Z-scheme Photocatalytic System Research Articles

Construction of Z-scheme ZnO/g-C3N4 photocatalytic systems for degradation of dyeing wastewater

A novel heterogeneous nanocomposite photocatalyst ZnO/g-C3N4 was fabricated by secondary high-temperature calcination using g-C3N4 and ZnO as raw materials and characterized by XRD, SEM, TEM, EDS, FT-IR, Zeta potential, UV-Vis and XPS. The results displayed that the ZnO/g-C3N4 components were tightly bound, evenly distributed and significantly reduced in size, which could provide more active sites. The heterogeneous types, photocatalytic performance, degradation mechanism of ZnO/g-C3N4 for dyeing wastewater were speculated by REDOX potential, heterojunction, and quenching experiments. The degradation efficiency of ZnO/g-C3N4 on MB was much higher compared with that of single ZnO, g-C3N4 and the mechanical mixture of ZnO and g-C3N4, which can reach more than 95% at 60 min. The degradation rate was also significantly improved, with the degradation rate exceeding 50% at 20 min. The composite ZnO/g-C3N4 could degraded 90% MB after 5 cycles. The quenching experiment showed that hydroxyl (·OH) and photogenerated hole (h+) played the main role in the reaction process. It was confirmed that the prepared ZnO/g-C3N4 formed a Z-scheme photocatalytic system by examining the transfer paths of e- and h+ in various types of heterojunction and contrasting the CB and VB energy levels with the REDOX potentials of ZnO and g-C3N4. The Z-Scheme ZnO/g-C3N4 photocatalyst has the characteristics of stability, reusability, and no by-product, making it an ideal choice for environmental purification.

Poly Meta-Aminophenol (PmAP) as a Solid-State Electron Mediator in the Z-Scheme, Ag3PO4/CoFe2O4 Heterojunction: Mineralization of Highly Concentrated Bisphenol-A and Reactive Dyes Water Pollutants.

This study demonstrated the effectiveness of poly meta-aminophenol (PmAP) as a solid electron mediator in the Z-scheme photocatalytic system for organic pollutants (viz. bisphenol-A and reactive dyes) mineralization and also illustrated how PmAP transported the photogenerated electrons from an O2-emitting photocatalyst (Ag3PO4) to a H2-emitting photocatalyst (CoFe2O4) enabling enhanced photocatalytic activity under visible light irradiation. The PmAP/Ag3PO4-CoFe2O4 (PAC-10), was prepared by a two-step process and characterized by various analytical methods to assess the impact of PmAP on optical, photocatalytic, and electrochemical characteristics of the CoFe2O4 (CFO)/Ag3PO4 composite. The morphological investigation revealed that the PmAP sheet was nicely decorated with evenly distributed Ag3PO4 and CoFe2O4 particles. The M-S plot and impedance analyses were used to assess the electrochemical capabilities of the catalyst. Z-scheme charge transfer pathways were well supported by the radical trapping experiment and HRTEM analysis of Pt photodeposited PAC-10 photocatalysts during the photoreaction. Because of its magnetic nature and ease of synthesis, the PAC-10 offers an easily recyclable Z-scheme photocatalytic system that has the potential for purifying wastewater with high concentrations (up to 100 mg/L) of organic pollutants within 30 min of visible light exposition.

Novel Ag-Bridged Z-Scheme CdS/Ag/Bi2WO6 Heterojunction: Excellent Photocatalytic Performance and Insight into the Underlying Mechanism

