High photocatalytic and photoelectrochemical performance of a novel 0D/2D heterojunction photocatalyst constructed by ZnSe nanoparticles and MoSe2 nanoflowers

Metal oxide photocatalysts have the disadvantages of large band gap and high internal resistance, and their photoelectrochemical properties are restricted. Metal selenides are generally characterized by narrow bandgap width, low internal resistance, high utilization rate of sunlight and superior photoelectrochemical performance. The ZnSe/MoSe₂ heterostructure composite was successfully constructed by loading ZnSe nanoparticles onto MoSe₂ nanoplates with three-dimensional flower-like structure. In this heterostructure composite, ZnSe nanoparticles are uniformly encapsulated by MoSe₂ nanoplates, and the larger contact surface facilitates the transfer of carriers between heterojunction, while the three-dimensional flower structure of MoSe₂ can transport and collect photogenerated carriers. This heterojunction composite has a full-band absorption capability of UV and visible light. Photocatalytic tests showed that the photocatalytic activity of the heterojunction photocatalyst was more than twice of MoSe₂ and more than 4 times of ZnSe at the optimum ZnSe composite ratio, and photoelectric performance of that was 2.75 times of MoSe₂. The results show that the photoelectrochemical performance of ZnSe/MoSe₂ has been greatly improved, mainly because of the 0D/2D structure and band matching of ZnSe/MoSe₂, so that the photogenerated electrons excited on the ZnSe conduction band can be transported to the conduction band of MoSe₂, thereby improving the carriers’ separation efficiency and photoelectrochemical performance.     

In situ synthesis of Bi2O3/Bi2MoO6 heterostructured microspheres for efficiently removal of acid orange 7

Flower-like Bi₂O₃/Bi₂MoO₆ heterostructured microspheres with excellent photocatalytic performance were successfully constructed by in situ ion exchange and calcination, employing Bi₂MoO₆ microspheres prepared by solvothermal method as raw material and template. Various characterization techniques including XRD, FE-SEM, EDS, UV–vis DRS and XPS have been adopted to analyze the composition, structure and optical absorption property of the obtained sample. Their photocatalytic properties for degrading acid orange 7 (AO7) were investigated with visible light. Experimental results show that all Bi₂O₃/Bi₂MoO₆ composites have a higher catalytic activities than pure Bi₂MoO₆. Remarkably, 0.2Bi₂O₃/Bi₂MoO₆ show best activity and the degradation efficiency is up to 99% under visible light for 100?min, which is ascribed to the synergistic effect and big heterojunction interface, and promoting rapid transmission of photogenerated charge. Moreover, There is negligible reduction on the degradation efficiency after catalysts was reused for 4 times. The photogenerated holes (h⁺) and superoxide radical anions (?O₂^-) were major active species by radical scavenger experiments. A possible mechanism is proposed to explain rationally enhancement of photocatalytic activity.     

Fabrication of direct Z-scheme FeIn2S4/Bi2WO6 hierarchical heterostructures with enhanced photocatalytic activity for tetracycline hydrochloride photodagradation

A series of direct Z-scheme FeIn₂S₄/Bi₂WO₆ hierarchical heterostructures with intimate interface contacts were synthesized by in-situ growth route and characterized by systematical analyses. All as-prepared FeIn₂S₄/Bi₂WO₆ nanocomposites showed significantly enhanced photocatalytic activity towards photodegradation for the removal of tetracycline hydrochloride (TCH) in comparison with individual FeIn₂S₄ and Bi₂WO₆. Meanwhile, the highest photocatalytic degradation activity can be achieved by modulating adding amount of FeIn₂S₄ in FeIn₂S₄/Bi₂WO₆ nanocomposites and the optimized component ratio of FeIn₂S₄ to Bi₂WO₆ is determined to be 10 wt%. The enhanced photocatalytic activity could be ascribed to efficient separation between photogenerated holes and electrons based on the construction of direct Z-scheme system. The high photocatalytic stability of resultant 10 wt% FeIn₂S₄/Bi₂WO₆ nanocomposites was revealed through six successive recycling reactions. The main intermediate generated during TCH photodegradation was explored by HPLC-MS. Besides, the direct Z-scheme photocatalytic mechanism was confirmed by band position analysis, electron spin resonance (ESR) and active species capture experiment.     

