Co3O4 with upshifted d-band center and enlarged specific surface area by single-atom Zr doping for enhanced PMS activation

Spinel-based zinc-doped Co3O4 (ZCO) catalytic membrane for efficient peroxymonosulfate activation and chloroquine phosphate degradation: An atom doping strategy

The degradation of emerging contaminants (ECs) in wastewater remains a significant challenge, primarily due to the low activation efficiency and difficulty in catalyst recovery associated with traditional heterogeneous peroxymonosulfate (PMS) systems. In this study, a zinc (Zn)-doped Co3O4 spinel (ZCO) catalyst was designed via an atom doping strategy and immobilized onto a polyvinylidene fluoride (PVDF) membrane to construct a ZCO@PVDF catalytic membrane, thereby developing an efficient and innovative approach for ECs degradation. The innovation of this study is the Zn doping-induced electron-polarized distribution, which creates electron-rich Co centers and significantly enhances the PMS activation efficiency. The porous structure and confined space of the membrane significantly improved the exposure of active sites, facilitated interfacial mass transfer, and promoted reactant enrichment. Consequently, the ZCO@PVDF membrane/PMS system enabled the efficient filtration-based removal of Chloroquine phosphate, with the pseudo-first-order rate constant K of 0.035 ms-1 for its removal. The system exhibited exceptional catalytic performance, achieving 99.9 % Chloroquine phosphate degradation within 30 min, with the pseudo-first-order rate constant K dominating the reaction (pH = 6.8, PMS = 1.6 mM, Chloroquine phosphate = 10 mg L-1, Catalyst loading = 2.0 mg cm-2). The active species responsible for the degradation of emerging pollutants in the ZCO@PVDF membrane/PMS system was SO4·-, ·OH, and 1O2. The degradation pathway and toxicity evolution of Chloroquine phosphate were identified through molecular orbital calculations, Fukui index analysis, HPLC testing, and T.E.S.T. software predictions. This immobilized catalytic membrane-based AOPs presents an innovative solution to overcome the limitations of conventional heterogeneous catalysis.

In Situ Construction of the van Der Waals Heterojunction Based on Co3O4/g-C3N4 for the Highly Efficient Degradation of Tetracycline under Visible Light

Advanced oxidation processes have been increasingly applied to degrade organic pollutants through the generation of strong oxidizing radicals by catalyst activation reactions. In this study, the Co3O4/g-C3N4 van der Waals heterojunction (CCN) was successfully prepared by calcining a mixture of Co3O4 and g-C3N4 (BCN) in order to improve the performance and elucidate the mechanism of the CCN-activated peroxymonosulfate (PMS) catalytic degradation of tetracycline (TC) under visible light. This unique nanostructure possesses an abundance of active sites, thus significantly facilitating the transport of charge. The TC removal rate of the optimized heterojunction reaches 300.1 × 10-3 min-1 within 10 min under visible light, nearly 46.2 times that of BCN. The degradation of TC was dominated by h+ and 1O2. The degradation pathways of TC were analyzed in detail. The reduced toxicity of the intermediates reveals the potential risk to the environment posed by the CCN-3/PMS system. Finally, a preliminary economic analysis of this process was carried out. The study provides a simple and promising route for the efficient activation of PMS by CCN for photocatalytic remediation of water pollution.

Zirconium-doped iron oxide nanoparticles for enhanced peroxidase-like activity

Fe3O4 nanoparticles (NPs) have emerged as pioneering nanozymes with applications in clinical diagnosis, environmental protection and biosensing. However, it is currently limited by insufficient catalytic activity due to poor electron transfer. In this study, we synthesized electron-rich-Zr-doped defect-rich Fe3O4 NPs (Zr3Fe3O4) using a one-pot solvothermal method. Compared with intrinsic Fe3O4 NPs, the resultant Zr3Fe3O4 NPs exhibit enhanced peroxidase (POD)-like activity attributed to the presence of active centers of Zr-O-Fe bridges and adsorption sites of asymmetric oxygen vacancies (OVs) Zr-OVs-Fe. The Zr-O-Fe bridges facilitate electron transfer from Zr to Fe, promoting the regeneration of surface Fe2+ in Fe3O4 NPs. Furthermore, the rich Zr-OVs-Fe significantly enhances the adsorption and electron transfer between catalyst and substrates, thereby regulating the generation pathway of 1O2. Leveraging the remarkable POD-like activity of Zr3Fe3O4 NPs, we developed a tandem enzyme-catalyzed reaction for colorimetric detection of glucose. This strategy of constructing active centers by atom doping provides valuable guidance for the development of more efficient Fenton-like catalytic systems with broad applications on a large scale.

