Novel flower-like (Bi(Bi2S3)9I3)2/3 nanostructure as efficient photocatalyst for photocatalytic desulfurization of benzothiophene under visible light irradiation

Here, we report the preparation of hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures that acts as a strong photocatalyst in the desulfurization of benzothiophene. We optimized the reaction time, type of capping agent and reflux temperature to tune the shape of porous flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures to achieve the highest desulfurization performance. We investigated the characteristic shape, size, purity, and optical response of the flower-shape nanostructures using XRD, EDS, FESEM, UV–Vis-DRS analysis. The flower-like (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures showed a significant photocatalytic property in desulfurization of benzothiophene as a model fuel. The hierarchical flower-like (Bi(Bi₂S₃)₉I₃)_2/3 photocatalyst with an energy gap of 1.15 eV, exhibits a 92% photocatalytic desulfurization performance after 2 h of visible light irradiation. The (Bi(Bi₂S₃)₉I₃)_2/3 nanostructures show a high photocatalytic reproducibility after 4 rounds of exposure. We proposed a photo-oxidation mechanism based on the active species scavenging, which revealed the role of photo-produced h⁺ and O₂^? species as essential in the photocatalytic desulfurization process. These findings provide a new prospect and design strategy for the development of efficient photocatalysts in desulfurization process.     

Facile preparation of heterostructured Bi2O3/Bi2MoO6 hollow microspheres with enhanced visible-light-driven photocatalytic and antimicrobial activity

Hierarchical β-Bi₂O₃/Bi₂MoO₆ heterostructured flower-like microspheres assembled from nanoplates with different β-Bi₂O₃ loadings (0–26.5 mol%) were synthesized through a one-step template-free solvothermal route. Under visible-light illumination (λ > 420 nm), over 99% of rhodamine B was degraded within 90 min on the 21.9 mol% of β-Bi₂O₃ loading Bi₂O₃/Bi₂MoO₆ microspheres. The remarkable enhancement of photocatalytic activity of the hierarchical Bi₂O₃/Bi₂MoO₆ micro/nanostructures can be attributed to the effective separation of the photoinduced charge carriers at the interfaces and in the semiconductors. The electrons (e⁻) are the main active species in aqueous solution under visible-light irradiation. The Bi₂O₃/Bi₂MoO₆ also displays visible-light photocatalytic activity for the destruction of E. coli. In addition, the β-Bi₂O₃ in the hierarchical Bi₂O₃/Bi₂MoO₆ microspheres is very stable and the composite can be easily recycled by a simple filtration step, thus the second pollution can be effectively avoided. A possible photocatalytic mechanism was proposed based on the experimental results.     

PH-induced structural evolution,photodegradation mechanism and application of bismuth molybdate photocatalyst

In this work, we have elucidated the pH-induced structural evolution of bismuth molybdate photocatalyst based on a hydrothermal synthesis route. With increasing the pH value of precursor solution, pure Bi₂MoO₆ was synthesized at pH 2–5, Bi₂MoO₆-Bi₄MoO₉ mixture was obtained at pH 7–9, pure Bi₄MoO₉ was obtained at pH 11, and pure α-Bi₂O₃ was derived at pH 13. The as-derived samples mainly present particle-like shapes but with different particle sizes (except the observation of Bi₂MoO₆ nanowires in sample S-pH9). The photocatalytic performances between the samples were compared via the degradation of methylene blue (MB) under irradiation of simulated sunlight. The Bi₂MoO₆ sample synthesized at pH 2 exhibited the highest photodegradation performance (η(30 min) = 89.8 %, k_app = 0.05007 min^?1) among the samples. The underlying photocatalytic mechanism and degradation pathways of MB were systematically analyzed. Moreover, the photodegradation performance of the Bi₂MoO₆ photocatalyst was further evaluated at different acidic-alkaline environments as well as in degrading various color and colorless organic pollutants, which provides an important insight into its practical application.     

