Lasers Research Articles

Perylene diimide configuration to construct g-C3N4 and iron phthalocyanine composite catalyst as PMS activator for contaminant degradation

The photocatalysis-assisted peroxymonosulfate (PMS) activation process has shown great potential for organic wastewater treatment. Herein, the composite photocatalyst (FeTAPc/PDI/CN) was obtained by grafting graphitic carbon nitride (CN) and amino iron phthalocyanine (FeTAPc) onto both ends of perylene tetracarboxylic anhydride (PTCDA) through an imidization process. Under simulated solar irradiation, the catalyst exhibited a remarkable degradation performance toward the target pollutant by activated PMS over a wide pH range from 3 to 11. The degradation efficiency of SMX reached 100 % in 7 min with the reaction kinetic constant of 0.845 min−1, which was 13 times higher than that of pure CN. In addition, the removal rate of FeTAPc/PDI/CN-4 for SMX was more than 80 % after 9 cycles. The introduction of phthalocyanine and PDI improved the separation efficiency of photogenerated electron-hole pairs. Furthermore, the active species involved in the SMX degradation were identified as •OH, SO4•-, •O2– and 1O2. The possible degradation pathways were proposed based on the identified intermediates, in which the oxidation of the amino group on the benzene ring was the main degradation pathway. This study is anticipated to result in a favorable method for designing CN-based photocatalysts with high stability and excellent catalytic activity for environmental remediation.

Intraplanar heterostructure-mediated activation of peroxydisulfate for singular-electron-transfer degradation of organic pollutants

Activating peroxydisulfate (PDS) through electron transfer pathways (ETP) is promising for degrading organic pollutants in aquatic environments. However, enhancing the activation selectivity remains a challenge. Herein, this study developed an intraplanar heterojunction with C-ring grafted g-C3N4 (CCN) as the catalyst, enabling PDS activation through a singular ETP. The CCN/PDS system achieved complete degradation and efficient mineralization (87.15 %) of bisphenol F (BPF), significantly reducing its ecological toxicity. Both experimental and theoretical investigations revealed that the intraplanar heterojunction could modulate the orbital occupation in g-C3N4/PDS, enhancing PDS adsorption and activation selectivity. Driven by the differences in the frontier orbital energy, the CCN/PDS system achieved a singular ETP without active species formation. The CCN/PDS system efficiently degraded BPF in complex water environments, showing performance stability across a wide pH range and against various coexisting ions. In a continuous-flow automatic catalytic device, the CCN/PDS system maintained a constant 100 % BPF degradation for 600 min. This study advances the understanding of PDS activation via singular ETP and introduces a new approach to water purification.

Highly efficient reduction of Cr(VI) from industries sewage using novel biomass-driven carbon dots modified TiO2 under sunlight

Hexavalent chromium (Cr(VI)) pollution poses a significant global environmental challenge, with current photocatalysts exhibiting limited efficiencies under natural sunlight, especially in neutral to alkaline conditions or at high Cr(VI) concentrations. In this study, amine-rich biomass-derived carbon dots (CDs) were synthesized from peanut shells and ethylenediamine via a hydrothermal method, combined with titanium dioxide (TiO2) to form a composite with a narrower band gap. This enhanced the electrostatic interactions with Cr(VI), thus improving photocatalytic performance. The composite (1 % CDs) effectively reduced 50 mg/L of Cr(VI) within 60 min under sunlight irradiation, demonstrating stable performance across various pH levels (3, 5, 7, and 9) and Cr(VI) concentrations (10 to 60 mg/L). Even after five cycles, the reduction efficiency remained high at 96.83 %. The composite also achieved reduction rates of 90.09 % and 89.01 % for domestic and electroplating wastewater, respectively, while exhibiting antibacterial properties. Free-radical scavenging experiments confirmed that electrons and holes were the primary active species driving the reduction. This work highlights the potential of the composites for efficient and stable Cr(VI) reduction in real-world water treatment applications.