Cobalt-modification on UiO-bpydc MOF facilitates ligand-to-metal charge transfer for superior visible-light photocatalytic degradation of refractory fluoroquinolone antibiotics

Pollutant removal through green photocatalysis combined with advanced oxidation processes (AOPs) is critical for efficient wastewater treatment but is limited by poor light harvesting and inefficient oxidant activation. This study addresses these challenges through developing a Co-incorporated UiO-bpydc MOF for enhanced visible-light-driven photocatalysis via peroxymonosulfate (PMS) bridged ligand-to-metal charge transfer (LMCT). The MOF was synthesized through direct cobalt complexation into the UiO-bpydc framework for enabling visible light absorption. The UiO-bpydc(Co) achieved 95.8 % degradation of lomefloxacin (LOM) within 30 min in the presence of PMS, attributing to narrowed bandgap (i.e., 2.82 eV), improved charge transfer via Co centers, and increased pollutant affinity due to electron-rich ligand. Additionally, the generation of long-lifespan singlet oxygen (1O2, 41.8 %) was identified as the key reactive species. Theoretical calculations indicated a reduced HOMO-LUMO gap upon the formation of a -Co-OOSO3 bridge, which promotes carrier separation and improves pollutant-catalyst interactions. The degradation pathways and toxicity evolution of intermediates were clarified, while the exceptional stability, recyclability, and broad pollutant applicability of UiO-bpydc(Co) demonstrate its potential for utilization in oxidative environments This work highlights the potential of transition metal doping to alter the electronic structure of MOFs for target-specific catalytic reactions, offering new opportunities for advanced environmental remediation technologies.

Efficient and stable copper tungstate catalyst for water treatment with peroxymonosulfate: Effect of synthetic pH, primary oxidant, and practical feasibility

In this study, copper tungstate (CuWO4) nanoparticles, which are highly efficient and stable catalysts for water treatment, were synthesized via a hydrothermal method under various pH conditions. CuWO4 synthesized at pH 10 (CuWO4@10) exhibited the highest degradation efficiency and the lowest metal ion leaching. In the presence of CuWO4@10 (0.5 g/L) and peroxymonosulfate (PMS, 1 mM), 4-chlorophenol (4-CP, 100 μM) was completely degraded within 5 min, and the total metal ion leaching concentration after 4 h was only 10.2 μM. The catalytic activity of CuWO4 for 4-CP degradation was 4.7-99.0 times greater than that of CuO catalysts. This enhanced performance is attributed to the presence of W, which increases the surface area and reduces charge transfer resistance. Based on the results of radical-quenching experiments, solvent exchange experiments, PMS decomposition measurements, electron paramagnetic resonance spectroscopy, and Raman spectroscopy, high-valent copper (Cu(III)) was identified as the primary oxidant responsible for degradation in the CuWO4/PMS system. The CuWO4/PMS system rapidly degraded various phenolic compounds, and its degradation efficiency remained consistent across repeated uses of the CuWO4 catalyst. Degradation in groundwater also occurred efficiently in the CuWO4/PMS system. This study provides valuable insights into the development of practical PMS-based water treatment processes.

Boosting Alkaline Hydrogen Evolution by Creating Atomic-Scale Pair Cocatalytic Sites in Single-Phase Single-Atom-Ruthenium-Incorporated Cobalt Oxide

Compared with acidic environments, promoting the water dissociation process is crucial for speeding up hydrogen evolution reaction (HER) kinetics in alkaline electrolyte. Although the construction of heterostructured electrocatalysts by hybridizing noble metals with metal (hydr)oxides has been reported as a feasible approach to achieve high performance, the high cost, complicated fabrication process, and unsatisfactory mass activity limit their large-scale applications. Herein, we report a single-phase HER electrocatalyst composed of single-atom ruthenium (Ru) incorporated into a cobalt oxide spine structure (denoted as Ru SA/Co3O4), which possesses exceptional HER performance in alkaline media via unusual atomic-scale Ru-Co pair sites. In particular, Ru SA/Co3O4 exhibits a very low overpotential of 44 mV at 10 mA cm-2 and an outstanding mass activity of 4700 mA mg-1 at 50 mV overpotential, superior to those of commercial Pt/C, Ru nanoparticles supported on Co3O4 (denoted as Ru NP/Co3O4) and other reported Ru-based electrocatalysts. With insights from theoretical calculations, the synergistic interactions between Ru and Co pair active sites in Ru SA/Co3O4 are revealed to catalyze diverse fundamental steps of the alkaline HER; i.e., the Ru sites can effectively accelerate water adsorption/dissociation and OH- desorption, whereas the Co sites are favorable for H* adsorption and H2 evolution.

