Adsorption/photocatalytic performances of hierarchical flowerlike BiOBrxCl1−x nanostructures for methyl orange, Rhodamine B and methylene blue (original) (raw)
Related papers
Optical and Quantum Electronics, 2017
In this work we report smallest band gap composites BiOCl/Br, BiOCl/I and BiOBr/I with concentration of 50-50% synthesized using wet chemical method. Structural, morphological, compositional, optical and comparative study of photocatalytic properties of BiOCl/Br, BiOCl/I and BiOBr/I are studied. XRD analysis, from the intensity peaks, confirms the presence of both plate and flower like structures in the samples. BET confirms average surface area well in accordance with the XRD analysis. The morphology of the as prepared composites, studied using SEM characterization, is found to be interwoven nano-petals. It appears as 3D hierarchical microspheres with diameter ranging from 2 to 5 lm. Compositional study, using EDAX analysis, confirms the presence of constituents in order of their atomic and weight ration percentage. In FTIR analysis no absorption peaks related to impurity or solvent residue is obtained which is consider as a good agreement with respect to XRD results. Organic dye (methylene blue) reduction of composites sample within 5 h reaction time in the presence of UV-visible light was carried out using UV-visible spectroscopy techniques. The present work provides a simple way to prepare more active photocatalyst composites BiOCl/Br, BiOCl/I and BiOBr/I which finds industrial applications.
Korean Journal of Chemical Engineering, 2018
The main environmental problems associated with water body pollution are typically those caused by the discharge of untreated effluents released by various industries. Wastewater from the textile dye industry is itself a large contributor and contains a huge number of complex components, a wide spectrum of organic pollutants with high concentration of biochemical oxygen demand (BOD)/chemical oxygen demand (COD) and other toxic elements. One of several potential techniques to degrade such reactive dyes before being discharged to water bodies is photocatalysis, and bismuth-based photocatalysts are rapidly gaining popularity in this direction. Bismuth oxyhalides, BiOX (X=Cl, Br, I, F), as a group of ternary compound semiconductors (V-VI-VII), have been explored extensively for their photocatalytic activity due to their unique crystal lattice with special layered structure in pure as well as modified form. With suitable band gap and band edge positions, which are a required condition for efficient water breakup and high photon absorption, BiOCl scores over other oxyhalides. Photocatalytic activity depends on many factors such as synthesis method, morphology, size, illumination type, dye choice among others. This paper gives a critical review on bismuth oxyhalides as a family on various aspects of modifications such as doping (with unique and interesting metals as well), morphology and synthesis parameters, polymer and carbon assisted composites in order to further enhance the photocatalytic efficiency in UV/visible region of solar spectrum.
Materials (Basel, Switzerland), 2018
Novel green bismuth oxybromide (BiOBr-G) nanoflowers were successfully synthesized via facile hydrolysis route using an (Neem plant) leaf extract and concurrently, without the leaf extract (BiOBr-C). The leaf extract was employed as a sensitizer and stabilizer for BiOBr-G, which significantly expanded the optical window and boosted the formation of photogenerated charge carriers and transfer over the BiOBr-G surface. The photocatalytic performance of both samples was investigated for the degradation of methyl orange (MO) and phenol (Ph) under the irradiation of visible light. The leaf extract mediated BiOBr-G photocatalyst displayed significantly higher photocatalytic activity when compared to BiOBr-C for the degradation of both pollutants. The degradation rate of MO and Ph by BiOBr-G was found to be nearly 23% and 16% more when compared to BiOBr-C under visible light irradiation, respectively. The substantial increase in the photocatalytic performance of BiOBr-G was ascribed to the...
ACS Catalysis
With careful rational optimization and substantial simplification of the syntheses of the recently reported alloys BiO(Cl x Br 1−x), we fabricated, via a very simple procedure and at room temperature, a unique visible-lightdriven photocatalyst with excellent activity. The alloy BiOCl 0.875 Br 0.125 totally decomposed 15 mg/L aqueous Rhodamine B solution within 120 s upon irradiation with visible light (λ > 422 nm). The transparent substrate acetophenone was also swiftly destroyed under the above conditions. The catalyst maintained partial activity even after switching off the light source. Initial mechanistic studies clearly suggest that the mode of action of these materials is fundamentally different from previously reported photocatalytic mechanisms. Evidently, the putative molecular mechanism does not engage dye photosensitization or oxygen radicals.
2014
BiOCl and BiOCl x I 1−x were synthesized in two different solvents of ethylene glycol (EG) and water, and their natures were examined by scanning electron microscopy (SEM), electron transmission microscopy (TEM), X-ray diffraction, UV-vis absorption and Raman, Fourier-transform infrared, and photoluminescence spectroscopy. The Ag and Au-doping effects on the fundamental nature and photocatalytic activity of BiOCl and BiOCl x I 1−x were investigated in detail. SEM revealed that 3D flower-like and 2D plate-like microstructures were formed with EG and water solvents, respectively. The as-synthesized samples were tested for the adsorption and photocatalytic degradation of methyl orange and Rhodamine B, with the flower-like 3D-structure showing superior adsorption performance relative to the stacked 2D plate-like structures. Upon introducing iodine into BiOCl, we observed a dramatic increase in the adsorption ability and Brunauer-Emmett-Teller surface area, with an order of 2D BiOCl < 3D BiOCl BiOCl x I 1−x (x = 0.8, 0.6 and 0.4). The dye degradation performance was further markedly enhanced under irradiation by visible light. However, a small amount of Ag and Au-doping drastically negated the adsorption and photocatalytic performance. The photocatalytic mechanism was elucidated by an indirect chemical probe method using active species scavengers, and photoluminescence spectroscopy. On the basis of the results obtained, we propose a dye-sensitized photodegradation mechanism, and the active species play roles in the order of • OH • O 2 − ≈ h + under visible light irradiation.
