Covalent-Organic Framework Nanomaterials: Energy Band Engineering Generating Ultrathin Lubrication Films for Excellent Lubrication.

It is, in fact, inevitable for steel to be covered with a layer of iron oxides and/or peroxides on its surface. However, knowledge of its existence and functionality for tribological behaviors is usually ignored. Herein, covalent-organic framework nanomaterials (CONs) composed of three well-screened acceptors and a donor through the imide linkage were fabricated to explore their lubrication performances. The results indicate that the energy-level matching between CONs and iron oxides or peroxides leads to the formation of a Z-scheme heterojunction structure at the rubbing interface. Also, the friction produces an internal electric field in the heterojunction, which drives the negative atomic/ionic species from the sliding interface to immigrate into the pore of CONs and resettle inside to engender the pinning effects, producing a fixed lubrication layer. Synchronously, it also attracts the free CONs in the base oil to form an easy-shear lubrication layer assembling onto the fixed one, producing a lubrication film with two layered configurations. Finally, the unique lubrication film, despite its thickness of a dozen nanometers, still exhibits impressive friction reduction and antiwear. This finding will inspire the technology to utilize the intrinsic surface nature of steel materials to exploit lubricant additives or modulate tribological behaviors.

Surface plasmon resonance effect cooperated with Z-scheme heterostructure for enhancing photocatalytic nitrogen reduction to ammonia.

The photocatalytic efficiency can be improved by constructing a Z-scheme heterojunction, but hindered by the only half utilization efficiency of photogenerated carriers. Thus, a novel material, UiO-66-NH2@TAPB-BTCA-COP-Ag (U6N@COP-Ag), with surface plasmon resonance (SPR) effect synergistic Z-scheme heterostructure has been prepared by depositing Ag nanoparticles (Ag NPs) on TAPB-BTCA-COP (COP)-coated UiO-66-NH2. The deposited Ag NPs expand the range of light absorption and introduce more photogenerated electrons in the composite. The SPR effect of noble metal compensates for the limited utilization of the Z-scheme heterojunction photogenerated carriers and the increased density of semiconductor carriers at the reducing end, which is more conducive to the redox reaction of the catalyst. Without sacrificial agents, U6N@COP-Ag shows great photocatalytic nitrogen reduction conversion efficiency with the rate of NH4+ in ammonia water at 167.63µmol g-1h-1, which is 6.6 and 2.8 times that of the original UiO-66-NH2 and COP, respectively. In-situ XPS and Kelvin probe technology verify that UiO-66-NH2 and Ag nanoparticles provide more photogenerated electrons to COP. The cleavage and conversion of N2 to NH4+ on U6N@COP-Ag was confirmed by the enhancement of NH bonds and NH4+ characteristic absorption peaks in the in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). This work presents a great method to improve the Z-scheme heterojunction photogenerated carrier utilization and the density of semiconductor carriers at the reducing end by the noble metal SPR effect, which is more conducive to enhance the redox reaction of the catalyst.

Z-Scheme Heterojunction of Hierarchical Cu2S/CdIn2S4 Hollow Cubes to Boost Photoelectrochemical Performance.

The exaltation of light-harvesting efficiency and the inhibition of fast charge recombination are pivotal to the improvement of photoelectrochemical (PEC) performance. Herein, a direct Z-scheme heterojunction is designed of Cu2S/CdIn2S4 by in situ growth of CdIn2S4 nanosheets on the surface of hollow CuS cubes and then annealing at 400 °C. The constructed Z-scheme heterojunction is demonstrated with electron paramagnetic resonance and redox couple (p-nitrophenol/p-aminophenol) measurements. Under illumination, it shows the photocurrent 6 times larger than that of hollow Cu2S cubes, and affords outstanding PEC performance over the known Cu2S and CdIn2S4-based photocatalysts. X-ray photoelectron spectroscopy and density functional theory results demonstrate a strong internal electric field formed in Cu2S/CdIn2S4 Z-scheme heterojunction, which accelerates the Z-scheme charge migration, thereby promoting electron-hole separation and enhancing their utilization efficiency. Moreover, the hollow structure of Cu2S is conducive to shortening the charge transport distance and improving light-harvesting capability. In proof-of-concept PEC application, a PEC detection method for miRNA-141 based on the sensitivity of benzo-4-chloro-hexadienone to light absorption on Cu2S/CdIn2S4 modified electrode is developed with good selectivity and a limit of detection of 32 aM. This work provides a simple approach for designing photoactive materials with highly efficient PEC performance.

