MoS2 nanosheets anchored on porous ZnSnO3 cubes as an efficient visible-light-driven composite photocatalyst for the degradation of tetracycline and mechanism insight

Simultaneous removal of tetracycline hydrochloride and hexavalent chromium by heterogeneous Fenton in a photocatalytic fuel cell system

In this work, a novel double-chamber system (PFC-Fenton), combined photocatalytic fuel cell (PFC) with Fenton, was constructed for tetracycline hydrochloride (TCH) and hexavalent chromium (Cr(VI)) removal and electricity production. Therein, Zn5(OH)6(CO3)2/Fe2O3/BiVO4/fluorine-doped SnO2 (ZIO/BiVO4/FTO) and carboxylated carbon nanotubes/polypyrrole/graphite felt (CCNTs/Ppy/GF) were served as photoanode and cathode, respectively. Under light irradiation, the removal efficiencies of TCH and Cr(VI) with the addition of H2O2 (2 mL) could reach 93.1% and 80.4%, respectively. Moreover, the first-order kinetic constants (7.37 × 10-3 min-1 of TCH and 3.94 × 10-3 min-1 of Cr(VI)) were 5.26 and 5.57 times as much as the absence of H2O2. Simultaneously, the maximum power density could be obtained 0.022 mW/cm2 at a current density of 0.353 mA/cm2. Therein, the main contribution of TCH degradation was ·OH and holes in anode chamber. The synergistic effect of photoelectrons, generated ·O2-, and H2O2 played a crucial role in the reduction of Cr(VI) in cathode chamber. The high-performance liquid chromatography-mass spectrometry indicated that TCH could be partially mineralized into CO2 and H2O. X-ray photoelectron spectroscope and X-ray absorption near-edge structure spectra showed that Cr(VI) could be reduced to Cr(III). After 5 times of cycling, the removal efficiencies of TCH and Cr(VI) were still greater than 70%, indicating the remarkable stability of the PFC-Fenton system. Overall, this system could remove TCH/Cr(VI) and generate power simultaneously without iron sludge formation, demonstrating a promising method to further develop PFC-Fenton technology.

Highly efficient recovery of Zn (II) from zinc-containing wastewater by tourmaline tailings geopolymers to in-situ construct nanoscale ZnS for the photodegradation of tetracycline hydrochloride

While treating zinc-containing wastewater, recovering zinc for reuse as a secondary resource has significant environmental and economic benefits. Herein, based on the alkali-activated tourmaline tailings geopolymers (TTG) after adsorption of zinc ions (Zn (II)), a series of new composites with in-situ construction ZnS nanoparticles on TTG (ZnS/TTG) were synthesized, and used as photocatalysts for the photodegradation of tetracycline hydrochloride (TCH) in solution. Specifically, ZnS nanoparticles were uniformly and stably distributed in the layered structure of TTG, interweaving with each other to generate an interfacial electric field, which could induce more photocarrier generation. Meanwhile, TTG acted as an electron acceptor to accelerate the electron transfer at the interface, thus enhancing the photodegradation activity for TCH. The active radical quenching experiments combined with the ESR indicated that the active species produced during the photocatalytic degradation of TCH by ZnS/TTG composites were •O2- and photogenerated h+. When the initial concentration of Zn (II) was 60 mg/L, the synthesized 60-ZnS/TTG composites (0.5 g/L) reached 91.53% degradation efficiency of TCH (10 mg/L) at pH = 6. Furthermore, the possible pathways and mechanism of 60-ZnS/TTG composites photodegraded TCH were revealed with the aid of degraded intermediates. This report not only proposed valuable references for reusing heavy metal ions and removing TCH from wastewater, but also provided promising ideas for realizing the conversion of used adsorbents into high-efficiency photocatalysts.

A novel BiOBr/rGO photocatalysts for degradation of organic and antibiotic pollutants under visible light irradiation: Tetracycline degradation pathways, kinetics, and mechanism insight

In this study, the BiOBr/rGO nanocomposite photocatalysts are fabricated by a facile solvothermal method. The BiOBr growth on reduced graphene oxide (rGO) sheet could improve BiOBr's photocatalytic activity by increasing its adsorption ability, surface area, and charge carriers' separation efficiency. The prepared nanocomposites were characterized by XRD, Raman, FESEM, EDS, XPS, and UV-visible DRS. The BiOBr/rGO (BRG) nanocomposites showed improved photocatalytic activity for the photodegradation of Rhodamine B (RhB) dye and Tetracycline (TC) under visible light irradiation. Rhodamine B and tetracycline degradation efficiency were about 96% and 73% within 120 min under visible light irradiation. The PL analysis indicates that BiOBr/rGO nanocomposite exhibited maximum separation efficiency of photoinduced charge carriers. The trapping test confirmed that O2- and h+ are significant active photodegradation species. The GC-MS spectra detected the two plausible transformation routes of tetracycline degradation. The current work presented a low-cost and facile approach for fabricating Bi-based composites.

