Minqiang He

Preparation of sphere-like g-C3N4/BiOI photocatalysts via a reactable ionic liquid for visible-light-driven photocatalytic degradation of pollutants

Novel sphere-like g-C3N4/BiOI composite photocatalysts were prepared by a one-pot EG-assisted solvothermal process in the presence of reactable ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I). The nanostructured heterojunction was formed with g-C3N4 covering the surface of BiOI microspheres uniformly. Multiple techniques were applied to investigate the structure, morphology and photocatalytic properties of as-prepared samples. During the reactive process, the ionic liquid acted as solvent, reactant, template and dispersing agent at the same time, leading to g-C3N4 being uniformly dispersed on the sphere-like BiOI surface. Three different types of dyes rhodamine B (RhB), methylene blue (MB), methyl orange (MO) were chosen as model pollutants to evaluate the photocatalytic activity of g-C3N4/BiOI composite. The as-prepared g-C3N4/BiOI composite exhibited much higher photocatalytic activity than the pure BiOI. At the same time, colourless endocrine disrupting chemical bisphenol A (BPA) and phenols 4-chlorophenol (4-CP) were chosen to further evaluate the photocatalytic activity of g-C3N4/BiOI composite. The g-C3N4/BiOI composite also exhibited much higher photocatalytic activity than the pure BiOI, which showed a broad spectrum of photocatalytic degradation activities. The results indicated that the formed heterojunction of g-C3N4 covers the BiOI microspheres contributed to improved electron–hole separation and enhancement in photocatalytic activity. A photocatalytic mechanism of g-C3N4/BiOI composites is also proposed.

A g-C3N4/BiOBr visible-light-driven composite: synthesis via a reactable ionic liquid and improved photocatalytic activity

g-C3N4/BiOBr composite photocatalysts have been synthesized in the presence of the reactable ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br). The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), and photocurrent analysis. During the reaction process, the ionic liquid [C16mim]Br acted as solvent, reactant, template and dispersing agent at the same time, leading the g-C3N4 to disperse well on the surface of the BiOBr flower-like microspheres. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. The photocatalysts exhibited a significantly enhanced photocatalytic performance in the degradation of RhB. The results of PL, EIS, and photocurrent tests indicated that g-C3N4 combined and dispersed well on the surface of BiOBr which facilitated electron–hole separation, and led to the increased photocatalytic activity. The optimal g-C3N4 content for the photocatalytic activity of the g-C3N4/BiOBr composites was determined. Radical trap experiments certified that the hole was the main reactive species for the photocatalytic degradation of RhB. A possible mechanism of g-C3N4 for the enhancement of visible light performance was proposed.

Reactable ionic liquid-assisted rapid synthesis of BiOI hollow microspheres at room temperature with enhanced photocatalytic activity

BiOI hollow microspheres have been rapidly synthesized through a facile reactable ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I)-assisted microemulsion method at room temperature. The formation mechanism of the BiOI hollow microspheres has been investigated. The BiOI hollow microspheres were formed through self-assembly and inside-out Ostwald ripening growth mechanism. During the reactive process, the ionic liquid, which acts as the solvent, reactant and template at the same time, plays a crucial role on the formation of hollow microspheres. In addition, the influencing factors (such as the reactant, the concentration of ionic liquids and the amount of acetic acid) of the formation of BiOI hollow microsphere have also been explored. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. After systematic characterizations, the relationship between the structure of the photocatalyst and the photocatalytic activities were also discussed in detail. It can be assumed that the enhancing photocatalytic activity of BiOI hollow microspheres could be attributed to the improved light harvesting, shortened diffusion pathways, high BET surface area and faster interfacial charge separation. O2˙− and h+ were the main active species for the photocatalytic degradation of RhB. It is hoped that this rapidly synthetic route at room temperature can be extended to the purposive preparation of other hollow microsphere materials.

