The optimized Fenton-like activity of Fe single-atom sites by Fe atomic clusters-mediated electronic configuration modulation

Multifunctional Nanozyme with Aptamer-Based Ratiometric Fluorescent and Colorimetric Dual Detection of Prostate-Specific Antigen

The adsorption of DNA probes onto nanomaterials represents a promising bioassay technique, generally employing fluorescence or catalytic activity to generate signals. A significant challenge is maintaining the catalytic activity of chromogenic catalysts during detection while enhancing accuracy by overcoming the limitations of single-signal transmission. This article presents an innovative multimodal analysis approach that synergistically combines the oxidase-like activity of Fe-N-C nanozyme (Fe-NC) with red fluorescent carbon quantum dots (R-CQDs), further advancing the dual-mode analysis method utilizing R-CQDs@Fe-NC. In this system, R-CQDs integrate with Fe-NC to provide a steady reference red fluorescence signal, while Fe-NC serves as the catalytic active site. The adsorption of 6-carboxyfluorescein-labeled aptamers (FAM-apt) significantly enhanced the electron transfer capability of R-CQDs@Fe-NC, enhancing its catalytic performance and resulting in increased oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Concurrently, the green fluorescence of FAM-apt diminishes due to energy competition, photoinduced electron transfer, and the internal filtration effect by R-CQDs@Fe-NC, while the red fluorescence from R-CQDs@Fe-NC remains stable. Upon recognizing and binding to prostate-specific antigen (PSA), FAM-apt detaches from the surface of R-CQDs@Fe-NC. This leads to simultaneous variations in both the fluorescence signal of the system and the colorimetric signal of TMB. Based on these properties, a colorimetric/fluorescence dual-mode detection method for PSA was established, with detection limits of 0.054 and 0.16 ng/mL, respectively. Furthermore, a smartphone-based sensing device facilitated rapid and convenient detection. This study presents a multisignal output sensing strategy and a simple capillary sensing device, presenting a promising approach for PSA diagnostic analysis and the potential detection of other biomarkers.

Nitrogen-phosphorus codoped biochar prepared from tannic acid for degradation of trace antibiotics in wastewater

This study was designed to develop a one-step pyrolysis process that could efficiently activate peroxymonosulfate (PMS) and degrade tetracycline hydrochloride (TCH) by producing N, and P codoped carbon materials (NPTC3-800). Furthermore, it exhibited a high specific surface area (658 cm2 g-1), a larger pore volume (0.3 cm3 g-1), and a certain content of heteroatoms (nitrogen and phosphorus). PMS-activated NPTC3-800 attained a TCH removal efficiency of over 90% within 40 min, with an observed rate constant (kobs) of 0.0307 min-1. Similarly, the materials exhibited strong resistance to ionic interferences and showed broad applicability across various water bodies. Mobility experiments were conducted to further assess the stability of catalyst (92%, 40 h). Non-radical oxidation pathways, particularly including the singlet oxygen (1O2), were evidenced to play dominant roles in TCH degradation, as demonstrated by electron paramagnetic resonance (EPR) observations and experiments with free radical quenching. Theoretical calculations demonstrated that the N and P codoped domains substantially improve TCH removal compared to pure biochar. Finally, the proposed degradation pathways for TCH were identified, and the resulting degradation products demonstrated reduced biological toxicity.

Tailoring peroxyacetic acid(PAA) activation by sewage sludge derived atomic-Fe clusters/Fe-N4 catalyst via thermally drivenspin manipulation

Fe nanoclusters/FeN4 units embedded in graphitized carbon derived from biomass are highly efficient catalysts. However, simple physical mixing of precursors during pyrolysis tends to cause Fe to agglomerate into large nanoparticles. In this study, we introduce a novel peroxyacetic acid (PAA) conditioning strategy to transform sewage sludge (SS) into an enhanced Fe single-atom catalyst. This strategy modulates the evolution of Fe active sites by promoting the formation of adjacent Fe atomic clusters through thermal treatment. During sludge conditioning, PAA/Fe2+ triggers the dissolution and breakdown of SS, exposing nitrogen (N) and oxygen (O) atoms that bind with iron, thereby creating Fe immobilization sites. Characterization results show that conditioning promotes the formation of highly dispersed, few-atom Fe clusters/Fe-N4 sites (FeN4-FeNCP@SBC) at elevated temperatures, with Fe content exceeding 2.34 %. In contrast, untreated samples easily form Fe nanoparticles. The FeN4-FeNCP@SBC can be used as superior Fenton-like catalyst in PAA-triggered antibiotic degradation. Singlet oxygen (1O2) plays a dominant role in degradation, as demonstrated by scavenging and ESR analysis. O2 and HO are identified as important intermediates in the generation of 1O2 and are recognized as key species in FeN4-FeNCP@SBC-initiated PAA activation. The atomic-Fe cluster induced shift of the Fe center from low-spin (t2g6 eg0) to medium-spin (t2g5 eg1) facilitates partial occupation of the dz2 orbital, forming a σ* bond with OH. This promotes H being lost from OH to form O, and subsequent direct desorption of O can generate 1O2. The study provides a method to create SS catalysts with single atoms and Fe clusters for PAA and antibiotic degradation.

Non-metallic iodine single-atom catalysts with optimized electronic structures for efficient Fenton-like reactions

In this study, we introduce a highly effective non-metallic iodine single-atom catalyst (SAC), referred to as I-NC, which is strategically confined within a nitrogen-doped carbon (NC) scaffold. This configuration features a distinctive C-I coordination that optimizes the electronic structure of the nitrogen-adjacent carbon sites. As a result, this arrangement enhances electron transfer from peroxymonosulfate (PMS) to the active sites, particularly the electron-deficient carbon. This electron transfer is followed by a deprotonation process that generates the peroxymonosulfate radical (SO5•-). Subsequently, the SO5•- radical undergoes a disproportionation reaction, leading to the production of singlet oxygen (1O2). Furthermore, the energy barrier for the rate-limiting step of SO5•- generation in I-NC is significantly lower at 1.45 eV, compared to 1.65 eV in the NC scaffold. This reduction in energy barrier effectively overcomes kinetic obstacles, thereby facilitating an enhanced generation of 1O2. Consequently, the I-NC catalyst exhibits remarkable catalytic efficiency and unmatched reactivity for PMS activation. This leads to a significantly accelerated degradation of pollutants, evidenced by a relatively high observed kinetic rate constant (kobs ~ 0.436 min-1) compared to other metallic SACs. This study offers valuable insights into the rational design of effective non-metallic SACs, showcasing their promising potential for Fenton-like reactions in water treatment applications.

Nano-island-encapsulated cobalt single-atom catalysts for breaking activity-stability trade-off in Fenton-like reactions

Single-atom catalysts (SACs) have been increasingly acknowledged for their performance in sustainable Fenton-like catalysis. However, SACs face a trade-off between activity and stability in peroxymonosulfate (PMS)-based systems. Herein, we design a nano-island encapsulated single cobalt atom (CoSA/Zn.O-ZnO) catalyst to enhance the activity and stability of PMS activation for contaminant degradation via an "island-sea" synergistic effect. In this configuration, small carrier-based ZnO nanoparticles (the "islands") are utilized to confine and stabilize Co single atoms. The expansive ZnO substrate (the "sea") upholds a neutral microenvironment within the reaction system. The CoSA/Zn.O-ZnO/PMS system exhibits a remarkable selectivity in exclusively generating sulfate radicals (SO4•-), leading to a complete removal of various recalcitrant pollutants within a shorter period. Characterized by minimal leaching of active sites, robust catalytic performance, and low-toxicity decontamination, this system proves highly efficient in multiple treatment cycles and complex water matrices. The design effectively breaks the activity-stability trade-off typically associated with SACs.

Enhanced Photosensitizer Wettability via Anchoring Competition of Violet Phosphorus Quantum Dots for Breakthroughs in Photodynamic Film Sterilization

Wettability is important for photodynamic film sterilization since higher wettability enhances the capture of bacteria in contact with photosensitizers. Herein, a small number of violet phosphorus quantum dots (VPQDs) are anchored into hypericin bacterial cellulose films (VP/Hy-BC films) to improve wettability, reducing the water contact angle from 56.8° to 33.0°. This modification facilitated more effective interactions between the bacteria and photosensitizers, rapidly inactivating 7 log10 CFU/mL of Staphylococcus aureus within 60 min. First-principles calculations and molecular dynamics simulations reveal that VPQDs, with their low spatial site resistance, reduced the intermolecular Hy self-aggregation force. This increased the solvent-accessible surface area of VP/Hy by ≈25.7%, thereby decreasing hydrophobic photosensitizer aggregation. Consequently, more active sites are exposed, remarkably improving the photoelectron transfer efficiency. VP/Hy-BC demonstrated exceptional efficacy in inhibiting bacterial proliferation; for instance, it extended beef shelf life by up to 10 days. The findings of this study will aid the development of health-conscious, eco-friendly, and efficient antimicrobial packaging films.

