BiOxCly/BiOmBrn/BiOpIq/GO quaternary composites: Syntheses and application of visible-light-driven photocatalytic activities (original) (raw)
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Journal of Colloid and Interface Science, 2018
This paper presents an unprecedented systematic synthetic study of a controlled hydrothermal method for the preparation of bismuth oxychloride/bismuth oxybromide/bismuth oxyiodide ternary composites (BiO x Cl y /BiO m Br n /BiO p I q). The pH, temperature, and KCl:KBr:KI molar ratio for the reactions were adjusted to control the compositions and morphologies of BiO x Cl y /BiO m Br n /BiO p I q composites. Scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, Brunauer-Emmett-Teller specific surface areas, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy were applied to the products. The photocatalytic activities of dispersions were examined by monitoring the 2-hydroxybenzoic acid (HBA) and crystal violet concentrations. Various scavengers 2 demonstrated quenching effects. O 2 •− was crucial to HBA degradation, whereas h + and • OH played minor roles in HBA degradation. This text hypothesizes possible photodegradation mechanisms. Keywords: Photocatalysis, BiO x Cl y /BiO m Br n /BiO p I q , composites, 2-hydroxybenzoic acid, crystal violet
The Journal of Physical Chemistry C, 2012
In this study, a facile and effective method to modify the photocatalytic performance of a bismuth oxybromide (BiOBr) semiconductor through the fabrication of a heterojunction with a hydrated bismuth oxide (BHO) is reported. The new yBiOBr-(1 − y)BHO heterojunction, synthesized by a simple hydrothermal method, exhibits a high photocatalytic activity under visible light irradiation for the photodegradation of typical organic pollutants in water, such as Rhodamine B (RhB) and acetophenone (AP). Both the individual BiOBr and BHO components show very low photocatalytic efficiency. Furthermore, the unique photocatalytic performance of the new hybrid material was demonstrated through the uphill photocatalytic reaction that involves the oxidation of potassium iodide (KI) to triiodide. The remarkable photocatalytic activity of the coupled system is directly related to the effectual charge carrier separation due to the formation of the heterostructure. 0.9BiOBr-0.1BHO shows a higher photocatalytic activity as compared with other members of the same family, 0.8BiOCl-0.2BHO and 0.8BiOI-0.2BHO, which is directly ascribed to a synergistic effect of the energy bandgap structure and flow of charge carriers through the heterojunction, surface area, and light absorbance. In comparison with TiO 2 (Degussa P25), the new composite material demonstrated 10.7 times higher activity in removing aqueous RhB under visible light (λ ≥ 420 nm) irradiation. Study of the photocatalytic mechanism proves that the degradation of RhB under visible light irradiation over the as-prepared 0.9BiOBr-0.1BHO is mainly via a direct hole oxidation mechanism and superoxide oxidation pathways. The resulting yBiOBr-(1 − y)BHO composites exhibit high photocatalytic and thermal stabilities and are very promising photocatalysts for degradation of organic pollutants in water and for other applications.
New efficient visible light photocatalyst based on heterojunction of BiOCl–bismuth oxyhydrate
Applied Catalysis A: General, 2012
A novel active photocatalyst, which is a heteroconjuction of a bismuth oxyhydrate and BiOCl, has been synthesized by a simple hydrothermal method. The photocatalytic activity of the new material was measured in the degradation of Rhodamine B (RhB) and Acetophenone (AP) and in the photocatalytic oxidation of iodide in water under UV-vis and visible light irradiations respectively. The heterojunction between bismuth oxyhydrate and BiOCl provided exceptional photocatalytic activity, whereas both the individual bismuth oxyhydrate and BiOCl showed a negligible efficiency. Compared to Degussa P25, the new composite material demonstrated 5 times higher activity in removing aqueous RhB under visible light ( ≥ 420 nm) irradiation. The chemical composition and crystal structure were investigated using powder X-ray diffraction, scanning and transmission electron microscopy, and thermal methods. The preliminary study has revealed the bismuth oxyhydrate has tetragonal crystal structure with unit cell parameters a = b = 5.674Å, c = 10.353Å, unit cell volume V = 333.3Å 3 and possible P4/mmm (No. 123) space group. Temperature behavior of new photocatalyst has been investigated. It was found that at heating to 550 • C for 45 min the new phase transforms into well-known monoclinic Bi 2 O 3 .
