Surface Of BiOI Research Articles

Facile synthesis of metallic Bi deposited BiOI composites with the aid of EDTA-2Na for highly efficient Hg0 removal

BiOI microparticles with different I/Bi molar ratios were synthesized via a facile coprecipitation method in the absence and presence of EDTA-2Na and were characterized by various techniques. Their activity were evaluated using toxic elemental mercury as model pollutant under fluorescent lamp irradiation. The presence of EDTA-2Na would lead to the production of Bi, facilitating an effective separation of electron and hole pairs due to the transfer of electrons from BiOI surface to Bi. The lower the I/Bi molar ratio, the higher the Hg0 removal efficiency. The superoxide radicals and holes were the main reactive species for enhanced Hg0 removal.

Fabrication of CeO2 nanoparticles decorated three-dimensional flower-like BiOI composites to build p-n heterojunction with highly enhanced visible-light photocatalytic performance

Three-dimensional (3D) flower-like CeO2/BiOI heterostructures with different Ce/Bi molar ratio were successfully synthesized via a hydrothermal method using polyvinylpyrrolidone (PVP) as surfactant. The X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) results indicate that the CeO2 nanoparticles were successfully loaded on the surface of the flower-like BiOI. The photodegradation experiment demonstrated that the photocatalytic efficiency of CeO2/BiOI samples were higher than that of pure BiOI and CeO2, and CeO2/BiOI heterostructure showed the best photocatalytic performance when the amount of CeO2 located at BiOI up to 15%. The result also exhibits that CeO2/BiOI catalysts possess higher photocatalytic efficiency for Rhodamine B (RhB) and methylene orange (MO) degradation, while it has a slight influence for phenol elimination. Meanwhile, the repeated photocatalytic degradation of RhB experiment reveals excellent photostability. A possible mechanism of photocatalysis was also explored and proposed. Furthermore, loading CeO2 on the surface of BiOI can accelerate the separation rate of photogenerated electron-hole pairs, which is analyzed by photoluminescence (PL) spectroscopy, photocurrent experiments (PC) and electrochemical impedance spectroscopy (EIS). These results exhibit that BiOI can be modified by CeO2 and there exists synergistic effect between CeO2 and BiOI. The present work provides a new means to synthesize heterostructured photocatalyst for environmental remediation.

Enriched photoelectrocatalytic degradation and photoelectric performance of BiOI photoelectrode by coupling rGO

Reduced graphene oxide (rGO) wrapped n-type BiOI hybrids for enhanced photoelectrocatalytic (PEC) degradation of organic pollutants is reported. The Scanning Electron Microscope (SEM) images showed that the rGO was homogeneously coated on the surface of BiOI, forming a core@shell structure. Raman spectra, Fourier transform infrared (FT-IR) spectra, and X-ray photoelectron spectroscopy (XPS) analyses showed that an intense interaction was formed between rGO and BiOI, which could highly promote the photo-generated charge transfer rate and photoelectric conversion efficiency. It was experimentally demonstrated that the degradation efficiency of organic pollutants for PEC process was 40.6% and 62.7% higher than that of photocatalytic (PC) and electrocatalytic (EC) processes, respectively. Further analyses indicated that the improvement in PEC degradation of organic pollutants benefited from: (1) a strong interaction and a wide range of conjugation were formed in the hybrid system; (2) negative shifts for the flat band potential in case of BiOI@rGO composites.

Structural and electronic properties of low-index stoichiometric BiOI surfaces

As promising photocatalyst driven by visible-light, BiOI has attracted more and more attention in the past years. However, the surface structure and properties of BiOI that is the most important place for the photocatalytic have not been investigated in details. To this end, density functional theory was performed to calculate the structural and electronic properties of four low-index stoichiometric surfaces of BiOI. It is found that the relaxation of the low-index BiOI surfaces are relatively small, especially the (001) surface. Thus, the surface energies of BiOI are very relatively small. Moreover, there are a few surface states below the bottom of conduction band in the first layer except the (001) surface, which maybe capture the photo-excited carriers. In all of the most stable terminated planes, all the dangling bonds are cleaved from the broken BiO bonds. In the case of (001) surface, the dangling bond density of Bi atoms for the (001) surface is zero per square nano. Therefore, the (001) surface is thermodynamically lowest-energy surface of BiOI, and it is the predominant surface (51.4%). As a final remark, the dangling bonds density of bismuth atoms determines not only the surface energy, but also the surface relaxation. Finally, the equilibrium morphology of BiOI was also proposed and provided, which is determined through the Wulff construction. These results will help us to better understand the underlying photocatalytic mechanism that is related to BiOI surfaces, and provide theoretical support for some experimental studies about BiOI-based photocatalyst in future.

Photocatalytic NO removal on BiOI surface: The change from nonselective oxidation to selective oxidation

Numerous publications have investigated nitric oxide (NO) removal through semiconductor photocatalytic technology. However, few reports are available on the products and mechanisms of the photocatalytic NO removal process. In this study, BiOI hollow microspheres are synthesized for the photocatalytic removal of NO under the visible light irradiation. Results show that NO removal product and NO removal mechanism could interfere with each other. NO removal process could be changed from nonselective oxidation to selective oxidation as the irradiation time increases. Meanwhile, the product of NO removal could be changed from nitrate (NO3−) to nitrogen dioxide (NO2). These interesting changes were attributed to the generated NO3−, which was produced from the reactions between NO and OH. The generated NO3− could inhibit OH generation, thus leading to a change in the NO removal products and NO removal mechanism. This study can improve our understanding of NO removal on the photocatalyst surface and serve as a guide in using photocatalysts for NO removal.

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.