Sonochemical preparation and photocatalytic properties of CdS QDs /Bi2WO6 3D heterojunction

Hierarchical CdS quantum dots (QDs)/ Bi₂WO₆ three-dimensional (3D) heterojunction photocatalyst was successfully synthesized by a facile green ultrasonic method for the first time. Photocatalytic activities under visible light irradiation were tested by the degradation of Rhodamine B (RhB) and tetracycline hydrochloride (TC), and the reduction of Cr(VI) in aqueous solution. As compared to pure CdS and Bi₂WO₆, CdS QDs/ Bi₂WO₆ heterojunctions manifested a significantly enhanced photocatalytic activity for these treatments. When the effect of the mass ratio of CdS QDs to Bi₂WO₆ was investigated, 3% CdS QDs/ Bi₂WO₆ heterojunction showed the highest photocatalytic efficiency: the efficiency for RhB degradation was 94.5% for 30?min and this value was about 6 times and 1.5 times higher than those of pure Bi₂WO₆ and CdS QDs. This enhancement was majorly accredited to the synergetic effect between Bi₂WO₆ and CdS QDs, which included intimate contact and matched band gap potentials between 0D CdS QDs and 3D Bi₂WO₆, which contributed to the efficient electron-hole separation and fast transfer of charge carriers between CdS QDs and Bi₂WO₆. A possible Z-scheme photocatalytic mechanism was proposed, in which the sample was provided with the efficient charge transfer pathway and was endowed with excellent oxidation and reduction ability.     

In-situ room-temperature synthesis of amorphous/crystalline contact Bi2S3/Bi2WO6 heterostructures for improved photocatalytic ability

We developed a facile in-situ growth method to construct amorphous-based Bi₂S₃/Bi₂WO₆ heterostructures at room temperature. As demonstrated by HRTEM, XPS and EDX-mapping, amorphous state Bi₂S₃ dispersed uniformly on the surface of crystalline Bi₂WO₆ hollow spheres. The photocatalytic activities of prepared Bi₂S₃/Bi₂WO₆ heterostructures were evaluated by the photodegradation of RhB and TC under visible light irradiation, indicating that the introduction of appropriate amorphous Bi₂S₃ significantly improved the photocatalytic activity of Bi₂WO₆. The amorphous/crystalline contact in Bi₂S₃/Bi₂WO₆ heterostructures played a crucial role in the enhancement of photocatalytic efficiency. Based on DRS, photoluminescence spectra, photocurrent intensity, electrochemical impedance spectroscopy and OCVD measurements, it was proposed that the enhanced performance could be ascribed to increased visible light utilization, promoted separation efficiency and prolonged life time of photogenerated electron-hole pairs by the introduction of amorphous Bi₂S₃. This work may provide new insights into the construction of amorphous-based composited heterostructures for improving photocatalytic activity.     