The construction of semiconductor heterojunction photocatalysts that improve the separation and transfer of photoinduced charge carriers is an effective and widely employed strategy to boost photocatalytic performance. Herein, we have successfully constructed a CdS/Ag/Bi2WO6 Z-scheme heterojunction with an Ag-bridge as an effective charge transfer channel by a facile process. The heterostructure consists of both CdS and Ag nanoparticles anchored on the surface of Bi2WO6 nanosheets. The photocatalytic efficiency of the CdS/Ag/Bi2WO6 system was studied by the decontamination of tetracycline (TC) and Rhodamine B (RhB) under visible light irradiation (λ ≥ 420). The results exhibited that CdS/Ag/Bi2WO6 shows markedly higher photocatalytic performance than that of CdS, Bi2WO6, Ag/Bi2WO6, and CdS/Bi2WO6. The trapping experiment results verified that the •O2− and h+ radicals are the key active species. The results of photoluminescence spectral analysis and photocurrent responses indicated that the CdS/Ag/Bi2WO6 heterojunctions exhibit exceptional efficiency in separating and transferring photoinduced electron−hole pairs. Based on a series of characterization results, the boosted photocatalytic activity of the CdS/Ag/Bi2WO6 system is mostly due to the successful formation of the Ag-bridged Z-scheme heterojunction; these can not only inhibit the recombination rate of photoinduced charge carriers but also possess a splendid redox capacity. The work provides a way for designing a Z-scheme photocatalytic system based on Ag-bridged for boosting photocatalytic performance.

Perovskite-based Z-scheme photocatalytic system for hydrogen production

Photocatalytic hydrogen production is recognized as a promising approach to produce greener hydrogen. The development of next-generation photocatalytic materials aims to enhance photocatalysis efficiency. Perovskite, a third-generation photocatalytic material, has gained interest in photocatalytic water splitting due to its optical stability, structural flexibility, bandgap tunability, and charge transfer efficiency. However, the perovskites are not able to achieve the targeted efficiency. Perovskite-based Z-scheme heterojunction photocatalysts can enhance efficiency. This review gives special attention to types and the formation of Z-schemes. In particular, photocatalysts involved in all-solid-state and direct Z-scheme for photocatalytic hydrogen production have been discussed.

Direct Z-scheme photocatalytic systems based on vdW heterostructures for water splitting and CO2 reduction: fundamentals and recent advances

Direct Z-scheme photocatalytic systems based on vdW heterostructures for water splitting and CO2 reduction: fundamentals and recent advances

Enhanced photocatalytic performance of 3d flower-like Ag@Ag2CO3/Bi2O2CO3 all-solid-state Z-scheme heterojunction

Heterojunction construction is an enduring topic for semiconductor photocatalytic performance enhancement. In this study, a novel Ag@Ag2CO3/Bi2O2CO3 heterojunction photocatalyst was prepared by precipitation method, in which Ag2CO3 nanorods was coated by Ag nanoparticles and 3D flower-like Bi2O2CO3. The Ag@Ag2CO3/Bi2O2CO3 all-solid-state Z-scheme photocatalytic system boosted the photocatalytic degradation of the sodium isobutyl xanthate and o-cresol, as compared to bare Bi2O2CO3 and Ag@Ag2CO3. Benefitting from the morphology modulation, the significant increase in photocatalytic activity of Ag@Ag2CO3/Bi2O2CO3 was achieved owing to the enhanced light-harvesting and increased specific surface area. The in-situ formed Ag0 nanoparticles simultaneously forms Z-scheme all-solid-state heterojunctions (Ag2CO3/Bi2O2CO3) and accelerates the photogenerated charge separation with surface plasmon resonance effect. A possible mechanism of 3D Ag@Ag2CO3/Bi2O2CO3 Z-scheme system with a strengthened photocatalytic performance was proposed based on the characterization results and trapping experiments.

