Yuanwei Sun

Facile Fabrication of Bi2

In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h+) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater.

Enhanced photocatalytic performance in Bi2WO6/SnS heterostructures: Facile synthesis, influencing factors and mechanism of the photocatalytic process.

Highly-efficient photocatalyst based on Bi2WO6/SnS heterostructure was prepared via a surface functionalization method using 3-mercaptopropionic (MPA) as the surface functionalizing agent. Compared to bare Bi2WO6 and SnS nanoparticles, the as-formed Bi2WO6/SnS heterostructure exhibits enhanced photocatalytic activity for the degradation of Rhodamine B (Rh B). Photoluminescence and photocurrent measurements demonstrate that the enhanced photocatalytic activity during the photocatalytic process is closely related to the enhanced electron-hole separation efficiency. The photocatalytic activity of the as-formed Bi2WO6/SnS heterostructure can be perfectly remained even after being used for five times, showing excellent durability during the photocatalytic process. The influence of pH and inorganic ions are systematically investigated. And the optimum pH for the photocatalytic process is determined to be 6. The addition of chloride ion will exert negative effect on the photodegradation process of Rh B. The mechanism of photodegradation process was investigated by exploring the quenching effects of different scavengers and the results suggest that the reactive holes play the major role in the photodegradation process of Rh B.

Facile Fabrication of Bi2WO6/Ag2S Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Performances

In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h+) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater.

Novel Bake-in-Salt Method for the Synthesis of Mesoporous Mn3O4@C Networks with Superior Cycling Stability and Rate Performance

The commercial applications of Mn3O4 in lithium ion batteries (LIBs) are greatly restricted because of the low electrical conductivity and poor cycling stability at high current density. To overcome these drawbacks, mesoporous Mn3O4@C networks were designed and synthesized via an improved bake-in-salt method using NaCl as the assistant salt, and without the protection of inert gas. The added NaCl plays a versatile role during the synthetic process, including the heat conducting medium, removable hard template and protective layer. Because of the homogeneous distribution of Mn3O4 nanoparticles within the carbon matrix, the as-prepared Mn3O4@C networks show excellent cycling stability in LIBs. After cycling for 950 times at a current density of 1 A g-1, the discharge capacity of the as-prepared Mn3O4@C networks is determined to be 754.4 mA h g-1, showing superior cycling stability as compared to its counterparts. The valuable and promising method, simple synthetic procedure and excellent cycling stability of the as-prepared Mn3O4@C networks makes it a promising candidate as the potential anode material for LIBs.

Antisolvent diffusion-induced growth, equilibrium behaviours in aqueous solution and optical properties of CH3NH3PbI3 single crystals for photovoltaic applications

Crystallization and decomposition of organolead trihalide perovskites (OTPs) are very sensitive to the presence of water in precursor or in ambient conditions. Thus, understanding equilibrium behaviours (crystallization and decomposition) of OTPs in aqueous solution is very critical for OTP solar cells fabricated with water-based precursor solutions. Here, equilibrium behaviours in an aqueous solution of CH3NH3PbI3 (MAPbI3) single crystals (MSCs) were studied. Diethyl ether, as an antisolvent, effectively diffused and induced MSC growth by screening different solvents (diethyl ether, tetrahydrofuran, dichloromethane, and chloroform). The structure transforms from the initial PbI2 to intermediate (HxPbI2+x·xH2O) and finally MSCs were observed by X-ray diffraction. Decomposition of MSCs in aqueous solution was significantly enhanced by potassium iodide coordination and inhibited by CH3NH3I (MAI) addition. We ascribed this inhibition behaviour to suppressing MAI migration from the MSC crystal structure. Finally, the optical properties of MSC were studied.

Enhanced visible-light-driven photocatalytic performances using Bi2WO6/MS (M = Cd, Zn) heterostructures: facile synthesis and photocatalytic mechanisms

The formation of type II heterostructures is proved to be an effective method to improve the photocatalytic performance of semiconductors. In this report, a surface functionalization method using 3-mercaptopropionic acid (MPA) as the surface functionalizing agent was adopted for the fabrication of Bi2WO6/MS (M = Cd and Zn) heterostructures. The composition and microstructures of the as-prepared heterostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and X-ray photoelectron spectroscopy (XPS). The as-prepared Bi2WO6/CdS and Bi2WO6/ZnS heterostructures exhibit enhanced photocatalytic activities for the degradation of Rhodamine B (Rh B) as compared to pure Bi2WO6, CdS, ZnS nanoparticles and Degussa P25. The enhanced photocatalytic activities of the as-prepared heterostructures may relate to the effective electron–hole separation during the photocatalytic process. A series of scavengers (benzoquinone for O2˙−, ammonium oxalate for h+, AgNO3 for e−, and t-BuOH for ˙OH) were employed to investigate the possible mechanism of the photocatalytic process. The results clearly indicate that the photogenerated holes are the main active species during the photocatalytic process.

Theoretical screening of novel alkyne bridged zinc porphyrins as sensitizer candidates for dye-sensitized solar cells

Alkyne bridged porphyrin sensitizers have attracted great attention in the field of dye-sensitized solar cells (DSSCs) because of their excellent photo-to-electric conversion efficiencies, among which YD2 has reached 11% while YD2-o-C8 has reached 11.9% solely and 12.3% co-sensitized with other sensitizers. Design and screening of porphyrin sensitizer candidates with wider electronic absorption spectra to further improve the photo-to-electric conversion efficiencies of corresponding solar cells is still very important. Twenty novel alkyne bridged zinc porphyrin sensitizer candidates composed of the donors diarylamino-, tri-4-methylphenyl-, tri-hydroxyl- and tri-amino-substituted zinc porphyrins as well as the selected acceptors E, M, Q, R and S have been designed and calculated at the density functional B3LYP level. YD2 and YD2-o-C8 are also calculated at the same level for comparison. The result shows that the sensitizer candidates all have smaller HOMO-LUMO gaps as well as wider and red-shifted absorption bands than those of YD2 and YD2-o-C8. Most of the sensitizer candidates have appropriate HOMO and LUMO energy levels relative to the redox potential of the mediator and the TiO2 conduction band, showing that they are promising to provide comparable or even higher photo-to-electric conversion efficiencies than 11% of YD-2 or 11.9% of YD2-o-C8.

Mono-Disperse CaWO4 Microsphere with Hierarchical Structures: Room Temperature Synthesis and its Optical Properties

In this report, an inorganic salt assisted micro-emulsion method was reported for the preparation of mono-disperse CaWO4 microspheres with hierarchical structures. The as-obtained microspheres are composed of tiny nanorods, which have been proved by the field emission scanning electronic microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) observations. The formation of these hierarchical mono-disperse microspheres is considered to be the synergistic effect of both surfactant and the inorganic salt. Based on the time-dependent experiments, a probable formation mechanism based on surface adsorption and oriented attachment has been proposed. The photoluminescence properties of the microspheres were investigated. The generality of this synthetic method for other metal tungstates were also carefully investigated, which indicates that the morphologies of the final product not only depend on the synthetic conditions, but also depend on the growth habit of the materials.

Facile Fabrication of Bi 2WO 6/Ag 2S Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Performances

In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h+) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater.

Facile Fabrication of Bi 2 WO 6 /Ag 2 S Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Performances

In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h+) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater.