Z-scheme Mechanism Research Articles

Design plasmonic nanostructure of silicon dioxide and titanium dioxide loaded on a nano surface for clean water production through photocatalysis and electrochemical techniques

The work is targeted to rebuild the framework of a nanocatalyst (NCat) that depends on the n/p-type heterojunction through the plasmonic structure of reduced graphene oxide (rGO), silicon oxide nanoparticles (SiO2 NPs), polyvinyl alcohol (PVA NPs), and titanium dioxide (TiO2 NPs). The removal of medical and organic contaminants occurs via photocatalysis operation which follows through the electrochemical technique and UV-spectrophotometer under visible light with nanocatalyst (rGO@SiO2@PVA@TiO2) for clean water and a safe medical environment. The Z-Scheme mechanism explains the development of electron maps in fabricated nanocatalyst engineering to increase the efficiency of the photocatalytic activity. The high activity of the NCat appeared, after 160 min, and the photocatalytic efficiency for methylene blue (MB), methyl orange (MO), rhodamine B (RhB), moxifloxacin (MFX), and colchicine, was 90 %, 76 %, 88 %, 84 %, and 91 % respectively. The stability of NCat was confirmed via the recyclability process, with the efficiency at 58 % after the fifth cycle. The high stability of NCat was proved by the electrochemical technique performed after 100 cycles. The safety of the NCat for the generation of clean water was highlighted by the cytotoxicity test using normal mouse liver cells. It is suggested to use the new NCat design because of its distinctive optical characteristics, which make it a viable candidate for use as a revolutionary nanomaterial with high efficiency and safety for clean water and removal of medical contaminants.

Activated charge transfer by interfacial S−O “bridge” at MnIn2S4/WO3 for eliminating kanamycin: Z-scheme mechanism, pathways and toxicity assessment

In the realm of heterojunction photocatalysis, the efficiency of carrier separation and overall photocatalytic reactions are significantly influenced by the accompanying resistance at the interface as well as the pathway of charge transfer. Herein, a covalently linked Z-scheme MnIn2S4/WO3 heterojunction with interfacial S−O bonds was synthesized through simple calcination and hydrothermal strategies. This tight heterostructure exerted the collaborative impact of interfacial covalent bonding in a Z-scheme model, and its significant role in facilitating the separation of charge carriers was investigated. 19 wt% WO3 combined MnIn2S4 (MIS/WO-19) delivered a remarkable degradation efficiency of 97.4 % for kanamycin, which was 8.8 times higher than that of pure MnIn2S4. The formation of S−O linkages between MnIn2S4 and WO3 was confirmed through experimental analyses and theoretical modeling. The proposed Z-scheme charge transfer pathway was examined by integrating quenching experiments, ESR tests, and DFT computations. This distinctive S−O bond, acting as a specialized “bridge”, in combination with the Z-scheme pathway, efficiently promoted the migration and segregation of photo-induced charges, leading to a notable enhancement in the degradation of kanamycin. Furthermore, the decomposition pathways of kanamycin were investigated through a collaborative approach involving mass spectrometry and DFT simulations, and a toxicity analysis of the intermediates was conducted by the computational toxicology.

Oxygen Vacancies-Mediated Z-Scheme Mechanism Promotes Synergistic Photoelectrocatalysis for Hydroxyl Radical and Singlet Oxygen-Cooperating on Selective Pollutant Degradation

Oxygen Vacancies-Mediated Z-Scheme Mechanism Promotes Synergistic Photoelectrocatalysis for Hydroxyl Radical and Singlet Oxygen-Cooperating on Selective Pollutant Degradation

Hydrothermal synthesis and characterization of 0D/2D SrMoO4/g-C3N4 composite with direct Z-scheme heterojunction: Efficient photocatalytic Ciprofloxacin degradation