Sabatier Principle-Driven Single-Atom Coordination Engineering for Enhanced Fenton-Like Catalysis

Single-atom catalysts (SACs) are widely employed in Fenton-like catalysis, yet guidelines for their high-performance design remain elusive. The Sabatier principle provides guidance for the ideal catalyst with the highest activity. Herein, the study meticulously engineered a series of SACs featuring a broad distribution of d-band center through single-atom coordination engineering, facilitating a comprehensive exploration of the Sabatier relationship in Fenton-like catalysis. A volcanic correlation between d-band centers and catalytic activity is identified. Theoretical and experimental results show that moderate d-band center and peroxymonosulfate adsorption energy can lead to the lowest reaction barriers in the rate-determining step for generating singlet oxygen, thus enhancing catalytic efficiency toward the Sabatier optimum. As proof of concept, the Fe-N2O2/C catalyst demonstrates a degradation rate constant of 1.89 min-1, surpassing Fe-N4/C by 3.2 times and Fe-O4/C by 272 times. Moreover, Fe-N2O2/C shows exceptional tolerance to various environmental challenges, providing opportunities for achieving nearly eco-friendly pollutant degradation. The findings reveal how to use the Sabatier principle to guide the design of advanced SACs for efficient pollutant removal.

Overlooked risks of photoaging of nitrogenous microplastics with natural organic matter in water: Augmenting the formation of nitrogenous disinfection by-products

In aqueous environments, microplastics (MPs) undergo photoaging, releasing dissolved organic matter (DOM). Disinfection byproducts (DBPs) formation from natural organic matter (NOM) phototransformation has been reported. However, the impact of NOM on the photoaging of MPs (especially nitrogen-containing MPs) and subsequent nitrogenous DBPs (N-DBPs) formation remains unknown. Herein, this study investigated polyamide (PA) with NOM (fulvic acid [FA], humic acid [HA] and biochar-derived DOM [BDOM]) on N-DBPs formation. Results showed that the levels of the main DBPs, N-nitrosamine, formed in the FA+PA, BDOM+PA, and HA+PA systems were 3.0. 2.7 and 1.6 folds higher, respectively, compared to those in the corresponding NOM treatments. NDMA was found to be the dominant N-nitrosamine species, with the highest level of 202 ng/L, exceeding the WHO guideline of 100 ng/L. The main reactive intermediates (RIs) were 1O2 and reactive nitrogen species (RNS) during the first stage (0-3d), and •OH and RNS during the second stage (3-7d), which were confirmed by quenching experiment. For the first time, we found the formation of N-DBPs during photoaging of N-containing MPs, and proposed a two-stages, two-processes, and two-pathways theory of N-DBPs formation. This work emphasizes the importance to understand the interactions between the MPs and NOM in photoaging to better assess the risk of DBPs formation in aqueous environment.

Silver and g-C3N4 co-modified biochar (Ag-CN@BC) for enhancing photocatalytic/PDS degradation of BPA: Role of carrier and photoelectric mechanism

Photocatalytic property of nano Ag is weak and its enhancement is important to enlarge its application. Herein, a novel strategy of constructing silver g-C3N4 biochar composite (Ag-CN@BC) as photocatalyst is developed and its photocatalytic degradation of bisphenol A (BPA) coupled with peroxydisulfate (PDS) oxidation process is characterized. Characterization result showed that silver was evenly embedded into the g-C3N4 structure of the nitrogen atoms format, impeding agglomeration of Ag by distributing stably on biochar. In optimum condition, BPA of 10 mg/L could be degraded completely at pH of 9.0 with a 0.5 g/L photocatalyst, 2 mM PDS in Ag-CN@BC-2 (Ag/melamine molar ratio of 0.5)/PDS system (99.2%, k = 4.601 h-1). Ag-CN@BC shows superior mineralization ratio in degrading BPA to CO₂ and H₂O via active radical way, including holes (h⁺), superoxide radicals (•O2⁻), sulfate radicals (SO4•⁻), and hydroxyl radicals (•OH). Proper amount of silver can be dispersed effectively by gC3N4, which is responsible for improving the visible-light absorbing capability and accelerate charge transfer during activation of PDS for BPA degradation, while biochar as carrier in the composite is supposed to enhance the photoelectric degradation of BPA by reducing the band gap and increasing the photocurrent of Ag-CN@BC catalyst. Ag-CN@BC exhibits excellent catalyst stability and photocatalytic activity for treatment of toxic organic contaminants in the environment.

Unraveling the Fundamentals of Axial Coordination FeN4+1 Sites Regulating the Peroxymonosulfate Activation for Fenton-Like Activity

Precise modulation of the axial coordination microenvironment in single-atom catalysts (SACs) to enhance peroxymonosulfate (PMS) activation represents a promising yet underexplored approach. This study introduces a pyrolysis-free strategy to fabricate SACs with well-defined axial-FeN4+1 coordination structures. By incorporating additional out-of-plane axial nitrogen into well-defined FeN4 active sites within a planar, fully conjugated polyphthalocyanine framework, FeN4+1 configurations are developed that significantly enhance PMS activation. The axial-FeN4+1 catalyst excelled in activating PMS, with a high bisphenol A (BPA) degradation rate of 2.256 min-1, surpassing planar-FeN4/PMS systems by 6.8 times. Theoretical calculations revealed that the axial coordination between N and the Fe sites forms an optimized axial FeN4+1 structure, disrupting the electron distribution symmetry of Fe and optimizing the electron distribution of the Fe 3d orbital (increasing the d-band center from -1.231 to -0.432 eV). Consequently, this led to an enhanced perpendicular adsorption energy of PMS from -1.79 to -1.82 eV and reduced energy barriers for the formation of the key reaction intermediate (O*) that generates 1O2. This study provides new insights into PMS activation through the axial coordinated engineering of well-defined SACs in water purification processes.

Lattice-Confined Single-Atom Catalyst: Preparation, Application and Electron Regulation Mechanism

Lattice-confined single-atom catalyst (LC SAC), featuring exceptional activity, intriguing stability and prominent selectivity, has attracted extensive attention in the fields of various reactions (e.g., hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), etc.). To design a "smart" LC SAC for catalytic applications, one must systematically comprehend updated advances in the preparation, the application, and especially the peculiar electron regulation mechanism of LC SAC. In this review, the specific preparation methods of LC SAC based on general coordination strategy are updated, and its applications in HER, OER, ORR, N2 reduction reaction (NRR), advanced oxidation processes (AOPs) and so forth are summarized to display outstanding activity, stability and selectivity. Uniquely, the electron regulation mechanisms are first and deeply discussed and can be primarily categorized as electron transfer bridge with monometallic active sites, novel catalytic centers with polymetallic active sites, and positive influence by surrounding environments. In the end, the existing issues and future development directions are put forward with a view to further optimize the performance of LC SAC. This review is expected to contribute to the in-depth understanding and practical application of highly efficient LC SAC.

Decoding the entropy-stabilized matrix of high-entropy layered double hydroxides: Harnessing strain dynamics for peroxymonosulfate activation and tetracycline degradation

The current understanding of the mechanism of high-entropy layered double hydroxide (LDH) on enhancing the efficiency of activating peroxymonosulfate (PMS) remains limited. This work reveals that a strong strain effect, driven by high entropy, modulates the structure of FeCoNiCuZn-LDH (HE-LDH) as evidenced by geometric phase analysis (GPA) and density functional theory (DFT) calculations. Compared to FeCoNiZn-LDH and FeCoNi-LDH with weaker strain effects, the high entropy-driven strain effect in HE-LDH shortens metal-oxygen-hydrogen (MOH) bond lengths, allows system to be in a constant steady state during catalysis, reduces the leaching of active M-OH sites, and enhances the adsorption capacity of these sites and the excess strain strength of the interfacial stretches the IO-O of the PMS, facilitates reactive oxygen species (·OH, SO4·-, 1O2 and O2·-) generation, and thereby improving the efficiency of PMS in degrading tetracycline (TC). Consequently, HE-LDH demonstrated a 90% TC degradation within 3 min, maintained over 92% TC removal across a wide pH range (3-11), and achieved over 90% degradation performance after 6 cycles. This study reports the first use of high-entropy LDH material as a non-homogeneous catalyst and provides insights into the extremely different catalytic behaviors of high entropy mechanisms for the activation of PMS.