Ag/Bi2WO6 plasmonic composites with enhanced visible photocatalytic activity

Three-dimensional flower-like Bi₂WO₆ microspheres with the diameter of about 4 μm were prepared by a facile hydrothermal method using bismuth nitrate pentahydrate and sodium tungstate dihydrate as raw materials. A novel Ag-modified Bi₂WO₆ was synthesized through a simple and practical photoreduction process. The UV–vis diffuse reflectance spectra indicate that the Ag/Bi₂WO₆ samples have a significantly enhanced optical absorption in the visible light region than that of pure Bi₂WO₆ microspheres due to the surface plasmon resonance (SPR) of Ag nanoparticles on the surface of pure Bi₂WO₆. The photocatalytic activities of the as-prepared samples were evaluated by the decolorization of rhodamine B under simulated sun-light irradiation. The results reveal that the photocatalytic activities of the Ag/Bi₂WO₆ samples increase first and then decrease with increasing amount of loading Ag and the 1.0 wt% Ag-loaded Bi₂WO₆ sample exhibits the best photocatalytic activity compared with the other samples. The enhanced photocatalytic activity could be attributed to the synergistic effect of the strong SPR and the effective separation of photogenerated electrons and holes caused by Ag nanoparticles.     

LaCoO3 acts as a high-efficiency co-catalyst for enhancing visible-light-driven tetracycline degradation of BiOI

Exploring noble-metal-free co-catalysts highly flexible for separating the photogenerated charge carriers is of prime importance for the visible-light-driven photocatalysis. Herein, three-dimensional flower-like BiOI microspheres were fabricated and applied to support noble-metal-free LaCoO₃ co-catalysts to construct a unique LaCoO₃/BiOI hybrid photocatalyst with a higher ability in charge separation. As expected, the optimum tetracycline degradation rate of LaCoO₃ (4.0 wt%)/BiOI was up to 0.0161 min⁻¹, which was nearly 3.4 fold larger than that of pure BiOI (0.0048 min⁻¹). The enhanced photocatalytic performance was mainly ascribed to the vital role of LaCoO₃ co-catalyst, which acted as an excellent electron collector for capturing the electrons generated by BiOI, effectively promoting the separation of photogenerated charge carriers and prolonging the lifetime of photo-induced electron-hole pairs at the same time. Furthermore, the active species trapping experiments revealed that the excellent photocatalytic activity was primarily driven by photogenerated holes and superoxide radicals. This work is expected to provide a new inspiration for rationally designing and fabricating noble-metal-free co-catalyst system with high efficiency applied in environment purification.     

Thermoelectric properties of Bi2O3-added WO3 ceramics

Tungsten trioxide (WO₃) ceramics were prepared by firing Bi₂O₃-added WO₃ compacts with atomic ratios of Bi/W?=?0.00, 0.01, 0.03, or 0.05, in which Bi₂O₃ was mixed as a sintering agent. Dense ceramics consisting of remarkably grown WO₃ grains were obtained for Bi-containing samples with Bi/W?=?0.01, 0.03, and 0.05. The grain growth was enhanced by the liquid phase of Bi₂W₂O₉ formed among the WO₃ grains while firing. The XRD patterns did not show evidence for Bi inclusion into the WO₃ lattice, but the SEM-EDX showed an intensive distribution of Bi into the grain boundaries. Electrical conductivity σ and Seebeck coefficient S were measured in a temperature range of 373–1073?K. The temperature dependences indicated that the Bi₂O₃-added WO₃ ceramics were n-type semiconductors. It was considered that the electron carriers were generated from oxygen vacancies included into the WO₃ grains. The thermoelectric power factors S²σ for the ceramics ranged from 1.5?×?10^?7 W?m^?1 K^?2 to 2.8?×?10^?5 W?m^?1 K^?2, and the highest value occurred at 970?K for the ceramic with Bi/W?=?0.01.     

Facile one-pot preparation of Bi6O6(OH)3(NO3)3•1.5H2O-Bi2WO6 heterostructure with superior photocatalytic activity

Basic bismuth nitrate Bi₆O₆(OH)₃(NO₃)₃•1.5H₂O (BBN) modified Bi₂WO₆ heterostructures was facilely synthesized by one-pot hydrothermal strategy. The modification of BBN effectively improves the photocatalytic activity of Bi₂WO₆ for degradation and mineralization of Rhodamine B. The enhanced photocatalytic performance is attributed to the increased surface area and effective separation of photogenerated carriers induced by the potential difference at BBN/Bi₂WO₆ interface. Furthermore, the micro-scaled heterostructure is easily recycled with excellent circulating stability. The work provides some new insights for the rational design and synthesis of basic salt modified Bi-system photocatalyst with high efficiency.     