Ciprofloxacin (Cip) is a common pollutant that causes sewage problems, and its effective removal is a great contribution to the clean water environment. Direct Zener-scheme (Z-scheme) heterojunction photocatalyst is a promising design idea for the removal of residual antibiotics in water. The goal of this study is to construct a binary composite photocatalyst with Z-scheme heterojunction to effectively remove residual ciprofloxacin in wastewater. Herein, a direct Z-scheme 0D/2D SrMoO4/g-C3N4 (SMOCN) composite photocatalyst was synthesized by ultrasonic-assisted hydrothermal way and its interior information (chemical structure, micromorphology, and physic-optical property) was detected by various characterization instruments (XRD, FT-IR, EDX, XPS, UV–Vis DRS, and PL). Meanwhile, the photocatalytic activity of all-prepared catalysts were estimated by Cip photodegradation experiments under simulated sunlight (500 W Xenon lamp). Among them, 89.9 % of Cip was broken down by 30SMOCN composite within 180 min at pH 7.0, which respectively reached 2.56 times of bare SMO and 2.03 times of bare CN. Furthermore, 85.2 % of Cip targeted molecule is still removed by SMOCN (excellent stability and recyclability) after five cycle runs. Finally, the reasonableness of SMOCN conforming to the direct Z-scheme mechanism is verified by comparison of optical properties, quenching experiment results and photogenerated carrier migration paths: 1) There is optical complementarity between SMO and CN, which is represented by redshifted absorption edge, narrowed band gap and weaken PL intensity. 2) The key active site on the SMOCN composite surface is photogenerated carriers in Cip photocatalytic degradation, which given full play to the direct synergistic catalytic effect between SMO and CN heterojunction. 3) The direct Z-scheme mechanism preserves the carriers of SMOCN with effective photo-redox function, promotes their separation and prolongs their lifetime.

Direct Z-scheme ZnS/HfS2 heterojunction for photocatalytic overall water splitting with high carrier mobility

The electronic and photocatalytic properties of a type-II ZnS/HfS2 heterojunction are comprehensively analyzed through first-principles calculations in this paper. By calculating the binding energy and phonon spectrum of five potential stacking patterns, the stable structure of the ZnS/HfS2 heterojunction is determined. The electronic structure calculations indicate that the heterojunction has a type-II alignment with a 1.26 eV band gap. The heterojunction exhibits high carrier mobilities (4387.36 and 9561.39 cm2V–1S−1 for X and Y directions). The photocatalytic water splitting process of the heterojunction can be explained by the direct Z-scheme mechanism. The built-in electric field enables rapid recombination of electron-hole pairs at CBM and VBM, while the hydrogen evolution reaction and oxygen evolution reaction can separately be achieved at the ZnS layer and HfS2 layer to complete the overall water splitting. The free energy analysis indicates that the ZnS/HfS2 heterojunction has high activity for overall water splitting under illumination. Moreover, the calculated solar-to-hydrogen efficiency of the heterojunction reaches 30%, ensuring its photocatalytic performance. Remarkably, the type-II alignment is maintained and the catalytic performance can be further improved under biaxial strain because of the enhanced optical absorption in visible light and the reduced band gap. This work reveals that ZnS/HfS2 heterojunction is a potentially novel photocatalytic material for efficient overall water splitting.

Co-W18O49/PDI Z-scheme heterojunction photocatalyst for photocatalytic BPA degradation and mechanism

Efficient migration and separation of photogenerated carriers in semiconductors is crucial to the photocatalytic activity, but significant challenges remain. Herein, the Co-W18O49/PDI composite is prepared, and the Z-scheme mechanism is investigated. The Co-W18O49 nanowires are evenly distributed on the PDI nanorods to create closely connected heterojunctions for enhanced interfacial charge-carrier separation and transfer. The photocatalytic activity of Co-W18O49/PDI is monitored by photocatalytic degradation of BPA by visible light irradiation. The degradation rate of BPA by Co-W18O49/PDI composites was 91.2% within 150 minutes of visible light irradiation. Based on the experimental results of LC-MS and ESR, the photocatalytic degradation mechanism is proposed. The synergistic effect not only improve the generation rate of the active species and reduces the activation energy barrier, but also significantly increases O2 adsorption to make activation easier for efficient photocatalytic BPA degradation.

