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

Near-infrared photothermal catalysis for biomass upgrading

The efficient conversion of biomass into value-added chemicals via sunlight-driven processes remains a significant challenge in energy chemistry, particularly within the domain of photothermal catalysis. In this study, we demonstrate that doping Mn2O3 with Na+-induced oxygen vacancies (OVs) significantly enhances its catalytic performance under near-infrared (NIR) irradiation. This modification unveils a novel mechanism for the generation of singlet oxygen (1O2), facilitated by the synergistic action of OVs and hVB+. Utilizing NIR solar energy to activate peroxymonosulfate (PMS), we achieve a high-value oxidation process, employing the bio-based platform molecule 5-hydroxymethylfurfural (HMF) as a model substrate to selectively convert it into 5-formyl-2-furancarboxylic acid (FFCA). This work offers new perspectives on sustainable green chemistry, advancing the efficient transformation of biomass into high-value chemicals through solar-driven processes.

MnO/MnS nanoparticles encapsulated in Lycopodium spores derived nitrogen-doped porous carbon as a cost-effective peroxymonosulfate activator for pollutant decontamination: Insight into the mechanism of electron transfer-dominated non-radical pathway

The rational design and exploitation of cost-effective and robust catalysts for peroxymonosulfate (PMS) activation is of great significance. Herein, MnO/MnS nanoparticles encapsulated in Nitrogen-doped porous carbon skeleton (abbreviated as MnO/MnS@NPC) were first constructed through an easy two-step of impregnation along with subsequent pyrolysis technique and utilized to activate PMS for the elimination and mineralization of tetracycline (TC). Benefiting from the strong coupling of transition metal Mn with carbon-based material, the co-doping of heteroatom N and S, the enhanced electrical conductivity, and the hierarchical porous microarchitecture, the obtained MnO/MnS@NPC composite has been expected to present superior PMS activation capacity and pollutant elimination efficiency to its benchmark NPC and MnO@NPC, with 92.5 % degradation rate of TC within 60 min. Comprehensive investigations, involving quenching experiments, electron paramagnetic resonance (EPR) studies, in situ Raman identification, and electrochemical tests, jointly indicated that the non-radical pathways including electron-transfer, single oxygen (1O2) and the high-valent Mn-oxo species, especially the electron transfer process (ETP) from TC molecule to the metastable MnO/MnS@NPC-PMS* complex were dominantly responsible for PMS activation and further decomposition of TC, which greatly enhanced the selective removal of TC and the anti-interference capacity of the PMS system. Furthermore, the possible TC degradation routes were predicted by Density Functional Theory (DFT) calculation and the toxicity of degradation intermediates were also analyzed by toxicity assessment software. In addition, the heterogeneous catalyst displayed outstanding stability and reusability owing to the shield effect of NPC framework to MnO/MnS nanoparticles. Overall, this work proposed a prospective strategy for rationally designing and exploring heterogeneous PMS activator towards wastewater purification.

Differential catalytic mechanism induced by selective adsorption of pollutants in metal clusters decorated single atom catalyst mediated heterogeneous Fenton-like reaction

Although metal clusters are generally considered as impurities accompanying the synthesis of single atom catalysts, their extraordinary potential in regulating single atom catalytic reactions has attracted widespread attention. In this study, iron cluster decorated single atom iron catalyst (Fe-SACAs) were synthesized to activate peroxymonosulfate (PMS) for the removal of organic pollutants, and a differential PMS activation mechanism induced by selective adsorption of pollutants was observed for the first time. The chemical coordination between pollutants and active sites was identified as the dominant chemisorption mechanism for the adsorption of organic pollutants by Fe-SACAs. The competitive occupation of PMS activation sites by pollutants induced by the diversity of targeted pollutant molecules in ionization potentials was thereby revealed to be the inducement for the adsorption-dependent oxidation. The adsorption-dependent oxidation mechanism was fully elucidated using density functional theory (DFT). Finally, an optimized treatment process was proposed based on the adsorption-dependent oxidation mechanism, which achieved zero oxidant residue and pollutant emission simultaneously. This study unveils the crucial effect of reactant mass transfer and adsorption on the oxidation process in Fe-SACAs mediated Fenton-like reactions.