Fundamental Insights into the Direct Electron Transfer Mechanism on Ag Atomic Cluster

The nonradical oxidation pathway for pollutant degradation in Fenton-like catalysis is favorable for water treatment due to the high reaction rate and superior environmental robustness. However, precise regulation of such reactions is still restricted by our poor knowledge of underlying mechanisms, especially the correlation between metal site conformation of metal atom clusters and pollutant degradation behaviors. Herein, we investigated the electron transfer and pollutant oxidation mechanisms of atomic-level exposed Ag atom clusters (AgAC) loaded on specifically crafted nitrogen-doped porous carbon (NPC). The AgAC triggered a direct electron transfer (DET) between the terminal oxygen (Oα) of surface-activated peroxodisulfate and the electron-donating substituents-containing contaminants (EDTO-DET), rendering it 11-38 times higher degradation rate than the reported carbon-supported metal catalysts system with various single-atom active centers. Heterocyclic substituents and electron-donating groups were more conducive to degradation via the EDTO-DET system, while contaminants with high electron-absorbing capacity preferred the radical pathway. Notably, the system achieved 79.5% chemical oxygen demand (COD) removal for the treatment of actual pharmaceutical wastewater containing 1053 mg/L COD within 30 min. Our study provides valuable new insights into the Fenton-like reactions of metal atom cluster catalysts and lays an important basis for revolutionizing advanced oxidation water purification technologies.

Aeration-Free Photo-Fenton-Like Reaction Mediated by Heterojunction Photocatalyst toward Efficient Degradation of Organic Pollutants

The regulation of peroxymonosulfate (PMS) activation by photo-assisted heterogeneous catalysis is under in-depth investigation with potential as a replaceable advanced oxidation process in water purification, yet it remains a significant challenge. Herein, we demonstrate a strategy to construct polyethylene glycol (PEG) well-coupled dual-defect VO-M-Co3O4@CNx S-scheme heterojunction to degrade organic pollutants without aeration, which dramatically provides abundant active sites, excellent photo-thermal property, and distinct charge transport pathway for PMS activation. The degradation rate of VO-M-Co3O4@CNx in anaerobic conditions shows a higher efficient rate (4.58 min-1 g-2) than in aerobic conditions (1.67 min-1 g-2). Experimental evidence reveals that VO-M-Co3O4@CNx promotes more rapid redox conversion of photoexcited electrons induced by defects with PMS under anaerobic conditions compared to aerobic conditions. Additionally, in situ experiments and DFT provide mechanistic insights into the regulation pathway of PMS activation via synergistic defect-induced electron, revealing the competitive effect between O2 and PMS over VO-M-Co3O4@CNx during the reaction process. The continuous flow reactor and flow cytometry results demonstrated that the VO-M-Co3O4@CNx/PMS/Vis system has remarkably enhanced stability and purification capability for removing organic pollutants. This work provides valuable insights into regulating the heterologous catalysis oxidation process without aeration through the photoexcitation synergistic PMS activation.

Fe3C@Fe decorated carbonized wood Fiber catalyst for organic dyes degradation: Preparation, characterization and mechanism

The extensive use of organic dyes has led to significant water pollution. Using lignocellulosic waste as a precursor for catalysts preparation for sewage remediation presents an effective alternative with numerous advantages in sustainability, cost-effectiveness, and environmental compatibility. In this work, wood fiber waste collected from wood processing plants was decorated with Prussian blue (PB) and then annealed to produce carbonized wood fiber catalyst (Fe3C@Fe-CB). In the presence of peroxymonosulfate (PMS), the prepared catalyst could achieve over 98.69 % efficiency in degrading methylene blue (MB) solutions (20 mg/L) in 60 min across a pH range of 3 to 11. Electrochemical test and electron paramagnetic resonance (EPR) analysis respectively verified that electron transfer pathway and radical pathway were the key factors for the degradation of MB. Cyclic degradation tests demonstrated that the degradation efficiency remained above 93.67 % after five recycling experiments. Moreover, the used magnetic catalyst can be easily recycled by magnet. This study proposed a facile and sustainable carbonized wood fiber catalyst decorated by Fe3C@Fe-CB, which could realize efficient elimination of organic dyes. Moreover, we offered a novel choice for dyes-polluted water treatment and paving a new route for converting low-value lignocellulosic waste to high-value utilizations.

Remarkable Active Site Utilization in Edge-Hosted-N Doped Carbocatalysts for Fenton-Like Reaction

Improving the utilization of active sites in carbon catalysts is significant for various catalytic reactions, but still challenging, mainly due to the lack of strategies for controllable introduction of active dopants. Herein, a novel "Ar plasma etching-NH3 annealing" strategy is developed to regulate the position of active N sites, while maintaining the same nitrogen species and contents. Theoretical and experimental results reveal that the edge-hosted-N doped carbon nanotubes (E-N-CNT), with only 0.29 at.% N content, show great affinity to peroxymonosulfate (PMS), and exhibit excellent Fenton-like activity by generating singlet oxygen (1O2), which can reach as high as 410 times higher than the pristine CNT. The remarkable utilization of edge-hosted nitrogen atom is further verified by the edge-hosted-N enriched carbocatalyst, which shows superior capability for 4-chlorophenol degradation with a turnover frequency (TOF) value as high as 3.82 min-1, and the impressive TOF value can even surpass those of single-atom catalysts. This work proposes a controllable position regulation of active sites to improve atom utilization, which provides a new insight into the design of excellent Fenton-like catalysts with remarkable atom utilization efficiency.

A Critical Review of Deep Oxidation of Gaseous Volatile Organic Compounds via Aqueous Advanced Oxidation Processes

Volatile organic compounds (VOCs) are considered to be the most recalcitrant gaseous pollutants due to their high toxicity, diversity, complexity, and stability. Gas-solid catalytic oxidation methods have been intensively studied for VOC treatment while being greatly hampered by energy consumption, catalyst deactivation, and byproduct formation. Recently, aqueous advanced oxidation processes (AOPs) have attracted increasing interest for the deep oxidation of VOCs at room temperature, owing to the generation of abundant reactive oxygen species (ROS). However, current reviews mainly focus on VOC degradation performance and have not clarified the specific reaction process, degradation products, and paths of VOCs in different AOPs. This study systematically reviews recent advances in the application of aqueous AOPs for gaseous VOC removal. First, the VOC gas-liquid mass transfer and chemical oxidation processes are presented. Second, the latest research progress of VOC removal by various ROS is reviewed to study their degradation performances, pathways, and mechanisms. Finally, the current challenges and future strategies are discussed from the perspectives of synergistic oxidation of VOC mixtures, accurate oxidation, and resource utilization of target VOCs via aqueous AOPs. This perspective provides the latest information and research inspiration for the future industrial application of aqueous AOPs for VOC waste gas treatment.

Photothermal nano-confinement reactor with bimetallic sites for enhanced peroxymonosulfate activation in antibiotic degradation

In recent years, photothermal-assisted Fenton-like degradation of organic pollutants has become a prominent green method in environmental pollution control. Nevertheless, the design of suitable catalysts remains a significant challenge for this approach. Herein, zeolite-imidazolate framework-derived CoMn bimetallic nanoparticles embedded in hollow carbon nanofibers (CoMnHCF) have been developed as a photothermal nano-confinement reactor with multiple active sites to enhance reaction performance and promote peroxymonosulfate (PMS) activation. Under light irradiation, the local temperature within the porous spaces of CoMnHCF was significantly higher than the liquid temperature. The confined space concentrated heat, minimized thermal loss, and effectively utilizes this feature to activate PMS for antibiotic degradation. The results demonstrated that this system efficiently degraded various antibiotics, including tetracycline hydrochloride, levofloxacin, sulfamethoxazole, norfloxacin and chlorotetracycline. Photothermal contribution analysis revealed that thermal effects predominate in this system. Further DFT simulations explored the coordination environment of metal elements and the properties of related pollutants, predicting potential structures and reaction sites. A series of water quality experiments and cyclic tests demonstrated the system's significant application potential. This study offered new insights into advancing the integrated use of photothermal conversion and nano-confinement reactor activation of PMS in sewage purification.