Design and construction of a novel immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co photocatalyst composite film for efficient norfloxacin degradation with simultaneous hydrogen evolution

The Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4 photocatalyst composite film (PCF) was prepared on the cobalt foil by using spin-coating and incomplete solid-state chemical reaction method, which solves the problems that the powder photocatalyst is difficult to recover and reuse and realizes the separation of CO2 and H2. In PCF, ZnO and ZnCo2O4 form a Z-scheme photocatalytic system and ZnCo2O4 and Co3O4 constitute a Type II-heterojunction photocatalytic system. The used cobalt foil acts as both a carrier of photocatalyst and a cathode. The structures and properties of PCF were studied by XRD, SEM, TEM, EDX, XPS, PL, TPR and EIS. Through photocatalytic norfloxacin degradation and hydrogen evolution, the effects of cobalt foil thickness, the coating Zn(OH)2 precipitation layer number, calcination temperature and calcination time on the photocatalytic performance of the Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co PCFs were investigated. When the cobalt foil thickness is 0.10 mm, coating Zn(OH)2 precipitation layer number is 2, composite film is calcined under 500 °C for 3.0 h and norfloxacin concentration is 10 mg/L and 50 mg/L, norfloxacin degradation ratio and H2 evolution amount reach 80.70 % and 357.12 μmol/dm2, respectively. In addition, a possible mechanism of norfloxacin degradation with simultaneous H2 evolution caused by immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4–Co3O4|Co PCF was proposed. It is hoped that the work has certain guiding significance to design an immobilized PCF for organic pollutants degradation with synchronous large-scale hydrogen evolution.

Facile in-situ synthesis of solid mediator based CdS-rGO-WO3 Z-scheme photocatalytic system for efficient photocatalytic hydrogen generation

Reduced graphene oxide (rGO) solid state mediator based Z scheme photocatalyst CdS-rGO-WO3 heterojunction comprising of nano-rods of CdS and nanoplates of WO3 was fabricated in-situ by a facile hydrothermal process, characterized and tested for solar hydrogen generation. The systematically designed heterojunction created separated oxidative and reductive sites for photo generated electron hole pairs with enhanced redox ability, improving the charge separation and photo-stability, mitigating the problem of photo-corrosion of CdS. This was evident from an enhanced photocatalytic activity of 11.69 mmolg−1h−1 which was almost 2.3 times than pristine CdS (4.9 mmolg−1h−1), in presence of simulated solar light. Due to the high electron mobility property of graphene sheet, rapid transport of electrons was possible at the interface between CdS and WO3. The charge transfer via Z scheme mechanistic pathway was verified by X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) and photocurrent measurement studies. This research study will provide a newer insight in engineering nano-hetero-structures for enhanced photocatalytic hydrogen evolution, in an attempt to make the process commercially viable.

Immobilized Z-scheme Ag|AgBr/Ag/FeTiO3 nanocomposite film photocatalyst for visible-light-driven photocatalytic degradation of norfloxacin with simultaneous hydrogen evolution and mechanism perspective

A novel immobilized Z-scheme Ag|AgBr/Ag/FeTiO3 nanocomposite film photocatalytic system was constructed, and applied within the photocatalytic degradation of norfloxacin with simultaneous hydrogen evolution under visible light. The photocatalytic performance of Z-scheme Ag|AgBr/Ag/FeTiO3 nanocomposite film was estimated. A series of factors affecting the photocatalytic activity of Ag|AgBr/Ag/FeTiO3 were investigated. The possible mechanism of the immobilized Z-scheme Ag|AgBr/Ag/FeTiO3 nanocomposite photocatalytic system was proposed. The results reveal that the Ag|AgBr/Ag/FeTiO3 system exhibits superior photocatalytic activity, due to the surface plasmon resonance effect produced by the Ag nanoparticles and the high separation efficiency of electron-hole pairs caused by the Z-scheme photocatalytic system. Importantly, the Z-scheme Ag|AgBr/Ag/FeTiO3 composite film is immobilized on the carrier, which facilitates the recycling and reuse of photocatalysts. The degradation extent of norfloxacin can reach 90.16%, and the hydrogen production can achieve 304.08 µmol within 180 min. Moreover, after five cycles, the Ag|AgBr/Ag/FeTiO3 photocatalyst possesses preeminent stability. During photocatalytic degradation, the hydroxyl radical plays a dominant role. Therefore, the immobilized Z-scheme Ag|AgBr/Ag/FeTiO3 photocatalytic technology holds good application value in the purification of antibiotics wastewater and the simultaneous hydrogen production.