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.

Tailoring d-Band Center of Single-Atom Nickel Sites for Boosted Photocatalytic Reduction of Diluted CO2 from Flue Gas

Photocatalytic reduction of diluted CO2 from anthropogenic sources holds tremendous potential for achieving carbon neutrality, while the huge barrier to forming *COOH key intermediate considerably limits catalytic effectiveness. Herein, via coordination engineering of atomically scattered Ni sites in conductive metal-organic frameworks (CMOFs), we propose a facile strategy for tailoring the d-band center of metal active sites towards high-efficiency photoreduction of diluted CO2. Under visible-light irradiation in pure CO2, CMOFs with Ni-O4 sites (Ni-O4 CMOFs) exhibits an outstanding rate for CO generation of 13.3 μmol h-1 with a selectivity of 94.5 %, which is almost double that of its isostructural counterpart with traditional Ni-N4 sites (Ni-N4 CMOFs), outperforming most reported systems under comparable conditions. Interestingly, in simulated flue gas, the CO selectivity of Ni-N4 CMOFs decreases significantly while that of Ni-O4 CMOFs is mostly unchanged, signifying the supremacy for Ni-O4 CMOFs in leveraging anthropogenic diluted CO2. In situ spectroscopy and density functional theory (DFT) investigations demonstrate that O coordination can move the center of the Ni sites' d-band closer to the Fermi level, benefiting the generation of *COOH key intermediate as well as the desorption of *CO and hence leading to significantly boosted activity and selectivity for CO2-to-CO photoreduction.

Co3O4 with the Enhancement of Peroxymonosulfate Adsorption Capacity by Rare Earth Europium-Doping for High-Efficiency Organic Dye Degradation

Cobalt-based metal-organic framework (MOFs)-derived catalysts are acknowledged for their effectiveness in activating peroxymonosulfate (PMS) for the treatment of persistent pollutants. However, the limited adsorption of PMS on the catalyst surface markedly reduces its degradation efficiency. To overcome this limitation, nanoflower-like Eu2O3/Co3O4-0.3 catalysts were successfully fabricated by incorporating europium (Eu) into cobalt-based MOF via the hydrothermal and calcination techniques. The doping of Eu not only enhances the adsorption of more PMS on the catalyst's surface but also serves as an electron transfer mediator to regulate the Co2+/Co3+ redox cycle and promote the generation of oxygen vacancies (OV). The catalyst Eu2O3/Co3O4-0.3 was used to activate PMS for the degradation of rhodamine B (RhB), and it was found that the degradation rate constant (k) of the Eu2O3/Co3O4-0.3/PMS system was approximately 8 times higher than that of the Co3O4/PMS system, achieving complete degradation within 20 min. Furthermore, Eu2O3/Co3O4-0.3 exhibited excellent mineralization capacity, stability, and recyclability. Trapping experiments indicated that singlet oxygen (1O2) is the primary active species, suggesting that this material is applicable in complex aqueous environments. Density Functional Theory (DFT) calculations revealed that the adsorption energy (Eads) of PMS on the Eu2O3 surface is -4.05 eV, which is much greater than that on Co3O4 (Eads = -0.32 eV). This study provides a new method for designing nonhomogeneous catalysts to activate PMS for efficient degradation of pollutants.