One-pot solvothermal synthesis of Cu-modified BiOCl via a Cu-containing ionic liquid and its visible-light photocatalytic properties

Novel visible-light-driven Cu-modified BiOCl uniform sphere-like materials have been successfully synthesized through a one-pot ethylene glycol (EG)-assisted solvothermal process in the presence of 1-octyl-3-methylimidazolium copper trichloride ([Omim]CuCl3). The Cu-modified BiOCl materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Raman, photoluminescence (PL) and UV-vis diffuse reflectance spectroscopy (DRS). The results of the XRD, XPS, SEM, EDS, Raman analyses indicated that metal Cu was evenly distributed on the surface of the BiOCl microspheres in the form of Cu2+. During the reaction process, the metal-based ionic liquid acted as the solvent, the template, the Cl source and the Cu source at the same time. It is possible to tune the morphology of the Cu-modified BiOCl materials by varying the amount of ionic liquid used. In addition, the electrochemical and photocatalytic properties of the Cu-modified BiOCl materials were investigated. After the introduction of Cu2+, the photocurrent of the Cu-modified BiOCl materials was higher than that of the pure BiOCl. And the Cu-modified BiOCl materials exhibited higher photocatalytic activity for the degradation of methylene blue (MB) and bisphenol A (BPA) than that of pure BiOCl. The increased photocatalytic activity of the Cu-modified BiOCl materials was attributed to its large adsorption capacity, broad light absorption band and high separation efficiency of photo-generated electrons and holes. On the basis of these findings, the Cu-modified BiOCl materials showed great promise as photocatalysts for degrading organic pollutants and other applications.

Ionic liquid assisted synthesis and photocatalytic properties of α-Fe2O3 hollow microspheres

α-Fe2O3 hollow microspheres have been successfully prepared in the presence of metal ion-containing reactable ionic liquid 1-octyl-3-methylimidazolium tetrachlorideferrate(III) ([Omim]FeCl4) under the solvothermal condition. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), FT-IR spectrum, and diffuse reflectance spectroscopy (DRS). The effect of concentration of ionic liquids on the morphology of α-Fe2O3 had been investigated in detail. It was found that [Omim]FeCl4 acted not only as Fe source but also as solvent and template for the fabrication of α-Fe2O3 hollow microspheres. In addition, the electrochemical and photocatalytic properties of α-Fe2O3 were investigated. The α-Fe2O3 hollow microspheres exhibited high conductivity, high photocurrent, and high photocatalytic activity. The designed hollow microsphere showed potential applications in photocatalysis.

α‐Fe2O3 Cubes with High Visible‐Light‐Activated Photoelectrochemical Activity towards Glucose: Hydrothermal Synthesis Assisted by a Hydrophobic Ionic Liquid

A liquid/liquid interfacial reaction system was designed to fabricate α-Fe2O3 cubes. The reaction system uses a hydrophobic ionic liquid containing iron ions ([(C8H17)2(CH3)2N]FeCl4) for manufacturing α-Fe2O3 cubes by a novel and environmentally friendly hydrothermal method under low-temperature conditions (140 °C). The iron-containing ionic liquid is hydrophobic and can form a liquid/liquid interface with water, which is vital for fabrication of the α-Fe2O3 cubes. Nanomaterials synthesized from hydrophobic iron-containing ionic liquids show good crystallinity, well-developed morphology, and uniform size. The effect of different ionic liquids on the morphology of α-Fe2 O3 was investigated in detail. [(C8H17)2(CH3)2N]FeCl4 is assumed to perform the triple role of forming a liquid/liquid interface with water and acting as reactant and template at the same time. The effect of the reaction temperature on the formation of the α-Fe2O3 cubes was also studied. Temperatures lower or higher than 140 °C are not conducive to formation of the α-Fe2O3 cubes. Their photoelectrochemical properties were tested by means of the transient photocurrent response of electrodes modified with as-prepared α-Fe2O3 cubes. The photocurrent response of an α-Fe2O3 cubes/indium tin oxide electrode is high and stable, and it shows great promise as a photoelectrochemical glucose sensor with high sensitivity and fast response, which are beneficial to practical applications of nanosensors.