Bi2MoO6 dielectric thin films fabricated by thermal oxidation of Bi/Mo thin films at ultra-low temperature

Bi/Mo multilayer thin films are deposited on Si/SiO₂/Pt substrates by direct current magnetron sputtering. The effect of annealing temperature on the microstructure, dielectric and electrical properties of the as-sputtered films is characterized systematically. X-ray diffraction data indicate that the films annealed at 450–600 °C are a mixture of diphase with the main phase Bi₂MoO₆ and secondary phase Bi₂Mo₂O₉. Results of scanning electron microscope observation show that the films annealed at 500–550 °C are dense and uniform, in particular the films annealed at 500 °C exhibit optimal dielectric and electrical properties with dielectric constant as high as 37.5, dielectric loss 1.06 %, temperature coefficient of dielectric constant ?10.86 ppm °C^?1 at 1 kHz, and leakage current density of 1.46 × 10^?7 A mm^?2 at an electric field of 18.2 kV mm^?1. With the advantages of ultralow densification temperature (500 °C) and very high sputtering deposition rate (76 nm min^?1), it is anticipated that thermal oxidation method of the sputtered Bi/Mo thin films could be a promising technique for fabrication of Bi₂MoO₆ ceramic thin film embedded-capacitors.     

Nanoarchitectonics on Bi2MoO6 by alkali etching for enhanced photocatalytic performance

As a layered photocatalyst, the photogenerated carriers separation efficiency of bismuth molybdate (Bi₂MoO₆) can be improved by introduction of oxygen vacancy. The alkali etching method provides a facile structural tuning way for modifying the bismuth-based semiconductors. Defect state bismuth molybdate (Bi₂MoO₆) photocatalyst was synthesized by alkali etching. The structure of Bi₂MoO₆ was tuned by adjusting the concentration of alkali solution. The phase structure, morphology, surface chemistry, and optical property of Bi₂MoO₆ were characterized by kinds of characterization methods such as X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance absorption spectroscopy. The phase of Bi₂MoO₆ can be transformed to Bi₂O₃ accompanied with the change of morphology due to the etching of molybdenum atom and oxygen atom from the Bi₂MoO₆ body structure by sodium hydroxide solution. Meanwhile, the concentration of oxygen vacancy increased obviously as indicated by the XPS results. Therefore, the separation efficiency of photogenerated carriers was enhanced because of the promotion of oxygen vacancy. Alkali etching Bi₂MoO₆ by 0.075 M sodium hydroxide solution exhibited an excellent photocatalytic performance owing to the suitable vacancy concentration. Superoxide free radicals instead of hydroxyl radicals took the important role in the photodegradation process.     

Multiple heterojunction system of Bi2MoO6/WO3/Ag3PO4 with enhanced visible-light photocatalytic performance towards dye degradation

Multiple heterojunction system of Bi₂MoO₆/WO₃/Ag₃PO₄ was designed via constructing binary heterojunction Bi₂MoO₆/WO₃, followed by the deposition of nano-Ag₃PO₄ on the surface of Bi₂MoO₆/WO₃. Various techniques were employed to characterize the properties of the as-prepared catalytic system. In this study, the decomposition efficiency of C.I. reactive blue 19 (RB-19) was used as a measure of photocatalytic activity and the Bi₂MoO₆/WO₃/Ag₃PO₄ composite exceeded its stand-alone components (pristine Ag₃PO₄, WO₃/Ag₃PO₄ and Bi₂MoO₆/Ag₃PO₄) by 3.16 times, 2.63 times and 1.75 times, respectively. The photocatalytic tests implied that the construction of multiple heterojunction could achieve efficient separation of photo-generated electrons and holes. A possible photocatalytic mechanism for Bi₂MoO₆/WO₃/Ag₃PO₄ system was also proposed according to the results of trapping experiments.     

Photocatalytic activities of coke carbon/g-C3N4 and Bi metal/Bi mixed oxides/g-C3N4 nanohybrids for the degradation of pollutants in wastewater

Different g-C₃N₄ composite systems (coke carbon/g-C₃N₄, Bi/Bi₂WO₆/g-C₃N₄ and Bi/Bi₂MoO₆/g-C₃N₄) have been assessed as photocatalysts for wastewater pollutants removal. The coke carbon/g-C₃N₄ hybrid, produced by thermal treatment at 550 °C of a composite made from melamine cyanurate and coke, only showed activity under UV-light irradiation. On the other hand, inorganic Bi spheres/Bi mixed oxides/g-C₃N₄ nanohybrids (Bi/Bi₂WO₆/g-C₃N₄ and Bi/Bi₂MoO₆/g-C₃N₄ composites), produced by thermal reduction of Bi₂WO₆ or Bi₂MoO₆ by g-C₃N₄, exhibited a remarkable red-shift, up to 620 nm, and allowed the visible-light driven degradation of the contaminant, albeit in combination with some adsorption.     