Control interfacial charge transfer behavior by creating surface defects on structure unit of heterojunction to drive carrier separation for enhancing photocatalytic CO2 reduction

Controlling interfacial charge transfer behavior of heterojunction is an arduous issue to efficiently drive separation of photogenerated carriers for improving the photocatalytic activity. Herein, the interface charge transfer behavior is effectively controlled by fabricating an unparalleled VO-NiWO4/PCN heterojunction that is prepared by encapsulating NiWO4 nanoparticles rich in surface oxygen vacancies (VO-NiWO4) in the mesoporous polymeric carbon nitride (PCN) nanosheets. Experimental and theoretical investigations show that, differing with the traditional p-n junction, the direction of built-in electric field between p-type NiWO4 and n-type PCN is reversed interestingly. The strongly codirectional built-in electric field is also produced between the surface defect region and inside of VO-NiWO4 besides in the space charge region, the dual drive effect of which forcefully propels interface charge transfer through triggering Z-Scheme mechanism, thus significantly improving the separation efficiency of photogenerated carriers. Moreover, the unique mesoporous encapsulation structure of VO-NiWO4/PCN heterostructure can not only afford the confinement effect to improve the reaction kinetics and specificity in the CO2 reduction to CO, but also significantly reduce mass transfer resistance of molecular diffusion towards the reaction sites. Therefore, the VO-NiWO4/PCN heterostructure demonstrates the preeminent activity, stability and reusability for photocatalytic CO2 reduction to CO reaction. The average evolution rate of CO over the optimal 10 %-VO-NiWO4/PCN composite reaches around 2.5 and 1.8 times higher than that of individual PCN and VO-NiWO4, respectively. This work contributes a fresh design approach of interface structure in the heterojunction to control charge transfer behaviors and thus improve the photocatalytic performance.

Investigating the Z-scheme mechanism on the optimized oxygen vacancies ZnO/Co3S4 photocatalyst for the efficient photocatalytic removal of ciprofloxacin

The waste of human and animal antibiotics is an inescapable problem and a severe threat to the continuation of human life. A logical strategy to face the challenge of antibiotic contamination is to design active, stable, environmentally friendly, and economical photocatalysts. Hence, oxygen vacancies ZnO/Co3S4 (ZnO-OV/Co3S4) photocatalyst was successfully fabricated for the first time and used for the photocatalytic removal of ciprofloxacin (CIP) as a widely used antibiotic under visible light. Several techniques were engaged in exploring the crystallinity, morphology, structure, chemical and elemental composition, and electrochemical and optical properties of the constructed nanocomposites. The band gap of ZnO-OV and Co3S4 nanoparticles was determined at 2.95 and 1.58 eV by evaluating the optical properties and using the Tauc plots. To optimize the conditions of the photocatalytic process, factors such as the weight percentage of the nanocomposite components, the photocatalyst dosage, the initial concentration of CIP, the pH of the test solution, and the presence of bubbled oxygen were varied. The optimal degradation rate constant (0.0720 min−1) was obtained for ZnO-OV/Co3S4 (15 %) nanocomposite at pH 9, nanocomposite dosage of 1.5 g/L, and 10 mg/L of CIP in the visible spectrum. The experimental and characterization outcomes indicated that the significantly boosted photocatalytic activity of the ZnO-OV/Co3S4 composite was chiefly attributed to the oxygen vacancies, retard charge carriers recombination by the construction of heterojunction between the ZnO-OV and Co3S4. Finally, the possible Z-scheme mechanism was proposed to illuminate the migration of charge carriers.

Heteroepitaxial MOF-on-MOF Photocatalyst for Solar-Driven Water Splitting.