Photocatalytic inactivation of bacteria by photocatalyst Bi2WO6 under visible light

The photocatalytic inactivation of Escherichia coli under visible light irradiation (λ > 420 nm) was performed with Bi₂WO₆ to investigate the photocatalytic bactericidal capability. Our work shows that the single phase oxide photocatalyst Bi₂WO₆ is effective in photocatalytic inactivation on E. coli. And the results revealed that the photocatalytic inactivation rate of E. coli with Bi₂WO₆ followed pseudo-first-order kinetics. The bactericidal action was directly observed by TEM and further proved by the measurement of K⁺ leakage from the inactive E. coli through the ICP-OES analysis. The results demonstrated that the photocatalysis could cause drastic damage in E. coli cells.     

Band engineering of Ag-Bi12GeO20-Bi2WO6 composite photocatalyst: Interface regulation and enhanced photocatalytic performance

Novel Ag-Bi₁₂GeO₂₀-Bi₂WO₆ heterojunction was developed and demonstrated as an excellent photocatalyst to degrade the Rhodamine B (RhB) aqueous solution with the help of UV–vis light. The Bi₁₂GeO₂₀-Bi₂WO₆ heterojunction was firstly fabricated through a facile partial chemical conversion strategy, employing pre-prepared Bi₂WO₆ nanosheets as Bi³⁺ source. Under the high temperature and high pressure environments, partially released Bi³⁺ ions derived from the Bi₂WO₆ nanosheets could react with Ge source, leading to the formation of Bi₁₂GeO₂₀ tetrahedrons. Meanwhile, the remaining Bi₂WO₆ nanosheets were also anchored in situ onto the surface of the Bi₁₂GeO₂₀ tetrahedrons, thus forming a unique heterojunction with “face-to-face” connection form of heterogeneous interface. After the loading of Ag nanoparticles, the as-obtained Ag-Bi₁₂GeO₂₀-Bi₂WO₆ heterogeneous structure exhibited outstanding catalytic efficiency toward the decomposition of RhB. Due to the structural and compositional features such as matching band structure, intimate interfacial contacts, unique interface contact structure and the well-known “schottky barriers", the photo-generated charges of the resulting ternary composite photocatalyst was efficiently separated and thus exhibited improved catalytic activity. This rational construction of Ag-Bi₁₂GeO₂₀-Bi₂WO₆ ternary photocatalytic system based on energy band engineering is ingenious and can provide a mirror for the fabrication of other photocatalytic materials.     

Generation of hydrogen under visible light irradiation with enhanced photocatalytic activity of Bi2WO6/Cu1.8Se for organic pollutants under Vis‐NIR light reign

To make better use of solar light, a new Bi₂WO₆/Cu_1.8Se photocatalyst active to visible and near‐infrared light has been synthesized by a facile hydrothermal method. The composites were characterized by X‐ray diffractometry (XRD), scanning electron microscopy (SEM), UV‐vis diffuse reflectance spectroscopy (DRS), and photoluminescene (PL). The photocatalytic activities of Bi₂WO₆/Cu_1.8Se are evaluated by degrading Congo red solution and hydrogen generation from water. It was found that the molar percentage of Cu_1.8Se had great effects on the morphology and photocatalytic property of the Bi₂WO₆/Cu_1.8Se heterojunctions, and the composite with suitable molar amount of Cu_1.8Se exhibits much enhanced photocatalytic activity for Congo red degradation under visible and near‐infrared light irradiation and for hydrogen generation under visible light compared to Bi₂WO₆. The significant improvement photocatalytic activity of the composite could be attributed to its good light absorption, suitable band gap structure, and effective separation of photogenerated electron‐hole pairs of Bi₂WO₆/Cu_1.8Se heterojunction. This work presents an efficient multifunction photocatalyst owning the activity both for water splitting under visible light and for organic contaminants decomposition under visible‐near‐infrared light.     