Multi-Enzyme Mimetic MoCu Dual-Atom Nanozyme Triggering Oxidative Stress Cascade Amplification for High-Efficiency Synergistic Cancer Therapy

Single-atom nanozymes (SAzymes) with ultrahigh atom utilization efficiency have been extensively applied in reactive oxygen species (ROS)-mediated cancer therapy. However, the high energy barriers of reaction intermediates on single-atom sites and the overexpressed antioxidants in the tumor microenvironment restrict the amplification of tumor oxidative stress, resulting in unsatisfactory therapeutic efficacy. Herein, we report a multi-enzyme mimetic MoCu dual-atom nanozyme (MoCu DAzyme) with various catalytic active sites, which exhibits peroxidase, oxidase, glutathione (GSH) oxidase, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mimicking activities. Compared with Mo SAzyme, the introduction of Cu atoms, formation of dual-atom sites, and synergetic catalytic effects among various active sites enhance substrate adsorption and reduce the energy barrier, thereby endowing MoCu DAzyme with stronger catalytic activities. Benefiting from the above enzyme-like activities, MoCu DAzyme can not only generate multiple ROS, but also deplete GSH and block its regeneration to trigger the cascade amplification of oxidative stress. Additionally, the strong optical absorption in the near-infrared II bio-window endows MoCu DAzyme with remarkable photothermal conversion performance. Consequently, MoCu DAzyme achieves high-efficiency synergistic cancer treatment incorporating collaborative catalytic therapy and photothermal therapy. This work will advance the therapeutic applications of DAzymes and provide valuable insights for nanocatalytic cancer therapy.

The surface functional groups-driven fast and catalytic degradation of naproxen on sludge biochar enhanced by citric acid

In this work, a sludge biochar (CA-SBC-300) with efficient activation of peroxymonosulfate (PMS) was prepared by citric acid modification. CA-SBC-300 achieved efficient degradation of naproxen (NPX) (95.5%) within 10 min by activating PMS. This system was highly resilient to common disruptive factors such as inorganic anions, humic acid (HA) and solution pH. The results of XPS and Raman showed that the content of oxygenated functional groups (OFGs) and the degree of defects on the sludge biochar increased after citric acid modification, which may be an important reason for the enhanced catalytic performance of SBC. In the CA-SBC-300/PMS system, 1O2 and O2•- made the main contributions to the degradation of NPX. XPS analysis and DFT calculations demonstrated that C=O/C-O and pyridine N on CA-SBC-300 were the crucial active sites for PMS activation. According to the results of UPLC-MS analysis, three possible pathways for NPX degradation were inferred. This study provided a feasible strategy for sludge resource utilization combined with efficient catalytic degradation of toxic organic contaminants in wastewater.

Asymmetric defective sites-mediated high-valent cobalt-oxo species in self-suspension aerogel platform for efficient peroxymonosulfate activation

The main pressing problems should be solved for heterogeneous catalysts in activation of peroxymonosulfate (PMS) are sluggish mass transfer kinetics and low intrinsic activity. Here, oxygen vacancies (Vo)-rich of Co3O4 nanosheets were anchored on the superficies of spirulina-based reduced graphene oxide-konjac glucomannan (KGM) aerogel (R-Co3O4-x/SRGA). The porous structure and superhydrophilicity conferred by KGM maximized the diffusion and transport of reactant. More interestingly, R-Co3O4-x/SRGA came true self-suspension rather than conventional self-floating without the aid of external force, maximizing space utilization and facilitating catalysts recovery. Anchored R-Co3O4-x nanosheets acted as "engines" to drive the reaction. Density functional theory (DFT) manifested Vo was capable of breaking the symmetry of the electronic structure of Co3O4. The formation of asymmetric active sites (Vo) was revealed to modulate the d-band center, enhanced affinity for PMS, and promoted evolution of high-valent cobalt-oxo (Co(IV)=O) species. R-Co3O4-x/SRGA achieved complete removal of sulfamethoxazole (SMX) within 12 min. Furthermore, R-Co3O4-x/SRGA demonstrated exceptional stability in the presence of various environmental interference factors and continuous flow device. This insightful work cleverly integrates the macroscopic design of structure, and the microscopic regulation of active sites is expected to open up new opportunities for the development of water treatment.

Construction of the Co3O4/Nb2O5 Composite Catalyst with a Prickly Spherelike Architecture for CO2 Cycloaddition with Styrene Oxide

A high-performance Nb2O5-based catalyst for the cycloaddition of CO2 with SO is designed by properly unifying the concepts of compositional regulation and architectural engineering. The Co3O4/Nb2O5 composite catalyst shows an intriguing prickly spherelike morphology. It exhibits a high styrene carbonate (SC) yield of 94.3% within 4 h (0.0824 mol g-1 h-1) under mild reaction conditions (0.4 MPa of CO2 and a reaction temperature of 90 °C) assisted by tetrabutylammonium bromide (TBAB). The coupling of Co3O4, which chemically interacts with Nb2O5, can effectively modulate the electronic structures of Nb2O5, constructing abundant acid/base sites for effectively activating the reactants and boosting the intrinsic activity. The high activity, cost-effectiveness, and good recyclability make the tailor-made Co3O4/Nb2O5 prickly spheres more appealing for commercial applications. This work offers new insights into designing and constructing well-integrated metal oxide composites for the cycloaddition of CO2 with an epoxide.