Pore modulation of single atomic Fe sites for ultrafast Fenton-like chemistry with amplified electron migration oxidation

The limited interaction between pollutants, oxidants, and the surface catalytic sites of single atom catalysts (SACs) restricts the water decontamination effectiveness. Confining catalytic sites within porous structures enables the localized enrichment of reactants for optimized reaction kinetics, while the specific regulatory mechanisms remain unclear. Herein, SACs with porous modification significantly improves the utilization of peroxymonosulfate (PMS) and pollutant degradation activity. Confining catalytic sites in porous structure effectively reduces the mass transfer distance between radicals (SO4•- and •OH) and pollutants, thereby improving reaction performance. Pore modulation changes the surface electronic structure, leading to a significant improvement in the electron migration process. The system shows significant potential in effectively oxidizing various common emerging pollutants, and exhibits robust resistance to interference from environmental matrices. Moreover, a quantitative evaluation using life cycle assessment (LCA) indicates that the pFe-SAC/PMS system showcases superior environmental importance and practicality.

Interlayer synergistic reaction of radical precursors for ultraefficient 1O2 generation via quinone-based covalent organic framework

Singlet oxygen (1O2) is important in the environmental remediation field, however, its efficient production has been severely hindered by the ultrafast self-quenching of the as-generated radical precursors in the Fenton-like reactions. Herein, we elaborately designed lamellar anthraquinone-based covalent organic frameworks (DAQ-COF) with sequential localization of the active sites (C═O) at molecular levels for visible-light-assisted peroxymonosulfate (PMS) activation. Theoretical and experimental results revealed that the radical precursors (SO5·-) were formed in the nearby layers with the migration distance less than 0.34 nm, via PMS donating electrons to the photogenerated holes. This interlayer synergistic effect eventually led to ultraefficient 1O2 production (14.8 μM s-1), which is 12 times that of the highest reported catalyst. As an outcome, DAQ-COF enabled the complete degradation of bisphenol A in 5 min with PMS under natural sunlight irradiation. This interlayer synergistic concept represents an innovative and effective strategy to increase the utilization efficiency of ultrashort-lived radical precursors, providing inspirations for subtle structural construction of Fenton-like catalysts.

Stabilizing Fe Single Atoms on Rutile-TiO2(110) Surface Via Atomic Substitution

Stable anchoring of dispersed metal atoms through either surface adsorption or lattice substitution on support surfaces is a prerequisite for highly efficient catalytic performance. Atomic-level insights into these processes are necessary to understand the metal-support interactions. Here, we identify multiple Fe single-atom configurations on the rutile-TiO2(110) surface using scanning tunneling microscopy (STM) and density functional theory (DFT). Our results show that an Fe atom can either adsorb on a surface O site (configuration I) or stably substitute a surface lattice Ti atom (configuration II). A transformation from configuration I to configuration II can be induced by STM manipulation. Furthermore, the substitutional Fe atom can capture an additional Fe atom to form a dual Fe-Fe complex (configuration III). DFT calculations reveal that these Fe species contribute different states in either the bandgap or the conduction band. These atomistic insights pave the way for interrogating the integrated performance of nonprecious, TiO2-supported Fe single-atom catalysts.

Performance enhancement and mechanism of electroenhanced peroxymonosulfate activation by single-atom Fe catalyst modified electrodes

Peroxymonosulfate-based electrochemical advanced oxidation processes (PMS-EAOPs) have great potential for sustainable water purification, so an in-depth understanding of its catalytic mechanism is imperative to facilitate its practical application. Herein, the performance enhancement and mechanism of electroenhanced PMS activation by single-atom Fe catalyst modified carbon felt was investigated. Compared with the anode, the cathode exhibited faster bisphenol A degradation (kcathode = 0.073 vs. kanode = 0.015 min-1), increased PMS consumption (98.8 vs. 10.3%), and an order of magnitude reduction of Fe dissolution (0.068 vs. 0.787 mg L-1). Mass transfer is a key factor limiting PMS activation, while the electrostriction of water in the hydrophobic region caused by cathode electric field (CEF) significantly increased mass transfer coefficient (km, cathode = 1.49 × 10-4 vs. km, anode = 2.68 × 10-5 m s-1). The enhanced activation of PMS is a synergistic result between electroactivation and catalyst-activation, which is controlled by the applied current density. 1O2 and direct electron transfer are the main active species and activation pathway, which achieve high degradation efficiency over pH 3 to 10. Density functional theory calculations prove CEF increases the adsorption energy, lengthens the O-O bond in PMS, and promotes charge transfer. A flow-through convection unit achieves sustainable operation with high removal efficiency (99.5% to 97.5%), low electrical energy consumption (0.15 kWh log-1 m-3), and low Fe leaching (0.81% of the total single atom Fe). This work reveals the critical role of electric fields in modulating Fenton-like catalytic activity, which may advance the development of advanced oxidation processes and other electrocatalytic applications.

Long-range interactions driving neighboring Fe-N4 sites in Fenton-like reactions for sustainable water decontamination

Actualizing efficient and sustainable environmental catalysis is essential in global water pollution control. The single-atom Fenton-like process, as a promising technique, suffers from reducing potential environmental impacts of single-atom catalysts (SACs) synthesis and modulating functionalized species beyond the first coordination shell. Herein, we devised a high-performance SAC possessing impressive Fenton-like reactivity and extended stability by constructing abundant intrinsic topological defects within carbon planes anchored with Fe-N4 sites. Coupling atomic Fe-N4 moieties and adjacent intrinsic defects provides potent synergistic interaction. Density functional theory calculations reveal that the intrinsic defects optimize the d-band electronic structure of neighboring Fe centers through long-range interactions, consequently boosting the intrinsic activity of Fe-N4 sites. Life cycle assessment and long-term steady operation at the device level indicate promising industrial-scale treatment capability for actual wastewater. This work emphasizes the feasibility of synergistic defect engineering for refining single-atom Fenton-like chemistry and inspires rational materials design toward sustainable environmental remediation.

Cu-optimized long-range interaction between Co nanoparticles and Co single atoms: Improved Fenton-like reaction activity

The interplay between multi-atom assembly configurations and single atoms (SAs) has been gaining attention in research. However, the effect of long-term range interactions between SAs and multi-atom assemblies on the orbital filling characteristics has yet to be investigated. In this context, we introduced copper (Cu) doping to strengthen the interaction between cobalt (Co) nanoparticles (NPs) and Co SAs by promoting the spontaneous formation of Co-Cu alloy NPs that tends toward aggregation owing to its negative cohesive energy (-0.06454), instead of forming Cu SAs. The incorporation of Cu within the Co-Cu alloy NPs, compared to the pure Co NPs, significantly expedites the kinetics of peroxymonosulfate (PMS) oxidation processes on Co SAs. Unlike Co NPs, Co-Cu NPs facilitate electron rearrangement in the d orbitals (especially dz2 and dxz) near the Fermi level in Co SAs, thereby optimizing the dz2-O (PMS) and dxz-O (SO5-) orbital interaction. Eventually, the Co-Cu alloy NPs embedded in nitrogen-doped carbon (CC@CNC) catalysts rapidly eliminated 80.67% of 20 mg L-1 carbamazepine (CBZ) within 5 min. This performance significantly surpasses that of catalysts consisting solely of Co NPs in a similar matrix (C@CNC), which achieved a 58.99% reduction in 5 min. The quasi in situ characterization suggested that PMS acts as an electron donor and will transfer electrons to Co SAs, generating 1O2 for contaminant abatement. This study offers valuable insights into the mechanisms by which composite active sites formed through multi-atom assembly interact at the atomic orbital level to achieve high-efficiency PMS-based advanced oxidation processes at the atomic orbital level.

Atomic-Level Engineered Cobalt Catalysts for Fenton-Like Reactions: Synergy of Single Atom Metal Sites and Nonmetal-Bonded Functionalities

Single atom catalysts (SACs) are atomic-level-engineered materials with high intrinsic activity. Catalytic centers of SACs are typically the transition metal (TM)-nonmetal coordination sites, while the functions of coexisting non-TM-bonded functionalities are usually overlooked in catalysis. Herein, the scalable preparation of carbon-supported cobalt-anchored SACs (CoCN) with controlled Co─N sites and free functional N species is reported. The role of metal- and nonmetal-bonded functionalities in the SACs for peroxymonosulfate (PMS)-driven Fenton-like reactions is first systematically studied, revealing their contribution to performance improvement and pathway steering. Experiments and computations demonstrate that the Co─N3C coordination plays a vital role in the formation of a surface-confined PMS* complex to trigger the electron transfer pathway and promote kinetics because of the optimized electronic state of Co centers, while the nonmetal-coordinated graphitic N sites act as preferable pollutant adsorption sites and additional PMS activation sites to accelerate electron transfer. Synergistically, CoCN exhibits ultrahigh activity in PMS activation for p-hydroxybenzoic acid oxidation, achieving complete degradation within 10 min with an ultrahigh turnover frequency of 0.38 min-1, surpassing most reported materials. These findings offer new insights into the versatile functions of N species in SACs and inspire rational design of high-performance catalysts in complicated heterogeneous systems.