Construction of Bi2Fe4O9/red phosphorus heterojunction for rapid and efficient photo-reduction of Cr(VI)

Construction of heterojunctions with matching energy band structures between two semiconductors displays great potential in promoting the separation and transfer of photogenerated charge carriers and is one of the effective strategies for obtaining high active photocatalysts. In this study, a type-II heterojunction photocatalyst was designed and prepared using Bi₂Fe₄O₉ (BFO) nanoparticles and hydrothermal-treated red phosphorus (HRP). The photocatalytic performance test exhibited that the 3%BFO/HRP composite photocatalyst with 3% mass fraction of BFO rapidly and efficiently photoreduced Cr(VI), and the reduction was completed within 25 min, with a rate constant of 0.15 min⁻¹, which was 15 times higher than that of pure HRP. Further mechanistic investigation revealed that the photocatalytic activity was enhanced due to the tight heterojunction between BFO and HRP, thereby effectively promoting carrier transfer, destroying the carrier recombination, and reducing the charge-transfer resistance of composite catalyst. Mott–Schottky diagrams and UV-vis diffuse reflectance spectroscopy data indicated the theoretical feasibility of establishing a close contact between BFO and HRP. X-ray photoelectron spectroscopy provided evidence for the way in which interfacial charges were transferred. This work provides a new possibility to construct heterojunction photocatalysts for the rapid and efficient reduction of Cr(VI).     

Facile fabrication of 3D interconnected porous boron doped polymeric g-C3N4 with enhanced visible light photocatalytic hydrogen evolution and dye contaminant elimination

Researchers have attempted to developing high-efficiency catalysts for photocatalytic hydrogen evolution and organic pollution elimination simultaneously to alleviate the issues of energy shortage and water pollution. In this work, we fabricated 3D interconnected porous boron doped polymeric g-C₃N₄ catalysts with efficient photocatalytic activity for hydrogen evolution and dye contaminant elimination under visible-light irradiation. The as-fabricated catalysts exhibited significantly enhanced hydrogen evolution (4.37 mmol g ^?1 h^?1) and RhB contaminant elimination (96.37%) activity. Based on characterization and photocatalytic tests, an enhanced mechanism of the superior photocatalytic performance was proposed: 3D interconnected porous structure and B-doping have a synergistic effect on the greatly improved photocatalytic activity. The 3D interconnected structures endowed g-C₃N₄ with a higher specific surface area and abundant active sites and improved the capacity of rapid absorption to facilitate the photocatalytic process. B doping provided enhanced visible-light absorption capacity and a narrowed bandgap and served as a “highway” for electron-hole pairs to facilitate migration and separation and suppress the combination of photogenerated carriers. Besides, the possible mechanism of enhanced photocatalytic performance was elucidated according to the results of characterization measurements and active species analysis.     

Piezotronic effect boosted photocatalytic performance of NiO@PbTiO3 p-n heterojunction

The built-in electric field existing in heterojunction of hybrid photocatalyst is favorable to separate the photogenerated carriers in photocatalytic reaction. Besides, the electric field existing in the whole ferroelectric bulk can also effectively separate the photogenerated carriers. Here the catalytic reaction is enhanced through the enlarged electric field contributed by both p-n junction and the ferroelectric polarization. A new composite is prepared with the n-type single-crystal PbTiO₃ nanoplate coated with the p-type NiO particles, and its photocatalytic degradation rate of RhB (0.253 min^?1) is 4.71 times of pure PbTiO₃ (0.0537 min^?1) due to the contribution of p-n junction. In addition, the piezo-phototronic effect is applied to further enhance the photocatalytic performance. Under light and ultrasonic excitation, the screening effect of ferroelectric polarization can be broken by the alternating piezoelectric potential due to the periodic mechanical stress, and thus the reaction rate of piezo-photocatalytic degradation of RhB (0.461 min^?1) is 1.82 times of photocatalytic reaction rate (0.253 min^?1) for NiO@PbTiO₃ composite and 3.34 times of the piezo-photocatalytic reaction rate for pure PbTiO₃ (0.138 min^?1). This work is helpful to clarify the piezo-photocatalytic mechanism and develop efficient photocatalysts.     