A Bioinspired Single-Atom Fe Nanozyme with Excellent Laccase-Like Activity for Efficient Aflatoxin B1 Removal

The applications of natural laccases are greatly restricted because of their drawbacks like poor biostability, high costs, and low recovery efficiency. M/NC single atom nanozymes (M/NC SAzymes) are presenting as great substitutes due to their superior enzyme-like activity, excellent selectivity and high stability. In this work, inspired by the catalytic active center of natural enzyme, a biomimetic Fe/NC SAzyme (Fe-SAzyme) with O2-Fe-N4 coordination is successfully developed, exhibiting excellent laccase-like activity. Compared with their natural counterpart, Fe-SAzyme has shown superior catalytic efficiency and excellent stability under a wide range of pH (3.0-9.0), temperature (4-80 °C) and NaCl strength (0-300 mm). Interestingly, density functional theory (DFT) calculations reveal that the high catalytic performance is attributed to the activation of O2 by O2-Fe-N4 sites, which weakened the O─O bonds in the oxygen-to-water oxidation pathway. Furthermore, Fe-SAzyme is successfully applied for efficient aflatoxin B1 removal based on its robust laccase-like catalytic activity. This work provides a strategy for the rational design of laccase-like SAzymes, and the proposed catalytic mechanism will help to understand the coordination environment effect of SAzymes on laccase-like catalytic processes.

Constructing High-Performance Cobalt-Based Environmental Catalysts from Spent Lithium-Ion Batteries: Unveiling Overlooked Roles of Copper and Aluminum from Current Collectors

Converting spent lithium-ion batteries (LIBs) cathode materials into environmental catalysts has drawn more and more attention. Herein, we fabricated a Co3O4-based catalyst from spent LiCoO2 LIBs (Co3O4-LIBs) and found that the role of Al and Cu from current collectors on its performance is nonnegligible. The density functional theory calculations confirmed that the doping of Al and/or Cu upshifts the d-band center of Co. A Fenton-like reaction based on peroxymonosulfate (PMS) activation was adopted to evaluate its activity. Interestingly, Al doping strengthened chemisorption for PMS (from -2.615 eV to -2.623 eV) and shortened Co-O bond length (from 2.540 Å to 2.344 Å) between them, whereas Cu doping reduced interfacial charge-transfer resistance (from 28.347 kΩ to 6.689 kΩ) excepting for the enhancement of the above characteristics. As expected, the degradation activity toward bisphenol A of Co3O4-LIBs (0.523 min-1) was superior to that of Co3O4 prepared from commercial CoC2O4 (0.287 min-1). Simultaneously, the reasons for improved activity were further verified by comparing activity with catalysts doped Al and/or Cu into Co3O4. This work reveals the role of elements from current collectors on the performance of functional materials from spent LIBs, which is beneficial to the sustainable utilization of spent LIBs.

Single-atom catalysts activate persulfate to degrade emerging organic contaminants in aqueous environments

Single-atom catalysts (SACs) exhibit outstanding catalytic activity due to their highly dispersed metal centers. Activating persulfates (PS) with SACs can generate various reactive oxygen species (ROS) to efficiently degrade emerging organic contaminants (EOCs) in aqueous environments, offering unique advantages such as high reaction rates and excellent stability. This technique has been extensively researched and holds enormous potential applications. In this paper, we comprehensively elaborated on the synthesis methods of SACs and their limitations, and factors influencing the catalytic performance of SACs, including metal center characteristics, coordination environment, and types of substrates. We also analyzed practical considerations for application. Subsequently, we discussed the mechanism of SACs activating PS for EOCs degradation, encompassing adsorption processes, radical pathways, and non-radical pathways. Finally, we provide prospects and outline our vision for future research, aiming to guide advancements in applying this technique.