Enhanced tetracycline degradation with TiO2/natural pyrite S-scheme photocatalyst

In this study, TiO2 nanoparticles were employed as a photocatalyst for the degradation of tetracycline (TC) under visible light irradiation. The TiO2 nanoparticles were decorated on natural pyrite (TiO2/NP) and characterized using XRD, FTIR, and SEM-EDX methods. This study evaluated the impacts of various operational parameters such as pH, catalyst dosage, initial TC concentration, and light intensity on TC removal. The findings revealed that under optimal conditions (pH 7, catalyst: 2 g/L, TC: 30 mg/L, and light intensity: 60 mW/cm2), 100% of TC and 84% of TOC were removed within 180 min. The kinetics of TC elimination followed a first-order model. The dominant oxidation species involved in the photocatalytic elimination of TC was found to be ·OH radicals in the TiO2/NP system. The reuse experiments showed the high capability of the catalyst after four consecutive cycles. This study confirmed that the TiO2/NP system has high performance in photocatalytic TC removal under optimized experimental conditions.

Integration of ohmic junction and step-scheme heterojunction for enhanced photocatalysis

A novel and efficient photocatalyst, Cu2WS4/MoS2-Au plasmonic Step-scheme (S-scheme) heterojunction, was constructed for the first time and applied to remove environmental pollutants. Among all the prepared photocatalysts, the. Cu2WS4/MoS2-Au-5 exhibited the highest catalytic activity with an 89.1% reduction efficiency for Cr6+ and a 98.7% oxidation efficiency for Benzophenone-1 (BP-1) under visible light irradiation. The Cu2WS4/MoS2-Au photocatalyst exhibits stable performance and efficient photocatalytic activity due to effective charge separation, enhanced light absorption from localized surface plasmon resonance (LSPR) of gold nanoparticles, and the formation of an S-scheme heterojunction with strong oxidation-reduction capabilities. In addition, through analysis of experiments and theoretical calculations, it is speculated that the Cu2WS4/MoS2-Au follows a typical S-scheme photogenerated carrier transferring mechanism, which is verified by the finite difference time domain simulation, the free radical quenching experiments, the electron paramagnetic resonance analysis and the simulated charge density distribution. More importantly, the simulations of the work function and charge density distribution confirm the built-in electric field and the ohmic junction have been established at the interfaces between the Cu2WS4 and MoS2 (Cu2WS4/MoS2) as well as the interface between MoS2 and Au (MoS2-Au), respectively. The built-in electric field and ohmic junction enable efficient separation of photogenerated electrons and holes, ensuring the superior catalytic oxidation and reduction activities of the Cu2WS4/MoS2-Au photocatalyst. Finally, we propose a photocatalytic mechanism for the Cu2WS4/MoS2-Au plasmonic S-scheme heterojunction based on experimental results and simulated calculations. The research results of this study are significance for the development of the plasmonic S-scheme photocatalytic system.

Facile synthesis of NiAl2O4/g-C3N4 composite for efficient photocatalytic degradation of tetracycline

Designing high-efficiency photocatalysts responsive to visible light is important for the degradation of antibiotics in water. Heterojunction engineering is undoubtedly an effective strategy to improve the photocatalytic performance. In this work, spinel-type metal oxides (NiAl₂O₄, NAO) are synthesized by a simple sol-gel and calcination process. After compounding graphitic carbon nitride (g-C₃N₄), NAO/g-C₃N₄ heterojunction is obtained, which then is used as the photocatalyst for tetracycline hydrochloride (TC). The effects of photocatalyst dosage, the initial concentration of TC, and solution pH on photodegradation performance are systematically studied. The removal rate of TC on NAO/g-C₃N₄ reach up to ∼90% after visible light irradiation for 2 hr and the degradation rate constant is ∼7 times, and ∼32 times higher than that of pure NAO and g-C₃N₄. The significantly improved photocatalytic activity can be attributed to the synergistic effect between well matched energy levels in NAO/g-C₃N₄ heterojunctions, improvement of interfacial charge transfer, and enhancement of visible light absorption. This study provides a way for the synthesis of efficient photocatalysts and an economic strategy for removing antibiotics contamination in water.

Janus Z-scheme heterostructure of ZnIn2S4/MoSe2/In2Se3 for efficient photocatalytic hydrogen evolution

