for BPAF degradation were also investigated. Radical quenching experiments combined with electron spin resonance analysis indicated that singlet oxygen (1O 2) was the main reactive oxygen species, and · SO 4 - and · OH– radicals participated in the process. X-ray photoelectron spectroscopy revealed the main catalytic mechanism: lattice oxygen (O vac) was extruded during the transformation of Bi(V) to Bi(III) to form and activate oxygen (O*), and the generated O* between the [BiO 6 ] regular octahedral layers reacted with PMS on the NBO surface to form 1O 2. Based on the results of the Bi element, it is suggested that the activation process proceeded through electron transfer from NBO to PMS. The stability of NBO and applicability of the NBO/PMS system in a natural water environment were explored. This work provides a novel approach to PMS activation and the potential use of NBO for the decontamination of organic pollutants. [ABSTRACT FROM AUTHOR]