Electro-photocatalyst effect of N-S-doped carbon dots and covalent organic triazine framework heterostructures for boosting photocatalytic degradation of phenanthrene in water.

In the present study, we introduce a covalent organic triazine framework polymer (COTF-P) using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with triazine-based amine. The resulting dark red COTF-P illustrated potential behavior as a photocatalyst under visible light. Due to the inadequate solar energy capture and ultrafast charge recombination of the resulting COTF-P, the prepared COTF-P has been decorated with CQDs (N-CQD and N-S-CQD) to build a Z-scheme CQDs/COTF-P heterojunction photocatalyst and utilizes as photocatalyst for the breakdown of phenanthrene (PHE) exposed to visible light. The prepared COTF-P and CQDs/COTF-P were fully characterized, analyzing the textural (N2 isotherms), structural (XRD and FTIR), chemical (EDX and XPS), morphological (FESEM and TEM), optical (DRS-UV-Vis and photoluminescence), and electrochemical properties (EIS impedance, transient photocurrent, and flat band potential). The prepared N-S-CQD/COTF-P heterojunction displayed optimum activity for the photocatalytic oxidation of PHE from water, owing to an enhanced separation of the photogenerated charges and lower bandgap value, 2.1 vs. 1.9 eV. The N-S-CQD/COTF-P heterojunction showed acceptable stability in terms of activity and structural properties after 5 cycles of reuse. The mechanism of activation highlights the importance played by superoxide radicals and hydroxyl radicals. This project sheds light on the potential use of CQDs for the decoration of polymers, extending the absorbance in the visible region and boosting the migration of charge, which boosts the activity of the resulting material.

MIL-Derived Hollow Tubulous-Shaped In2O3/ZnIn2S4 Z-Scheme Heterojunction for Efficient Antibacterial Performance via In Situ Composite.

In this study, a hollow tubulous-shaped In2O3 derived from MIL (MIL-68 (In)) exhibited an enhanced specific surface area compared to MIL. To further sensitize In2O3, ZnIn2S4 was grown in situ on the derived In2O3. The 40In2O3/ZnIn2S4 composite (1 mmol ZnIn2S4 loaded on 40 mg In2O3) exhibited degradation rates of methyl orange (MO) under visible light (80 mW·cm-2, 150 min) that were 17.9 and 1.4 times higher than those of the pure In2O3 and ZnIn2S4, respectively. Moreover, the 40In2O3/ZnIn2S4 exhibited an obviously improved antibacterial performance against Pseudomonas aeruginosa, with an antibacterial rate of 99.8% after visible light irradiation of 80 mW cm-2 for 420 min. The 40In2O3/ZnIn2S4 composite showed the highest photocurrent density, indicating an enhanced separation of photogenerated charge carriers. Electron spin resonance results indicated that the 40In2O3/ZnIn2S4 composite generated both ·O2- and ·OH radicals under visible light, whereas ·OH radicals were almost not detected in ZnIn2S4 alone, suggesting the presence of a Z-scheme heterojunction between In2O3 and ZnIn2S4, thereby enhancing the degradation and antibacterial capabilities of the composite. This offers fresh perspectives on designing effective photocatalytic materials for use in antibacterial and antifouling applications.

A review on development and modification strategies of MOFs Z-scheme heterojunction for photocatalytic wastewater treatment, water splitting, and DFT calculations.