Artificial manipulation of charge separation and transfer are central issues dominating hydrogen evolution reaction triggered via photocatalysis. Herein, through elaborate designing on the architecture, band alignment, and interface bonding mode, a sulfur vacancy-rich ZnIn₂S₄-based (Vs-ZIS) multivariate heterostructure ZnIn₂S₄/MoSe₂/In₂Se₃ (Vs-ZIS/MoSe₂/In₂Se₃) with specific Janus Z-scheme charge transfer mechanism is constructed through a two-step hydrothermal process. Steering by the Janus Z-scheme charge transfer mechanism, photogenerated electrons in the conduction band of MoSe₂ transfer synchronously to the valence band of Vs-ZIS and In₂Se₃, resulting in abundant highly-active photogenerated electrons reserved in the conduction band of Vs-ZIS and In₂Se₃, therefore significantly enhancing the photocatalytic activity of hydrogen evolution. Under visible light irradiation, the optimized Vs-ZIS/MoSe₂/In₂Se₃ with the mass ratio of MoSe₂ and In₂Se₃ to ZnIn₂S₄ at 3 % and 30 %, respectively, performs a high hydrogen evolution rate of 124.42 mmol·g^-1·h^-1, about 43.5-folds of the original ZIS photocatalyst. Besides, an apparent quantum efficiency (AQE) of 22.5 % at 420 nm and favorable durability are also achieved over Vs-ZIS/MoSe₂/In₂Se₃ photocatalyst. This work represents an important development in efficient photocatalysts and donates a sound foundation for the design of regulating charge transfer pathways.

Insights into Photocatalytic Degradation Pathways and Mechanism of Tetracycline by an Efficient Z-Scheme NiFe-LDH/CTF-1 Heterojunction

Photocatalysis offers a sustainable approach for recalcitrant organic pollutants degradation, yet it is still challenging to seek robust photocatalysts for application purposes. Herein, a novel NiFe layered double hydroxide (LDH)/covalent triazine framework (CTF-1) Z-scheme heterojunction photocatalyst was rationally designed for antibiotics degradation under visible light irradiation. The NiFe-LDH/CTF-1 nanocomposites were readily obtained via in situ loading of NiFe-LDH on CTF-1 through covalent linking. The abundant coupling interfaces between two semiconductor counterparts lay the foundation for the formation of Z-scheme heterostructure, thereby effectively promoting the transfer of photogenerated electrons, inhibiting the recombination of carriers, as well as conferring the nanocomposites with stronger redox ability. Consequently, the optimal photocatalytic activity of the LDH/CTF heterojunction was significantly boosted for the degradation of a typical antibiotic, tetracycline (TC). Additionally, the photodegradation process and the mineralization of TC were further elucidated. These results envision that the LDH/CTF-1 can be a viable photocatalyst for long-term and sustainable wastewater treatment.

Novel fabrication of the recyclable MoS2/Bi2WO6 heterostructure and its effective photocatalytic degradation of tetracycline under visible light irradiation

Developing cost-effective and highly effective visible-light-driven photocatalysts for decomposition of organic contaminants has been deliberated as an important and viable strategy for environmental remediation. Herein, MoS₂/Bi₂WO₆ heterostructure photocatalysts were fabricated with excellent visible light absorption performance and efficient electron/hole (e^-/h⁺) separation efficacy. As-prepared all photocatalysts were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution TEM, X-ray photoelectron spectroscopy (XPS). Although photocatalytic experiments were examined by UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectroscopy (PL), and transient photocurrent (I-t). Among all the photocatalysts, that synthesized by using the components 10 mg of Bi₂WO₆ with 100 mg of MoS₂ (denoted as MSBW-10), displayed high photocatalytic performance (96.31%) for tetracycline (TC) under visible light irradiation within 90 min. The kinetic rate constant of the MSBW-10 heterostructure was 5.51 and 6.71 times higher than those of MoS₂ and Bi₂WO₆, respectively. Further, radical trapping experiments revealed that ˙OH radicals and holes were the predominant reactive species involved in the photocatalytic course. The recycle tests revealed the stability of the photocatalyst, which exhibited 91.85% TC removal efficacy without obvious decay even after the fourth cycle. Furthermore, the type-II MoS₂/Bi₂WO₆ heterostructure photocatalyst exhibited a slighter band gap with energy band alignments and enhanced visible-light absorption, separation of charge carriers, and good oxidation/reduction capacities. These deeper insights and synergetic effects can afford a new approach for flourishing novel heterostructure photocatalysts.

Solar-driven zinc-doped graphitic carbon nitride photocatalytic fibre for simultaneous removal of hexavalent chromium and pharmaceuticals

The current environmental problems urgently require researchers to seek an environmentally friendly, effective and easy to operate sewage treatment method. Graphite carbon nitride (g-C₃N₄), which has the advantages of simple preparation, safety, non-toxicity and chemical resistance, was expected to become a photocatalyst for solving environmental pollution. However, the performances of g-C₃N₄ still have some limitations that the electron hole recombination is fast and the powder is not easy to recover. In this study, zinc-doped graphite carbon nitride photocatalyst (Zn-g-C₃N₄) was mixed with polyacrylonitrile (PAN) to produce photocatalyst fibres by electrospinning. It not only solves the problem that the powder catalyst is difficult to recycle, but also effectively inhibits the recombination of photoelectron-hole pairs. Zn-g-C₃N₄/PAN has good photocatalytic activity for the simultaneous reduction of hexavalent chromium and degradation of pharmaceuticals. When organic pollutants are present, the reduction efficiency of hexavalent chromium was improved without affecting its own removal efficiency. The potential application value of Zn-g-C₃N₄/PAN catalytic fibre was further explored by simulating the complex actual water environment. The composite fibre can be easily reused and keep its superior photocatalytic performance. The mechanism of pharmaceuticals degradation was proposed, in which ∙O2- is the most important active species, which leads to the oxidation of pharmaceuticals. Besides, the photoelectrons generated by the catalyst can reduce the toxic hexavalent chromium. The efficiency of Zn-g-C₃N₄ to remove pollutants is improved by PAN fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts, but also provides more active sites.