Improved ultrafiltration performance through dielectric barrier discharge/sulfite pretreatment: Effects of water matrices and mechanistic insights

The feasibility of utilizing a dielectric barrier discharge (DBD)/sulfite-ultrafiltration system was investigated in various real water bodies, aiming to clarify the mechanism behind alleviating membrane fouling while synchronously degrading perfluorooctanoic acid (PFOA) during the treatment process of Yangtze River water. The results demonstrated that the DBD/sulfite pretreatment exhibited remarkable rates of membrane flux mitigation (>84.10%) and efficient degradation rates of PFOA (>85.13%), which decreased with increasing pH from 3.0 to 11.0. The presence of anions, cations, and natural organic matter slightly hindered the membrane fouling mitigation and PFOA degradation by quenching free radicals; however, the addition of SO42− had a negligible impact. The mitigation of membrane fouling was attributed to the significant involvement of various radicals, including hydroxyl radical (•OH), sulfate radical (SO4•−), electron (e−/eaq−), su-peroxide anion radicals (•O2−), and other radicals such as SO3•−, exhibiting respective contributions of 33.25%, 28.49%, 20.56%, 11.32%, and 6.39% in a synergistic redox effect. The pretreatment effectively reduced standard blocking and cake filtration fouling mechanisms by creating a sparse fouling layer on the membrane surface while increasing its roughness. Additionally, the main active species that played a significant role in the degradation of PFOA were identified as SO4•−, •OH, and eaq−. These species contributed approximately 43.63%, 24.39%, and 20.65% respectively to the degradation process. By employing mass spectrometry and density functional theory, a proposed pathway for PFOA degradation was established, effectively reducing the toxicity associated with its degradation byproducts. This study provides innovative insights into membrane-based water treatment technologies that effectively tackle both membrane fouling mitigation and PFOA degradation.

Magnetic MgFeO@BC Derived from Rice Husk as Peroxymonosulfate Activator for Sulfamethoxazole Degradation: Performance and Reaction Mechanism.

Heterogeneous Mg-Fe oxide/biochar (MgFeO@BC) nanocomposites were synthesized by a co-precipitation method and used as biochar-based catalysts to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) removal. The optimal conditions for SMX degradation were examined as follows: pH 7.0, MgFeO@BC of 0.4 g/L, PMS concentration of 0.6 mM and SMX concentration of 10.0 mg/L at 25 ℃. In the MgFeO@BC/PMS system, the removal efficiency of SMX was 99.0% in water within 40 min under optimal conditions. In the MgFeO@BC/PMS system, the removal efficiencies of tetracycline (TC), cephalexin (CEX), ciprofloxacin (CIP), 4-chloro-3-methyl phenol (CMP) and SMX within 40 min are 95.3%, 98.4%, 98.2%, 97.5% and 99.0%, respectively. The radical quenching experiments and electron spin resonance (ESR) analysis suggested that both non-radical pathway and radical pathway advanced SMX degradation. SMX was oxidized by sulfate radicals (SO4•-), hydroxyl radicals (•OH) and singlet oxygen (1O2), and SO4•- acted as the main active species. MgFeO@BC exhibits a higher current density, and therefore, a higher electron migration rate and redox capacity. Due to the large number of available binding sites on the surface of MgFeO@BC and the low amount of ion leaching during the catalytic reaction, the system has good anti-interference ability and stability. Finally, the intermediates of SMX were detected.

Design of MnO2/g-C3N4 heterojunction composite photocatalysts for augmented charge separation and photocatalytic degradation performance with superior antibacterial activity