Increasing water pollution and decreasing energy reserves have emerged as growing concerns for the environment. These pollution are due to the dangerous effects of numerous pollutants on humans and aquatic organisms, such as hydrocarbons, biphenyls, pesticides, dyes, pharmaceuticals, and metal ions. On the other hand, the need for a clean environment, finding alternatives to fossil and renewable fuels is very important. Hydrogen (H2) is regarded as a viable and promising substitute for fossil fuels, and a range of methodologies have been devised to generate this particular source of energy. Metal-organic frameworks (MOFs) are a new generation of nanoporous coordination polymers whose crystal structure is composed of the juxtaposition of organic and inorganic constituent units. Due to their flexible nature, regular structure, and high surface area, these materials have attracted much attention for removing various pollutants from water and wastewater, and water splitting. MOFs Z-scheme heterojunctions have been identified as an economical and eco-friendly method for eliminating pollutants from wastewater systems, and producing H2. Their low-cost synthesis and unique properties increase their application in various energy and environment fields. The heterojunctions possess diverse properties, such as exceptional surface area, making them ideal for degradation and separation. The development and formulation of Z-scheme heterojunctions photocatalytic systems using MOFs, which possess stable and potent redox capability, have emerged as a successful approach for addressing environmental pollution and energy shortages in recent times. Through the utilization of the benefits offered by MOFs Z-scheme heterojunctions photocatalysts, such as efficient separation and migration of charge carriers, extensive spectrum of light absorption, among other advantages, notable enhancements can be attained. This review encompasses the synthesis techniques, structure, and properties of MOFs Z-scheme heterojunctions, and their extensive use in treating various wastewaters, including dyes, pharmaceuticals, and heavy metals, and water splitting. Also, it provides an overview of the mechanisms, pathways, and various theoretical and practical aspects for MOFs Z-scheme heterojunctions. Finally, it thoroughly assesses existing challenges and suggests further research on the promising applications of MOFs Z-scheme in industrial-scale wastewater treatment.

Attapulgite-intercalated g-C3N4/ZnIn2S4 3D hierarchical Z-scheme heterojunction for boosting photocatalytic hydrogen production.

Construction of hierarchical architecture with suitable band alignment for graphitic carbon nitride (g-C3N4) played a pivotal role in enhancing the efficiency of photocatalysts. In this study, a novel attapulgite-intercalated g-C3N4/ZnIn2S4 nanocomposite material (ZIS/CN/ATP, abbreviated as ZCA) was successfully synthesized using the freeze-drying technique, thermal polymerization, and a simple low-temperature hydrothermal method. Attapulgite (ATP) was intercalated into g-C3N4 to effectively regulate its interlayer structure. The results reveal a substantial enlargement of its internal space, thereby facilitating the provision of additional active sites for improved dispersibility of ZnIn2S4. Notably, the optimized photocatalyst, comprising a mass ratio of ATP, g-C3N4, and ZnIn2S4 at 1:1:2.5 respectively, achieves an outstanding hydrogen evolution rate of 3906.15 µmol g-1h-1, without the need for a Pt co-catalyst. This rate surpasses that of pristine g-C3N4 by a factor of 475 and ZnIn2S4 by a factor of 5, representing a significant improvement in performance. This significant enhancement can be primarily attributed to the higher specific surface area, richer active sites, broadened light response range, and efficient interfacial charge transfer channels of the ZCA composite photocatalyst. Furthermore, the Z-scheme photocatalytic mechanism for the sandwich-like layered structure heterojunction was thoroughly investigated using diverse characterization techniques. This work offers new insights for enhancing photocatalytic performance through the expanded utilization of natural minerals, paving the way for future advancements in this field.

Oxygen vacancy-rich ß-Bi2O3/Bi2O2SiO3 Z-Scheme heterojunction: A strategy to enhance visible light-driven photocatalytic removal of ARB and ARGs.