Enhanced visible-light-induced photocatalytic disinfection of Escherichia coli by ternary Bi2WO6/TiO2/reduced graphene oxide composite materials: Insight into the underlying mechanism

Composites coupling different semiconductors have attracted increasing attention for photocatalytic application owing to low visible-light absorption capability and weak photocatalytic activity of the single-component system. In this study, Bi₂WO₆/TiO₂/rGO ternary composites, successfully synthesized by a facile hydrothermal method, were manifested as an outstanding visible-light-response photocatalyst for the disinfection towards E. coli. X-ray diffraction, Fourier-transform infrared, and X-ray photoelectron spectroscopy demonstrated that GO coupled in the composites was efficiently reduced to rGO during the hydrothermal process, which was greatly beneficial for enhancing light harvest, promoting charge separation, and improving photocatalytic disinfection activity. UV–vis diffuse reflectance spectra, photoluminescence and time-resolved photoluminescence, photocurrent measurements, and ultraviolet photoelectron spectroscopy clearly showed that Bi₂WO₆/TiO₂/rGO composites had narrower band gap energy and much better suppression capability of photoinduced electron-hole recombination in comparison to the pure Bi₂WO₆ and TiO₂, and Bi₂WO₆/TiO₂. The radical trapping results revealed that the photogenerated holes (h⁺) were the leading active species responsible for the effective inactivation of E. coli under visible-light irradiation. Hence, the underlying mechanism for the enhanced photocatalytic disinfection performance of Bi₂WO₆/TiO₂/rGO composites was proposed. This study provides new insight into the design and development of composite materials with enhanced photocatalytic activity, which can be an inspiring alternative for environmental application.     

Mechanochemical homodisperse of Bi2MoO6 on Zn-Al LDH matrix to form Z-scheme heterojunction with promoted visible-light photocatalytic performance

In this work, a Z-scheme Bi₂MoO₆/Zn-Al LDH heterojunction photocatalyst with excellent visible light responsiveness was fabricated via a two-step mechanochemical ball-milling process, where amorphous Bi₂MoO₆ particles were homodispersed upon the surface of lamellar LDH matrix. BPA was selected as the targeted organic contaminant to quantitatively evaluate the photocatalytic capacity of Bi₂MoO₆/Zn-Al LDH, in which the optimal 30 wt%Bi₂MoO₆/LDH exhibited a degradation rate of 96% within 300 min, over 9.25 and 18.5 times higher than that of individual pristine Bi₂MoO₆ and LDH, respectively. The crystal structure, microtopography, interfacial physicochemical interaction, optical and electrochemical properties of as-fabricated hybrids were systematically evaluated, and the DFT theoretical calculation was used to confirm the electronic structural characteristics in the Bi₂MoO₆/LDH heterojunction. A possible photocatalysis reaction mechanism was interpreted through ESR where the major manner of ?O^2– proved the Z-scheme electron migration within matched band levels.     

Solvent directed fabrication of Bi2WO6 nanostructures with different morphologies: Synthesis and their shape-dependent photocatalytic properties

In this work, Bi₂WO₆ with complex morphologies, namely, flower-like, pancake-like, and tubular shapes have been controllably synthesized by a facile solvothermal process. The as-obtained samples are systematically investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effects of solvents on the morphologies of Bi₂WO₆ nanostructures are systematically investigated. According to the time-dependent experiments, a two-step growth mode basing on Ostwald ripening process and self-assembly has been proposed for the formation of the flower-like and pancake-like Bi₂WO₆ nanostructures. The photocatalytic properties of Bi₂WO₆ nanostructures are strongly dependent on their shapes, sizes, and structures for the degradation of rhodamine B (RhB) under visible-light irradiation. The deduced reasons for the differences in the photocatalytic activities of these Bi₂WO₆ nanostructures are further discussed.     