The development of advanced photocatalysts is critical for addressing environmental pollution and enhancing water purification processes. Our study has effectively developed a novel MnO2/g-C3N4 (MGC) heterojunction composite photocatalyst exhibiting superior photo-degradation under visible-light (VL) conditions and also established antibacterial activities. Comprehensive characterization was acquired using XRD, FT-IR, FE-SEM with EDX-associated mapping images, TEM, UV–Vis DRS and PL investigations, indicating the successful formation of well-dispersed MnO2 nanoparticles (NPs) over the g-C3N4 catalyst. The MGC composite heterojunction photocatalyst demonstrated increased photocatalytic degradation activity of 77.2 % in aqueous crystal violet (CV) under VL within 120 min, significantly outperforming pure g-C3N4 and MnO2 by 3.02 and 2.37 times, respectively. The MGC composite demonstrates remarkable stability and reusability, retaining 73.7 % of its efficiency after five consecutive cycles. Additionally, the as-synthesised composite endows potent antibacterial action against various pathogenic bacteria including K. pneumonia, S. aureus, E. coli and B. cereus. The active species analysis indicates that the composite photocatalyst facilitates charge transfer, while effectively preventing the recombination of photo-produced carriers via an effective Z-scheme mechanism, and the synergistic things among MnO2 and g-C3N4 are accredited to the boosted photocatalytic and antibacterial activities. This research describes a photocatalytic approach for efficiently eliminating various contaminants from water bodies, which has significant implications for the future development of photocatalytic technology for wastewater handling.

Removal of antibiotics from aquaculture wastewater using a continuous flow/EC/PMS coupled system

The electricity activated peroxomonosulfate (ion) coupled system (EC/PMS) has important application value in water pollution treatment. However, the traditional batch system commonly used in this coupled system poses significant challenges in treating large volume and low concentration aquaculture wastewater, such as poor mass transfer, long treatment time, and increased risk of secondary pollution. Therefore, this study proposed to introduce the continuous flow operation mode into the EC/PMS system to form a continuous flow electrocatalytic peroxomonosulfate (ion) (CF/EC/PMS) coupling system, achieving 100 % removal of tetracycline (TC) with an initial concentration of 2 mg/L. Subsequently, through cathodic optimization, an 85 % removal efficiency was achieved for antibiotics with secondary pollution risks, such as norfloxacin and NOR. It is worth noting that the secondary pollutants (such as fluoride ions, F−) generated during the degradation process have also successfully achieved a removal efficiency of 70 %. In this system, singlet oxygen (1O2) was the main active species. This system has advantages such as a processing volume of at least 3L, a wide pH range (3–9), low oxidant dosage (PMS = 2 mM), and low energy consumption (EEO = 0.018 kWh/m3 log). The coupling system effectively removes the main pollutants, and the optimized cathode coupling system achieves safe removal of fluorinated drugs, reducing the risk of secondary pollution. In summary, this study has the characteristics of low cost and engineering applicability, providing a promising method for economically, efficiently, and environmentally friendly treatment of aquaculture wastewater.

Modifying d–p orbital hybridization of Ni/Fe[sbnd]O species by high-valence ruthenium doping to enhance oxygen evolution performance

The electron distribution of catalysts can be modulated by high-valence metal doping, thus enhancing the intrinsic activity. Herein, we adopt Ru modification to adjust the d–p orbital hybridization of Ni-Fe oxyhydroxides, significantly increasing the oxygen evolution reaction (OER) activity. The amorphous NiFe0.5Ru0.1OxHy catalyst synthesized by sol–gel method exhibits excellent OER activity, far superior to commercial RuO2. In situ Raman and XPS results confirm that the NiOOH/FeOOH active species gradually form with increasing applied voltage. Density functional theory (DFT) calculations reveal that high-valence Ru dopants can effectively regulate the hybridization of d–p orbital of Ni/FeO, significantly increase the electron density around Fermi level, promote charge transfer, make them have more anti-bonding orbitals, enhance the binding ability of active sites to intermediates, reduce the reaction energy barrier of the rate-determining step (H2O → *OH), and thus improve the OER activity. In addition, NiFeRuOxHy as a cathode catalyst in a rechargeable zinc-air battery shows an outstanding cycle life of 600 h. This study provides a promising hybrid orbital method for designing high-performance OER catalysts for water splitting and rechargeable zinc-air batteries.