Conjugated Microporous Polymers-Based Catalytic Membranes with Hierarchical Channels for High-Throughput Removal of Micropollutants

Engineering a catalytic membrane capable of efficiently removing emerging organic microcontaminants under ultrahigh flux conditions is of significance for water purification. Herein, drawing inspiration from the functional attributes of lymphatic vessels involved in immunosurveillance and fluid transport with minimal energy consumption, a novel hierarchical porous catalytic membrane is engineered. This membrane, based on an innovative nitrogen-rich conjugated microporous polymer (polytripheneamine, PTPA), is synthesized using an electrospinning coupled in situ polymerization approach. The resulting bioinspired membrane with hierarchical channels comprises a thin layer (≈1.7 µm) of crosslinked PTPA nanoparticles covering the interconnected electrospun nanofibers. This unique design creates an intrinsic microporous angstrom-confined system capable of activating peroxymonosulfate (PMS) to generate 98.7% singlet oxygen (1O2), enabling durable and highly efficient degradation of microcontaminants. Additionally, the presence of a thin layer of mesoporous structure between PTPA nanoparticles and macroporous channels within the interwoven nanofibers enhances mass transfer efficiency and facilitates high flux rates. Notably, the prepared hierarchical porous organic catalytic membrane demonstrates enduring high-efficiency degradation performance with a superior permeance (>95% and >2500 L m-2 h-1 bar-1) sustained over 100 h. This work introduces an innovative pathway for the design of high-performance catalytic membranes for the removal of emerging organic microcontaminants.

Oxygen-bridging Fe, Co dual-metal dimers boost reversible oxygen electrocatalysis for rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) are regarded as a remarkably promising alternative to current lithium-ion batteries, addressing the requirements for large-scale high-energy storage. Nevertheless, the sluggish kinetics involving oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hamper the widespread application of ZABs, necessitating the development of high-efficiency and durable bifunctional electrocatalysts. Here, we report oxygen atom-bridged Fe, Co dual-metal dimers (FeOCo-SAD), in which the active site Fe-O-Co-N6 moiety boosts exceptional reversible activity toward ORR and OER in alkaline electrolytes. Specifically, FeOCo-SAD achieves a half-wave potential (E1/2) of 0.87 V for ORR and an overpotential of 310 mV at a current density of 10 mA cm-2 for OER, with a potential gap (ΔE) of only 0.67 V. Meanwhile, FeOCo-SAD manifests high performance with a peak power density of 241.24 mW cm-2 in realistic rechargeable ZABs. Theoretical calculations demonstrate that the introduction of an oxygen bridge in the Fe, Co dimer induced charge spatial redistribution around Fe and Co atoms. This enhances the activation of oxygen and optimizes the adsorption/desorption dynamics of reaction intermediates. Consequently, energy barriers are effectively reduced, leading to a strong promotion of intrinsic activity toward ORR and OER. This work suggests that oxygen-bridging dual-metal dimers offer promising prospects for significantly enhancing the performance of reversible oxygen electrocatalysis and for creating innovative catalysts that exhibit synergistic effects and electronic states.

Single Atom Catalyst in Persulfate Oxidation Reaction: From Atom Species to Substance

With maximum utilization of active metal sites, more and more researchers have reported using single atom catalysts (SACs) to activate persulfate (PS) for organic pollutants removal. In SACs, single metal atoms (Fe, Co, Cu, Mn, etc.) and different substrates (porous carbon, biochar, graphene oxide, carbon nitride, MOF, MoS2, and others) are the basic structural. Metal single atoms, substances, and connected chemical bonds all have a great influence on the electronic structures that directly affect the activation process of PS and degradation efficiency to organic pollutants. However, there are few relevant reviews about the interaction between metal single atoms and substances during PS activation process. In this review, the SACs with different metal species and substrates are summarized to investigate the metal-support interaction and evaluate their effects on PS oxidation reaction process. Furthermore, how metal atoms and substrates affect the reactive species and degradation pathways are also discussed. Finally, the challenges and prospects of SACs in PS-AOPs are proposed.

Size-Dependent Catalysis in Fenton-like Chemistry: From Nanoparticles to Single Atoms

State-of-the-art Fenton-like reactions are crucial in advanced oxidation processes (AOPs) for water purification. This review explores the latest advancements in heterogeneous metal-based catalysts within AOPs, covering nanoparticles (NPs), single-atom catalysts (SACs), and ultra-small atom clusters. A distinct connection between the physical properties of these catalysts, such as size, degree of unsaturation, electronic structure, and oxidation state, and their impacts on catalytic behavior and efficacy in Fenton-like reactions. In-depth comparative analysis of metal NPs and SACs is conducted focusing on how particle size variations and metal-support interactions affect oxidation species and pathways. The review highlights the cutting-edge characterization techniques and theoretical calculations, indispensable for deciphering the complex electronic and structural characteristics of active sites in downsized metal particles. Additionally, the review underscores innovative strategies for immobilizing these catalysts onto membrane surfaces, offering a solution to the inherent challenges of powdered catalysts. Recent advances in pilot-scale or engineering applications of Fenton-like-based devices are also summarized for the first time. The paper concludes by charting new research directions, emphasizing advanced catalyst design, precise identification of reactive oxygen species, and in-depth mechanistic studies. These efforts aim to enhance the application potential of nanotechnology-based AOPs in real-world wastewater treatment.

Pyrazine-based iron metal organic frameworks (Fe-MOFs) with modulated O-Fe-N coordination for enhanced hydroxyl radical generation in Fenton-like process

Rational design of coordination environment of Fe-based metal-organic frameworks (Fe-MOFs) is still a challenge in achieving enhanced catalytic activity for Fenten-like advanced oxidation process. Here in, novel porous Fe-MOFs with modulated O-Fe-N coordination was developed by configurating amino terephthalic acid (H2ATA) and pyrazine-dicarboxylic acid (PzDC) (Fe-ATA/PzDC-7:3). PzDC ligands introduce pyridine-N sites to form O-Fe-N coordination with lower binding energy, which affect the local electronic environment of Fe-clusters in Fe-ATA, thus decreased its interfacial H2O2 activation barrier. O-Fe-N coordination also accelerate Fe(II)/Fe(III) cycling of Fe-clusters by triggering the reactive oxidant species mediated Fe(III) reduction. As such, Fe-ATA/PzDC-7:3/H2O2 system exhibited excellent degradation performance for typical antibiotic sulfamethoxazole (SMX), in which the steady-state concentration of hydroxyl radical (OH) was 1.6 times higher than that of unregulated Fe-ATA. Overall, this study highlights the role of O-Fe-N coordination and the electronic environment of Fe-clusters on regulating Fenton-like catalytic performance, and provides a platform for precise engineering of Fe-MOFs.

Selective and ultrafast oxidation of multiple pollutants by biomorphic diatomite-based catalyst and stable catalytic Fenton-like membrane: Degradation behavior and mechanism analysis

Carbon-driven advanced oxidations show great potential in water purification, but regulating structures and properties of carbon-based catalysts to achieve ultrafast Fenton-like reactions remains challenging. Herein, a biomorphic diatomite-based catalyst (BD-C) with Si-O doping was prepared using natural diatomite as silicon source and porous template. The results showed that the metal-free BD-C catalyst exhibited ultrafast oxidation performances (0.95-2.58 min-1) towards a variety of pollutants in PMS-based Fenton-like reaction, with the Fenton-like activity of metal-free catalyst comparable to metal-based catalysts or even single-atom catalysts. Pollutants (e.g., CP, BPA, TC, and PCM) with electron-donating groups exhibited extremely low PMS decomposition with overwhelmed electron transfer process (ETP), while high PMS consumption was induced by the addition of electron-withdrawing pollutants (e.g., MNZ and ATZ), which was dominated by radical oxidation. The BD-C/PMS system also showed a high ability to resist the environmental interference. In-depth theoretical investigations demonstrated that the coordination of Si-O can lower the potential barrier of PMS activation for accelerating the generation of radicals, and also promote the electron transfer from pollutants to the BD-C/PMS complexes. In addition, BD-C was deposited onto a polytetrafluoroethylene membrane (PTFEM) with 100% of pollutants removal over 10 h, thereby revealing the promising prospects of utilizing BD-C for practical applications.