Assembly of different metal-organic frameworks (MOFs) into hybrid MOF-on-MOF heterostructures has been established as a promising approach to develop synergistic performances for a variety of applications. Here, we explore the performance of a MOF-on-MOF heterostructure by epitaxial growth of MIL-88B(Fe) onto UiO-66(Zr)-NH2 nanoparticles. The face-selective design and appropriate energy band structure alignment of the selected MOF constituents have permitted its application as an active heterogeneous photocatalyst for solar-driven water splitting. The composite achieves apparent quantum yields for photocatalytic overall water splitting at 400 and 450 nm of about 0.9%, values that compare much favorably with previous analogous reports. Understanding of this high activity has been gained by spectroscopic and electrochemical characterization together with scanning transmission and transmission electron microscopy (STEM, TEM) measurements. This study exemplifies the possibility of developing a MOF-on-MOF heterostructure that operates under a Z-scheme mechanism and exhibits outstanding activity toward photocatalytic water splitting under solar light.

Fe3O4/ZnO/L-lysine functionalized graphene oxide a promising nanocomposite with double Z-scheme visible photocatalytic and dark catalytic activity for water remediation

Developing multifunctional catalysts for efficient pollutant degradation in dark and visible light conditions represents a significant advancement in water remediation technology. This study reports the synthesis of a novel Fe3O4/ZnO/Lys-rGO nanocomposite via environmentally friendly methods that exhibit catalytic-photocatalytic activity for efficient degradation of organic pollutants. The synergistic effect of compositing Lys-rGO, a bio-organic component with a narrow band gap (1.08 eV), into the Fe3O4/ZnO inorganic composite induces a double Z-scheme mechanism by providing two pathways for effective charge separation in the visible photocatalytic activity of the nanocomposite. Additionally, the stored electrons in the very conductive Lys-rGO layers offer active sites for the catalytic activity of the nanocomposite in the dark. Meanwhile, ZnO generates reactive oxygen species (ROS) through surface oxygen vacancies, further contributing to the nanocomposite’s dark catalytic activity. The degradation of various organic pollutants (Methylene Blue, Tetracycline, Ciprofloxacin, Rhodamine B, and their mixture), as well as Congo Red, with low catalyst dosage and visible light irradiation time, demonstrates the high performance and versatility of this nanocomposite. This research highlights the potential of Lys-rGO in compositing with semiconductors to design multifunctional catalysts for cost-effective sustainable water purification technologies.

Boosted photocatalytic performance of cobalt ferrite anchored g-C3N4 nanocomposite toward various emerging environmental hazardous pollutants degradation: insights into stability and Z-scheme mechanism.

In this study, a highly efficient CoFe2O4-anchored g-C3N4 nanocomposite with Z-scheme photocatalyst was developed by facile calcination and hydrothermal technique. To evaluate the crystalline structure, sample surface morphology, elemental compositions, and charge conductivity of the as-synthesized catalysts by various characterization techniques. The high interfacial contact of CoFe2O4 nanoparticles (NPs) with g-C3N4 nanosheets reduced the optical bandgap from 2.67 to 2.5eV, which improved the charge carrier separation and transfer. The photo-degradation of methylene blue (MB) and rhodamine B (Rh B) aqueous pollutant suspension under visible-light influence was used to investigate the photocatalytic degradation activity of the efficient CoFe2O4/g-C3N4 composite catalyst. The heterostructured spinel CoFe2O4 anchored g-C3N4 photocatalysts (PCs) with Z-scheme show better photocatalytic degradation performance for both organic dyes. Meanwhile, the efficiency of aqueous MB and Rh B degradation in 120 and 100min under visible-light could be up to 91.1% and 73.7%, which is greater than pristine g-C3N4 and CoFe2O4 catalysts. The recycling stability test showed no significant changes in the photo-degradation activity after four repeated cycles. Thus, this work provides an efficient tactic for the construction of highly efficient magnetic PCs for the removal of hazardous pollutants in the aquatic environment.