Recyclable 0D/2D ZnFe2O4/Bi5FeTi3O15 S-scheme heterojunction with bismuth decoration for enhanced visible-light-driven tetracycline photodegradation

Practical application of photocatalysis is often challenged by some intrinsic issues such as recombination of photogenerated charge carriers, stability and separation, etc. Herein, bismuth decorated 0D/2D ZnFe₂O₄/Bi₅FeTi₃O₁₅ (Bi/ZF/BFT) step-scheme (S-scheme) heterojunction was fabricated by an in-situ method. Due to the advantages of structure and composition, the Bi/ZF/BFT with the desired proportion (Bi/ZF/BFT-35) exhibits favorable photocatalytic performance towards tetracycline (TC) degradation. Compared with the pure ZF, the nanohybrid shows superior stability after 5 times cycle tests. Moreover, Bi/ZF/BFT-35 is convenient to be separated from the reaction system due to its magnetic nature. As identified by ESR measurement, ?O₂^? and ?OH radicals were involved in the photodegradation of TC, which supports that the S-scheme is successfully prepared. Also, the Bi/ZF/BFT-35 shows great ability of chemical oxygen demand (COD) removal in the practical wastewater as well. Importantly, antibacterial activity against E. coli test indicates that photodegraded TC has lower biotoxicity. The present work demonstrates that cocatalyst Bi modified ZF/BFT S-scheme can not only significantly improve its stability with good recyclability from the reaction system, but also inhibits the recombination of charge carriers, giving insight on the strategy of fabricating a promising photocatalyst for practical wastewater treatment.     

Photocatalytic Degradation of Tetracycline by Z-Scheme Bi2WO6/ZIF-8

To improve the photocatalytic activity of Bi₂WO₆, ZIF-8 was successfully introduced with the in-situ growth for the first time. The addition of ZIF-8 effectively inhibited the recombination of photogenerated electron–hole pairs with further improved electron utilization efficiency. The superoxide anion, .O₂^?, generated, greatly improved the photocatalytic activity. The performance of Bi₂WO₆/ZIF-8 in the photodegradation of tetracycline (TC) was studied under different conditions, including the proportions of ZIF-8, the dosage of catalyst, and the concentration of TC. The results indicated that 10 mg of B/Z/5/1 offered the best photocatalytic activity under UV light, achieving 97.8% degradation of TC (20 mg/L) within 80 min. The measured rate constant (k) for TC degradation was almost 3 times that of pure Bi₂WO₆. The effects of pH, HA, and inorganic anions on the degradation of TC were also studied for the simulated real water. Further, B/Z/5/1 could be reutilized up to five cycles without reduction of the catalysis performance. Therefore, the Bi₂WO₆/ZIF-8 heterojunction composite material can be utilized as an efficient photocatalyst for remediation of environmental pollution.