The Unique Fe3Mo3N Structure Bestowed Efficient Fenton-Like Performance of the Iron-Based Catalysts: The Double Enhancement of Radicals and Nonradicals

Iron-based catalysts are widely used in Fenton-like water pollution control technology due to their high efficiency, but their practical applications are limited by complex preparation conditions and strong blockage of Fe2+/Fe3+ cycle during the reaction. Here, a new iron-molybdenum bimetallic carbon-based catalyst is designed and synthesized using cellulose hydrogel for adsorption of Fe and Mo bimetals as a template, and the effective iron cycle in water treatment is realized. The integrated materials (Fe2.5Mo@CNs) with "catalytic/cocatalytic" performance have higher Fenton-like activation properties and universality than the equivalent quantity iron-carbon-based composite catalysts (Fe@CNs). Through the different characterization methods, experimental verifications and theoretical calculations show that the unique Fe3Mo3N structure promotes the adsorption of persulfate and reduces the energy barrier of the reaction, further completing the double enhancement of radicals (such as SO4·-) and nonradicals (1O2 and electron transport process). The integrated "catalytic/cocatalytic" combined material is expected to provide a new promotion strategy for Fenton-like water pollution control.

How hetero-single-atom dispersion reconstructed electronic structure of carbon materials and regulated Fenton-like oxidation pathways

Single-atom catalysts (SACs) have emerged as competitive candidates for Fenton-like oxidation of micro-pollutants in water. However, the impact of metal insertion on the intrinsic catalytic activity of carrier materials has been commonly overlooked, and the environmental risk due to metal leaching still requires attention. In contrast to previous reports, where metal sites were conventionally considered as catalytic centers, our study investigates, for the first time, the crucial catalytic role of the carbon carrier modulated through hetero-single-atom dispersion and the regulation of Fenton-like oxidation pathways. The inherent differences in electronic properties between Fe and Co can effectively trigger long-range electron rearrangement in the sp2-carbon-conjugated structure, creating more electron-rich regions for peroxymonosulfate (PMS) complexation and initiating the electron transfer process (ETP) for pollutant degradation, which imparts the synthesized catalyst (FeCo-NCB) with exceptional catalytic efficiency despite its relatively low metal content. Moreover, the FeCo-NCB/PMS system exhibits enduring decontamination efficiency in complex water matrices, satisfactory catalytic stability, and low metal leaching, signifying promising practical applications. More impressively, the spatial relationship between metal sites and electron density clouds is revealed to determine whether high-valent metal-oxo species (HVMO) are involved during the decomposition of surface complexes. Unlike single-type single-atom dispersion, where metal sites are situated within electron-rich regions, hetero-single-atom dispersion can cause the deviation of electron density clouds from the metal sites, thus hindering the in-situ oxidation of metal within the complexes and minimizing the contribution of HVMO. These findings provide new insights into the development of carbon-based SACs and advance the understanding of nonradical mechanisms underpinning Fenton-like treatments.

Molecular level removal of antibiotic resistant bacteria and genes: A review of interfacial chemical in advanced oxidation processes

As a kind of novel and persistent environmental pollutants, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have been frequently detected in different aquatic environment, posing potential risks to public health and ecosystems, resulting in a biosecurity issue that cannot be ignored. Therefore, in order to control the spread of antibiotic resistance in the environment, advanced oxidation technology (such as Fenton-like, photocatalysis, electrocatalysis) has become an effective weapon for inactivating and eliminating ARB and ARGs. However, in the process of advanced oxidation technology, studying and regulating catalytic active sites at the molecular level and studying the adsorption and surface oxidation reactions between catalysts and ARGs can achieve in-depth exploration of the mechanism of ARGs removal. This review systematically reveals the catalytic sites and related mechanisms of catalytic antagonistic genes in different advanced oxidation processes (AOPs) systems. We also summarize the removal mechanism of ARGs and how to reduce the spread of ARGs in the environment through combining a variety of characterization methods. Importantly, the potential of various catalysts for removing ARGs in practical applications has also been recognized, providing a promising approach for the deep purification of wastewater treatment plants.

From nano- to macroarchitectures: designing and constructing MOF-derived porous materials for persulfate-based advanced oxidation processes

Persulfate-based advanced oxidation processes (PS-AOPs) have gained significant attention as an effective approach for the elimination of emerging organic contaminants (EOCs) in water treatment. Metal-organic frameworks (MOFs) and their derivatives are regarded as promising catalysts for activating peroxydisulfate (PDS) and peroxymonosulfate (PMS) due to their tunable and diverse structure and composition. By the rational nanoarchitectured design of MOF-derived nanomaterials, the excellent performance and customized functions can be achieved. However, the intrinsic fine powder form and agglomeration ability of MOF-derived nanomaterials have limited their practical engineering application. Recently, a great deal of effort has been put into shaping MOFs into macroscopic objects without sacrificing the performance. This review presents recent advances in the design and synthetic strategies of MOF-derived nano- and macroarchitectures for PS-AOPs to degrade EOCs. Firstly, the strategies of preparing MOF-derived diverse nanoarchitectures including hierarchically porous, hollow, yolk-shell, and multi-shell structures are comprehensively summarized. Subsequently, the approaches of manufacturing MOF-based macroarchitectures are introduced in detail. Moreover, the PS-AOP application and mechanisms of MOF-derived nano- and macromaterials as catalysts to eliminate EOCs are discussed. Finally, the prospects and challenges of MOF-derived materials in PS-AOPs are discussed. This work will hopefully guide the design and development of MOF-derived porous materials in SR-AOPs.

Electronic structure modulation of iron sites with fluorine coordination enables ultra-effective H2O2 activation

Electronic structure modulation of active sites is critical important in Fenton catalysis as it offers a promising strategy for boosting H2O2 activation. However, efficient generation of hydroxyl radicals (•OH) is often limited to the unoptimized coordination environment of active sites. Herein, we report the rational design and synthesis of iron oxyfluoride (FeOF), whose iron sites strongly coordinate with the most electronegative fluorine atoms in a characteristic moiety of F-(Fe(III)O3)-F, for effective H2O2 activation with potent •OH generation. Results demonstrate that the fluorine coordination plays a pivotal role in lowering the local electron density and optimizing the electronic structures of iron sites, thus facilitating the rate-limiting H2O2 adsorption and subsequent peroxyl bond cleavage reactions. Consequently, FeOF exhibits a significant and pH-adaptive •OH yield (~450 µM) with high selectivity, which is 1 ~ 3 orders of magnitude higher than the state-of-the-art iron-based catalysts, leading to excellent degradation activities against various organic pollutants at neutral condition. This work provides fundamental insights into the function of fluorine coordination in boosting Fenton catalysis at atomic level, which may inspire the design of efficient active sites for sustainable environmental remediation.

Self-motivated photoaging of microplastics by biochar-dissolved organic matter under different pyrolysis temperatures

Dissolved organic matter (DOM) released from biochar (BDOM) can interact with microplastics (MPs) in the environment, inevitably affecting their environmental behaviour. Information regarding the influence of BDOM on MPs during photoaging and associated variations in the MP aging mechanism remains unclear. This study evaluated the effect of BDOM on the aging of polystyrene (PS) MPs. The results showed that among three pyrolysis temperatures, low-temperature BDOM significantly enhanced the photoaging process of PS MPs, with the smallest average particle size and highest carbonyl index value after 15 days of aging under light conditions. The DOM level decreased after 5 days, increased after 5-10 days, and stabilised after 15 d. BDOM accelerates PS MPs aging, leading to more DOM released from PS, which can be transformed into 1O2 via triplet-excited state (3DOM⁎ and 3PS⁎) to further enhance PS MPs aging, resulting in the realisation of the self-accelerated aging process of PS MPs. 1O2 plays a crucial role in the self-motivated accelerated aging process of PS MPs. These findings provide new insights into the effects of the DOM structure and composition on reactive oxygen species generation during MPs aging.