Oxygen Vacancy-Mediated CuWO4/CuBi2O4 Samples with Efficient Charge Transfer for Enhanced Catalytic Activity toward Photodegradation of Pharmacologically Active Compounds.

Photocatalytic degradation is a promising method for controlling the increasing contamination of the water environment due to pharmacologically active compounds (PHACs). Herein, oxygen vacancy (OV)-modulated Z-scheme CuWO4/CuBi2O4 hybrid systems were fabricated via thermal treatment by loading of CuWO4 nanoparticles with OVs on CuBi2O4 surfaces. The synthesized CuWO4/CuBi2O4 hybrid samples exhibited an enhanced photodegradation ability to remove PHACs under visible-light irradiation. More importantly, an optimized sample (10 wt % CuWO4/CuBi2O4) exhibited superior catalytic activity and excellent recycling stability for PHAC photodegradation. In addition, possible degradation paths for PHAC removal over the CuWO4/CuBi2O4 hybrid systems were proposed. The enhanced photocatalytic performance could be attributed to the efficient separation and transfer of photoformed charge pairs via the Z-scheme mechanism. This Z-scheme mechanism was systematically analyzed using trapping experiments of active species, ultraviolet photoelectron spectroscopy, electron spin resonance, and the photodepositions of noble metals. The findings of this study can pave the way for developing highly efficient Z-scheme photocatalytic systems for PHAC photodegradation.

Surface diffusion induced degradation enhancement and zero-order kinetics in edge-connected MoS2/Au/TiO2 Z-scheme photocatalytic system

Heterostructured photocatalysts have demonstrated great potential in the photodegradation of organic pollutants, while the surfaces & interfaces of their multiple structural components play critical roles in determining their photocatalytic mechanisms and kinetics. Here, we fabricate an edge-connected MoS2/Au/TiO2 photocatalytic system via a selective photodeposition method and utilize a surface-diffusion mechanism to maximize the synergistic effects among the components. The resultant photocatalytic system behaves as a Z-scheme with well spatially separated redox reaction sites. The optimal catalyst 10 % MS/Au/T exhibited a pseudo 1st-order rate constant of 0.0145 min−1 within 120 min, which is seven times more than that of pristine TiO2. The edge-deposited MoS2 in the nanocomposite serves as a reservoir to adsorb and then transport the pollutant molecules rapidly to TiO2 surface for oxidation. Such a pre-concentration effect, as well as the Z-scheme charge transfer mechanism, has enhanced the overall degradation efficiency, and induced the occurrence of zero-order degradation kinetics. The charge transfer behaviors, the diffusion-enhancement mechanism, zero-order kinetics, and the order transition are then thoroughly studied against the MoS2 mass loading. 10 % MS/Au/T showed the highest values of zero and first-order constants, which were 0.073 ppm/min and 0.011 min−1, respectively. A diffusion-enhanced model is developed and validated to explain the experimental observations. This work provides meaningful insights into degradation enhancement and kinetic analysis for heterostructured photocatalytic systems.

N-doped C layer boost Z-scheme interfacial charge transfer in TiO2/ZnIn2S4 heterojunctions for enhance photocatalytic hydrogen evolution

Inspired by natural photosynthesis, the design of novel Z-scheme photocatalytic systems holds great promise for improving photocatalytic hydrogen production performance. Here, we constructed a Z-scheme heterojunction to effectively improve the charge separation of TiO2/ZnIn2S4, with the N-doped C layer acting as an electron bridge. The T@NC-A/ZIS-72 heterojunctions demonstrated hydrogen production activity approximately 12.1 and 97.9 times higher than those of ZnIn2S4 and TiO2@NC-A, respectively. The excellent electron migration ability of the carbon layer accelerated the photocatalytic hydrogen production performance. Our design introduces a component to provide a dedicated charge transport pathway, overcoming the inherent properties of the material and providing a new perspective for enhancing photocatalytic performance.