Enhanced Photocatalytic Performances of SnS2/TiO2 Composites via a Charge Separation Following Z-Scheme at the SnS2/TiO2{101} Facets

The formation of heterojunctions for efficient charge separation has been practiced for the preparation of efficient semiconductor-based photocatalysts for applications such as hydrogen production and environmental remediation. In this study, we synthesized a composite structure with a heterojunction between SnS2 and TiO2 through a microwave-assisted hydrothermal process, in which SnS2 nanoparticles grew on nanocrystalline TiO2 nanosheets preferentially at the exposed {101} facets. Appropriate exposure of the {001} and {101} facets of the TiO2 nanosheet in the composite with a preferential growth of SnS2 nanoparticles at the {101} facets was the origin of the charge separation following a direct Z-scheme mechanism to result in enhanced photocatalytic performances in photodegradation of organic dyes such as methylene blue (MB) and rhodamine B (RhB) compared to that of SnS2 and TiO2 alone. A plot of photodegradation rates vs. SnS2 ratios in the composites gave an overall volcano-shaped curve with a maximum at the SnS2 ratio of about 33% at which small SnS2 nanoparticles were populated at the {101} facets of the TiO2 nanosheets with a high surface area (118.2 m2g−1). Our results suggest the microwave-assisted hydrothermal process can be a good synthetic approach for composite-based photocatalysts with a preferential heterojunction structure.

GO/Bi2O2CO3/NiWO4 with Z-scheme heterojunction: Efficiently enhanced degradation of organic pollutants under visible light and DFT studies

A ternary composite of GO/Bi2O2CO3/NiWO4 (GBCNWO) was prepared via an in-situ of Bi2O2CO3 onto the surface of NiWO4 and Bi2O2CO3/ NiWO4 being warped by GO, which was thereafter untilled as catalyst in photodegradation of organic pollutants. The microstructure, and optical properties of all the prepared samples were characterized using various techniques such as XRD, FT-IR, SEM, TEM, TG-DTG, XPS, UV-Vis, ESR, and N2-adsorption. Amongst the studied samples, GBCNWO possessed the largest specific surface area, which would efficiently afford much more spaces for the exposing of active sites. Results of UV–vis and XPS suggested that GBCNWO was more efficient for the adsorption and conversion of visible light, and photocurrent conduction through graphite carbon ring could lessen the recombination rate of photoelectrons and holes. Also, the minor arc radius of GBCNWO unveiled its lowest photoresistors among the composites, indicating that the GBCNWO structured with GO, Bi2O2CO3 and NiWO4 has synergistic catalysis in the photodegradation. Importantly, 95.15 % of degradation rate was observed under the optimized conditions (pH=7, catalyst weight of 30 mg, 40 mg/L of MB, 25 °C). Additionally, the degradation rate of various substrates followed the order: MB (99.34 %) > ciprofloxacin (97.28 %) > RHB (97.01 %) > indole (27.47 %) > phenol (9.47 %). The quenching experiment and ESR test suggested that three kinds of active species (•OH, •O2− and h+) can be photogenerated during visible light radiation. Among them, •O2− was confirmed as the key species during the photocatalytic process, which could be adduced that the existence of oxygen vacancies made the receiving photoelectrons to reduce O2, forming the superoxide radical. Finally, a Z-scheme mechanism about the production of active radicals was proposed, which was also validated by DFT calculations.

Protonated Z-scheme CdS-covalent organic framework heterojunction with highly efficient photocatalytic hydrogen evolution

The low efficiency of photocatalytic hydrogen production from water is mainly suffer from limited light absorption, charge separation and water delivery to the active centers. Herein, an inorganic–organic Z-scheme heterojunction (CdS-COF-Ni) is constructed by in-situ growth of CdS nanosheets on the porphyrin-based covalent organic framework with nickel ions (COF-Ni) in the porphyrin centers. A built-in electric field is formed at the interface, which accelerates the separation and transfer of photogenerated charges. Moreover, through the surface protonation treatment in ascorbic acid (AC) solution, the hydrophilicity of the obtained composite is obviously increased and facilitates the transport of water molecules to the photocatalytic centers. Under the synergistic effect of the interfacial interaction and surface protonation treatment, the photocatalytic hydrogen production rate is optimized to be 18.23 mmol h−1 g−1 without adding any cocatalysts, which is 21 times that of CdS. After a series of photoelectrochemical measurements, in situ X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations, it is found that the photocatalytic charge transfer pathway conforms to the Z-scheme mechanism, which not only greatly accelerates the separation and transfer of photogenerated charges, but also retains a high reduction capacity for water splitting. This work offers a good strategy for constructing highly efficient organic–inorganic heterojunctions for water splitting.