Investigation on visible-light photocatalytic performance and mechanism of zinc peroxide for tetracycline degradation and Escherichia coli inactivation

In this study, zincperoxide (ZnO₂) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO₂ (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4-12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO₂ could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O₂^-) and singlet oxygen (¹O₂) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H₂O₂ under the catalysis of Zn(OH)₂ from the hydrolysis of partial ZnO₂, respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO₂ for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation andE. coli inactivation over ZnO₂.

A novel g-C3N4 nanosheet/Ag3PO4/α-Bi2O3 ternary dual Z-scheme heterojunction with increased light absorption and expanded specific surface area for efficient photocatalytic removal of TC

A novel ternary dual Z-scheme 2D g-C₃N₄ nanosheet/Ag₃PO₄/α-Bi₂O₃ (CNN/AP/BO) photocatalyst was successfully synthesized by an in situ deposition and hydrothermal-calcination method. The coupling of AP and BO remarkably enhanced the photocatalytic tetracycline (TC) degradation under visible light illumination, with an optimal removal efficiency of 91.6% (60 min), which can be attributed to the extended visible-light absorption and increased specific surface area owing to the interfacial intimate coupling with well-matched energy band positions between semiconductors. The improved photocatalytic activity resulted from the abundant free radicals by the order of ˙O₂^- > h⁺ > ˙OH based on the electron spin resonance (ESR) and quenching experiment results. In addition, the possible mechanism of TC degradation over the ternary dual Z-scheme heterojunction CNN/AP/BO was proposed.

Degradation and detoxification of broad-spectrum antibiotics by small molecular intercalated BiOCl under visible light

In view of the increasing threat of overuse of broad-spectrum antibiotics to water environment, here, a series of small molecular intercalated bismuth oxychloride (SBC-X) composite photocatalysts were successfully constructed by a simple stirring synthesis at room temperature. Among them, SBC-0.5 showed excellent photocatalytic performance against the three target broad-spectrum antibiotics in visible light, which was 3.06 times, 5.93 times and 11.64 times higher than that of monomer for degrading tetracycline, norfloxacin and ciprofloxacin, respectively. Through analysis, it was found that the excellent photocatalytic degradation performance of SBC-0.5 was mainly attributed to the greatly improved specific surface area, which increased to 14 times of monomer, providing a large number of reaction sites for the subsequent photocatalytic degradation. Besides, intercalated molecules as charge transfer bridges between nanosheets greatly accelerated the efficiency of photogenerated charge transfer between layers. Free radical trapping experiments and electron spin resonance indicated that superoxide anion radicals played a major role in the photocatalytic degradation, followed by singlet oxygen. Furthermore, nine potential degradation intermediates were identified, and the toxicity was greatly reduced confirmed by ECOSAR software prediction and soybean seed germination and seeding growth experiment. Our work will provide useful information for the purification of wastewater containing antibiotics.

Complete photocatalytic degradation of tetracycline by carbon doped TiO2 supported with stable metal nitrate hydroxide

Visible light-driven carbon-doped TiO₂ supported with metal nitrate hydroxide (CT-Ni/Co/Cu) nanocomposites were prepared and characterized by various studies. It is fascinating to note that particle size of TiO₂ was substantially reduced from 5 μm to 50 nm after doping of carbon which was confirmed by FESEM. Moreover, the incorporation of stable metal (Cu) nitrate hydroxide further enhanced the visible light absorption up to 800 nm as evident by UV-DRS. The carbon doping and copper nitrate formation are validated by the Ti-O-C and N-O bonds using XPS and FTIR spectra. The photocatalytic activity of as-prepared photocatalyst was tested for the tetracycline degradation (TC, 10 mg/mL) under light irradiation. Significantly, 3 wt% carbon-doped TiO₂ (31CT) with Cu (II) hydroxide nitrate nanocomposite photocatalyst exhibited an excellent photocatalytic activity (97%, within 1 h), and the corresponding reaction rate was around 2 times higher than bare TiO₂. The excellent photocatalytic activity of 31CT-Cu nanocomposite was due to enhanced adsorbent of TC via carbon doping, visible light absorption, improved photo-generated carrier separation and migration by metal nitrate hydroxide as a support. This work may promote the development of a new carbon-doped TiO₂ supported with highly stable metal nitrate hydroxide nanocomposite by facile method and used as an efficient photocatalyst for photodegradation of environmental pollutants.