Oxygen vacancy-rich ß-Bi2O3/Bi2O2SiO3 (BO/BOS) Z-Scheme heterojunction was prepared by hydrothermal method-assisted calcination. Under visible light, ß-Bi2O3/Bi2O2SiO3 photocatalyst demonstrated superior photocatalytic efficacy in degrading antibiotics and antibiotic-resistant Escherichia coli (AR E. coli) compared to individual ß-Bi2O3 and Bi2O2SiO3. The experimental results showed that BO/BOS-450 sample possessed the best photocatalytic activity against tetracycline (2 h, 80.8%), amoxicillin (4 h, 57.9%) and AR E. coli (3 h, 107.43 CFU·mL-1). BO/BOS-450 sample showed 91.8% electrostatic capture of AR E. coli in the bacterial capture experiment. In the antibiotic-resistant genes (ARGs) degradation experiment, BO/BOS-450 sample was able to bring the log10 (Ct/C0) value of tetA to -3.49 after 2 h. Oxygen vacancies (OVs) were verified through HR-TEM, XPS and EPR analyses. ESR experiments aligned with the quenching experiment results, confirming that the crucial active species were ‧O2- and h+ during photocatalytic sterilization. A small-scale sewage treatment equipment was designed for the effective removal of ARB from real water samples.

Novel defect-transit dual Z-scheme heterojunction: Sulfur-doped carbon nitride nanotubes loaded with bismuth oxide and bismuth sulfide for efficient photocatalytic amine oxidation.

The rational design of Z-scheme heterojunction hybrid photocatalysts is considered a promising way to achieve high photocatalytic activity. In this study, a dual Z-scheme heterojunction with bismuth sulfide (Bi2S3) nanorods and bismuth oxide (Bi2O3) nanoparticles anchored Sulfur-doped carbon nitride (S-CN) nanotubes (Bi2S3/S-CN/Bi2O3) is designed and fabricated through the ordinal metal ion adsorption, pyrolysis, and sulfidation processes using supramolecular rods as precursor. Compared with pristine Bi2S3, Bi2O3, and CN, the dual Z-scheme tube-shaped Bi2S3/S-CN/Bi2O3 catalyst exhibited a significantly improved photocatalytic activity in amine oxidation. The optimized Bi2S3/S-CN/Bi2O3 nanostructure exhibits a 97.6 % benzylamine conversion and 99.4 % imine selectivity within 4 h under simulated solar light irradiation. The excellent activity of Bi2S3/S-CN/Bi2O3 nanotubes can be attributed to the characteristic hollow defect band structure and efficient charge separation and transfer achieved by the dual Z-scheme charge transfer mechanism, which was systematically studied using electron spin resonance spectroscopy, Kelvin probe force microscope, and other techniques. The optimized dual Z-scheme heterojunction hybrid photocatalyst maintains the high oxidizing ability of Bi2S3 and Bi2O3 and the excellent reducing ability of CN, thereby significantly enhancing the photocatalytic activity. This research provides a facile and feasible synthesis strategy for designing dual Z-scheme heterojunctions with defect band structure to improve the photocatalytic activity.

Efficient Photocatalytic Desulfurization in Air through Improved Photogenerated Carriers Separation in MOF MIL101/Carbon Dots-g-C3N4 Nanocomposites.

The extensive industrial applications of fuel oil, a critical strategic resource, are accompanied by significant environmental and health concerns due to the presence of sulfur-containing compounds in its composition, which result in hazardous combustion waste. Extensive research has been conducted to develop technologies for low-vulcanization fuel production to address this issue. Consequently, the investigation of catalysts for environmentally friendly and safe photocatalytic desulfurization becomes imperative. To that end, we have designed efficient MIL-101(Fe)/CQDs@g-C3N4 (MIL101/CDs-C3N4) Z-scheme heterojunction photocatalysts with high carrier separation and mobility through a thermal polymerization-hydrothermal strategy. The high concentration of photogenerated carriers facilitates the activation of oxygen and H2O2, leading to increased production of ROS (⋅O2 -, ⋅OH, h+), thereby enhancing the photocatalytic desulfurization (PODS). Additionally, DFT (Density functional theory) calculations were utilized to determine the electron migration pathways of the catalysts and adsorption energies of DBT (dibenzothiophene). Moreover, Gibbs free energy calculations indicated that MIL101/CDs-C3N4 exhibited the lowest activation energy for oxygen and H2O2. The mechanism of photocatalytic desulfurization was proposed through a combination of theoretical calculations and experimental studies. This study provides guidance for the development of MOF-based Z-scheme systems and their practical application in desulfurization processes.

