Papers by Keyword: Photocatalytic Performance

Abstract: Elements doping is a powerful way to alter the electronic structure and enhancing the photo catalytic activity of materials by relaxing the surrounding chemical bonds and forming new chemical bond. In this work, we have performed, the first principle density functional theory calculations to investigate the geometric, electronic and optical properties of pristine, Na-doped and P-doped as well as Na and P (Na/P) co-doped heptazine based monolayer graphitic carbon nitride (g-C₃N₄). The co-doping process results in significantly narrow band gap of g-C₃N₄. The optical absorption shows better visible-light response compare to pristine g-C₃N₄. After doping the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) show strong delocalization and indicates photo generated electron/hole (e^-/h⁺) pair disunion abilities of doped systems are superior than pristine heptazine based monolayer g-C₃N₄. Thus the co-doping with Na and P elements is an effective technique to boost the photocatalytic performance of heptazine based monolayer g-C₃N_4.

Abstract: Azo dyes are usually used in textile industry. However, they can cause water contamination, lead to water pollution, damage to aquatic lives and degenerate scenery due to their toxicity. These problems can be overcome by photocatalytic process in which the azo dyes are converted to CO₂ and water. This research concentrates on effect of Bi₂O₃, BiOBr and BiOI contents on titanium dioxide substance (TiO₂) for the photocatalytic process. In the study, photocatalysts were synthesized by sol-gel and wetness impregnation methods. They were studied in surface area by BET technique, chemical composition by FT-IR spectroscopy and optical properties by UV-DRS technique. Increase in bismuth content on TiO₂ results in decreasing surface area. In FT-IR spectra, Ti-O-Ti stretching bands at 400-800 cm^-1 were detected. The band gap energy of these photocatalysts is decreased when bismuth was doped. Since efficiency of CO₂ and water conversion of the photocatalysts can be determined indirectly via determinaiton of decreasing Methyl Orange (MO) concentration, the lowest MO concentration was observed in the 4%Bi₂O₃T photocatalyst after 16 hours when compared to the other photocatalyst samples and Degussa P25. In other words, this photocatalyst efficiently converts the azo dyes to CO₂ and water.

Abstract: In this paper, a simple, efficient and environmental friendly method was proposed to fabricate TiO₂/CdS nanotube arrays. The composite nanotubes with a core-shell coaxial structure were fabricated via a simple method of liquid deposition and double diffusion using anodic aluminum oxide (AAO) templates. The photocatalytic properties of the nanotube arrays (TiO₂, TiO₂/CdS) were confirmed by the degradation of methyl orange (MO) under UV irradiation. Compared to bare TiO₂ nanotube arrays, TiO₂/CdS composite nanotube arrays showed improved photocatalytic performance: The degradation efficiency of TiO₂/CdS and TiO₂ nanotube arrays towards methyl orange was 65% and 39%, respectively.

Abstract: In this study, the hydrothermal method was used for synthesizing ZnSe/graphene nanocomposites with the amount of graphene oxide (GO) and hydrazine. Obtained ZnSe/graphene photocatalysts were characterized by X-ray diffraction analysis (XRD) and transmission electron microscope (TEM). Photocatalytic activity under visible light is evaluated in methylene blue (MB) dye degradation reaction in aqueous phase. The results show that the amount of graphene oxide (GO) and hydrazine have an effect on the degradation efficiency of the ZnSe/graphene nanocomposite. When GO/ZnSe ratio was 1. The optimum degradation efficiency of the ZnSe/graphene nanocomposites prepared with 5 mL of N₂H₄ was 99.6% after 5h of visible light irradiation.

Abstract: Nature is a perfect designer in fabricating biomaterials with well-defined and hierarchical nanostructures. Here we report a biomineralization-inspired approach for preparing hierarchical ZnO structure with high UV-light efficiency. The results show that biomacromolecules play an important role on controlling growth and assembly of ZnO nanostructures. It is found that the biomacromolecules favoring the isotropic growth of ZnO at the high concentration.

Abstract: This study aimed to use the zinc dust which is a waste from hot-dip galvanizing plant for the synthesis of ZnO nanoparticles using microwave-assisted process. The precursor solution was prepared by dissolved as received zinc-dust powder in nitric acid. Then it was precipitated by NaOH at required pH and microwave irradiated in a household microwave oven at power of 100W for 10-20 min. The effects of preparation conditions and an addition amount of poly ethylene glycol (PEG; MW2000) for synthesis of ZnO on its properties were investigated. The synthesized nanoparticles were characterized for their phase structure, morphology and surface area by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET), respectively. The photocatalytic activity was determined by the degradation of methylene blue solution under UV irradiation. It was found that microwave heat treatment and addition of optimum amount of PEG could enhance the photocatalytic activity of precipitated ZnO particles. The resultant ZnO particles prepared by an addition of 0.25wt% PEG and microwave irradiation for 20 min exhibited the highest photodegradation rate among other products.

Abstract: ZnO photocatalyst was prepared by sol-gel method with the assistance of cetyltrimethylammonium bromide (CTAB). The specific surface area and structure were characterized by Brunauer-Emmett-Teller (BET) method and X-ray diffraction (XRD), respectively. The photocatalytic activity of ZnO prepared for decolorization of methyl orange (MO) aqueous solution was evaluated. The results show that ZnO (mol ratio of ZnO/CTAB is 10) baked at 500°C holds the best photocatalytic activity.

Abstract: Nanostructured SnO₂ was prepared by a parallel flow method under ultrasonic vibration. The photocatalytic performance of SnO2 was investigated by utilizing photocatalytic decolorization of methyl orange used as model organic pollutant. SnO2 prepared was characterized by BET, XRD and SEM. The results show that ultrasonication can influence greatly the specific surface parameters, SEM image and particle size, thus leading to better photocatalytic performance. The photocatalytic performance of SnO2 prepared by ultrasonication is 1.5 times of that of SnO2 prepared without ultrasonication.

Abstract: In this paper, SnO₂ and Fe₂O₃ doped-SnO₂ photocatalysts with different molar ratio of Fe/Sn were synthesized by a parallel flow coprecipitation method. The photocatalysts prepared were characterized by Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD) and UV/Vis diffuse reflectance, respectively. The photocatalytic activity of photocatalysts prepared toward decolorization of methyl orange (MO) solution was evaluated. Of all of the photocatalysts prepared among the experimented compositions, Fe₂O₃ doped-SnO₂ with 1.5%Fe possesses the best photocatalytic activity.

Abstract: BiOCl nanosheets were annealed at different temperatures. The effect of annealing on structures and properties was characterized by X-ray diffraction (XRD), N₂ adsorption-desorption, UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The photocatalytic performance was evaluated by photodegrading Rhodamine B (RhB) under UV light irradiation. It was found oxygen vacancy defects (OVDs) could be generated during the annealing treatment and the best photocatalytic efficiency was obtained when the annealing temperature was 450 °C. The enhanced photocatalytic efficiency was ascribed to the high separation efficiency of the photogenerated electron-hole pairs due to the existence of the OVDs as positively charged centers.