2D Molybdenum Sulfide-Based Materials for Photo-Excited Antibacterial Application

Bacterial infections have seriously threatened human health and the abuse of natural or artificial antibiotics leads to bacterial resistance, so development of a new generation of antibacterial agents and treatment methods is urgent. 2D molybdenum sulfide (MoS₂ ) has good biocompatibility, high specific surface area to facilitate surface modification and drug loading, adjustable energy bandgap, and high near-infrared photothermal conversion efficiency (PCE), so it is often used for antibacterial application through its photothermal or photodynamic effects. This review comprehensively summarizes and discusses the fabrication processes, structural characteristics, antibacterial performance, and the corresponding mechanisms of MoS₂ -based materials as well as their representative antibacterial applications. In addition, the outlooks on the remaining challenges that should be addressed in the field of MoS₂ are also proposed.

A review of volatile organic compounds (VOCs) degradation by vacuum ultraviolet (VUV) catalytic oxidation

Volatile organic compounds (VOCs), one of the most important gaseous air pollutants, are getting more and more attention, and a lot of technologies have been studied and applied to eliminate VOCs emissions. Advanced oxidation processes (AOPs) are considered as one of the most promising techniques used for the degradation of VOCs. Vacuum ultraviolet (VUV) catalytic oxidation system is a typical composite AOPs system involving several processes such as VUV photodegradation, photocatalytic oxidation (PCO), ozone catalytic oxidation (OZCO) and their combinations. VUV based catalytic oxidation processes have been intensively studied for degrading VOCs. This review summarizes the recent studies on the use of VUV catalytic oxidation for degrading VOCs. All the processes involved in VUV catalytic oxidation and their combinations have been reviewed. Studies of VOCs degradation by VUV catalytic oxidation can be generally divided into two aspects: developments of catalysts and mechanistic studies. Principles of different processes, strategies of catalyst development and reaction mechanism are summarized in this review. Two directions of prospective future work were also proposed.

Synergistic Effects of Redox Couples and Oxygen Vacancies Improve the Tetracycline Degradation Property of La2NiMnO6

Improving the e^- and h⁺ separation efficiency and promoting the production of more radicals is the key to improving the degradation efficiency of catalytic degradation of antibiotics. On the other hand, intermediate analysis of antibiotics in the dark adsorption and light irradiation process is very important to clarify the entire antibiotic degradation pathway. Here, the La₂NiMnO₆ (LNMO) catalyst was prepared by the sol-gel method and the calcination method. By changing the calcination temperature (800, 900, and 1000 °C), the LNMO-based catalysts were successfully formed, abbreviated as L-800, L-900, and L-1000. XPS measurements demonstrated the presence of Mn⁴⁺, Mn³⁺, Mn²⁺, and oxygen vacancies (OVs) in the LNMO-based catalysts. Analysis of PL, PC, EIS, and TR-PL demonstrated that L-900 had the highest separation efficiency and fastest carrier mobility. The LNMO-based catalysts were used to degrade tetracycline (TC). With the optimized catalyst L-900, the decomposition rate of TC reached 99.57% in 120 min. The entire TC degradation pathway was analyzed according to LC-MS measurements. Radical trap experiments and ESR technology revealed that the synergistic effect of Mn⁴⁺/Mn³⁺, Mn⁴⁺/Mn²⁺, and OVs not only effectively separated e^- and h⁺ but also facilitated the formation of superoxide radicals (^•O₂^-) to accelerate TC degradation. Radicals ^•OH, h⁺, and ^•O₂^- all contributed to TC deterioration in increasing order of importance. In addition, XPS measurements of the L-900 catalyst before and after use indicated that Mn⁴⁺/Mn³⁺, Mn⁴⁺/Mn²⁺, and OVs were not reactants but mediators of e^- and h⁺. Finally, the mechanism of TC degradation with the LNMO-based catalysts was discussed. This work provided new material for TC degradation in the wastewater.

Sheet-on-sheet TiO2/Bi2MoO6 heterostructure for enhanced photocatalytic amoxicillin degradation

Developing sheet-on-sheet (2D/2D) heterostructure with built-in electric field (BIEF) is effective in boosting the performance of photocatalysts for emerging contaminants degradation. Herein, the 2D/2D microtopography and (-)TiO₂/(+)Bi₂MoO₆ BIEF were precisely integrated into hierarchical nanosheets, which can provide the basis and driving force for charge transfer both in in-plane and interface of heterojunction. The prepared photocatalyst (TiO₂/Bi₂MoO₆) showed high-efficiency and stable performance for photocatalytic amoxicillin (AMX) degradation, which was 18.2 and 5.7 times higher than TiO₂ and Bi₂MoO₆, respectively. More importantly, TiO₂/Bi₂MoO₆ showed more efficient photocatalytic activity and photogenerated charge separation than TiO₂@Bi₂MoO₆ (different morphology). Besides, four possible pathways of AMX degradation were proposed depending on Gaussian calculations and intermediates analysis by GC-MS and HPLC-TOFMS. This work sheds light on the design and construction of unique 2D/2D heterostructure photocatalysts for AMX degradation.