Preparation of a 3D flower-like spherical structure g-C3N4/CuBi2O4/Bi2MoO6 photocatalyst for efficient removal of antibiotics under visible light

For the remediation of antibiotic-contaminated water bodies, this study synthesized g-C₃N₄/CuBi₂O₄/Bi₂MoO₆ 3D flower-like spherical photocatalysts by a solvothermal method. The tetracycline antibiotics were used as the target pollutants and degraded under visible light to evaluate the photocatalytic performance of the prepared photocatalysts. Notably, the g-C₃N₄/CuBi₂O₄/Bi₂MoO₆ photocatalyst achieved 84.6 % and 91.6 % for the degradation of tetracycline hydrochloride and chlortetracycline (100 mL, 20 mg/L), respectively, within 2 h under visible light irradiation. Furthermore, we found that the composites showed very low degradation rates for dye-based contaminants, but still exhibited excellent photocatalytic activity for antibiotics in a mixed contaminant system of dyes and antibiotics. And the intermediate was detected by gas chromatography-mass spectrometry (GC–MS), suggesting a possible photo-degradation pathway for tetracycline. Finally, biochemical experiments were carried out to further illustrate the effective degradation of antibiotics in water after photocatalytic degradation by observing and comparing the growth of mung bean seeds.     

Synthesis and characterization of Bi2MoO6/MIL-101(Fe) as a novel composite with enhanced photocatalytic performance: Effect of water matrix and reaction mechanism

The integration of Bi₂MoO₆ with MIL-101(Fe) as a novel structure enhanced photocatalytic activity for RhB degradation. Bi₂MoO₆/MIL-101(Fe) composites were synthesized via the solvothermal procedure and characterized by XRD, EDX, FE-SEM, TEM, FT-IR, BET, TGA, UV–vis DRS, and PL. The optimal molar ratio Bi₂MoO₆:MIL-101(Fe) equal to 1:1 showed better photocatalytic activity than Bi₂MoO₆ and MIL-101(Fe) and other heterostructure composites. The effect of pH (5–9), reaction time (60–120 min), catalyst concentration (0.1–0.5 g/L), and dye concentration (10–20 ppm) were investigated on the removal performance of RhB by using central composite face-centered (CCF). In the optimal process factors where the [Catalyst]:0.4 g/L, [RhB]:20 ppm, pH: 6.5, irradiation time: 120 min, the RhB and TOC removal efficiency were 85% and 84.2%, respectively. The holes and superoxide radicals played a major role in the degradation of RhB. The addition of salt (NaCl, Na₂SO₄, and NaHCO₃) at different concentrations (100, 200, 400, and 800 ppm) revealed that the salts have an inhibitory role in the photocatalytic performance. At low concentrations of 100 ppm, the salts had a negative effect on removal efficiency (k_{Pure water} = 0.0155 min^?1, k_NaCl = 0.0075 min^?1, k_Na2SO4 = 0.0132 min^?1, k_NaHCO3 = 0.006 min^?1). Increasing the salt concentration to 800 ppm caused improved efficiency for NaCl (k_NaCl = 0.0141 min^?1), while for Na₂SO₄ this trend was decreasing (k_Na2SO4 = 0.011 min^?1), and for NaHCO₃ sharply diminished (k_NaHCO3 = 0.0026 min^?1).     

Synthesis of Bi2Fe4O9/reduced graphene oxide composite by one-step hydrothermal method and its high photocatalytic performance

Visible-light-driven degraded organic pollutant with high efficiency is crucial in the current photocatalysis research. A new kind composite photocatalyst with high visible-light photocatalytic activity which consists of Bi₂Fe₄O₉ and reduced graphene oxide (RGO) has been synthesized through one-step hydrothermal method at low temperature. Pure Bi₂Fe₄O₉ was formed with the addition of graphene oxide (GO) when the concentration of NaOH is 12 mol/L (M) at 180 °C for 72 h hydrothermal reaction. At the same time, the GO was reduced to RGO and adsorbed on the surface of Bi₂Fe₄O₉. The resultant composite photocatalyst showed higher absorption not only in the UV range but also in the visible light than pure Bi₂Fe₄O₉ indicating more electron–hole pairs generated. The band gap of photocatalysis was reduced from 1.91 to 1.69 eV and recombination of photo-generated electron–hole pairs in composites were decreased through marrying RGO with Bi₂Fe₄O₉. As a result, the Bi₂Fe₄O₉/RGO composite photocatalyst displayed higher catalytic activity for the degradation of methyl violet under visible light irradiation than rare Bi₂Fe₄O₉, promising the use of the Bi₂Fe₄O₉/RGO composite in visible-light photocatalysis.     