Fenton-like membrane reactor assembled by electron polarization and defect engineering modifying Co3O4 spinel for flow-through removal of organic contaminants

The application of Fenton-like membrane reactors for water purification offers a promising solution to overcome technical challenges associated with catalyst recovery, reaction efficiency, and mass transfer typically encountered in heterogeneous batch reaction modes. This study presents a dual-modification strategy encompassing electron polarization and defect engineering to synthesize Al-doped and oxygen vacancies (OV)-enriched Co3O4 spinel catalysts (ACO-OV). This modification empowered ACO-OV with exceptional performance in activating peroxymonosulfate (PMS) for the removal of organic contaminants. Moreover, the ACO-OV@polyethersulfone (PES) membrane/PMS system achieved organic contaminant removal through filtration (with a reaction kinetic constant of 0.085 ms-1), demonstrating outstanding resistance to environmental interference and high operational stability. Mechanistic investigations revealed that the exceptional catalytic performance of this Fenton-like membrane reactor stemmed from the enrichment of reactants, exposure of reactive sites, and enhanced mass transfer within the confined space, leading to a higher availability of reactive species. Theoretical calculations were conducted to validate the beneficial intrinsic effects of electron polarization, defect engineering, and the confined space within the membrane reactor on PMS activation and organic contaminant removal. Notably, the ACO-OV@PES membrane/PMS system not only mineralized the targeted organic contaminants but also effectively mitigated their potential environmental risks. Overall, this work underscores the significant potential of the dual-modification strategy in designing spinel catalysts and Fenton-like membrane reactors for efficient organic contaminant removal.

Heteroatom substitution enhances generation and reactivity of surface-activated peroxydisulfate complexes for catalytic fenton-like reactions

Peroxydisulfate (PDS)-based Fenton-like reactions are promising advanced oxidation processes (AOPs) to degrade recalcitrant organic water pollutants. Current research predominantly focuses on augmenting the generation of reactive species (e.g., surface-activated PDS complexes (PDS*) to improve treatment efficiency, but overlooks the potential benefits of enhancing the reactivity of these species. Here, we enhanced PDS* generation and reactivity by incorporating Zn into CuO catalyst lattice, which resulted in 99% degradation of 4-chlorophenol within only 10 min. Zn increased PDS* generation by nearly doubling PDS adsorption while maintaining similar PDS to PDS* conversion efficiency, and induced higher PDS* reactivity than the common catalyst CuO, as indicated by a 4.1-fold larger slope between adsorbed PDS and open circuit potential of a catalytic electrode. Cu-O-Zn formation upshifts the d-band center of Cu sites and lowers the energy barrier for PDS adsorption and sulfate desorption, resulting in enhanced PDS* generation and reactivity. Overall, this study informs strategies to enhance PDS* reactivity and design highly active catalysts for efficient AOPs.

Ultrafine Iridium Nanoparticles Anchored on Co-Based Metal-Organic Framework Nanosheets for Robust Hydrogen Evolution in Alkaline Media

A highly promising electrocatalyst has been designed and prepared for the hydrogen evolution reaction (HER). This involves incorporating well-dispersed Ir nanoparticles into a cobalt-based metal-organic framework known as Co-BPDC [Co(bpdc)(H2O)2, BPDC: 4,4'-biphenyldicarboxylic acid]. Ir@Co-BPDC demonstrates exceptional HER activity in alkaline media, surpassing both commercial Pt/C and recent noble-metal catalysts. Theoretical results indicate that electron redistribution, induced by interfacial bonds, optimizes the adsorption energy of water and hydrogen, thereby enhancing our understanding of the superior properties of Ir@Co-BPDC for HER.

Highly effective degradation of ibuprofen by alkaline metal-doped copper oxides via peroxymonosulfate activation: Mechanisms, degradation pathway and toxicity assessments

Redox ratios of Cu2+/Cu+ and adsorbed oxygen species (Oads) have shown great activity toward radical generation by activating peroxymonosulfate (PMS). Herein, different alkaline metal oxides (CaO, MgO and BaO) and various amounts of CaO are incorporated into CuO, which could tune the main active sites of redox ratios of Cu2+/Cu+ and Oads. The results show that CaO-CuO-5% exhibits the outstanding performance of PMS activation toward ibuprofen (IBF) degradation with excellent kinetics (k = 0.812 min-1). The X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation show that the CaO-CuO-5% has the higher electron density with superior electron transfer ability and lower PMS adsorption energy. Based on radical scavengers and electron paramagnetic resonance spectrometer (EPR), a nonradical process is proposed to play the dominant role. The degradation pathway and the corresponding toxicity of degraded intermediates with residue PMS after reaction is evaluated by LC-MS/MS and bioassay experiments, indicating the lower antagonistic influence on human hormone receptors after advanced oxidation process. Mitigation of the Cu leaching with cyclic stability can be achieved. This study provides a facile method to optimize high-performance catalysts to activate PMS and offer practical environmental applications in the remediation of emerging contaminants.