Molybdenum disulfide loading on a Z-scheme graphitic carbon nitride and lanthanum nickelate heterojunction for enhanced photocatalysis: Interfacial charge transfer and mechanistic insights

Interfacial design and the co-catalyst effect are considered to be effective to achieve separation and transport of photogenerated carriers in composite photocatalysts. In this study, a Z-scheme heterojunction was successfully combined with a co-catalyst to achieve a highly efficient LaNiO₃/g-C₃N₄/MoS₂ photocatalyst. MoS₂ flakes were loaded on a hybrid material surface, which was formed by LaNiO₃ nanocubes embedded on layered g-C₃N₄, and a good heterostructure with multiple attachment sites was obtained. Experimental studies confirmed that the Z-scheme heterojunction completely preserves the strong redox ability of the photogenerated electrons and holes. As a cocatalyst, MoS₂ further promoted interfacial charge separation and transport. The synergistic effect of the Z-scheme heterojunction and co-catalyst effectively realized the transfer of photogenerated carriers from "slow transfer" to "high transfer" and promoted water decomposition and pollutant degradation. Results revealed that under simulated sunlight irradiation, LaNiO₃/g-C₃N₄/MoS₂ composites exhibit superior hydrogen evolution of 45.1 μmol h^-1, which is 19.1 times that of g-C₃N₄ and 4.9 times that of LaNiO₃/g-C₃N₄, respectively. Moreover, the LaNiO₃/g-C₃N₄/MoS₂ Z-scheme photocatalyst exhibited excellent photocatalytic performance for antibiotic degradation and heavy-metal ion reduction under visible light. This study might provide some insights into the development of photocatalysts for solar energy conversion and environmental remediation.

Low-cost synthesis of a nanocomposite of MoS2 and alkali-activated halloysite nanotubes for photocatalytic RhB degradation

A novel nanocomposite of ultrathin MoS2 nanosheets/alkali-activated halloysite was fabricated via a hydrothermal method, which exhibited improved photocatalytic degradation of rhodamine B compared with the MoS2/HNTs and pristine MoS2.

MoS2 nanosheets loaded on collapsed structure zeolite as a hydrophilic and efficient photocatalyst for tetracycline degradation and synergistic mechanism

In this study, MoS₂@Z photocatalysts were synthesized by combining ultrasonic and hydrothermal methods, and used for the degradation of tetracycline. The structure characteristics and photocatalytic degradation mechanism of photocatalysts were also systematically investigated. The obtained MoS₂@Z-5 exhibits the highest photo-degradation efficiency of tetracycline (87.23%), which is 3.58 times more than alkali-modified zeolite (24.34%) and 1.80 times more than pure MoS₂ (48.53%). Furthermore, the MoS₂@Z-5 showed significant stability in three times photocatalytic recycles and the removal efficiency only decrease by 9.03%. Crystal structure and micromorphology analysis show modified zeolite with collapsed structure can regulate the morphology of nano-MoS₂ and make MoS₂ appear fault structure, which can expose more active sites. In addition, low Si/Al ratio zeolite increases the hydrophilia of MoS₂@Z-5. Reactive-species-trapping experiments show that the hole is the main reactive oxidizing species. The superior photo-degradation efficiency is mainly attributed to outstanding hydrophilia, exposure of the edge active sites, and efficient separation of photogenerated charge and holes. A possible photocatalytic mechanism and degradation pathways of tetracycline were proposed. The results indicate that MoS₂@Z-5 may become an efficient, stable, and promising photocatalyst in tetracycline wastewater treatment.

Formation of unique hollow ZnSnO3@ZnIn2S4 core-shell heterojunction to boost visible-light-driven photocatalytic water splitting for hydrogen production

Herein, it is reported that a batch of hollow core-shell heterostructure photocatalysts were carefully fabricated using a reliable and convenient low-temperature solvothermal method, and ultra-thin ZnIn₂S₄ nanosheets are grown in situ on the hollow ZnSnO₃ cubes to achieve efficient photocatalytic hydrogen evolution. This unique layered hollow structure utilizes multiple light scattering/reflection within the cavity to enhance light absorption, the thin shell reduces the path of charge transfer, and the irregular nanosheets-wrapped outer layer not only enhances the adsorption power, but also provides an abundant active sites to promote the efficiency of photocatalytic water splitting to produce hydrogen. Therefore, due to the matching energy band and unique structure, the ZnSnO₃@ZnIn₂S₄ hollow core-shell heterostructure photocatalyst exhibits superior H₂ production efficiency (16340.18 μmol h^-1 g^-1) and outstanding stability. This work emphasizes the importance of carefully designing a suitable material structure in addition to adjusting the chemical composition.