FeOOH Nanosheets Coupled with ZnCdS Nanoparticles for Highly Improved Photocatalytic Degradation of Organic Dyes and Tetracycline in Water.

Developing a low-cost and highly efficient semiconductor photocatalyst for the decomposition of organic pollutants and antibiotics is highly desirable. Herein, FeOOH nanosheets were prepared using a liquid-phase stirring technique and combined with ZnCdS (ZCS) nanoparticles to construct FeOOH/ZCS nanocomposite photocatalysts. The photocatalytic efficiency of the FeOOH/ZCS nanocomposite was evaluated for the decomposition of various pollutants, including rhodamine B, methylene Blue, and tetracycline. The FeOOH/ZCS nanocomposite exhibited significantly higher photocatalytic performance for the decomposition of various organics. Moreover, the optimized FeOOH/ZCS retained more than 90% of its initial photocatalytic activity even after five successful runs. Radical quenching test and electron spin resonance (ESR) analysis revealed that hydroxyl radicals (•OH) play a dominant role for the decomposition of organics. The FeOOH/ZCS Z-scheme heterojunction significantly facilitates higher charge transfer efficiency and the generation of reactive radicals, resulting in excellent photocatalytic degradation performance. This work offers a new approach to synthesis FeOOH-based photocatalyst for the elimination of organics and antibiotics in water.

Construction of Ultrathin BiVO4-Au-Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible-Light-Driven Photocatalytic Degradation of Tetracycline.

In this study, unique BiVO4-Au-Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X-ray photoelectron spectroscopy measurement during a light off-on-off cycle and redox capability tests of the photo-generated charge carriers confirmed the formation of Z-scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4-Au-Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra-high performance liquid chromatography-mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible-light-driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Oxygen vacancies and Y-O-Ag bonds in the Z-scheme heterojunction cooperate to promote photodegradation of organic pollutants.

Y2O3 is a cost-effective and environmentally friendly wide-band gap photocatalyst with extensive application potential. However, its limited ability to be excited by visible light restricts its practical uses. In this study, we coupled the narrow bandgap semiconductor AgI with Y2O3 to form a Z-scheme heterostructure, significantly promoting its photocatalytic degradation activity. Characterization and experimental results demonstrated the formation of Y-O-Ag bonds through coupling with AgI, leading to an increase in oxygen vacancies in Y2O3, which promotes the chemisorption of H2O and O2. The Y-O-Ag bond introduction promotes electron transfer, improves hole utilization, and boosts energy transfer efficiency, thus promoting the efficient generation of ·OH and 1O2. The photocatalytic degradation rates of RhB and o-nitrophenol by 7.5% AgI/Y2O3 were 26.5 and 4 times higher than those of pure Y2O3, respectively. This study provides theoretical support for the Z-scheme heterojunction to improve photocatalytic activity and offers efficient solutions and practical design ideas for sewage purification.

Dual Z-scheme heterojunction Ce2Sn2O7/Ag3PO4/V@g-C3N4 for increased photocatalytic degradation of the food additive tartrazine, in the presence of persulfate: Kinetics, toxicity, and density functional theory studies.

This study involved the synthesis of a Ce2Sn2O7/Ag3PO4/V@g-C3N4 composite through hydrothermal methods, followed by mechanical grinding. The resulting heterojunction exhibited improved catalytic activity under visible light by effectively separating electrons and holes (e-/h+). The degradation of Tartrazine (TTZ) reached 93.20% within 50 min by employing a ternary composite at a concentration of 10 mg L-1, along with 6 mg L-1 of PS. The highest pseudo-first-order kinetic constant (0.1273 min-1 and R2 = 0.951) was observed in this system. The dual Z-scheme heterojunction is developed by Ce2Sn2O7, Ag3PO4, and V@g-C3N4, and it may increase the visible light absorption range while also accelerating charge carrier transfer and separation between catalysts. The analysis of the vulnerability positions and degradation pathways of TTZ involved the utilization of density functional theory (DFT) and gas chromatography-mass spectrometry (GC-MS) to examine the intermediate products. Therefore, Ce2Sn2O7/Ag3PO4/V@g-C3N4 is an excellent ternary nanocomposite for the remediation of pollutants.