2020
BiOI, BiOCl, and their composites with different molar ratios have been synthesized and tested for photocatalytic application, using methyl orange as model pollutant, and three various LED light sources. Adsorption capacity of BiOI highly exceeds that of BiOCl. The composite having 80:20 molar ratio of BiOI:BiOCl showed similar adsorption capacity than BiOI, and the best photocatalytic activity: about three times higher than BiOI and nine times higher than BiOCl. Methyl orange effectively transformed under visible light radiation, but with lower rate than under UV radiation. HPLC-MS measurements proved that the transformation of methyl orange is initiated with a demethylation. Effect of methanol as HO scavenger, and 1-4 benzoquinone proved that, the transformation of dye is initiated via direct charge transfer, and/or via photosensitization. Hydroxyl radical has no contribution to the transformation. The change of photocatalytic efficiency was followed during three cycles. After the first one, the transformation rate of methyl orange decreased, but there was no significant difference between the rates determined in the case of the second and third cycles. Ecotoxicity measurements confirmed that no toxic substances were dissolved from the catalyst under radiation, but the toxicity of methyl orange solution significantly increased during the treatment.
Cogent Chemistry, 2015
BiOCl, BiOBr, and BiOI have been synthesized by wet chemical route using bismuth nitrate (Bi(NO3)3.5H2O) and potassium halides, KCl, KBr, and KI, using a mixture of de-ionized water and ethanol as the solvent. Synthesized samples were characterized by X-ray diffraction and high-resolution SEM to observe the crystalline phase and crystallite size. Effective surface areas of the synthesized samples were estimated by Brunauer-Emmett-Teller studies. Photoactive properties of these samples were studied under three types of light exposure conditions viz. UV light from mercury vapour lamp, natural sunlight, and visible radiations from a 100-W incandescent tungsten filament. Degradation of methyl orange (MO) in aqueous media was estimated spectrophotometerically in visible range from the area under the curve with a peak at 464 nm. Kinetic constant for degradation reaction was calculated assuming the pseudo-first-order degradation mechanism. It was revealed that all the three samples show excellent degradation of MO in UV exposure with BiOCl as the most efficient photocatalyst in these radiations. BiOBr shows highest photodegradation performance among the three samples under natural sunlight exposure. Overall performance of the three photocatalyst samples is much better than the popular titanium dioxide photocatalyst.
2019
Herein, we report the synthesis of RGO-β-Bi 2 O 3 nanocomposite for visible light driven efficient photocatalytic removal of wastewater pollutant. Improved oxidation of pristine graphite (PG) to graphene oxide (GO) was obtained by involving additional oxiding agent Na 2 S 2 O 8 in Hummer's method. The as-synthesized reduced graphene oxide (RGO) was decorated with β-bismuth oxide to develop RGO-β-Bi 2 O 3 nanocomposite via in-situ wet processing method. The as-prepared na-nocomposites were characterized by range of techniques. The photocatalytic activity of as-prepared RGO-β-Bi 2 O 3 nanocomposite was investigated for the degradation of commercially available dye Direct Yellow-27 (DY-27), which is extensively used in the textile industries. The as-syntesized RGO-β-Bi 2 O 3 nanocomposite's photocatalysis shows first order kinetic. Furthermore, effect of dye concentration, pH, catalyst loading and temperature were studied to optimize the photocatalytic performance. The enhanced photocatalytic efficiency of nanocomposite could be attributed to the greater surface area and reduction in recombination of excited electron and holes.