Construction of Z-scheme BiOCl/Bi2WO6 heterojunctions with oxygen vacancies for effectively destruction of two typical contaminants

In this study, Z-scheme BiOCl/Bi2WO6 heterojunctions with enriched oxygen vacancies (OVs) were fabricated. Enhanced separation efficiency of photogenerated electron-hole pairs from BiOCl/Bi2WO6 composite was confirmed through surfacephotovoltagespectroscopy (SPS), photocurrent and electrochemical impedance spectroscopy (EIS) analysis. Photocatalytic decontamination of rhodamine B (RhB) and tetracycline (TC) over BiOCl/Bi2WO6 composite was investigated, and BiOCl/Bi2WO6 heterojunctions reveal higher photocatalytic performance than BiOCl and Bi2WO6. The boosted activity of BiOCl /Bi2WO6 heterojunctions stems from the improved separation rate of carriers. In view of electron paramagnetic resonance (EPR) results and band structures of BiOCl and Bi2WO6, photocatalytic mechanism of the BiOCl/Bi2WO6 heterojunctions follows Z-scheme mechanism.

Synthesis and mechanism of hierarchical porous Ag/CuxO (x = 1, 2) nanowire hybrids for high photocatalytic degradation

To improve organic pollutant degradation ability, this work aims at designing a novel porous Cu-Ag bimetal hybrid with unique architecture, fertile porosity as well as Schottky junction. Herein, a free-standing hybrid with Ag nanoparticles modified CuxO (x = 1, 2) nanowires in-situ grown on the nanoporous Cu-Ag bimetal network (Ag/CuxO@NP-CuAg) was successfully synthesized by dealloying and then anodizing process. Compared with monometallic CuxO nanowires integrated with nanoporous Cu substrate (CuxO@NPC), the Ag/CuxO@NP-CuAg hybrids with the Ag/CuxO Schottky junction and SPR effect of Ag nanoparticles, are favorable to accelerate the transportation of photo-generated carriers and avoid the recombination of electrons (e-) and holes (h+), thus exhibiting the enhanced photocatalytic performance for RhB. Such remarkable performance is also contributed to the multimodal hierarchical porous structure and the integration design strategy. Moreover, by density functional theory (DFT) calculation, a typical Z-scheme mechanism is proposed to better understand the photocatalytic degradation process. The formation mechanism of the Ag/CuxO nanowires is also investigated.

Enhanced acetaminophen photodegradation under UV using anatase–rutile TiO2 phase heterojunction – Z-scheme mechanism and factors affecting efficiency

In this work, the commercial Hombikat UV-100 anatase (AH) was calcined at 1000 °C for 4 h to obtain a rutile phase grown on anatase (AR), proven by X-ray diffraction pattern. The dry powder of AH and AR were physically mixed to form AH + AR samples in different ratios. Although the characterization of AR revealed that it had microstructure bigger than AH, lower surface area, lower water-molecule absorption, higher surface states and lower charge separation, all mixed AH + AR samples, which had physically-induced tuning in phase heterojunction, outperformed the commercial TiO2 P25 in acetaminophen (ATM) photodegradation efficiency. This could be due to effective charge separation and more active sites involved in AH + AR samples as seen in the depicted Z-scheme mechanism based on their band-edge positions obtained from Mott-Schottky analysis, scavenger tests and ATM photodegradation efficiency. In addition, this work also showed that band-edge positions, band-gap energy and heterojunction were correlated in determining the ATM photodegradation efficiency.

In Situ Growth of CuBi2O4/Bi2O3 Z-Scheme Heterostructures for Bifunctional Photocatalytic Applications.