CdS/MoS2 nanoparticles anchored on oxygen-doped g-C3N4 nanosheets all-solid-state Z-scheme heterojunctions for efficient H2 evolution

Hydrogen evolution by photocatalysis is an ideal method to relieve the energy crisis. In this work, an all-solid-state Z-scheme photocatalytic system is developed via a simple hydrothermal strategy to anchor CdS–MoS2 hybrid nanoparticles onto oxygen-doped g-C3N4 nanosheets (OCN). The presence of MoS2 nanosheets serves as both an intermediary for electron transfer to enhance charge separation and enhance the durability of the CdS. Compared to the unmodified CdS, the H2 generation efficiency of the CdS–MoS2/OCN Z-scheme heterojunctions is significantly enhanced. Additionally, the optimized photocatalyst exhibits a remarkable 20.7-fold increase in H2 production rate compared to the pristine CdS. Based on the systematical characterization, the enhanced photocatalytic hydrogen evolution performance arises from the enhanced light absorption, the enlarged specific surface areas, as well as the improved charge separation. The systematic characterizations provided evidence for the demonstration of the Z-scheme photocatalytic mechanism. This work presents a novel perspective on the design of photocatalytic systems with an all-solid-state Z-scheme configuration.

Graphitic Carbon Nitride/Zinc Oxide-Based Z-Scheme and S-Scheme Heterojunction Photocatalysts for the Photodegradation of Organic Pollutants.

Graphitic carbon nitride (g-C3N4), a metal-free polymer semiconductor, has been recognized as an attractive photocatalytic material for environmental remediation because of its low band gap, high thermal and photostability, chemical inertness, non-toxicity, low cost, biocompatibility, and optical and electrical efficiency. However, g-C3N4 has been reported to suffer from many difficulties in photocatalytic applications, such as a low specific surface area, inadequate visible-light utilization, and a high charge recombination rate. To overcome these difficulties, the formation of g-C3N4 heterojunctions by coupling with metal oxides has triggered tremendous interest in recent years. In this regard, zinc oxide (ZnO) is being largely explored as a self-driven semiconductor photocatalyst to form heterojunctions with g-C3N4, as ZnO possesses unique and fascinating properties, including high quantum efficiency, high electron mobility, cost-effectiveness, environmental friendliness, and a simple synthetic procedure. The synergistic effect of its properties, such as adsorption and photogenerated charge separation, was found to enhance the photocatalytic activity of heterojunctions. Hence, this review aims to compile the strategies for fabricating g-C3N4/ZnO-based Z-scheme and S-scheme heterojunction photocatalytic systems with enhanced performance and overall stability for the photodegradation of organic pollutants. Furthermore, with reference to the reported system, the photocatalytic mechanism of g-C3N4/ZnO-based heterojunction photocatalysts and their charge-transfer pathways on the interface surface are highlighted.

Dual Z-scheme heterojunction NH2-UiO-66/BiOBr/AgI with enhanced performance on visible light driven elimination of tetracycline and Cr(VI)

To tackle the challenges for photocatalysts efficacy enhancement, a novel dual Z-scheme NH2-UiO-66/BiOBr/AgI (NUBA) ternary composite photocatalyst was constructed and systematically characterized. NUBA displayed much higher visible light photocatalytic efficacies in tetracycline (TC) degradation and Cr(VI) reduction than the corresponding single components and binary composites. With employment of NUBA and visible light irradiation, 97% of TC was removed in 40 min whereas 96% of Cr(VI) was reduced in 30 min for the individual TC and Cr(VI) solution. Furthermore, NUBA manifested superior efficacy in simultaneously and synergistically removing TC/Cr(VI) mixture than for corresponding single pollutant. A dual Z-scheme charge transfer mechanism was established which confirmed that •O2− and h+ dominated TC degradation, whereas photo-induced electrons implemented Cr(VI) reduction. The promoted activity of NUBA was attributed to the synergism through incorporating the advantages furnished by individual components with rich charge transfer channels, larger specific surface areas, and strengthen visible light harvest, thus preeminently reinforced the production, separation and transportation of photogenerated charge carriers. NUBA demonstrated good anti-interfering ability and wide applicability for organic pollutants degradation, along with exceptional stability and durability for cyclic use. This work may supply an inspiration for the construction of efficacious dual Z-scheme photocatalytic systems for wastewater remediation.