Modulating the electronic configuration of single-atom nanozymes using cobalt nanoclusters for enhanced mycotoxin degradation

Herein, Co- and Fe-based single-atom nanozymes (M/N-PC, M = Co or Fe) were successfully fabricated and their catalytic performances for patulin degradation were evaluated systematically. Co/N-PC, consisting of Co-N4 and nanoclusters sites, achieved a higher patulin degradation efficiency (99.4 %, within 60 min) than Fe/N-PC (only consisting of Fe-N5 sites). Synergistic interactions between Co-N4 and Co nanoclusters greatly enhanced electron density near the Fermi level in Co/N-PC, enabling its high catalytic performance. The degradation products of patulin exhibited negligible cytotoxicity. The M/N-PCs demonstrated good reusability, broad pH adaptability and high practical application potential for patulin degradation in apple juice. M/N-PC also exhibited high efficiency in degrading aflatoxin B1, deoxynivalenol and zearalenone (∼100 %, 10-40 min). This study provides in-depth insights into the relationship between metal active site structures in M/N-PCs and their catalytic properties for mycotoxin detoxification, offering guidance for the design of highly efficient single-atom nanozymes.

State-Of-The-Art Structural Regulation Methods and Quantum Chemistry for Carbon-Based Single-Atom Catalysts in Advanced Oxidation Process: Critical Perspectives into Molecular Level

Advanced oxidation processes (AOPs) by carbon-based single-atom catalysts (SACs) are recognized as an attractive scientific frontier for water treatment, with the outstanding benefits of ultra-effective and anti-interference capability. However, most of the research has paid more attention to the performance of SACs, while the in-depth understanding of catalytic regulation by molecular interaction is relatively deficient. This critical review delves into deciphering the catalytic mechanism through a micro-level, which makes it more convenient to interpret apparent catalytic phenomena. It first summarizes basic theories of quantum chemistry, which provide mechanism interpretation and prediction for molecular-oxidation systems. Additionally, corresponding oxidation pathways of common oxidants are underscored. Following the oxidants, state-of-the-art regulation methods are discussed with special attention to involved molecular interactions and pollutants. Particularly, the preliminary insights into the "oxidant-catalyst-pollutants" internal relationships are provided to help construct the SAC-AOP system from a molecular standpoint. Meanwhile, some cutting-edge laboratory devices and pilot-scale engineering are presented to illustrate the ultimate purpose of scientific molecular exploration. Eventually, relative challenges of SACs-AOPs upon the design of catalytic systems and investigation methods are provided. This review aims to promote the large-scale potential of SACs-based AOPs in practical water treatment by emphasizing the pivotal role of micro-insights.

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.

Temperature-induced atomic intrinsic sites evolution during waste dyeing sludge into the wealthy iron-based catalyst to sustainable decontamination

Although the worldwide spike in the production of dyeing sludge offers a tantalizing resource to be harnessed, effective waste-to-wealth strategies remain elusive due to its intricate toxic organic matter and metallic elements. Here, we developed a temperature-rebuilding strategy to transform discarded dyeing sludge into an iron-based catalyst with favorable charge transfer for the highly efficient and sustainable Fenton-like catalytic degradation of ppm-level contaminants in wash-tank water. Using X-ray diffraction, X-ray photoelectron spectroscopy, and synchrotron X-ray absorption spectroscopy, we could precisely track and identify the gradual formation of inherent sites (i.e., Fe2(SO4)3, FeOOH, and Fe1-xS) towards active sites (i.e., FeS and Fe0) at crystal, surface, and atomic levels. Benefiting from the reconstruction of iron sites, BC-800 effectively decomposed peroxymonosulfate into multiple radicals and nonradicals through electronic structure modulation, which enabled nearly 100 % degradation and over 60 % mineralization rate of common aromatic compounds within 30 min via ring-opening and dechlorination/substitution pathways. More delightedly, the BC-800 maintained excellent Fenton-like activity across a broad pH or multiple anions coexisted, and its device allowed extended parachlorophenol degradation for over 1 d. This work proposes a feasible "waste control by waste" approach to the reutilization of dyeing sludge, encouraging a potential solution for sustainable wastewater treatment.

Synchronization Strategy for Activity and Stability in Fenton-Like Single-Atom Catalysis

Single-atom catalysts (SACs) have garnered significant attention in the applications of environmental remediation based on Fenton-like systems. Current research on Fenton-like single-atom catalysis often emphasizes catalytic activity and mechanism regulation, while paying limited attention to the simultaneous enhancement of both activity and stability-a critical factor for the practical and scale-up applications of SACs. This review systematically summarizes recent advances in synchronization strategies for improving the activity and stability of Fenton-like single-atom catalysis, with a focus on the design principles and mechanisms of four key strategies: coordination engineering, confinement effects, carrier substitution, and catalytic module design. To the best of knowledge, this represents the first comprehensive review of Fenton-like single-atom catalysis from the perspective of concurrent optimization of activity and stability. Additionally, the auxiliary role of machine learning and lifecycle assessment (LCA) is evaluated in advancing these synchronization strategies. By investigating the interplay among different support materials, coordination configurations, and reaction environments, as well as enlarged modules, key factors governing the stability/activity of SACs are highlighted, and future directions are proposed for developing next-generation catalysts with high efficiency and long-term durability for practical environmental remediation.