Heterogeneous CuS QDs/BiVO4@Y2O2S Nanoreactor for Monitorable Photocatalysis.

Exploration of multifunctional integrated catalysts is of great significance for photocatalysis toward practical application. Herein, a 1D confined nanoreactor with a heterogeneous core-shell structure is designed for synergies of efficient catalysis and temperature monitoring by custom encapsulation of Z-scheme heterojunction CuS quantum dots/BiVO4 (CuS QDs/BiVO4) and Y2O2S-Er, Yb. The dispersed active sites created by the QDs with high surface energy improve the mass transfer efficiency, and the efficient electron transport channels at the heterogeneous interface extend the carrier lifetime, which endows the nanoreactor with excellent catalytic performance. Meanwhile, real-time temperature monitoring is realized based on the thermally coupled levels 2H11/2/4S3/2→4I15/2 of Er3+ using fluorescence intensity ratio, which enables the monitorable photocatalysis. Furthermore, the nanoreactor with a multidimensional structure increases effective intermolecular collisions to facilitate the catalytic process by restricting the reaction within distinct enclosed spaces and circumvents potential unknown interaction effects. The design of multi-space nanoconfined reactors opens up a new avenue to modulate catalyst function, providing a unique perspective for photocatalytic applications in the mineralization of organic pollutants, hydrogen production, and nitrogen fixation.

Preparation of S-C3N4/AgCdS Z-Scheme Heterojunction Photocatalyst and Its Effectively Improved Photocatalytic Performance.

In this study, S-doped graphitic carbon nitride (S-C3N4) was prepared using the high-temperature polymerization method, and then S-C3N4/AgCdS heterojunction photocatalyst was obtained using the chemical deposition method through loading Ag-doped CdS nanoparticles (AgCdS NPs) on the surface of S-C3N4. Experimental results show that the AgCdS NPs were evenly dispersed on the surface of S-C3N4, indicating that a good heterojunction structure was formed. Compared to S-C3N4, CdS, AgCdS and S-C3N4/CdS, the photocatalytic performance of S-C3N4/AgCdS has been significantly improved, and exhibits excellent photocatalytic degradation performance of Rhodamine B and methyl orange. The doping of Ag in collaboration with the construction of a Z-scheme heterojunction system promoted the effective separation and transport of the photogenerated carriers in S-C3N4/AgCdS, significantly accelerated its photocatalytic reaction process, and thus improved its photocatalytic performance.

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline.

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core-shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

Construction of a direct Z-scheme Cs3Bi2Cl9/g-C3N4 heterojunction composite for efficient photocatalytic degradation of various pollutants in water: Performance, kinetics and degradation mechanism.

The use of emerging composite materials has been booming to remove environmental pollutants. The aim of this research is to develop a new composite based on Cs3Bi2Cl9 perovskite and graphitic carbon nitride (g-C3N4) to investigate the photocatalytic performance under visible light irradiation. To achieve this, we produce the Cs3Bi2Cl9/g-C3N4 heterojunctions through a simple self-assembly synthesis. The as-synthesized composites are characterized using XRD, FTIR, FESEM, TEM, BET and EDX techniques. The photocatalytic performance of Cs3Bi2Cl9/g-C3N4 is examined in the degradation of various water contaminants, including 4-nitrophenol (4-NP), tetracycline antibiotic (TC), methylene blue (MB) and methyl orange (MO). The experimental results indicate the superior photocatalytic performance of the composites in the degradation of pollutants compared to pure Cs3Bi2Cl9 and g-C3N4. The 10% Cs3Bi2Cl9/g-C3N4 composite achieves the optimal degradation efficiency of 100, 92, 98.7, and 85.1% of 4-NP, TC, MB, and MO, respectively. This superior photocatalytic activity attributes to improved optical and electrochemical properties, including enhanced absorption ability, narrowing band gap, promoted separation efficiency of photogenerated carriers, and a high redox potential, which is confirmed by UV-vis DRS, PL, EIS, and CV analyses. The 10% Cs3Bi2Cl9/g-C3N4 composite also demonstrates high photocatalytic stability after four consecutive cycles. Radical trapping tests show that superoxide radicals (•O2-), holes (h+), and hydroxyl radicals (•OH) contribute to the photocatalytic process. Based on the obtained data, a direct Z-scheme heterojunction mechanism is proposed. Overall, this research offers a new stable photocatalyst with excellent prospect for photocatalytic applications.