     

Composite soft template-assisted construction of a flower-like β-Bi2O3/Bi2O2CO3 heterojunction photocatalyst for the enhanced simulated sunlight photocatalytic degradation of tetracycline

A three-dimensional (3D) flower-like β-Bi₂O₃/Bi₂O₂CO₃ heterojunction photocatalyst was synthesized via decomposition of the precursor fabricated using a composite soft template, which was constructed from dl-aspartic acid and nonionic amphiphilic triblock copolymer (Pluronic F127). The morphology, phase structure, composition, effect of reactant concentration, and possible formation mechanism were systematically studied. The results showed that dl-aspartic acid was chosen as the coordination- and structure-directing agent, while F127 was used as the capping agent during preparation of the precursor. The as-prepared flower-like β-Bi₂O₃/Bi₂O₂CO₃ heterojunction obtained after calcination of the self-sacrificing precursor at 290 °C showed excellent photocatalytic performance in the degradation of the refractory colorless antibiotic agent tetracycline (TC) under simulated sunlight irradiation, with 98.79% TC degradation being achieved within 60 min of irradiation. This excellent photocatalytic performance was attributed to the narrow band gap, heterojunction structure, and 3D hierarchical structure. The results further revealed that photogenerated holes (h⁺) and hydroxyl radicals (^•OH) dominated the photocatalytic process. Furthermore, the β-Bi₂O₃/Bi₂O₂CO₃ heterojunction catalyst was not photocorroded after six consecutive cycles, suggesting an excellent photostability.     

Construction of ternary rGO/1D TiO2 nanotubes/3D ZnIn2S4 microsphere heterostructure and mutually-reinforcing synergy for high-efficiency H2 production photoactivity under visible light

The novel ternary reduced graphene oxide/1D TiO₂ nanotubes/3D ZnIn₂S₄ microspheres (rGO/TiO₂/ZIS) heterostructured photocatalyst with high-efficiency H₂ production capacity under visible light illumination is designed and prepared in this work. In rGO/TiO₂/ZIS system, the 1D TiO₂ nanotubes are tightly inserted in the interspace of flower-like ZnIn₂S₄ microspheres, which are further covered by rGO, leading to an intimate contact among ZnIn₂S₄, TiO₂ and rGO. The exquisite design of rGO/TiO₂/ZIS makes it possess remarkable superiority in photocatalysis. Firstly, the unique 3D microsphere structure of ZIS increases the surface area and visible light absorption ability caused by their unique hollow structure. More importantly, the matched CB and VB positions between ZIS and TiO₂ contribute to separate photogenerated holes and electrons of ZIS efficiently under visible light; then, the separated electrons on TiO₂ are further transferred to rGO due to the superior-strong electron-attracting ability of rGO. At last, the thoroughly suppressing recombination of photogenerated holes and electrons is achieved by the mutually-reinforcing synergy among ZIS, TiO₂ and rGO, and thus the hydrogen generation capacity of ZIS is significantly enhanced. The H₂ production amount and rate of rGO/TiO₂/ZIS (2.0 wt% rGO and 50 wt% ZIS) after 10 h are 4623 μmol/g and 462.3 μmol/g/h, respectively, which is 71.1 times of pristine TiO₂ and 1.6 times of ZIS under the same condition. The apparent quantum yield of rGO/TiO₂/ZIS (2.0 wt% rGO and 50 wt% ZIS) in 10 h is about 0.6888%. This excellent photocatalytic performance is ascribed to the mutually-reinforcing synergy among ZIS, TiO₂ and rGO, which can be confirmed by X-ray photoelectron spectroscopy, photoelectrochemical measurements and photoluminescence spectrum. Based on the photocatalytic and characterization results, the corresponding mechanism is proposed.     

Enhanced visible light photocatalytic activity of QDS modified Bi2WO6 nanostructures

Bi₂WO₆ (BWO) nanostructures with QDS dispersed on single crystalline nanosheets were successfully prepared by a facile solvothermal method. The product possessed large surface area of 60 m²/g and exhibited excellent visible light absorption with a blue shift from 2.54 eV to 2.75 eV. The photocatalytic efficiency of the sample was six times that of nanoparticles assembled BWO nanostructures and three times that of nanoplates assembled BWO nanostructures. The photocatalytic mechanism for degradation of dyes over QDS modified BWO nanostructures was discussed, which revealed the important role of QDS in the generation, migration and consumption of the photogenerated electrons and holes.