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.

Structural evolution of metal single-atoms and clusters in catalysis: Which are the active sites under operative conditions?

The structural evolution of metal single-atoms and clusters has been recognized as the new frontier in catalytic reactions under operative conditions, playing a crucial role in key aspects of catalytic behavior, including activity, selectivity, stability, and atomic efficiency as well as precise tunability in heterogeneous catalysis. Accurately identifying the structural evolution of metal single-atoms and clusters during real reactions is essential for addressing fundamental issues such as active sites, metal-support interactions, deactivation mechanisms, and thereby guiding the design and fabrication of high-performance single-atom and cluster catalysts. However, how to evaluate the dynamic structural evolution of metal species during catalytic reactions is still lacking, hindering their industrial applications. In this review, we discuss the behaviors of dynamic structural evolution between metal single-atoms and clusters, explore the driving force and major factors, highlight the challenges and inherent limitations encountered, and present relevant future research trends. Overall, this review provides valuable insights that can inspire researchers to develop novel and efficient strategies for accurately identifying the structural transformations of metal single-atoms and clusters.

Sulfur Bridge Geometry Boosts Selective FeIV═O Generation for Efficient Fenton-Like Reactions

High-valent iron-oxo species (FeIV═O) is a fascinating enzymatic agent with excellent anti-interference abilities in various oxidation processes. However, selective and high-yield production of FeIV═O remains challenging. Herein, Fe diatomic pairs are rationally fabricated with an assisted S bridge to tune their neighbor distances and increase their loading to 11.8 wt.%. This geometry regulated the d-band center of Fe atoms, favoring their bonding with the terminal and hydroxyl O sites of peroxymonosulfate (PMS) via heterolytic cleavage of O─O, improving the PMS utilization (70%), and selective generation of FeIV═O (>90%) at a high yield (63% of PMS) offers competitive performance against state-of-the-art catalysts. These continuous reactions in a fabricated device and technol-economic assessment further verified the catalyst with impressive long-term activity and scale-up potential for sustainable water treatment. Altogether, this heteroatom-bridge strategy of diatomic pairs constitutes a promising platform for selective and efficient synthesis of high-valent metal-oxo species.

Improvement Catalytic Efficiency of the Fenton-Like Reaction via the Interaction among Fe Species Encapsulated in N-Doped Carbon Materials

The Fenton-like reaction has been widely used for environmental modification. However, improvement of the catalytic efficiency is still a challenge. In this study, a series of core-shell-shaped catalysts (FeNC-x, x presents the calcination temperature) for the Fenton-like reaction was fabricated through the pyrolysis of the Fe-based metal-organic frameworks (Fe-MOF). The Fe species were encapsulated by the N-doped carbon materials and changed from Fe3O4 to Fe3C, α-Fe, and Fe-N4 with the temperature increasing from 500 to 800 °C. Simultaneously, the electron density of the Fe atom obviously increased. FeNC-650 exhibited high efficiency, as more than 85.6% TC (40 mg/L) instantaneous removal through the H2O2-based Fenton-like reaction. The turnover number is about 70 and 64 times higher than that of Fe-MOF and FeNC-500. The synergistic interaction among Fe3C, α-Fe, and Fe-N4 induced electron distribution around the Fe atom and excellent catalytic performances. Moreover, FeNC-650 exhibited excellent interference resistance toward different anions and humic acid. The toxicity of intermediate products decreased during the TC degradation. This research may give a strategy for the synthesis of catalysts used in wastewater purification.

Integrated Three-in-one to Boost Nitrate Electroreduction to Ammonia Utilizing a 1D Mesoporous Carbon Cascade Nanoreactor

The electrochemical reduction of nitrate (NO3-) offers a promising waste-to-value strategy for synthesizing ammonia (NH3), yet it involves a complex multi-interface system with several stages such as mass transport, species enrichment, and interfacial transformation. This complexity necessitates catalysts with diverse structural characteristics across multiple temporal and spatial scales. Herein, a three-in-one nanoreactor system is designed with 1D geometry, open mesochannels, and synergistic active sites for optimized NH3 synthesis. Guided by finite element simulations, a 1D mesoporous carbon carrier is engineered to create a distinctive microenvironment that enhances NO3- transfer and adsorption while confining reaction intermediates. Meanwhile, iron single atomic sites (Fe-N4 SAs) and iron nanoclusters (Fe4 NCs) are embedded in situ into the carbon carrier, yielding an efficient cascade nanoreactor. This design demonstrates large Faraday efficiencies, rapid NO3- removal rates, and impressive NH3 yield rates under both neutral and alkaline conditions. Detailed in situ experimental results and theoretical analysis reveal that Fe-N4 SAs and Fe4 NCs can adapt their electronic structures in tandem, allowing the Fe-N4 SAs to effectively reduce NO3- and Fe4 NCs to oxidize H2O. As a demonstration, the assembled Zn-NO3- battery achieves a power density of 20.12 mW cm-2 coupled with excellent rechargeability.

