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Excessive consumption of energy and resources is a major challenge in wastewater treatment. Here, a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphene-like catalysts (Cu-GCD NSs) was first synthesized by an enhanced carbothermal reduction of β-cyclodextrin (β-CD). The catalyst exhibits excellent Fenton-like catalytic activity for the degradation of various pollutants under neutral conditions, accompanied by low H 2 O 2 consumption. The results of structural characterization and theoretical calculations confirmed that the dual reaction centers (DRCs) were constructed on Cu-GCD NSs surface through C-O-Cu bonds supported on zero-valent copper species, which play a significant role in the high-performance Fenton-like reaction. The pollutants that served as electron donors were decomposed in the electron-poor carbon centers, whereas H 2 O 2 and dissolved oxygen obtained these electrons in the electron-rich Cu centers through C-O-Cu bonds, thereby producing more active species. This study demonstrates that the electrons of pollutants can be efficiently utilized in Fenton-like reactions by DRCs on the catalyst surface, which provides an effective strategy to improve Fenton-like reactivity and reduce H 2 O 2 consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

• The Fenton-like Cu-PAN 3 catalysts is first synthesized by co-precipitation and carbon thermal reduction method. • Dual reaction centers are constructed around graphene-like carbon and Cu species. • The pollutants as electron donors inhibit the ineffective decomposition of H 2 O 2 at the electron-poor centers. • The pollutant removal mainly relies on the surface cleavage at the electron-poor centers. High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water. To solve this problem, we designed a novel Fenton-like catalyst (Cu-PAN 3) by coprecipitation and carbon thermal reduction. The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H 2 O 2 consumption. The experimental results indicate that the dual reaction centers (DRCs) are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon, which form electron-poor/rich centers on the catalyst surface. H 2 O 2 is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation. Meanwhile, pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst, which inhibits the ineffective decomposition of H 2 O 2 at the electron-poor centers. This therefore significantly reduces the consumption of H 2 O 2 and reduces energy consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

A twofold cation-π-assembled catalyst consisting of honeycomb microsphere-like MoS 2 cross-linking g-C 3 N 4 hybrid (HM-MS/CN) is first developed to address the bottleneck of excessive resource and energy consumption in Fenton chemistry. A series of modern characterization techniques combined with theoretical calculation are used to reveal and verify the twofold cation-π interaction (Mo-O-C and Mo-S-C bonding bridges). It is found that the electrons of pollutants can be captured by H 2 O 2 and O 2 through the twofold cation-π interaction during Fenton-like reaction, which inhibits the oxidative decomposition of H 2 O 2 and promotes its hydroxylation. As a result, HM-MS/CN shows excellent performance for water purification by initiating pollutants as electron donors substituting H 2 O 2 consumption under mild natural conditions, and the actual consumption of H 2 O 2 in this system is only 6–8% of that in the common Fenton systems. This discovery is of great significance for the development of novel water purification technology with high efficiency and low consumption. [Display omitted] • A twofold cation-π-assembled catalyst consisting of HM-MS/CN is first prepared. • HM-MS/CN shows excellent performance for actual water purification. • The actual consumption of H 2 O 2 is only 6–8% of that in the common Fenton systems. • Twofold cation-π interaction based on Mo-O-C and Mo-S-C is responsible for excellent performance. • Pollutants act as electron donors substituting H 2 O 2 consumption via twofold cation-π. [ABSTRACT FROM AUTHOR]

• nZVCu-Cu(II)-rGO is developed via an annealing reduction process for first time. • Nanoscale Cu(0) and Cu(II) are generated on rGO along with C-O-Cu formation. • Dual reaction centers form around Cu(II) and aromatic rings of rGO due to π→Cu. • Nanoscale Cu(0) accelerate the electron transfer of the dual reaction center system. • Pollutants are efficiently degraded by two ways: as electron donors and attacked by radicals. Nanoscale zero-valent copper combined with Cu(II)-doped reduced graphene oxide hybrid (nZVC-Cu(II)-rGO) is synthesized through an annealing reduction process, and it shows very high activity and efficiency for removing refractory organic compounds with H 2 O 2. The conversion rate for the organic pollutant in this system is ∼77 and ∼13 times higher than that in the graphene oxide (GO) and reduced graphene oxide (rGO) systems, respectively. The characterization shows that nanoscale Cu(0) and Cu(II) are generated on the rGO surface during the annealing process and they are accompanied by the C O Cu bonding formation between the rGO substrate and the Cu(II) species in nZVC-Cu(II)-rGO, which induces cation–π interactions on the surface, resulting in the reinforced electron-rich micro-centers formation around the nZVC-enhanced Cu(II) species and electron-poor micro-centers on rGO-aromatic rings. The generation of nanoscale Cu(0) consolidates the polarization of the dual reaction micro-centers and greatly accelerates the electron transfer of the system, thus promoting H 2 O 2 reduction to OH in the electron-rich micro-centers. Pollutants can obviously replace H 2 O 2 as the electron donors of the system and are efficiently oxidized and degraded in the electron-poor micro-centers, with their own electron energy being fully utilized in the nZVC-Cu(II)-rGO Fenton-like system. [ABSTRACT FROM AUTHOR]

