Guogang Tang

Z型Ag 3 PO 4 /Ag 2 MoO 4 异质结光催化剂构建和光催化降解有机污染物

Abstract Hole/electron separation and charge transfer are the key processes for enhancing the visible-light photocatalysis performance of heterogeneous photocatalytic systems. To better utilize and understand these effects, binary Ag3PO4/Ag2MoO4 hybrid materials were fabricated by a facile solution-phase reaction and characterized systematically by X-ray diffraction (XRD), energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, field-emission scanning electron microscopy and ultraviolet-visible diffuse-reflectance spectroscopy. Under visible-light illumination, a heterogeneous Ag3PO4/Ag/Ag2MoO4 photocatalyst was constructed and demonstrated enhanced photocatalytic activity and photostability compared with pristine Ag3PO4 toward the remediation of the organic dye rhodamine B. The Ag3PO4/Ag2MoO4 hybrid catalyst with 8% mole fraction of Ag2MoO4 exhibited the highest photocatalytic activity toward the removal of typical dye molecules, including methyl orange, methylene blue and phenol aqueous solution. Moreover, the mechanism of the photocatalytic enhancement was investigated via hole- and radical-trapping experiments, photocurrent measurements, electrochemical impedance spectroscopy and XRD measurements. The XRD analysis revealed that metallic Ag nanoparticles formed initially on the surface of the Ag3PO4/Ag2MoO4 composites under visible-light illumination, leading to the generation of a Ag3PO4/Ag/Ag2MoO4 Z-scheme tandem photocatalytic system. The enhanced photocatalytic activity and stability were attributed to the formation of the Ag3PO4/Ag/Ag2MoO4 Z-scheme heterojunction and surface plasmon resonance of photo-reduced Ag nanoparticles on the surface. Finally, a plasmonic Z-scheme photocatalytic mechanism was proposed. This work may provide new insights into the design and preparation of advanced visible-light photocatalytic materials and facilitate their practical application in environmental issues.

Band gap and morphology engineering of TiO2 by silica and fluorine co-doping for efficient ultraviolet and visible photocatalysis

Silicon and fluorine co-doped anatase TiO2 (Si–F–TiO2) photocatalysts with enhanced photocatalytic activity were successfully prepared via a facile two-step synthetic method by using SiO2 powders and (NH4)2TiF6 as the precursors. The obtained products were thoroughly characterized using various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy and N2 adsorption–desorption analysis. The characterization revealed the effects of molar ratio of silica to titanium (R) and pH value on morphology, size and crystal structure of Si–F–TiO2 samples. We find that the band gap of the catalyst can be engineered from 3.16 to 2.88 eV via altering the molar ratio of Si : Ti and the pH value. Compared with un-doped or F-doped TiO2, co-doped Si–F–TiO2 samples exhibited improved photocatalytic degradation toward different dye molecules under both ultraviolet and visible light illumination. With the aid of hole and radical trapping experiments, we proposed a photocatalytic mechanism for the examined systems. Furthermore, first-principle calculations provide theoretical insights for the enhanced photocatalytic performance of codoped Si–F–TiO2 photocatalyst.

Hydrothermal synthesis and tribological properties of FeS 2 (pyrite)/reduced graphene oxide heterojunction

An FeS2 (pyrite)/reduced graphene oxide (FeS2/RGO) heterojunction was synthesized by a facile and effective hydrothermal method. X-ray diffraction proved the high purity of the as-prepared product, and both scanning electron microscopy and transmission electron microscopy showed that FeS2 particles were well distributed on RGO nanosheets with controlled size and morphology. The performance of the FeS2/RGO composites as lubricating oil additive were investigated on a ball-plate tribotester. The results indicated that FeS2/RGO could improve the load-carrying capacity dramatically, as well as the friction-reduction and anti-wear properties of the paraffin oil. In addition, higher GO content is beneficial to improve the lubrication properties of FeS2/RGO composites. The excellent lubrication performance of FeS2/RGO composites can be attributed to the unique layered structure of FeS2 and RGO.

Core–shell structured AgBr incorporated g-C3N4 nanocomposites with enhanced photocatalytic activity and stability

Abstract Visible-light-driven core–shell structured AgBr/g-C3N4 heterogeneous photocatalyst have been synthesised by a sonication-assisted deposition-precipitation route at room temperature, and characterised by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscope, UV–visible diffuse reflectance spectroscopy and N2 adsorption–desorption analysis. Subsequently, the photocatalytic activity of AgBr/g-C3N4 is evaluated by the degradation of typical Rhodamine B (RhB), methyl blue (MB) and methyl orange (MO) dyes under visible-light irradiation (>420 nm). The as-prepared AgBr/g-C3N4 core–shell photocatalyst show higher photocatalytic activity than the pure g-C3N4 and AgBr nanoparticles, which is ascribed to synergistic effects at the interface of AgBr and g-C3N4 . Moreover, superior stability was also observed by recycling experiments indicating that core–shell structured AgBr/g-C3N4 was highly desirable for the remediation of organic contaminated wastewaters. In addition, the possible photocatalytic mechanism of AgBr/g-C3N4 composite with enhanced heterogeneous photocatalytic activity is also proposed in detail.

In situ ion exchange synthesis of stable AgBr/Ag3PO4 dumbbell-like heterojunction photocatalysts with enhanced visible light photocatalytic degradation

Abstract Novel dumb-bell-like AgBr/Ag3PO4 heterostructured photocatalyst was developed by a simple and efficient in situ ion exchange method in dimethyl sulfoxide (DMSO)/water mixed solvent systems at room temperature, and characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and UV–vis diffuse reflectance spectrometry. Subsequently, the photocatalytic experiment for this heterojunction was conducted under visible light irradiation using typical organic dyes including Rhodamine B, methyl blue and methyl orange dyes as targeted pollutant, which indicate AgBr/Ag3PO4 exhibited higher photocatalytic activity compared with pure AgBr or Ag3PO4, and the highest photocatalytic activity was reached by AgBr/Ag3PO4 hybrid photocatalyst with 20 w% of AgBr. Moreover, Superior stability was also observed by recycling experiments indicating that heterostructured AgBr/Ag3PO4 is highly desirable for the remediation of organic waste-contaminated wastewaters. In addition, the possible photocatalytic mechanisms of AgBr/Ag3PO4 heterojunction and degradation pathways on basis of the experimental results are also proposed in detail.

Surfactant-Assisted Solvothermal Synthesis and High Visible-Light-Induced Photocatalytic Activity of BiOBr Nanocomposite Photocatalyst

BiOCl/BiOBr composite microspheres were synthesized through a one-pot mixed surfactant-assisted solvothermal process. The morphology, crystal structure, surface area and photocatalytic activity of the as-prepared BiOCl/BiOBr composite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-visible diffuse reflectance spectroscopy. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. The BiOCl/BiOBr composite exhibited much higher photocurrent intensity than pure BiOBr, BiOCl and other different components, which perfectly coincided with the enhanced photocatalytic activity for the degradation of RhB under visible light (λ=554nm). Moreover, this novel and facile strategy to fabricate bismuth halide-based composite with high efficiency were widely used in other bismuth-based composite photocatalyst for removing organic contaminants in wastewater.