Fan Tian

Modification with Metallic Bismuth as Efficient Strategy for the Promotion of Photocatalysis: The Case of Bismuth Phosphate

A BiPO4 nanostructure modified with Bi nanoparticles rich in oxygen vacancies in the surface and subsurface was prepared through a one-pot solvothermal treatment utilizing the weak reductive ability of ethylene glycol (EG). The presence of Bi nanocrystals and oxygen vacancies is beneficial for the separation and consumption of photogenerated electrons and holes where Bi nanocrystals act as active sites for the formation of (.) OH and oxygen vacancies are active sites for (.) O2 (-) formation. The enhanced photocatalytic activity is ascribed to the synergistic effect of Bi nanocrystals and surface oxygen vacancies.

Thickness-tunable solvothermal synthesis of BiOCl nanosheets and their photosensitization catalytic performance

Bismuth oxychloride (BiOCl) nanosheets with tunable thickness were synthesized via a facile solvothermal method. The obtained BiOCl products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption. It was found that the metal ions (Fe3+, Co2+ and Na+) played a significant role in modulating the thickness of two-dimensional (2D) BiOCl nanostructures. Compared with commercial P25 and commercial BiOCl, the as-prepared BiOCl nanosheets exhibited superior activity for photosensitization degradation of organic dyes upon visible light irradiation. Furthermore, the photosensitization degradation activities were strongly correlated with the thickness of BiOCl nanosheets. The thinner nanosheets demonstrated a relatively high activity for the degradation of Rhodamine B (RhB). The enhanced photosensitization activities were ascribed to its low electron injection barrier and high electron mobility on the surface of BiOCl nanosheets, which was confirmed by transient photocurrent responses and electron impedance spectra of the samples.

Mannitol-assisted solvothermal synthesis of BiOCl hierarchical nanostructures and their mixed organic dye adsorption capacities

Three-dimensional (3D) hierarchical BiOCl nanostructures constructed by interconnected two-dimensional (2D) nanoplates have been successfully synthesized via a facile solvothermal process with the assistance of mannitol. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption. In the synthesis, mannitol acted both as a capping agent and a cohesive agent to mediate the formation of a hierarchical structure. A possible growth process involving crystal anisotropic growth habit and assembly process was proposed. The adsorption performance of BiOCl products for mixed organic dye removal was evaluated by using cationic rhodamine B (RhB) and anionic methyl orange (MO) as target substances. The as-prepared hierarchical BiOCl product exhibited excellent adsorption capacity and favorable recycling ability for mixed organic dye removal. This work demonstrated a novel strategy for the design and application of a well-defined complex hierarchical nanostructure.

Rhodamine B-sensitized BiOCl hierarchical nanostructure for methyl orange photodegradation

Loose-packed flower-like BiOCl hierarchical nanostructures (HNs) assembled by thin nanosheets were successfully synthesized via a facile solvothermal method. Based on the matchability analysis of band structure of BiOCl and the molecular orbitals of the dyes, the RhB dye-sensitized heterogeneous BiOCl HNs system was established for MO degradation under visible light irradiation. The mechanism of MO degradation over RhB-sensitized BiOCl was also discussed according to the photocurrent and photoluminescence results. It was found that MO degradation efficiency over RhB-sensitized BiOCl HNs was obviously improved due to the generation of superoxide radicals (˙O2−) through the reduction of surface-adsorbed O2 molecules by the injected electrons on the conduction band of BiOCl HNs from the excited RhB molecules. This work may provide insight on better understanding the organic dye photodegradation process in RhB dye-sensitized BiOCl heterogeneous systems and explore a dye-sensitized semiconductor photocatalyst strategy for environmental remediation.

Generation of defect clusters for 1O2 production for molecular oxygen activation in photocatalysis

Defect engineering on a semiconductor surface can provide coordinatively unsaturated sites for molecular oxygen activation in photocatalysis. In this work, we demonstrated that the vacancy type was key to modulate the molecular oxygen activation process on BiOBr nanosheets. By regulating the reaction time, an oxygen vacancy , a double atom defect cluster and triple atom clusters were accordingly generated on the surface, subsurface and bulk of BiOBr. More importantly, the newly-discovered defect cluster was highly related to the singlet oxygen (1O2) production ability of BiOBr. Meanwhile, the excellent photocatalytic selective oxidation reactions were successfully realized over BiOBr with the defect cluster. In addition, time-dependent defect cluster generation and the associated molecular oxygen activation were discussed.

Facile synthesis of Ag/AgCl/BiOCl ternary nanocomposites for photocatalytic inactivation of S. aureus under visible light

Ag/AgCl/BiOCl nanosheets were synthesized by a situ ion exchange between BiOCl nanosheets and AgNO3 solution followed by visible light reduction at room temperature. The obtained sample was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscope (TEM). Benefitting from the fact that Ag nanoparticles can respond to visible light and the ternary composite can effectively separate the photo-generated electrons and holes, the Ag/AgCl/BiOCl nanocomposite displayed enhanced visible-light-driven (VLD) photocatalytic inactivation of S. aureus, which was superior to BiOCl, Ag/BiOCl, AgCl/BiOCl, Ag/AgCl and Ag/AgCl/TiO2. Moreover, the mechanism of photocatalytic bacterial inactivation was investigated by using different scavengers and a simple partition system which is able to separate the catalyst and bacteria. It was found that the direct contact between Ag/AgCl/BiOCl nanocomposites and bacterial cells was unnecessary for the photocatalytic disinfection, and the diffusing H2O2 generated from holes reduction via a multi-electron pathway plays an important role in the photocatalytic disinfection. Finally, the photocatalytic destruction of the bacterial cells was directly observed by atomic force microscopy (AFM). This work provides a potential effective VLD photocatalyst to disinfect S. aureus cells.