Efficient photoelectrochemical water splitting and photocatalytic performance for graphene-bridged MoS2–Fe2O3 nanocomposite under visible light active: Insights into photocatalysis mechanism

In this work, we aim to design a new nanocomposite with an improved photocatalytic performance by the synergistic formation of a Z-scheme photocatalytic system with graphene-bridged molybdenum disulfide (MoS2) and iron oxide (Fe2O3). We fabricated graphene-bridged MoS2–Fe2O3 nanocomposites by a simple hydrothermal method for enhanced photoelectrochemical (PEC) performance and higher degradation of TC. This nanocomposite can increase carrier separation efficiency. Moreover, the photocatalysts exhibit excellent oxidation and reduction rates capabilities assessed by photocatalytic and photoelectrochemical experiments under visible light illumination. The photocatalyst showed 97% removal capability of tetracycline and photocurrent density is five times higher than of bare Fe2O3. The active specie of .O2− and ⋅OH radicals was detected by the ESR instruments during photocatalytic activity improvement that could confirm the constructed Z-scheme MoS2–Fe2O3-Graphene nanocomposite showed that two folds photocatalytic degradation greater than those of pristine MoS2 and Fe2O3. According to the results shows UV–Visible spectroscopy, photoluminescence spectroscopy, Electron impendence spectroscopy, and photocurrent response, the photo-response electrons of transfer from the conduction band of Fe2O3 could fast transport in the valence band of MoS2. The graphene bridge served as a charge-migrate channel between two materials, and the electrons in protonated MoS2 and Fe2O3 achieved a charge balance. This work provides a new strategy for further design of high-efficiency of MFG nanocomposite with graphene as the electronic mediator for environmental remediation.

Fabrication of loaded Ag sensitized round-the-clock highly active Z-scheme BiFeO3/Ag/Sr2MgSi2O7:Eu2+,Dy3+/Ag photocatalyst for metronidazole degradation and hydrogen production

To achieve efficient round-the-clock photocatalytic degradation of organic pollutants with simultaneous hydrogen production, Sr2MgSi2O7:Eu2+,Dy3+ with long-afterglow luminescence property and photocatalytic activity was selected to combine with BiFeO3 to construct a novel Z-scheme photocatalytic system. The luminescence intensity of Sr2MgSi2O7:Eu2+,Dy3+ and round-the-clock photocatalytic activity of the Z-scheme BiFeO3/Ag/Sr2MgSi2O7:Eu2+,Dy3+/Ag photocatalyst were enhanced by loading Ag nanoparticles. In the presence of BiFeO3/Ag/Sr2MgSi2O7:Eu2+,Dy3+/Ag photocatalyst, the metronidazole degradation rate and hydrogen production amount were 63.85% and 444.64 μmol/g, respectively, under sunlight irradiation for 240 min, which were approximately 3.39 and 3.63 times as high as ones of BiFeO3 and Sr2MgSi2O7:Eu2+,Dy3+. When the external light was removed for 240 min, the metronidazole degradation rate and hydrogen production amount increased by 9.08% and 57.07 μmol/g, which were 4.12 and 3.15 times as high as ones of BiFeO3 and Sr2MgSi2O7:Eu2+,Dy3+ photocatalysts. This work provides a new research orientation for the design of a highly active Z-scheme photocatalyst for round-the-clock photocatalytic organic pollutants degradation with simultaneous hydrogen production.