New modifications of PBAT by a small amount of oxalic acid: Fast crystallization and enhanced degradation in all natural environments

Biodegradable plastics are often mistakenly thought to be capable of degrading in any environment, but their slow degradation rate in the natural environment is still unsatisfactory. We synthetized a novel series of poly(butylene oxalate-co-adipate-co-terephthalate) (PBOAT) with unchanged melting point (135 °C), high elastic modulus (140 - 219 MPa) and elongation at break (478 - 769%). Fast isothermal crystallization with a semi-crystallization time < 20 s was demonstrated by the PBOAT. In N2 and air atmospheres, the PBOAT maintained the Td,5% higher than 329 °C. They also had good thermal stability at melt processing temperature for more than 20 min. PBOAT exhibited faster hydrolysis and seawater degradation, even under natural soil burial without light, but still kept stable under low humidity conditions during the storage and the shelf-life. Moreover, the hydrolysis mechanisms were clarified based on Fukui function analysis and DFT calculation, indicating that the hydrolysis of PBOAT would be more straightforward. The mechanism of soil burial is also elucidated through detailed characterization of the structure changes. The PBOAT offered a fresh approach to the development of high-performing, naturally degradable materials.

Regulating electronic structure of Fe single-atom site by S/N dual-coordination for efficient Fenton-like catalysis

The activity of single-atom catalysts in peroxymonosulfate activation process is bound up with the local electronic state of metal center. However, the large electronegativity of N atoms in Metal-N4 restricts the electron transfer between center metal atom and peroxymonosulfate. Herein, we constructed Fe-SN-C catalyst by incorporating S atom in the first coordination sphere of Fe single-atom site (Fe-S1N3) for Fenton-like catalysis. The Fe-SN-C with a low valent Fe is found to exhibit excellent catalytic activity for bisphenol A degradation, and the corresponding rate constant reaches 0.405 min-1, 11.9-fold higher than the original Fe-N-C. Besides, the Fe-SN-C/PMS system exhibits ideal catalytic stability under the effect of wide pH range and background substrates by the fast generation of high-valent Fe species. Experimental results and theoretical calculations reveal that the dual coordination of S and N atoms notably increases the local electron density of Fe atoms and electron filling in eg orbital, causing a d band center shifting close to the fermi level and thereby optimizes the activation energy for peroxymonosulfate decomposition via Fe 3d-O 2p orbital interaction. This work provides further development of promising SACs for the efficient activation of peroxymonosulfate based on direct regulation of the coordination environment of active center metal atoms.

Engineering Escherichia coli for cost-effective production of medium-chain fatty acids from soy whey using an optimized galactose-based autoinduction system

Medium-chain fatty acids (MCFAs) are essential chemical feedstocks. Microbial production of MCFAs offers an attractive alternative to conventional methods, but the costly media and external inducers limit its practical application. To address this issue and make MCFA production more cost-effective, an E.coli platform was developed using soy whey as a medium and galactose as an autoinducer. We first designed an efficient, stringent, homogeneous, and robust galactose-based autoinduction system for the expression of pathway enzymes by rationally engineering the promoter of the galactose-proton symporter (GalP). Subsequently, the intracellular acetyl-CoA availability and NADH regeneration were enhanced to improve the reversal of the β-oxidation cycle. The resulting strain yielded 8.20 g/L and 16.42 g/L MCFA in pH-controlled batch fermentation and fed-batch fermentation with glucose added using soy whey as medium, respectively. This study provided a cost-effective and promising platform for MCFA production, as well as future strain development for other value-added chemicals production.

Electronic configuration regulation of single-atomic Mn sites mediated by Mo/Mn clusters for an efficient hydrogen evolution reaction

Tuning the electron distribution of metal single-atom active sites via bimetallic clusters is an effective way to enhance their hydrogen evolution reaction (HER) activity, but remains a great challenge. A biochar-based electrocatalyst (BCMoMn800-2) with both MnN4 active sites and Mo2C/Mn7C3 clusters was synthesized using in situ enriched Mo/Mn biomass as a precursor to trigger the HER. Various characterization and density functional theory (DFT) calculation results indicated that the presence of Mo2C/Mn7C3 clusters in BCMoMn800-2 effectively induced the redistribution of charges at MnN4 sites, reducing the energy of H* activation during the HER. In 0.5 M H2SO4, the overpotential was 27.4 mV at a current density of 10 mA cm-2 and the Tafel slope was 31 mV dec-1, and its electrocatalytic performance was close to that of Pt/C. The electrocatalyst also exhibited excellent electrocatalytic stability and durability. This work might provide a new strategy for solid waste recycling and constructing efficient HER electrocatalysts.

Unlocking Bimetallic Active Centers via Heterostructure Engineering for Exceptional Phosphate Electrosorption: Internal Electric Field-Induced Electronic Structure Reconstruction

Development of electrode materials exhibiting exceptional phosphate removal performance represents a promising strategy to mitigate eutrophication and meet ever-stricter stringent emission standards. Herein, we precisely designed a novel LaCeOx heterostructure-decorated hierarchical carbon composite (L8C2PC) for high-efficiency phosphate electrosorption. This approach establishes an internal electric field within the LaCeOx heterostructure, where the electrons transfer from Ce atoms to neighboring La atoms through superexchange interactions in La-O-Ce coordination units. The modulatory heterostructure endows a positive shift of the d band of La sites and the increase of electron density at Fermi level, promoting stronger orbital overlap and binding interactions. The introduction of oxygen vacancies during the in situ nucleation process reduces the kinetic barrier for phosphate-ion migration and supplies additional active centers. Moreover, the hierarchical carbon framework ensures electrical double-layer capacitance for phosphate storage and interconnected ion migration channels. Such synergistically multiple active centers grant the L8C2PC electrode with high-efficiency record in phosphate electrosorption. As expected, the L8C2PC electrode demonstrates the highest removal capability among the reported electrode materials with a saturation capacity of 401.31 mg P g-1 and a dynamic capacity of 91.83 mg P g-1 at 1.2 V. This electrochemical system also performs well in the dephosphorization in natural water samples with low concentration that enable effluent concentration to meet the first-class discharge standard for China (0.5 mg P L-1). This study advances efficient dephosphorization techniques to a new level and offers a deep understanding of the internal electric field that regulates metal orbitals and electron densities in heterostructure engineering.

Deep Oxidation of Chlorinated VOCs by Efficient Catalytic Peroxide Activation over Nanoconfined Co@NCNT Catalysts

The catalytic removal of chlorinated VOCs (CVOCs) in gas-solid reactions usually suffers from chlorine-containing byproduct formation and catalyst deactivation. AOP wet scrubber has recently attracted ever-increasing interest in VOC treatment due to its advantages of high efficiency and no gaseous byproduct emission. Herein, the low-valence Co nanoparticles (NPs) confined in a N-doped carbon nanotube (Co@NCNT) were studied to activate peroxymonosulfate (PMS) for efficient CVOC removal in a wet scrubber. Co@NCNT exhibited unprecedented catalytic activity, recyclability, and low Co ion leakage (0.19 mg L-1) for chlorobenzene degradation in a very wide pH range (3-11). The chlorobenzene removal efficiency was kept stable above 90% over Co@NCNT, much higher than that of nonconfined Co@NCNS (45%). The low-valence Co NPs achieved a continuous electron redox cycling (Co0/Co2+ → Co3+ → Co0/Co2+) and greatly promoted the O-O bond dissociation of PMS with the least energy (0.83 eV) inside the channel of Co@NCNT to form abundant HO• and SO4•-. Thus, the deep oxidation of chlorobenzene was achieved without any biphenyl byproducts from the coupling reaction. This study provided a new avenue for designing novel nanoconfined catalysts with outstanding activity, paving the way for the deep oxidation of CVOC waste gas via AOP wet scrubber.

Precise coordination of high-loading Fe single atoms with sulfur boosts selective generation of nonradicals

Nonradicals are effective in selectively degrading electron-rich organic contaminants, which unfortunately suffer from unsatisfactory yield and uncontrollable composition due to the competitive generation of radicals. Herein, we precisely construct a local microenvironment of the carbon nitride-supported high-loading (~9 wt.%) Fe single-atom catalyst (Fe SAC) with sulfur via a facile supermolecular self-assembly strategy. Short-distance S coordination boosts the peroxymonosulfate (PMS) activation and selectively generates high-valent iron-oxo species (FeIV=O) along with singlet oxygen (1O2), significantly increasing the 1O2 yield, PMS utilization, and p-chlorophenol reactivity by 6.0, 3.0, and 8.4 times, respectively. The composition of nonradicals is controllable by simply changing the S content. In contrast, long-distance S coordination generates both radicals and nonradicals, and could not promote reactivity. Experimental and theoretical analyses suggest that the short-distance S upshifts the d-band center of the Fe atom, i.e., being close to the Fermi level, which changes the binding mode between the Fe atom and O site of PMS to selectively generate 1O2 and FeIV=O with a high yield. The short-distance S-coordinated Fe SAC exhibits excellent application potential in various water matrices. These findings can guide the rational design of robust SACs toward a selective and controllable generation of nonradicals with high yield and PMS utilization.