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite with enhanced photocatalytic activity for organic pollutant degradation and antibacterium

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite was synthesized through a facile solvothermal method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis) were applied to characterize the structures and properties of the as-prepared samples. The results indicate that Fe2O3 was coated on the surface of Ag/AgBr and heterostructures were formed. Electrochemistry analysis and photoluminescence (PL) spectra analysis indicate that the introduction of Fe2O3 could improve electron and hole separation efficiency. The photocatalytic activity of the Ag/AgBr@Fe2O3 composites was evaluated by using organic dye methyl orange (MO), endocrine disrupting chemical bisphenol A (BPA) and Escherichia coli (E. coli) as the target pollutants. The as-prepared Ag/AgBr@Fe2O3 composites exhibited much higher photocatalytic activities than pure Ag/AgBr, which was attributed to the effective charge separation of the Ag/AgBr@Fe2O3 composite. In addition, the as-prepared Ag/AgBr@Fe2O3 composite has magnetic properties, therefore after the photocatalytic reaction, it can be quickly separated from solution by an extra magnetic field. Trapping experiments and ESR analysis indicate that the h+ and ˙O2− are the main active species for the photocatalytic degradation. A possible Z-scheme pathway photocatalytic mechanism was proposed.

Facile synthesis of CNT/AgI with enhanced photocatalytic degradation and antibacterial ability

CNT/AgI composite with the diameter smaller than 1 µm was synthesized through a solvothermal method. The CNT/AgI hybrids were characterized by XRD, SEM, XPS, UV-Vis, photocurrent and so on. The results showed that the introduced CNT can greatly reduce the particle size of AgI without using surfactant. Besides, the introduced CNT transferred the electrons efficiently and enhanced the photoactivity of the CNT/AgI hybrids in degrading RhB dye. 0.3% CNT/AgI showed the highest photocatalytic activity, which was as high as about 2 times that of pure Ag/AgI. Trapping experiments and the electron spin resonance (ESR) results suggested the reactive species in the degradation process were h+, ˙OH and ˙O2−. Furthermore, the CNT/AgI still showed high photoactivity after 4 cycle experiments. Photocatalytic antibacterial experiments showed that the 0.3% CNT/AgI had better antibacterial ability than pure Ag/AgI. The results showed that the CNT/AgI can be used as a dual functional material in water treatment of removing the organic pollutant and killing the bacterium at the same time.

Synthesis and photocatalytic activity of g-C3N4/BiOI/BiOBr ternary composites

A novel ternary composite photocatalyst (g-C3N4/BiOI/BiOBr) was prepared via a facile solvothermal method. The samples were characterized by powder X-ray diffraction, transmission electron microscopy, UV-visible diffuse reflection spectrometry, X-ray photoelectron spectrometry and photoluminescence measurements. Under irradiation with visible light, the g-C3N4/BiOI/BiOBr photocatalyst showed a higher photocatalytic activity than pure g-C3N4 and BiOI/BiOBr for the degradation of methylene blue. Among the hybrid photocatalysts, 3% g-C3N4/BiOI/BiOBr showed the highest photocatalytic activity for the degradation of MB. These results suggest that the heterostructure combination of g-C3N4, BiOI and BiOBr provides a synergistic effect through an efficient charge transfer process.

Synthesis of mesoporous WO3/TiO2 catalyst and its excellent catalytic performance for the oxidation of dibenzothiophene

A series of WO3/TiO2 catalysts with a pore structure were successfully synthesized. The catalysts were systematically characterized and it was found that different calcination temperatures had great effects on the pore structure of the catalysts. The catalyst presented a mesoporous structure after calcining at 550 °C (expressed as 550-WO3/TiO2) and had the largest specific surface area among the mesoporous catalysts. The oxidation of dibenzothiophene (DBT) with 550-WO3/TiO2 catalyst reached 100% under optimum conditions. After recycling for 6 times, the oxidation of DBT could still achieve a DBT removal of 96.7%, suggesting that the catalyst had good stability and recycle performance. In addition, DBT sulfone (DBTO2) was proven to be the only oxidation product of DBT after the reaction, as observed by the GC-MS analysis. The catalytic activities of the catalyst on different substrates were also investigated, and the activities decreased in the order: DBT > 4-MDBT > 4,6-DMDBT > BT.