Modulation of Bi2MoO6‐Based Materials for Photocatalytic Water Splitting and Environmental Application: a Critical Review

Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, Bi₂MoO₆ has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi₂MoO₆ suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect‐introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi₂MoO₆. To accelerate further developments of Bi₂MoO₆ in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi₂MoO₆‐based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi₂MoO₆‐based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi₂MoO₆ are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi₂MoO₆‐based photocatalysts for environmental pollution control and green energy development.     

Bi4TaO8Cl/Graphene nanocomposite for photocatalytic water splitting

Sillen-Aurivillius structures like Bi₄NbO₈Cl, Bi₄TaO₈Cl, and Bi₄TaO₈Br have been expected as efficient visible light active photocatalysts thanks to their narrow band gaps less than 2.5 eV and suitable negative conduction band potential for hydrogen production reaction, 0.0 V vs NHE. However, despite their excellent potential the photocatalytic hydrogen generation efficiency of them under visible light has remained low. The low activity is usually attributed to the shallow defect levels near the conduction band, causing fast recombinations of photoexcited electrons and holes. In this study, a nanocomposite of Bi₄TaO₈Cl and graphene is proposed for overcoming this issue. The excellent electron conductivity and abundant delocalized electrons from the conjugated sp²-bonded carbon networks in graphene can facilitate the transfer of electrons from Bi₄TaO₈Cl conduction band and increase the photocatalytic efficiency. Bi₄TaO₈Cl/graphene nanocomposite was successfully prepared by a hydrothermal method, and photocatalytic activity enhanced both under UV and visible light.     

Fabrication of Ag-doped MoO3 and its nanohybrid with a two-dimensional carbonaceous material to enhance photocatalytic activity

Recently, two-dimensional (2D) carbon-based materials and their nanocomposites have gained considerable fascination as a photocatalysts due to their remarkable contribution towards photocatalytic water splitting and remediation. Herein, a novel 2D reduced graphene oxide (rGO) based silver doped molybdenum trioxide (Ag/MoO₃) photocatalyst was synthesized successfully via hydrothermal and ultra-sonication methods. The surface structure, morphology, functional group characterization, and bandgap of the synthesized photocatalysts were analyzed using advanced physicochemical techniques. The photocatalytic performance of the prepared materials was scrutinized for Methylene blue (MB) dye degradation under solar light illumination. Because of its lower charge transfer resistance (19.54 Ω) and higher electrical conductivity (12.74 × 10² Sm^?1) the rGO/Ag/MoO₃ photocatalyst demonstrated significantly higher photocatalytic activity for dye removal than pure MoO₃ and Ag/MoO₃ photocatalysts. In particular, the rGO/Ag/MoO₃ photocatalyst illustrated about 98% dye degradation at a rate constant (0.0571 min^?1) greater than MoO₃ (0.0097 min^?1) and Ag/MoO₃ (0.0184 min^?1). Ag doping and the addition of rGO sheets led to enhanced optical absorbance and effectual separation of photo-induced electron-hole pairs, causing major progress in the photocatalytic behavior of MoO₃. Transient photocurrent results revealed longstanding photo-excited charge carriers in the graphene-based material.     

In-situ preparation of porous carbon-supported molybdenum dioxide and its performance in the oxidative desulfurization of thiophene

Molybdenum dioxide (MoO₂) supported on porous carbon (MOPC) for the oxidative desulfurization of thiophene was prepared by in situ procedure, where MoO₂ was obtained from thermal conversion of the mixture of polyvinyl alcohol and ammonium molybdate tetrahydrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that formation of MoO₂ from bulk MoO₃ involved direct reduction from Mo(VI) to Mo(IV) while the surface reduction followed Mo(VI) to Mo(V) and finally to Mo(IV). Hexagonal-based MoO₂ platelets were observed to take shape with rising calcination temperature by scanning electron microscope test. Compared with the turnover frequency of MoO₃ (2.96 × 10^?2 h^?1), MOPC calcinated at 700 °C for 90 min exhibited a much higher turnover frequency of 6.15 × 10^?2 h^?1 on oxidative desulfurization of thiophene. The improved desulfurization efficiency of MOPC would be attributed to the more free electrons and smaller steric hindrance in MoO₂.     