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51% within just 11min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73% after 48hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Incorporating Si into NiO support to facilitate oxygen activation for CH4 combustion

In this study, high-performance Pd/NiO-Si catalysts for lean methane oxidation were synthesized using the solution combustion and impregnation method. The incorporation of silicon in NiO promoted the generation of Ni2+ and strengthened the metal-support interaction. This enhanced interaction promoted the generation and movement of active oxygen species on surface, which are essential for maintaining Pd species in an active oxidized state, thereby ensuring the effective activation of CH4. The Pd/NiO-Si catalyst with an optimal amount of Si exhibited an excellent catalytic performance, achieving a T90 of 440 °C for methane oxidation under wet conditions. The elemental doping strategy in this study, which significantly enhances the production of highly active oxygen species with strong mobility, plays a crucial role in the effective utilization of precious metals such as Pd.

Enhanced removal of phenolic pollutants over MnO2 initiated by peracetic acid: In situ generation of a heterogeneous Mn(III)-hydroperoxo complex

Widely distributed manganese oxides are among the strongest oxidants in nature and effectively enhance the water decontamination by peracetic acid (PAA) activation. However, the precise mechanism requires further investigation. In this work, the intrinsic mechanism of PAA activation by MnO2 was systematically studied. Through in situ diffuse-reflectance UV–vis spectra and resonance Raman spectra, the active species was identified as a non-radical heterogenous Mn(III)-hydroperoxo complex. During the process, PAA drastically converted Mn(IV) in MnO2 into homogeneous Mn(II), which subsequently generated the active Mn(III) species in the aid of PAA on the surface of MnO2. By interacting with pollutants, the peroxide bond in Mn(III)-hydroperoxo broke, accompanied by the regeneration of Mn(IV). Eight phenolic compounds having para-substituent of –CH3, −H, −Cl, –COCH3, –CHO, –COOH, –COOCH3, and –NO2 were selected for degradation. Due to the electrophilic character of Mn(III)-hydroperoxo, the removal rates were 100 %, 100 %, 98.8 %, 69.8 %, 49.6 %, 30.2 %, 28.1 %, and 3.0 % respectively at the 45 min of experiment. The MnO2/PAA system was also readily coupled with a filtration membrane for continuous treatment of phenol in nearly 100 % removal efficiency. This study not only offered an efficient non-radical PAA activation protocol for water decontamination, but also elucidated the catalytic mechanism and redox cycle of MnO2 in PAA solution in the selective oxidation process.

Cobalt doped MoS2: A photoactivated nanomaterial for removal of methylene blue and phenol

This research work reports the study about synthesis, characterizations and Photocatalytic applications of hydrothermally produced MoS2 and Cobalt doped MoS2 nanomaterials to overcome the environmental pollution caused by wastewater. MB dye and Phenol were used as model pollutants for evaluation of photocatalytic proficiency of MoS2 and Cobalt doped MoS2 nanostructures. The well matched ionic radius of Cobalt with host Mo atom increases their probability regarding alteration of nanomaterial’s optical, structural and catalytic properties. The Cobalt incorporation provided the synergistic effect attributed to efficient degradation up to 96 % and 80 % for MB dye and phenol respectively. Additionally, the prepared samples were characterized to elucidate their optical, electronic and structural properties. Scavenger analysis and reusability test had performed to check the role of active species and stability of optimized sample. This study predicts that the fabrication of Cobalt doped MoS2 can be used as potential and promising photocatalyst for industrial applications for wastewater treatment.

Synergistic Surface Engineering of BiVO4 Photoanodes for Improved Photoelectrochemical Water Oxidation.

Surface engineering of BiVO4 photoanodes is effective and feasible for photoelectrochemical (PEC) water splitting. To achieve superior PEC performance, however, more than one surface engineering method is usually indispensable, for which a positive synergistic effect is vital and thus highly desired. Herein, it is reported that the incorporation of borate moieties into ultrathin p-type NiOx catalysts can induce the reconfiguration of surface catalytic sites to form new highly active species, in addition to enhanced fast charge separation and transfer. The photocurrent density of BiVO4 photoanodes is enhanced from 1.49 to 5.76 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5G illumination, which is achieved by successive modifications of NiOx and borate moieties. It is found that BO3 groups anchored to Ni atoms by replacing the surface hydroxyl sites of NiOx catalysts not only increase the relative ratio of Ni3+ species to facilitate charge transfer but also provide efficient active sites for H2O molecule adsorption and oxidation reactions. This work demonstrates the positive synergistic effect of these two surface engineering methods and provides an effective pathway to construct highly efficient and stable photoanodes for PEC water splitting.