Well-designed three-dimensional hierarchical hollow tubular g-C3N4/ZnIn2S4 nanosheets heterostructure for achieving efficient visible-light photocatalytic hydrogen evolution

Photocatalytic water splitting for hydrogen production is an important strategy to achieve clean energy development. In this report, a novel three-dimensional (3D) hierarchical hollow tubular g-C₃N₄/ZnIn₂S₄ nanosheets (HTCN/ZIS) type-Ⅱ heterojunction photocatalyst was successfully prepared and applied for photocatalytic hydrogen production under visible light irradiation. The experimental results reveal that the optimal proportion of HTCN/ZIS with the remarkable photocatalytic H₂ evolution rate of 20738 μmol h^-1 g^-1 was obtained. The main reasons for the improvement of hydrogen production activity are as follows: (i) this unique tubular hollow structure can effectively enhances the light capturing ability by the multiple light scattering/reflection of incident light in the inner cavity; (ii) the shorten the phase plane transmission distance could reduce the path of charge transfer; (iii) the surface coated a large number of scaly ZnIn₂S₄ nanosheets can provide abundant reactive sites. Combining the various characterization tests, the enhanced spatial segregation of charge carriers could owning to the intimately interfacial contact and well-matched band gaps structure between g-C₃N₄ and ZnIn₂S₄ through the type-II heterojunction. This work provides a new prospect for the construction of a novel 3D hierarchical type-II heterojunction photocatalyst for highly efficient photocatalytic hydrogen production.

Oxidative Degradation of Tetracycline by Magnetite and Persulfate: Performance, Water Matrix Effect, and Reaction Mechanism

This study presents a strategy to remove tetracycline by using magnetite-activated persulfate. Magnetite (Fe3O4) was synthesized at high purity levels-as established via X-ray diffractometry, transmission electron microscopy, and N2 sorption analyses-and tetracycline was degraded within 60 min in the presence of both magnetite and persulfate (K2S2O8), while the use of either substance yielded limited degradation efficiency. The effects of magnetite and persulfate dosage, the initial concentration of tetracycline, and the initial pH on the oxidative degradation of tetracycline were interrogated. The results demonstrate that the efficiency of tetracycline removal increased in line with magnetite and persulfate dosage. However, the reaction rate increased only when increasing the magnetite dosage, not the persulfate dosage. This finding indicates that magnetite serves as a catalyst in converting persulfate species into sulfate radicals. Acidic conditions were favorable for tetracycline degradation. Moreover, the effects of using a water matrix were investigated by using wastewater treatment plant effluent. Comparably lower removal efficiencies were obtained in the effluent than in ultrapure water, most likely due to competitive reactions among the organic and inorganic species in the effluent. Increased concentrations of persulfate also enhanced removal efficiency in the effluent. The tetracycline degradation pathway through the magnetite/persulfate system was identified by using a liquid chromatograph-tandem mass spectrometer. Overall, this study demonstrates that heterogeneous Fenton reactions when using a mixture of magnetite and persulfate have a high potential to control micropollutants in wastewater.

Construction of S-scheme Bi2WO6/g-C3N4 heterostructure nanosheets with enhanced visible-light photocatalytic degradation for ammonium dinitramide

Photocatalysis technology is considered as a promising environmental remediation strategy. Herein, photocatalytic degradation of ammonium dinitramide (ADN, main component of propellant) was investigated over Bi₂WO₆/g-C₃N₄ (BWO/CN) heterostructure nanosheets prepared by a one-step in-situ hydrothermal method. The operating conditions including ADN initial concentration, catalyst dosage, initial pH, temperature and green oxidizer (hydrogen peroxide) were optimized systematically. Under optimal conditions, the photocatalytic degradation rate of ADN over BWO/CN can reach 98.93% after 80 min visible-light irradiation. Besides, the composite has excellent stability for ADN treatment and nitrate ions are the major degradation products. Furthermore, S-scheme heterojunction mechanism was proposed to explain the extremely high REDOX performance of BWO/CN composite.

Size-controlled synthesis of porous ZnSnO3 nanocubes for improving formaldehyde gas sensitivity

During the detection of formaldehyde, sensitivity and selectivity is still a challenging issue for most reported gas sensors. Herein, an alternative formaldehyde chemosensor that is based on porous ZnSnO₃ nanocubes was synthesized. The products are characterized by XRD, SEM, TEM (HRTEM), XPS, PL measurements and N₂ adsorption–desorption. The size of the ZnSnO₃ nanocubes is about 100 nm and the corresponding specific surface area is 70.001 m² g⁻¹. A gas sensor based on these porous ZnSnO₃ nanocubes shows high sensitivity and selectivity to formaldehyde. The porous ZnSnO₃ nanocube sensor could detect 50 ppm formaldehyde at about 210 °C with a response value of 21.2, which is twice as much as ethanol, and 3 times that of the other five gases. Moreover, the response of the sensor had an acceptable change after a pulse test for 90 days. The sensor can detect formaldehyde with a minimum concentration of 1 ppm, and it has a good linear relationship between 1–50 ppm formaldehyde. The gas sensor based on porous ZnSnO₃ nanocubes can be utilized as a promising candidate for a practical detector of formaldehyde due to its high gas response and excellent selectivity.

The size of the ZnSnO₃ nanocubes is about 100 nm with the corresponding specific surface area of 70.001 m² g⁻¹. A gas sensor based on porous ZnSnO₃ nanocubes shows high sensitivity and selectivity to formaldehyde.