CeVO4 nanoparticle coupled with Ag/AgBr as an efficient plasmonic photocatalyst for degradation of rhodamine B: Construction, characterization, and mechanism insight

The unique characteristics of the surface plasmon resonance effect significantly improve the utilization rate of solar energy and charge separation of narrow band-gap semiconductor materials. In this work, Ag/AgBr/CeVO4 plasmonic photocatalyst was synthesized by the microwave-assisted hydrothermal method, followed by in-situ precipitation and photoreduction process. The as-prepared Ag/AgBr/CeVO4-2.0 composite showed superior photocatalytic efficiency for degradation of rhodamine B (84.2% in 10 min), which was 1.45 and 84.2 times higher than that of Ag/AgBr and pristine CeVO4 nanoparticles (NPS, size 30–50 nm), respectively. Photoluminescence and photocurrent tests indicated the rapid transfer and separation of electron–hole pairs in this plasmonic system, which can be attributed to the localized surface plasmon resonance effect of Ag NPs. In investigations on band structure and radical quenching experiments, a Z-scheme photocatalytic system bridged by the Ag NPs was proposed. This research offers revealing insight into the design and fabrication of the CeVO4 plasmonic photocatalytic system for application in environment purification and remediation.

Poly(dibenzothiophene-S,S-dioxide)-Fe2O3 heterojunction for photocatalytic hydrogen production coupled with selective oxidation of benzyl alcohol

Photocatalytic conversion of benzyl alcohol (BA) into value-added fine chemicals and hydrogen (H2) in water medium provides a novel strategy for green synthesis. The construction of Z-scheme heterostructures not only realize enhanced charge-separation efficiency, but also remain strong drive force for photocatalytic reaction, which exhibit great potentials toward simultaneously generating benzaldehyde (BAD) and H2. Herein, we report a noble-metal-free Z-scheme photocatalytic system consisting poly(dibenzothiophene-S,S-dioxide) (PSO) and α-Fe2O3 for selective oxidation of BA with synchronous H2 production. Such nanocomposites can effectively transfer and reduce the recombination of photoexcited charge carriers, therefore maintaining the oxidizability of holes of α-Fe2O3 and the reducibility of electrons of PSO. As expected, PSO-Fe2O3 with a mass of ∼5 mg under optimal composition ratio exhibited an impressive photocatalytic activity with BAD and H2 yields up to 23.1 and 29.5 μmol h−1, respectively, which is among the top photocatalytic performance reported so far for selective photocatalytic oxidation of BA in the aqueous solution.

Synthesis of Z-scheme heterostructure FeWO<sub>4</sub>/rGO/g-C<sub>3</sub>N<sub>4</sub> as a visible-light photocatalyst for removal of organic pollutant

Photocatalysts have been effectively applied for water treatment. Narrow bandgap energy semiconductors show good photocatalytic performance at visible light. However, high recombination rate of the photogenerated electrons and holes leads to their low photocatalytic activity. Moreover, the conduction and valence band potentials of these materials are not suitable for the redox reactions with water and oxygen to generate HO• and •O2⁻ radicals, respectively. Therefore, the development of new photocatalyst systems to overcome these disadvantages is necessary. This study investigated the photocatalytic activity of FeWO4/rGO/g-C3N4 Z-scheme photocatalytic system via the degradation of Rhodamine B in water. The photocatalyst was synthesized by simple hydrothermal method and characterized by X-ray diffraction method (XRD), fluorescence spectroscopy (PL) and diffuse reflectance spectra (UV-vis). The results showed that after 150 minutes illumination, the Rhodamine B decomposition efficiency on FeWO4/g-C3N4 and FeWO4/rGO/g-C3N4 were 93.07 and 99.21%, respectively. These values were significantly higher than that of g-C3N4 under the same catalytic concentration of 0.1g/L. In the FeWO4/rGO/g-C3N4 heterostructure, rGO acted as electron mediator and transporter between two semiconductors, resulting in a lower recombination rate of photogenerated charges. As the results, the photocatalytic performance was enhanced.