Co-pyrolyzed biochar derived from microplastics and microalgae as peroxymonosulfate activator: Influence of microplastic types and analysis of systemic causes

This work investigated the catalytic activity of co-pyrolyzed biochar (MP-SBC) from microplastic (MP) and Spirulina biomass and its activation mechanism for peroxymonosulfate (PMS). Given that different types of MPs had varied effects on the properties of biochar, polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polylactic acid (PLA) were chosen as MP feedstocks. The results showed that the four kinds of MP-SBCs activated PMS more efficiently than the pristine algal-based biochar (SBC), with 100 % of the acetaminophen (ACT) degraded within 20 min. Based on the reaction mechanism analysis, the main pathways for the degradation of ACT by SBC and MP-SBC activated PMS were both non-radical pathways, and ACT was also efficiently degraded by the synergistic effect of 1O2 and electron transport pathway (ETP). Moreover, it was found that the microplastic modification could significantly enhance the efficacy of SBCs in triggering the non-radical pathway. Establishing the correlation between the structural features of BC and the degradation mechanism (active species contribution) revealed that the persistent free radicals (PFRs), defective structures, CO, and graphite N are all potential active sites. Thereinto, PFRs are the active sites for radicals, defects are the active sites for 1O2 production, and CO, defects, and graphitic N are the active sites for ETP. Overall, this work provides an innovative approach for designing efficient biochar-based catalysts for environmental remediation.

Tunable and selective transformation of aromatic thioether enabled by regulating active species under visible light irradiation

Through effective regulation of active species in photocatalytic process, the oxidation or C(sp3)‐S bond cleavage upgrading of widespread aryl alkyl sulfides under mild conditions was successfully achieved by using a pyridinium photocatalyst. Benefiting from the excellent redox ability of the photocatalyst, the electron transfer between the pyridinium molecule and the substrate, molecular oxygen, or counter‐anion effectively promotes the conversion and upgrading of the substrate thioether. Among them, the efficient generation of reactive oxygen species (ROS) enables the highly selective oxidation of sulfides to sulfoxides under visible light and air atmosphere. More importantly, the chlorine radical (Cl•) generated by electron transfer, reported for the first time, contributes to the cleavage of C(sp3)‐S bonds, achieving the transformation of aryl alkyl sulfides to disulfides. By harnessing the superior photocatalytic ability of pyridinium molecules, this work not only achieves the highly selective conversion of thioether by taming the active species in the photocatalytic process, but also sheds light on the untapped potential of chlorine radicals in the field of C(sp3)‐S bond activation and cleavage.

Modulation of the Microstructure and Enhancement of the Photocatalytic Performance of g-C3N4 by Thermal Exfoliation

This work explores the impact of reaction temperature during thermal exfoliation treatment of bulk-g-C3N4 in the air atmosphere on the structure and performance of the resulting CN photocatalyst. The analysis conducted using XRD, FT-IR, XPS, SEM, and elements mapping tests, illustrated an increase in nitrogen-vacancy and oxygen content on the surface of the CN photocatalyst, resulting in a porous and sparse structure, changes in crystal size, and improved visible light absorption performance. The photocatalytic reduction experiments of hexavalent chromium (Cr(VI)) showed that the CN-540 showed the highest reduction rate of 96.9%, with a reaction rate constant 6.21 times that of bulk-g-C3N4. After 100 min of illumination, the photocatalytic degradation rates of CN-540 for TC-HCl and RhB were 66.7% and 60.6%, respectively. The TOC test results indicated mineralization rates of 51.5% for TC-HCl and 46.6% for RhB. Room temperature fluorescence spectroscopy (PL), transient photocurrent response (TPC), and electrochemical impedance spectroscopy (EIS) measurements confirmed the excellent photogenerated charge carrier separation and transport efficiency of CN-540. The photocatalytic mechanism for reducing Cr(VI) by CN-540 was elucidated based on the active species •OH and •O2– and Mott-Schottky (M-S) tests. This study provides experimental data for optimizing the photocatalytic performance of g-C3N4 and paves a new way for developing efficient photocatalysts. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Shuttle HAT for mild alkene transfer hydrofunctionalization.