Adsorption and visible-light photocatalytic degradation of organic pollutants by functionalized biochar: Role of iodine doping and reactive species

Here we developed the functionalized biochar as low-cost and heavy metal-free photocatalysts via a facile iodine doping method, which exhibit efficient adsorption and visible-light-driven photocatalytic degradation of representative organic pollutants, phenol and tetracycline. On one hand, iodine doping elevates the adsorption via creating extra pores, e.g., the adsorbed amounts of phenol by iodine-doped WSP and OSR biochar are increased by 161.8% and 146.3%, respectively, which in turn facilitates the photocatalytic oxidation of the adsorbed pollutants. On the other hand, iodine doping leads to the strong photo-induced excitation and remarkably reduced charge carrier transfer resistance, boosting the photocatalytic activity of iodine-doped biochar by more than 20 orders towards organic pollutants (e.g., phenol) degradation. The systematic analysis of reactive species reveals the active roles of O₂^-, H₂O₂, ¹O₂, OH, electrons, and holes in photocatalytic process and identifies O₂^- to be the major contributor. This work affords a facile approach to generating porous and visible-light-driven photocatalyst from biomass for efficient adsorbing and degrading organic pollutants, opening up an avenue to turn biowaste into biomaterials for sustainable environmental remediation.

Bi2S3@Ag2S nano-heterojunction decorated self-floating carbon fiber cloth and enhanced solar-driven photothermal-photocatalytic performance

The difficult recycle, secondary pollution and insufficient sunlight utilization of powder photocatalysts are main obstacles for practical applications. Bi₂S₃@Ag₂S heterojunction supported on surface of carbon fiber cloth (CC) are fabricated through hydrothermal in-situ growth method combined with ultrasonic loading strategy, which can be self-floated on water surface. Bi₂S₃@Ag₂S nano-heterojunction with narrow band gap shows enhanced full spectrum absorption, which is in favor of improving the photocatalytic-photothermal performance. Self-floating CC as a substrate not only absorbs solar light converting to thermal energy, but also favors the recycle of catalysts. The resultant Bi₂S₃@Ag₂S/CC composite films exhibit excellent photothermal conversion performance and photocatalytic degradation activity for tetracycline hydrochloride in low temperature wastewater under simulated sunlight. Experimental results confirm that the superoxide group (·O₂^-) is the main factor for the robust catalytic performance. The good photothermal-photocatalytic performance can be ascribed to the efficient absorption of sunlight for self-floating characteristics and high charge carriers separation efficiency of Bi₂S₃@Ag₂S nano-heterojunction. This novel self-floating photothermal-photocatalytic film will have potential applications in fields of environment.

BiOBr/MoS2 catalyst as heterogenous peroxymonosulfate activator toward organic pollutant removal: Energy band alignment and mechanism insight

Utilization of heterogenous catalysts to trigger peroxymonosulfate (PMS) activation is considered an efficient strategy for environmental decontamination. Herein, a tightly bonded flake-like 2D/2D BiOBr/MoS₂ heterojunction was successfully designed through co-precipitation process. By virtue of matched energy levels and intimate interfacial coupling, the Type-II BiOBr/MoS₂ heterojunction significantly expedited charge carrier transfer and thereby promoted the catalytic performance for organic dye oxidation and Cr(VI) reduction. The specially designed BiOBr/MoS₂ heterojunction is also conducive to split PMS and continuously generated highly active species (SO₄^-, OH and O₂^-) in a photo-Fenton system, achieving extraordinary catalytic capacity for various emerging organic pollutants (including phenol, bisphenol A and carbamazepine). The photoexcited electron with prolonged lifetime and exposed Mo sites with multivalence and multiphase nature can effectively activate PMS, which further promotes the oxidation efficiency of holes, as confirmed by scavenging experiments. The excellent stability and oxidative properties could justify scale up using BiOBr/MoS₂ to a small pilot test, implementing the potential value in practical applications. This study would provide novel insight and cognition of PMS activation via a superior heterojunction for complex polluted wastewater treatment.

Emerging Hybrid Nanocomposite Photocatalysts for the Degradation of Antibiotics: Insights into Their Designs and Mechanisms

The raising occurrence of antibiotics in the global water bodies has received the emerging concern due to their potential threats of generating the antibiotic-resistive and genotoxic effects into humans and aquatic species. In this direction, the solar energy assisted photocatalytic technique offers a promising solution to address such emerging concern and paves ways for the complete degradation of antibiotics with the generation of less or non-toxic by-products. Particularly, the designing of hybrid photocatalyticcomposite materials has been found to show higher antibiotics degradation efficiencies. As the hybrid photocatalysts are found as the systems with ideal characteristic properties such as superior structural, surface and interfacial properties, they offer enhanced photoabsorbance, charge-separation, -transfer, redox properties, photostability and easy recovery. In this context, this review study presents an overview on the recent developments in the designing of various hybrid photocatalytic systems and their efficiency towards the degradation of various emerging antibiotic pharmaceutical contaminants in water environments.