Fenton-like activity and pathway modulation via single-atom sites and pollutants comediates the electron transfer process

The studies on the origin of versatile oxidation pathways toward targeted pollutants in the single-atom catalysts (SACs)/peroxymonosulfate (PMS) systems were always associated with the coordination structures rather than the perspective of pollutant characteristics, and the analysis of mechanism commonality is lacking. In this work, a variety of single-atom catalysts (M-SACs, M: Fe, Co, and Cu) were fabricated via a pyrolysis process using lignin as the complexation agent and substrate precursor. Sixteen kinds of commonly detected pollutants in various references were selected, and their lnkobs values in M-SACs/PMS systems correlated well (R2 = 0.832 to 0.883) with their electrophilic indexes (reflecting the electron accepting/donating ability of the pollutants) as well as the energy gap (R2 = 0.801 to 0.840) between the pollutants and M-SACs/PMS complexes. Both the electron transfer process (ETP) and radical pathways can be significantly enhanced in the M-SACs/PMS systems, while radical oxidation was overwhelmed by the ETP oxidation toward the pollutants with lower electrophilic indexes. In contrast, pollutants with higher electrophilic indexes represented the weaker electron-donating capacity to the M-SACs/PMS complexes, which resulted in the weaker ETP oxidation accompanied with noticeable radical oxidation. In addition, the ETP oxidation in different M-SACs/PMS systems can be regulated via the energy gaps between the M-SACs/PMS complexes and pollutants. As a result, the Fenton-like activities in the M-SACs/PMS systems could be well modulated by the reaction pathways, which were determined by both electrophilic indexes of pollutants and single-atom sites. This work provided a strategy to establish PMS-based AOP systems with tunable oxidation capacities and pathways for high-efficiency organic decontamination.

Enhancing methane production and organic loading capacity from high solid-content wastewater in modified granular activated carbon (GAC)-amended up-flow anaerobic sludge blanket (UASB)

Anaerobic digestion of high solid-content wastewater is hindered by high organic loading rates (OLRs). Granular activated carbon (GAC) was reported to promote direct interspecies electron transfer (DIET) and enhance reactor performance. In this study, three up-flow anaerobic sludge blanket (UASB) reactors were supplied with GAC in different locations: bottom (R1), top (R2), and bottom+top (R3). The performances of three reactors at different OLRs treating high solid-content wastewater were evaluated. At a low OLR, the highest methane yield (74 ± 4 %, g CH4-COD/g TCOD) was detected when GAC was supplied at top of the UASB (R2). When a high OLR was applied, the UASB supplemented with GAC at both bottom and top (R3) achieved the highest methane yield (66 ± 2 %, g CH4-COD/g TCOD), whereas the UASB supplemented with GAC at the top (R2) failed. Further studies on spatial distributions of sludge stability, specific methanogenic activities (SMAs), and microbial communities demonstrated the different impacts of GAC location on reactor performance and sludge characteristics under different OLRs. This study highlights the significance of considering organic loading capacity treating high solid-content wastewater when choosing GAC-based UASB systems.

N, S, and Cl tri-doped carbon boost the switching of radical to non-radical pathway in Fenton-like reactions: Synergism of N species and defects

Heteroatom doping represents a promising strategy for enhancing the generation of singlet oxygen (1O2) during the activation of peroxymonosulfate (PMS) using carbon-based catalysts; however, it remains a formidable challenge. In this study, we systematically controlled the structure of metal-free carbon-based materials by introducing different heteroatoms to investigate their efficacy in degrading organic pollutants in water via PMS activation. The results of reactive oxygen species detection showed that the dominant free radical in the four samples was different: CN (•SO4- and •OH), CNS (•O2-), CNCl (1O2), and CNClS (1O2). This led to the transformation of active species from free radicals to non-free radicals. The tri-doped carbons with nitrogen, sulfur, and chlorine (CNClS) exhibited exceptional performance in PMS activation and achieved a remarkable degradation efficiency of 95% within just 6 min for tetracycline. Moreover, a strong linear correlation was observed between the ratio of pyridine-N/graphite-N and ID/IG with the yield of 1O2, indicating that N species and defects play a crucial role in CNClS as they facilitate the transition from radical to non-radical pathways during PMS activation. These findings highlight the possibility that adjustable tri-heteroatom doping will expand the Fenton-like reaction for the treatment of actual wastewater.

Efficient Removal of Antibiotic Resistance Genes through 4f-2p-3d Gradient Orbital Coupling Mediated Fenton-Like Redox Processes

Peroxymonosulfate (PMS) mediated radical and nonradical active substances can synergistically achieve the efficient elimination of antibiotic resistance genes (ARGs). However, enhancing interface electron cycling and optimizing the coupling of the oxygen-containing intermediates to improve PMS activation kinetics remains a major challenge. Here, Co doped CeVO4 catalyst (Co-CVO) with asymmetric sites was constructed based on Ce 4f-O 2p-Co 3d gradient orbital coupling. The catalyst achieved approximately 2.51×105 copies/mL of extracellular ARGs (eARGs) removal within 15 minutes, exhibited ultrahigh degradation rate (k=1.24 min-1 ). The effective gradient 4f-2p-3d orbital coupling precisely regulates the electron distribution of Ce-O-Co active center microenvironment, while optimizing the electronic structure of Co 3d states (especially the occupancy of eg ), promoting the adsorption of oxygen-containing intermediates. The generated radical and nonradical generated by interfacial electron cycling enhanced by the reduction reaction of PMS at the Ce site and the oxidation reaction at the Co site achieved a significant mineralization rate of ARGs (83.4 %). The efficient removal of ARGs by a continuous flow reactor for 10 hours significantly reduces the ecological risk of ARGs in actual wastewater treatment.

Self-carbon-thermal-reduction strategy for boosting the Fenton-like activity of single Fe-N4 sites by carbon-defect engineering

Carbon-defect engineering in metal single-atom catalysts by simple and robust strategy, boosting their catalytic activity, and revealing the carbon defect-catalytic activity relationship are meaningful but challenging. Herein, we report a facile self-carbon-thermal-reduction strategy for carbon-defect engineering of single Fe-N4 sites in ZnO-Carbon nano-reactor, as efficient catalyst in Fenton-like reaction for degradation of phenol. The carbon vacancies are easily constructed adjacent to single Fe-N4 sites during synthesis, facilitating the formation of C-O bonding and lowering the energy barrier of rate-determining-step during degradation of phenol. Consequently, the catalyst Fe-NCv-900 with carbon vacancies exhibits a much improved activity than the Fe-NC-900 without abundant carbon vacancies, with 13.5 times improvement in the first-order rate constant of phenol degradation. The Fe-NCv-900 shows high activity (97% removal ratio of phenol in only 5 min), good recyclability and the wide-ranging pH universality (pH range 3-9). This work not only provides a rational strategy for improving the Fenton-like activity of metal single-atom catalysts, but also deepens the fundamental understanding on how periphery carbon environment affects the property and performance of metal-N4 sites.

Prussian blue analogues-derived zero valent iron to efficiently activate peroxymonosulfate for phenol degradation triggered via reactive oxygen species and high-valent iron-oxo complexes

It is of great significance to develop the effective technique to treat phenol-containing wastewater. Herein, Fe-based prussian blue analogues-derived zero valent iron (ZVI) was successfully synthesized by one-step calcination method. Owing to high specific surface area and rich active sites, ZVI-2 possessed excellent performance in charge transfer. Notably, in comparison with conventional ZVI and Fe2+, ZVI-2 can effectively activate peroxymonosulfate (PMS) for achieving rapid degradation of phenol, and the highest removal efficiency of phenol reached 94.9% within 24 min. More importantly, developed ZVI-2/PMS oxidation system with good stability displayed strong anti-interference capability. Interestingly, Fe0 loaded on the surface of ZVI-2 can efficiently break the O-O bond of PMS to generate reactive oxygen species (i.e., SO4•-, OH•, O2•- and 1O2). As main adsorption sites of PMS, the existence of oxygen vacancy promote the formation of high-valent transition metal complexes (namely ZVI-2≡Fe4+=O). Under the combined action of reactive oxygen species and ZVI-2≡Fe4+=O, phenol can be eventually degraded into CO2 and H2O. The possible degradation pathways of phenol were also investigated. Furthermore, proposed ZVI-2/PMS oxidation system displayed great potential for application in the field of wastewater treatment. All in all, current work provided a valuable reference for design and application of Fe-based catalysts in PS-AOPs.