Caimei Fan

Nitrogen-doped carbon quantum dots/Ag3PO4 complex photocatalysts with enhanced visible light driven photocatalytic activity and stability

Novel nitrogen-doped carbon quantum dots/Ag3PO4 (NCQDs/Ag3PO4) complex photocatalysts were synthesized by a facile precipitation method at room temperature. The physical and chemical properties of Ag3PO4 and NCQDs/Ag3PO4 photocatalysts were detected through X-ray powder diffraction, field emission scanning electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and electron spin resonance techniques. The as-prepared 3-NCQDs/Ag3PO4 composite exhibited much higher activity than the pure Ag3PO4 for eliminating methyl orange and bisphenol A solution under visible light (λ>420nm). Moreover, in the cyclic experiments, the 3-NCQDs/Ag3PO4 exhibited an excellent stability for the decolorization of methyl orange at some level. This suggested that NCQDs played an important role in the process of degradation. The function of NCQDs was discussed and a new mechanism was put forward for the degradation of methyl orange. The high activities and stability were attributed to the transfer of photogenerated charges through the vector of Ag3PO4→NCQDs→Ag in the photocatalytic process, leading to effective charge separation of Ag3PO4.

Controllable synthesis of phosphate-modified BiPO4 nanorods with high photocatalytic activity: surface hydroxyl groups concentrations effects

Surface properties of photocatalysts are crucial to improve their efficiency in the removal of wastewater pollutants. In this study, phosphate-modified BiPO4 photocatalysts with different PO43−/Bi molar ratios were controllably synthesized through a one-pot hydrothermal method. The concentrations of surface hydroxyl groups on BiPO4 samples can be tuned by adjusting the PO43−/Bi3+ molar ratios. XRD results showed that surface modification by phosphate could boost the crystallinity of BiPO4, which was beneficial to photocatalytic performance. XPS and IR spectra revealed that PO43− modified only the surface of BiPO4. The optical absorption of phosphate-modified BiPO4 samples showed an obvious blue shift compared with that of bare BiPO4. Photocatalytic activities of the as-prepared samples were evaluated by the decomposition of methylene orange (MO) under ultraviolet light and simulated solar-light irradiation. Experimental results demonstrated that the photocatalytic performance of the modified samples significantly improved after the BiPO4 surface was modified by different amounts of PO43−. Both an indirect scavenger method and an electron spin resonance method were adopted to determine the production and intensity of free radicals during photocatalytic degradation. Results suggested that MO was removed predominantly through oxidation by OH radicals, as confirmed by theoretical calculations. Moreover, the mechanism of photocatalytic degradation of MO over the as-prepared phosphate-modified BiPO4 was proposed.

Synthesis and evaluation of activated carbon spheres with copper modification for gaseous elemental mercury removal

Millimeter resin-based activated carbon spheres were introduced for the removal of elemental mercury, and some metallic oxides were doped to activated carbon spheres to enhance the Hg0 removal ability. The experimental results indicated that prepared activated carbon spheres (PAC) and PAC-Cu presented almost identical with a smooth surface without cracks and show well-developed pore structure with high surface area. The Hg0 removal performance of PAC was higher than that of commercial activated carbon spheres (SAC) due to the more active groups, and PAC-Cu showed the highest Hg0 removal ability among doped metallic oxides. Besides, the doped Cu can enhance the redox ability of PAC and be beneficial to activate the active component of PAC, which can promote observably the Hg0 removal performance. Meanwhile, PAC-Cu has an ability of sulfur resistance. Furthermore, the mercury combination property and XPS analysis results of the fresh and used PAC-Cu indicates that the possible removal mechanism of PAC-Cu is the synergism of Hg0 oxidation by active species of C=O or C–O and the doped Cu catalysis activation.

HCl post-processing BiOBr photocatalyst: structure, morphology, and composition and their impacts to activity

This work reports a systematic investigation on the structure, morphology, and composition, and their impacts on photocatalytic performance, for a HCl post-processing BiOBr photocatalyst. We dispersed BiOBr powders into different concentration HCl aqueous solutions to synthesize a series of samples at room temperature. With the HCl concentration increasing, SEM images revealed that as-prepared flower-like BiOBr microspheres transformed gradually into the interweaved nanosheets, and ultimately, obtaining the stacked nanosheet structures. The XRD, EDX, BET, UV-vis DRS and photocurrent data demonstrated that HCl post-processing had in-deep effects on the element composition, specific surface area, optical property and photoelectrochemical properties of samples. Moreover, the detailed formation mechanism and good correlations among their structure, composition, morphology, and enhanced activity have been established by degrading methyl orange (MO) dye molecules under simulated solar light. The HCl post-processing BiOBr samples exhibited better photocatalytic activity and stability than the pure BiOBr sample. Results indicate that there is particular emphasis placed on the roles of H+ and Cl− ions in the micro- and macro-performance improvements of BiOBr photocatalysts. Our findings should provide important knowledge for further understanding the roles of H+ and Cl− ions in such ‘like-BiOX’ layered-structure systems.