Co single-atom catalyst for efficient and long-acting activation of peroxymonosulfate: Formation of Co-N4 site and insight into the activation mechanism

While single-atom catalysts (SACs) have been extensively investigated as a high-atom-efficiency heterogeneous catalyst for peroxymonosulfate (PMS) oxidation reaction, the stable constructing and activation efficacy of the reaction sites remains less clarified. Herein, we employed gelatin as a N,O-bidentate ligand for Co (II) to form for a N-doped carbon precursor, while introducing NaCl as a template agent to induce the adoption of a Co-N conformation and disorganize the Co-O moiety. This approach facilitates uniform spatial isolation and atomic-level dispersion of Co atoms within the aerogel, effectively inhibiting the aggregation of Co during synthesis and enabling precise and controllable preparation of Co single-atom catalysts (SACs). As a result, the obtained SCAs/PMS system rapidly eliminated more than 99.6 % of 40 mg/L commercial dye in 10 min. Experimental and theoretical results reveal that the Co-N4 site can trigger facilitative dissociation/desorption of reaction intermediates and reduce energy barrier for SO5* and H* form, thereby redirecting the dissociation pathway from direct contiguous electron transfer to ROS-mediated degradation. Importantly, Co-N4 not only enhances the chemical adsorption and electron transfer between PMS and catalysts, but also functions as an interface electron bridge to facilitate internal electron hopping. As a beneficial effect that collectively endows the alternating of Co-N4 sites and ultimately improve the long-term catalytic stability. This study provides a comprehensive understanding of the Co-N4 sites and PMS activation mechanism in Co-SACs, shedding light on the structural-property correlation for PMS activation.

Surface-hydroxylated single-atom catalyst with an isolated Co-O-Zn configuration achieves high selectivity in regulating active species

Single-atom catalysts (SACs) are emerging as potent tools for the selective regulation of active species, offering substantial promise for green and sustainable Fenton catalysis. However, current SACs face limitations due to the specificity of their supports, which only allow selective regulation within certain oxidant systems. This constraint makes targeted regulation across different systems challenging. In response, this study designs a SAC, termed CoSAs-ZnO, featuring surface hydroxylation and an isolated asymmetric Co-O-Zn configuration. This SAC can realize a nearly 100% selective generation of sulfate radicals (SO4•-) and singlet oxygen (1O2) in peroxymonosulfate (PMS) and peracetic acid (PAA) systems, respectively. Moreover, the PMS-activated system can efficiently treat electron-deficient-dominated and refractory benzoic acid wastewater, achieving 100.0% removal in multiple consecutive pilot-scale experiments. The PAA-activated system facilitates the rapid conversion of benzyl alcohol to benzaldehyde, with a high selectivity of 89.0%. Detailed DFT calculations reveal that the surface hydroxyl groups on ZnO play a critical role in modulating the adsorption configurations of the oxidants, thus enabling the selective generation of specific active species in each system. This study provides insights into the design of SACs for multifunctional applications and paves the way for their deployment in wastewater treatment and high-value chemical conversion.

Robust Fe-N4-C6O2 single atom sites for efficient PMS activation and enhanced FeIV = O reactivity

The microenvironment regulation of Fe-N4 single atom catalysts (SACs) critically governs peroxymonosulfate (PMS) activation. Although conventional heteroatom substitution in primary coordination enhances activity, it disrupts Fe-N4 symmetry and compromises stability. Herein, we propose oxygen doping in the secondary coordination shell to construct Fe-N4-C6O2 SAC, which amplifies the localized electric field while preserving the pristine coordination symmetry, thus trading off its activity and stability. This approach suppresses Fe-N bond structural deformation (bond amplitude reduced from 0.875-3.175 Å to 0.925-2.975 Å) during PMS activation by lowering Fe center electron density to strengthen Fe-N bond, achieving extended catalytic durability (>240 h). Simultaneously, the weakened coordination field lowers the Fe=O σ* orbital energy, promoting electrophilic σ-attack of high-valent iron-oxo towards bisphenol A, and increasing its degradation rate by 41.6-fold. This work demonstrates secondary coordination engineering as a viable strategy to resolve the activity-stability trade-off in SAC design, offering promising perspectives for developing environmental catalysts.

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.

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.

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.

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.

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.