Hydrogen atom transfer (HAT) from a metal-hydride is a reliable and powerful method for functionalizing unsaturated C-C bonds in organic synthesis. Cobalt hydrides (Co-H) have garnered significant attention in this field, where the weak Co-H bonds are most commonly generated in a catalytic fashion through a mixture of stoichiometric amounts of peroxide oxidant and silane reductant. Here we show that the reverse process of HAT to an alkene, i.e. hydrogen atom abstraction of a C-H adjacent to a radical, can be leveraged to generate catalytically active Co-H species in an application of shuttle catalysis coined shuttle HAT. This method obviates the need for stoichiometric reductant/oxidant mixtures thereby greatly simplifying the generation of Co-H. To demonstrate the generality of this shuttle HAT platform, five different reaction manifolds are shown, and the reaction can easily be scaled up to 100 mmol.

Catalytic performances of Ag/SiC catalysts for styrene epoxidation in O2 atmosphere

SiC supported Ag catalysts were prepared by an impregnation-reduction method for styrene epoxidation in O2 atmosphere. Under the condition of 100 °C, 0.5 MPa O2 and 4 h, 5 wt% Ag/SiC catalyst achieved styrene conversion of 98.5 % and styrene oxide selectivity of 69.7 %. Further studies show that O2 was activated on the Ag surface and then formed reactive oxygen species, 1O2 and •O2-. Based on the O2 adsorption results, the atomic ratio of O/Ag larger than 0.5 indicated that more oxygen species had spilled over to the SiC surface. In-situ diffuse reflectance Fourier transform infrared spectroscopy and Density Functional Theory calculation results showed that styrene was adsorbed on the SiC surface. The active oxygen species generated on the Ag surface could spill over to the SiC surface, reacting with the adsorbed styrene to produce styrene oxide or benzaldehyde. In addition, the catalyst exhibits good stability.

Front Cover: A Cytochrome P450 TxtE Model System with Mechanistic and Theoretical Evidence for a Heme Peroxynitrite Active Species

Front Cover: A Cytochrome P450 TxtE Model System with Mechanistic and Theoretical Evidence for a Heme Peroxynitrite Active Species

Reduction Polymerization of CO2 with Phenylene Silanes Catalyzed by Single Component B(C6F5)3.

CO2 is an abundant C1 resource but a green-house gas and chemically inert. Thus, its utilization has been a promising but challenging project. Herein, we report the unprecedented polymerization of CO2 and C6H4(SiMe2H)2 using B(C6F5)3 alone under mild conditions to give poly(silphenylene siloxane) accompanied by releasing CH4. The copolymerization can be extended to comonomers of phenylene silanes bearing functional groups. Moreover, it combines with Piers-Rubinsztajn reaction to establish a tandem polymerization system to achieve super thermal resistant poly(siloxane-co-silphenylene siloxane)s. Density functional theory reveals that B(C6F5)3 is activated by silanes to form free HB(C6F5)2, which is the true active species for CO2 reducing to borylformate, the rate controlling step of the polymerization procedure. The subsequent multiple reductions of borylformate to CH4 and the step-growth to poly(silphenylene siloxane)s can be fulfilled by both B(C6F5)3 and HB(C6F5)2, and the former shows a slightly higher activity. This work opens a new avenue of utilizing CO2 to fabricate polysiloxanes that is unable to access using current manners.