Frontiers in Chemistry
An important target of photoelectrocatalysis (PEC) technology is the development of semiconductor-based photoelectrodes capable of absorbing solar energy (visible light) and promoting oxidation and reduction reactions. Bismuth oxyhalide-based materials BiOX (X = Cl, Br, and I) meet these requirements. Their crystalline structure, optical and electronic properties, and photocatalytic activity under visible light mean that these materials can be coupled to other semiconductors to develop novel heterostructures for photoelectrochemical degradation systems. This review provides a general overview of controlled BiOX powder synthesis methods, and discusses the optical and structural features of BiOX-based materials, focusing on heterojunction photoanodes. In addition, it summarizes the most recent applications in this field, particularly photoelectrochemical performance, experimental conditions and degradation efficiencies reported for some organic pollutants (e.g., pharmaceuticals, organ...
Photocatalytic Properties of BiOCl/Bi2WO6 Composite
Journal of Solar Energy Research Updates, 2015
BiOCl/Bi2WO6 composite was prepared by a hydrothermal synthesis method. The photocatalytic activity of the product was investigated by degrading Methyl Orange (MO) under visible light irradiation. The as-synthesized sample showed more efficient photocatalytic activity than that of single BiOCl or Bi2WO6 .
New metastable bismuth oxide-BiOCl heterojunction: efficient visible light photocatalyst
Applied Catalysis A General
A novel active photocatalyst, which is a heteroconjuction of a bismuth oxyhydrate and BiOCl, has been synthesized by a simple hydrothermal method. The photocatalytic activity of the new material was measured in the degradation of Rhodamine B (RhB) and Acetophenone (AP) and in the photocatalytic oxidation of iodide in water under UV-vis and visible light irradiations respectively. The heterojunction between bismuth oxyhydrate and BiOCl provided exceptional photocatalytic activity, whereas both the individual bismuth oxyhydrate and BiOCl showed a negligible efficiency. Compared to Degussa P25, the new composite material demonstrated 5 times higher activity in removing aqueous RhB under visible light ( ≥ 420 nm) irradiation. The chemical composition and crystal structure were investigated using powder X-ray diffraction, scanning and transmission electron microscopy, and thermal methods. The preliminary study has revealed the bismuth oxyhydrate has tetragonal crystal structure with unit cell parameters a = b = 5.674Å, c = 10.353Å, unit cell volume V = 333.3Å 3 and possible P4/mmm (No. 123) space group. Temperature behavior of new photocatalyst has been investigated. It was found that at heating to 550 • C for 45 min the new phase transforms into well-known monoclinic Bi 2 O 3 .
Journal of Colloid and Interface Science, 2019
In the recent past, due to the excellent optical properties and synergistic effect, bismuth oxyhalides based composites have gained significant attention in the field of photocatalysis. Herein, we demonstrate a green Azadirachta indica (Neem) (A.I.) leaf extract assisted hydrolysis method for the synthesis of green G-BiOBrxI1-x photocatalysts. The phytochemicals rich contents of the leaf extract demonstrated natural stabilizing properties, which effectively controlled the size of the composites and ultimately enhanced the specific surface area and porosity of the samples. Meanwhile, the leaf extract also proved to be an excellent sensitizer for the composites that boosted the optical window of the G-BiOBrxI1-x photocatalysts for high level of solar energy harvesting. The as-prepared G-BiOBrxI1-x photocatalysts possessed three dimensional nanoplates like structure with successive modulation of the band gaps from 2.28 eV to 1.98 eV by varying the Br/I ratio. Furthermore, the photocatalytic activity of the as-prepared G-BiOBrxI1-x samples were measured and compared with C-BiOBr0.5I0.5 synthesized by hydrolysis route without the leaf extract. The G-BiOBrxI1-x photocatalysts exhibited much improved photocatalytic performance than C-BiOBr0.5I0.5 for methyl orange (MO) and amoxicillin (AMX) degradation under visible light irradiation. In particular G-BiOBr0.2I0.8 exhibited the highest photocatalytic brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by SZTE Publicatio Repozitórium-SZTE-Repository of Publications activity, which was mainly attributed to the electron accepting π-conjugated system offered by the complex structural constituents of the leaf extract, thereby facilitating the charge transfer process and efficient separation of photogenerated electron-hole pairs. Furthermore, the high stability of BiOBr0.2I0.8 was demonstrated by the recyclability experiment, which offers promising opportunities for its practical application as a photocatalyst.