Uniform well crystallized flower-like three-dimensional (3D) BiOClBr and I-doped BiOClBr microspheres with diameter of 1 μm were synthesized through a simple EG-assisted solvothermal method. The existence of I atoms in the BiOClBr compound could greatly enhance both adsorption and photocatalytic activity as compared with the BiOClBr and BiOX (Cl, Br, I) monomers. The highest catalytic performance of the flower-like 3D I-doped BiOClBr microspheres was preliminary deduced to be due to the much higher specific surface area, efficient sorption capacity as well as the unique interfacial structure. These factors may favor the absorption of light and separation of photogenerated charged carriers more effectively.
Acta chimica Slovenica, 2018
BiOBr microspheres with hierarchical morphologies (BiOBr-MicSphe) has potential application in heterogeneous photocatalysis for decontamination of water and air. For this reason, the synthesis, characterization an evaluation of photocatalytic activity of these materials become important. In this article, BiOBr-MicSphe were synthesized using different ranges of reaction temperature (120-200 °C) and reaction time (12 h - 24 h). Samples grown at 145 °C and 18 h showed the higher photocatalytic activity on gallic acid degradation. Morphological properties, chemical composition and structural analysis revealed that sample with higher photocatalytic activity exhibited a microspherical morphology with pure BiOBr tetragonal phase. Besides, adsorption-desorption analysis showed a smaller pore diameter for sample grown at 145 °C and 18 hrs. The results showed that the reaction temperature has a strong influence on the different properties of the material, affecting the photocatalytic activity.
Correlation Between Morphology Control and Photocatalytic Performance of BiOBr Nano-Microstrutures
Chemistry Africa, 2019
A systematic approach to optimize the photocatalytic activity of BiOBr nanoparticles was investigated and compared. The resulting BiOBr powders were successfully synthesized through two different pathways: stirred solvothermal and stirred hydrothermal processes under identical synthesis conditions of temperature and time. The composition, morphology, structure and optical properties of as-prepared samples were characterized by means of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, diffuse reflectance UV-Visible spectroscopy. Effective surface areas of the synthesized samples were estimated by Brunauer-Emmett-Teller studies. Catalysts prepared by solvothermal process and named (S-BiOBr) were of hierarchical microspheres, while the hydrothermally prepared ones called (H-BiOBr) were nanoflakes, both with a pure crystalline phase. The photocatalytic activities of as-synthesized structures were then examined to evaluate the effect of the synthetic route on the degradation of methyl orange (MO) dye as an organic compound model under simulated solar light irradiation (250 W Xenon lamp, 300 ≤ λ ≤ 800 nm). The photodegradation of MO was monitored by UV-Visible spectroscopy, substantiated by total organic carbon analysis. Hydrothermal process was a non-template method while in solvothermal route ethylene glycol has been used indicating the relative effects of the relationship of medium viscosity on morphology. On the basis of such analysis, the degradation efficiency of S-BiOBr towards MO was found to be 97% compared to 56% using H-BiOBr for 20 ppm concentration of dye. The kinetic analysis confirmed that the reaction rate constant k app was nearly 3 times higher than that of H-BiOBr, suggesting that S-BiOBr displayed the highest photocatalytic activity for the effective decomposition of MO.
Journal of Nanomaterials, 2016
Photocatalytic degradation is a promising alternative to traditional wastewater treatment methods. Recently developed visible light-responsive photocatalyst, BiOBr, has attracted extensive attentions. Hereby, a detailed investigation of application of BiOBr to bacterial inactivation and organic pollutants degradation is reported. Hydrothermal catalyst was prepared using template-free method. While, for solvothermal synthesis, CTAB was used as a template. Results indicate a higher photocatalytic activity by the solvothermally prepared catalyst. Solvothermally prepared BiOBr exhibited high photocatalytic activities in both water detoxification and disinfection.
Solvothermal synthesis and photocatalytic activity of Al-doped BiOBr microspheres
Ceramics International, 2014
A series of Al-doped BiOBr microspheres with different Al contents were synthesized via a facile solvothermal method. The as-prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectrometry(EDS), X-ray photoelectron spectroscopy(XPS), N 2 adsorption-desorption and UV-visible diffuse reflectance spectroscopy(UV-vis DRS). The photocatalytic activity was evaluated by the photocatalytic degradation of methyl orange in an aqueous solution under visible light irradiation. The results revealed that Al doping could greatly improve photocatalytic performance of BiOBr and different Al contents resulted in different photocatalytic activities. The highest activity was achieved by 4 at%Al-BiOBr. The enhanced photocatalytic activity was attributed to efficient separation of photogenerated electron-hole pairs and large BET surface area.