Fabrication of plate-on-plate Z-scheme SnS<Subscript>2</Subscript>/Bi<Subscript>2</Subscript>MoO<Subscript>6</Subscript> heterojunction photocatalysts with enhanced photocatalytic activity

A class of direct plate-on-plate Z-scheme heterojunction SnS₂/Bi₂MoO₆ photocatalysts was synthesized via a two-step hydrothermal method. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, Fourier transform infrared photoluminescence emission spectra, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity was estimated via the degradation of crystal violet (CV) and ciprofloxacin (CIP). The experimental results indicated that the 5 wt% SnS₂/Bi₂MoO₆ composites exhibited significantly enhanced performance in contrast to pure Bi₂MoO₆ or SnS₂ nanoflakes, and were also superior to the popular TiO₂ (P25). The degradation reaction accorded well with the first-order reaction kinetics equation; the rate constant of CV using a SnS₂ content of 5 wt% photocatalyst was ~?3.6 times that of the Bi₂MoO₆ and 2.4 times that of SnS₂. Furthermore, a SnS₂ content of 5 wt% exhibited a 1.7 times higher photocatalytic activity of CIP than that of pure Bi₂MoO₆, and 1.3 times that of pure SnS₂. Radical trapping experiments and an electron spin resonance technique indicated that h⁺ and ·OH were the dominant active species involved in the degradation process. A plasmonic Z-scheme photocatalytic mechanism was proposed to explain the superior photocatalytic activities and efficient separation of photogenerated electrons and holes.     

Construction of 3D marigold-like Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript>/Ag<Subscript>2</Subscript>O/CQDs heterostructure with superior visible-light active photocatalytic activity toward tetracycline degradation and selective oxidation

A novel visible-light-driven photocatalyst Bi₂WO₆/Ag₂O/CQDs (BWO/Ag₂O/CQDs), which possesses hierarchical superstructure with marigold-like appearance, was fabricated via a hydrothermal method, followed by a simple precipitation process. Ag₂O nanoparticles sized around 25 nm and CQDs with diameters of about 10 nm were evenly deposited on Bi₂WO₆ to form a unique heterostructure. The obtained BWO/Ag₂O/CQDs heterostructure showed excellent adsorption and remarkably enhanced photocatalytic performance in the photodegradation of antibiotic tetracycline (TC) under visible-light irradiation compared to pristine Bi₂WO₆. The degradation rate of TC over BWO/Ag₂O/CQDs photocatalyst is 16.2 times higher than that of pristine Bi₂WO₆ and a possible mechanism for the enhanced photocatalytic performance was discussed. In addition, BWO/Ag₂O/CQDs was applied in the selective oxidation of benzyl alcohol to benzaldehyde under visible-light illumination. The result demonstrated that the conversion rate and product selectivity are greatly improved over BWO/Ag₂O/CQDs compared to pristine Bi₂WO₆ in the same reaction conditions, making it a promising photocatalyst in the application of green chemical transformation. The co-coupling of CQDs and Ag₂O with matched band potentials gives a substantial promotion for the light harvesting ability and effective separation of photogenerated charge carriers, synergistically accounting for the improvement of photocatalytic efficiency.     

Novel CuO/Bi2WO6 heterojunction with enhanced visible light photoactivity

Novel CuO/Bi₂WO₆ composites with different CuO to Bi₂WO₆ weight ratios were synthesized via a facile two-step approach. The as-prepared CuO/Bi₂WO₆ composite photocatalyst was characterized by XRD, SEM, TEM, XPS, BET, UV–vis diffused reflectance, fluorescence spectrum and photocurrent measurements to investigate their physical, optical and photochemical properties. The photocatalytic activity of CuO/Bi₂WO₆ composites was evaluated by the photocatalytic degradation of RhB under simulated sunlight. The optimum photocatalytic activity of the CuO/Bi₂WO₆ composites for the degradation of RhB is almost 2 times higher than those of bare Bi₂WO₆ and CuO. The enhanced photocatalytic performance could be mainly attributed to the improved light response and effective separation of the photogenerated electrons and holes at the heterojunction interface of p-CuO and n-Bi₂WO₆.