Low concentration of peroxymonosulfate coupled with visible light triggers oxygen reactive species generation over constructed Bi25FeO40/BiOCl Z-scheme heterojunction for various tetracycline antibiotics removal.

Photocatalytic peroxymonosulfate (PMS) oxidation systems demonstrate significant potential and promising prospects through the interconnection of photocatalytic and PMS oxidation for simultaneously achieving efficient pollutant removal and reduction of PMS dosage, which prevents resource wastage and secondary pollution. In this study, a Z-scheme Bi25FeO40/BiOCl (BOFC) heterojunction was constructed to carry out the photocatalytic PMS oxidation process for tetracyclines (TCs) pollutants at low PMS concentrations (0.08 mM). The photocatalytic PMS oxidation rate of Bi25FeO40/BiOCl composites for tetracycline hydrochloride (TCH), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DXC) reaches 86.6%, 83.6%, 86.7%, and 88.0% within 120 min. Simultaneously, the BOFC/PMS system under visible light (Vis) equally displayed the practical application prospects for the solo and mixed simulated TCs antibiotics wastewater. Based on the electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) valence band spectrum, a Z-scheme electron migration pathway was proposed to elucidate the mechanism underlying the performance enhancement of BOFC composites. Bi25FeO40 in BOFC composites can serve as active site for activating PMS by the formation of Fe3+/Fe2+ cycle. Toxicity estimation software tool (T.E.S.T.) and mung beans planting experiment demonstrates that BOFC/PMS/Vis system can reduce toxicity of TCs wastewater. Therefore, BOFC/PMS/Vis system achieves efficient examination in different water environments and efficient utilization of PMS, which displays a scientific reference for achieving environmentally-friendly and resource-saving handling processes.

Plant-mediated Z-scheme ZnO/TiO2-NCs for antibacterial potential and dye degradation: experimental and DFT study.

Efficient separation of electron-hole pairs remains pivotal in optimizing photogenerated carrier functionality across diverse catalytic and optoelectronic systems. This study presents the fabrication of a novel hollow direct Z-scheme photocatalyst, ZnO/TiO2. A thorough analysis encompassing various techniques such as Ultraviolet-Visible Spectroscopy (UV-Vis), X-ray Diffraction (XRD), Transmission electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Energy-Dispersive X-ray Spectroscopy (EDX) provided detailed insights into the complex material characteristics of the ZnO/TiO2 heterojunction catalyst. The findings revealed coexisting anatase TiO2 and wurtzite ZnO phases, each retaining distinct attributes within the nanocomposites (NCs) structure. The study showcased the photocatalytic efficacy of ZnO/TiO2-NCs in decomposing Methylene Blue and Acridine Orange under UV irradiation, correlated with their underlying structures. Enhanced degradation of these dyes resulted from the establishment of a direct Z-scheme heterojunction between ZnO and TiO2. Employing Density Functional Theory (DFT) using Quantum ESPRESSO, this research analyzed phase diagrams and band structures, elucidating electronic properties and structural correlations. The study characterized a ZnO/TiO2 composite, revealing a band gap of 3.1-3.3 eV through UV-Visible spectroscopy and confirming its formation without impurity phases via XRD analysis. TEM and EDX showed uniform element dispersion (Zn: 27%, Ti: 29.62%, C: 5.03%, O: 38.35%). Computational analysis using DFT indicated a reduction in stable phases with increasing temperature. Enhanced dye degradation was observed (MB: 88.9%, AO: 84%), alongside significant antibacterial activity. In the future we predict that research will focus on development of scaled up production and photocatalytic activity through surface modification, while unveiling mechanistic insights and environmental applicability for multifunctional use in water treatment and antibacterial applications, leading to further advancement of the field.