Mediated biosynthesis of CdS QDs by EPS from Desulfovibrio desulfuricans sub sp. under carbon source-induced reinforcement

This paper describes a unique molecular mechanism for the EPS-mediated synthesis of CdS QDs by sulfate-reducing bacteria (SRB) under carbon source-induced reinforcement. Under the induced by carbon sources (HCOONa, CH3COONa and C6H12O6), there was a significant increase in EPS production of SRB, particularly in protein, and the capacity of Cd(II) adsorption was further enhanced. CdS QDs were extracellularly synthesized by adding S2- after Cd(II) adsorption. The results showed that CdS QDs were wrapped or adhered by EPS, and the most significant increase in Arg and Lys among basic amino acids in EPS after HCOONa-induced was 133.34% and 63.89%, respectively. This may serve as a biological template for QD synthesis, producing protein gels with a large number of microcavities and controlling the nucleation of CdS QDs. The highest yield of HCOONa-CdS was achieved after induction, with 23.59 g/g biomass per unit strain, which was 447.34% higher than that before induction and was at a high level in previous studies. The synthesized CdS QDs were uniform in size distribution and had higher luminescence activity and a larger specific surface area than those synthesized by the chemical synthesis route, provides a new idea for EPS treatment of heavy metal wastewater and metal biorecovery.

Balance between Activity and Stability of Single Metal and Intermetallic Compounds for Electrocatalytic Hydrogen Evolution Reaction

The higher population of the antibonding state around the Fermi level will result in better activity yet lower stability of HER (Re vs Ru metal). There seems to be a limitation or balance for using a single metal since the bonding scheme of a single metal is relatively simple. Combining Re (strong bonding), Ru (HER active), and Zr metal (corrosion-resistant) grants ternary intermetallic compound ZrRe_1.75Ru₀₂₅, exhibiting excellent HER activity and stability in acidic and alkaline electrolytes. The overpotential at a current density of 10 mA/cm² (η₁₀) for ZrRe_1.75Ru₀₂₅ is much lower compared to that of ZrRe₂. Although the HER activity of ZrRe_1.75Ru₀₂₅ is not comparable to that of ZrRu₂, it demonstrates outstanding HER stability, while the current density of ZrRu₂ is over ca. 16% after 6 h. This suggests that intermetallic compounds can break the constraint between activity and stability in a single metal for HER, which may be applied in other fields as well.

Ultra-small Co3O4 particles embedded into N-doped carbon derived from ZIF-9 via half-pyrolysis for activating peroxymonosulfate to degrade sulfamethoxazole

The fabrication of novel and efficient transition metal-based catalysts for peroxymonosulfate (PMS) activation is of great significance for environmental remediation. Concerning energy consumption, the Co3O4@N-doped carbon (Co3O4@NC-350) was constructed via a half-pyrolysis strategy. The relatively low calcination temperature (350 °C) caused Co3O4@NC-350 to exhibit ultra-small Co3O4 nanoparticles, rich functional groups, uniform morphology, and a large surface area. For PMS activation, Co3O4@NC-350 could degrade 97% of sulfamethoxazole (SMX) in 5 min with a high k value of 0.73364 min-1, which was superior to the ZIF-9 precursor and other derived materials. Besides, Co3O4@NC-350 could be re-used over 5 times without obvious performance and structure change. The investigation of the influencing factors containing co-existing ions and organic matter demonstrated the Co3O4@NC-350/PMS system has satisfactory resistance. The quenching experiments and electron paramagnetic resonance (EPR) tests showed ˙OH, SO4˙-, ˙O2 - and 1O2 participated in the degradation process. Moreover, the structure and toxicity of intermediates during the SMX decomposing process have been evaluated. Overall, this research provides new prospects for exploring efficient and recycled MOF-based catalysts for PMS activation.

Fabrication of a Co3O4 monolithic membrane catalyst as an efficient PMS activator for the removal of methylene blue

An oxalate-pyrolysis method was proposed for the fabrication of an integral Co3O4 catalyst towards PMS activation to degrade MB.