In this study, we present an in situ solvothermal approach for synthesizing a highly efficient bifunctional CuBi2O4/Bi2O3 composite catalyst for applications in H2 production and the removal of organic pollutants. Various characterization techniques, including XRD, UV-vis DRS, SEM, TEM, and EIS, were used to characterize the prepared catalyst. Density functional theory calculations confirmed a Z-scheme mechanism, revealing the charge transfer mechanism from the Bi2O3 surface to the CuBi2O4 surface. The composite exhibited a photocurrent of 2.83 × 104 A/cm2 and a hydrogen production rate of 526 μmolg-1h-1 under natural sunlight. Moreover, the catalyst demonstrated efficient degradation of RhB up to 58% in 120 min under 50 W LED illumination. Additionally, multiple recycling tests confirmed its high stability and recyclability, making it a promising candidate for various applications in the field of photocatalysis.

Peroxymonosulfate-activated photocatalytic degradation of norfloxacin via a dual Z-scheme g-C3N5/BiVO4/CoFe − LDH heterojunction: Operation and mechanistic insights

The design of novel dual Z-scheme heterojunction plays a significant path in eradicating organic contaminants via enriched charge carrier separation. Herein, a wet chemical method was used to synthesize ternary g-C3N5/BiVO4/CoFe–LDH (CBCF) nanocomposites, and their corresponding abilities were characterized as follows: crystal phases, optical properties, surface morphologies, and compositions. The g-C3N5/BiVO4/CoFe–LDH-30% (CBCF-3) sample optimized the removal efficiency of norfloxacin (NOR) by up to 95.3% through peroxymonosulfate (PMS) activation in a visible light medium. The combined effects from the Vis/PMS/CBCF-3 catalytic system led to 7-times higher degradation efficiency than visible light only system. This improved performance was attributed to the generation of reactive radical species because of higher PMS utilization and an effective Z-charge transfer process from well-oriented band structures. Moreover, scavenging tests and electron spin resonance analysis revealed the production of active radical and non-radical species, namely •OH, SO4•−, •O2−, and 1O2. Based on the appropriate experimental analysis, the expected NOR degradation mechanism and possible pathways were proposed. Then, the toxicity evaluation results revealed that the intermediate products may not have an adverse effect on the aquatic ecosystems. This research study provides a positive outcome for wastewater remediation using enriched dual Z-scheme mechanism.

Hydrothermally synthesized ZnFe2O4/ZnO heterojunction nanocomposites for enhanced RB dye degradation via Z-scheme photocatalysis

ZnFe2O4/ZnO nanocomposites with 1:1, 1:2, 1:3 and 1:4 wt ratios synthesized by hydrothermal method are used as a photocatalyst to degrade Rose Bengal (RB) dye. For structural investigation X-ray diffraction (XRD) and Fourier transform Infrared (FTIR) was performed. The presence of both phases corresponding to ZnFe2O4 and ZnO in XRD suggests the successful formation of a nanocomposite. Value of crystallite size varies from 25.01 nm to 18.61 nm for 1:1 to 1:4 nanocomposite. Almost spherical morphology of nanocomposite obtained through High-resolution transmission electron microscopy (HRTEM). FTIR demonstrated Zn–O and Fe–O bonds in as synthesized samples. Also, X-ray photoelectron spectroscopy (XPS) is used to detect the presence of Fe2+, Zn2+ and O2− ions in synthesized nanocomposites. In UV-DRS, values of band gap vary from 1.73 to 1.88 eV in nanocomposite as the weight ratio of ZnO increases. The formation of heterojunction is responsible for enhancing electron hole mobility. Due to this enhancement, degradation efficiency of 88% is achieved in 90 min irradiation of UV light by ZnFe2O4/ZnO (1:4) nanocomposites for RB dye followed Z-scheme mechanism. Also, the magnetization value of different nanocomposites changes from 0.9 to 0.1 emu/g. Magnetization nature is responsible for separating the catalyst from the reaction mixture after use. So, the nanocomposite can be reused which maintains the green protocol in the environment. ZnFe2O4/ZnO nanocomposite with 1:4 wt ratio can be reused up to 5 cycles. The formation of such nanocomposites can offer unique properties and advantages by combining the characteristics of both materials can lead to enhanced functionalities suitable for various applications such as catalysis, sensors, and magnetic devices.