Herein, we fabricated CoCu-0.25-O v with ternary Co...O v ...Cu sites through simple co-precipitation to achieve effective co-utilization of organics and dissolved oxygen (DO) as endogenous electron donor-acceptor in Fenton-like system. Around 100% of dimethylamine (DMA) min within 30 is removed. The involved kinetics (0.22 min−1) and oxidant utilization efficiency (22.5%) are higher than controls with binary sites. Multi-scaled characterizations and theoretical calculations reveal that electron-polarized Co...O v ...Cu sites facilitate co-activation of DMA and DO as electron donor-acceptor through increasing d -band center and lowering work function of catalyst. Meanwhile, ternary sites favor 1O 2 and SO 4 •− generation, and shorten the migration distance of active species to pollutant, thus achieving excellent dual performance improvements. Semi-quantitative results of ESR indicate that DO activation and peroxymonosulfate (PMS) oxidation contribute about three-fourths and one-fourth to 1O 2 production, respectively. This contribution provides a new and sustainable strategy for high-efficiency and oxidant-saving removal of refractory pollutants in the environment. [Display omitted] • Co...O v ...Cu sites greatly improve removal performance of DMA and PMS utilization rate. • Ternary sites activate DMA and DO to replace PMS and favor the formation of ROSs. • Increased d -band center and lower work function of catalyst boost the co-activation. • DMA is removal by enhanced multipath (self-oxidation, 1O 2 and SO 4 •− attacks). • O 2 activation and PMS oxidation contribute 3/4 and 1/4 to 1O 2 formation, respectively. [ABSTRACT FROM AUTHOR]

• Mesoporous reduction state cobalt species-doped silica nanospheres are first prepared. • Excellent activity is realized in mp -RSCo-SiO 2 NSs/H 2 O 2 system. • Efficient dual-pathway degradation of pollutant is achieved in Fenton-like process. • Pollutants replace H 2 O 2 as electron donors for the mp -RSCo-SiO 2 NSs system. • A new interfacial Fenton-like reaction mechanism involving pollutants is proposed. A novel heterogeneous Co-containing Fenton-like catalyst consisting of mesoporous reduction state cobalt (RSCo)-doped silica (SiO 2) nanospheres (mp -RSCo-SiO 2 NSs) was prepared by an enhanced hydrothermal process. The catalyst exhibited very high activity and stability for a series of refractory pollutant degradation in a very wide pH range of 3.1–10.9. The Fenton-like reaction rate constant of this Co-containing catalyst was approximately 290 times higher than that of Co 3 O 4 for pollutant degradation under the neutral and mild conditions. Based on the characterization, the catalyst possessed a porous nanosphere morphology, and the reduction state cobalt species, including nano-zero-valent cobalt (nZVCo) and Co2+, were found to be generated in the SiO 2 framework through forming Co O Si bonds. During the Fenton-like reaction, the electron donation effect of organic pollutants was successfully realized through the interaction of "Pollutants → Co2+/0-SiO 2 ". The obtained electrons from pollutants were transferred to the catalyst surface and captured by H 2 O 2 , resulting in the generation of hydroxyl radicals (OH). Therefore, a dual-pathway degradation of the pollutants was realized: (I) oxidation and degradation as the electron donors for the system and (II) attacking and destruction by OH radicals. This work provided a new perspective on the effective utilization of the electrons of pollutants and the improvement of Fenton reaction efficiency. [ABSTRACT FROM AUTHOR]

• Excellent activity for water purification is realized in cobalt-zinc ferrite/PMS system. • Surface oxygen vacancy induces PMS activation to generate •OH, SO 4 •− and H 2. • An efficient dual-pathway removal of pollutants is first achieved in PMS activation. • Pollutants replace PMS as electron donors for the V O -rich ZnFe 0.8 Co 0.4 O 2.4 system. • A novel solid-liquid interfacial reaction mechanism is proposed in PMS activation. Peroxymonosulfate (PMS) activation in heterogeneous processes for pollutant degradation is a promising water purification technology. However, the existed rate limiting step greatly restrains its performance and increases the consumption of PMS and energy. Herein, we offer a new strategy to solve this problem. In this work, surface oxygen vacancy (V O)-rich ZnFe 0.8 Co 0.4 O 2.4 nanoparticles were prepared and characterized, which exhibited high activity and stability for refractory pollutant degradation with PMS activation. It was found that PMS ([O 3 S O I O II H]−) could be adsorbed and trapped by the surface oxygen vacancies in the form of O I - Vo or O II - Vo during the reaction. Different electron transfer pathways from Vo to different O sites of PMS was realized in the solid-liquid interface based on the generation of OH, SO 4 − or H 2 from PMS reduction. Pollutants were predominantly adsorbed at metal Co sites in which their electrons were captured by metal species and then transferred to the surface oxygen vacancies, achieving efficient recycling of electrons in the aqueous suspensions. This system achieves a dual-pathway degradation of pollutants and electron transfer from pollutants to PMS to produce free radicals and H 2 , essentially changing the traditional concepts of pollutant removal and providing a sustainable strategy for pollutant utilization during water purification. [ABSTRACT FROM AUTHOR]