Yingna Guo

Fabrication of Z-scheme plasmonic photocatalyst Ag@AgBr/g-C3N4 with enhanced visible-light photocatalytic activity

A series of Ag@AgBr grafted graphitic carbon nitride (Ag@AgBr/g-C3N4) plasmonic photocatalysts are fabricated through photoreducing AgBr/g-C3N4 hybrids prepared by deposition-precipitation method. The phase and chemical structures, electronic and optical properties as well as morphologies of Ag@AgBr/g-C3N4 heterostructures are well-characterized. Subsequently, the photocatalytic activity of Ag@AgBr/g-C3N4 is evaluated by the degradation of methyl orange (MO) and rhodamin B (RB) under visible-light irradiation. The enhanced photocatalytic activity of Ag@AgBr/g-C3N4 compared with g-C3N4 and Ag@AgBr is obtained and explained in terms of the efficient visible-light utilization efficiency as well as the construction of Z-scheme, which keeps photogenerated electrons and holes with high reduction and oxidation capability, evidenced by photoelectrochemical tests and free radical and hole scavenging experiments. Based on the intermediates identified in the reaction system, the photocatalytic degradation pathway of MO is put forward.

Mixed phase titania nanocomposite codoped with metallic silver and vanadium oxide: New efficient photocatalyst for dye degradation

Titania nanocomposite codoped with metallic silver and vanadium oxide was prepared by a one-step sol-gel-solvothermal method in the presence of a triblock copolymer surfactant (P123). The resulting Ag/V-TiO(2) three-component junction system exhibited an anatase/rutile (weight ratio of 73.8:26.2) mixed phase structure, narrower band gap (2.25 eV), and extremely small particle sizes (ca. 12 nm) with metallic Ag particles well distributed on the surface of the composite. The Ag/V-TiO(2) nanocomposite was used as the visible- and UV-light-driven photocatalyst to degrade dyes rhodamine B (RB) and coomassie brilliant blue G-250 (CBB) in an aqueous solution. At 1.8% Ag and 4.9% V doping, the Ag/V-TiO(2) system exhibited the highest visible- as well as UV-light photocatalytic activity; additionally, the activity of the three-component system exceeded that of Degussa P25, pure TiO(2), single-doped TiO(2) system (Ag/TiO(2) or V-TiO(2)) as well as P123-free-Ag/V-TiO(2) codoped system. The reasons for this enhanced photocatalytic activity were revealed.

Preparation and enhanced visible-light photocatalytic activity of graphitic carbon nitride/bismuth niobate heterojunctions

A series of graphitic carbon nitride/bismuth niobate (g-C3N4/Bi5Nb3O15) heterojunctions with g-C3N4 doping level of 10-90 wt% were prepared by a facile milling-heat treatment method. The phase and chemical structures, surface compositions, electronic and optical properties as well as morphologies of the prepared g-C3N4/Bi5Nb3O15 were well-characterized. Subsequently, the photocatalytic activity and stability of g-C3N4/Bi5Nb3O15 were evaluated by the degradation of aqueous methyl orange (MO) and 4-chlorophenol (4-CP) under the visible-light irradiation. At suitable g-C3N4 doping levels, g-C3N4/Bi5Nb3O15 exhibited enhanced visible-light photocatalytic activity compared with pure g-C3N4 or Bi5Nb3O15. This excellent photocatalytic activity was revealed in terms of the extension of visible-light response and efficient separation and transportation of the photogenerated electrons and holes due to coupling of g-C3N4 and Bi5Nb3O15. Additionally, the active species yielded in the pure g-C3N4- and g-C3N4/Bi5Nb3O15-catalyzed 4-CP photodegradation systems were investigated by the free radical and hole scavenging experiments.

Efficient degradation of tetrabromobisphenol A by heterostructured Ag/Bi5Nb3O15 material under the simulated sunlight irradiation.

Heterostructured metallic silver-layered bismuth niobate two-component system (Ag/Bi(5)Nb(3)O(15)) was developed for the first time by a mild hydrothermal method combined with photodeposition. The Ag/Bi(5)Nb(3)O(15) exhibited single-crystalline orthorhombic structure with small particle size (50-200 nm) and octahedral as well as sheet-like shape; additionally, it possessed photoresponse in both UV and visible region. As a novel alternative photocatalysts to TiO(2), the photocatalytic activity of the Ag/Bi(5)Nb(3)O(15) was evaluated by the degradation of tetrabromobisphenol A, a member from the family of the brominated flame retardant, under solar simulating Xe lamp irradiation, and enhanced photocatalytic activity in compared to Bi(5)Nb(3)O(15) itself and Degussa P25 was obtained.

Transesterification of soybean oil to biodiesel catalyzed by mesostructured Ta2O5-based hybrid catalysts functionalized by both alkyl-bridged organosilica moieties and Keggin-type heteropoly acid

A series of Ta2O5-based hybrid catalysts functionalized by both alkyl-bridged organosilica fragments and the Keggin-type heteropoly acid, Ta2O5/Si(R)Si-H3PW12O40 (R = –CH2CH2- or –C6H4–), were prepared via a one-pot co-condensation method in the presence of a triblock copolymer surfactant (P123). The materials were well characterized by spectroscopy methods, X-ray diffraction analysis, transmission electron microscopy, and nitrogen physisorption measurement to confirm the structural integrity of the Keggin unit and alkyl-bridged organosilica units in the hybrid materials, to investigate the interaction between the Ta2O5 matrix and the organic or inorganic functionalities, and to test the mesostructure, morphology, and porosity of the materials. The materials were subsequently utilized as environmentally-friendly solid acid catalysts in the transesterification of soybean oil (containing 20 wt% myristic acid) with methanol to produce fatty acid methyl esters under atmosphere refluxing. Compared with bulk H3PW12O40 and alkyl-free H3PW12O40/Ta2O5, as-prepared Ta2O5/Si(R)Si-H3PW12O40 hybrid materials with suitable concentrations of bridging alkyl groups exhibited higher reactivity toward the target reaction. This enhanced acid-catalytic reactivity after the introduction of both acidic and hydrophobic functionalities within the Ta2O5 matrix is discussed. Finally, the reusability of the hybrid materials was evaluated through three catalytic runs.

Simulated sunlight photodegradation of aqueous phthalate esters catalyzed by the polyoxotungstate/titania nanocomposite

A series of porous polyoxotungstate/titania nanocomposites (PW(12)/TiO(2)) with particle size lower than 10nm and BET surface area of ca. 200 m(2)g(-1) was prepared by sol-gel chemistry combined with solvothermal treatment. The composites were successfully applied to the degradation of aqueous phthalate esters (PAEs) including di-n-butyl phthalate (DBP), diethyl phthalate (DEP), and dimethyl phthalate (DMP) under the simulated sunlight irradiation (lambda=320-680 nm) for the first time, and the conversion of DBP, DEP, and DMP reached to 98%, 84%, and 80%, respectively, after the simulated sunlight irradiation the suspension including PAE (5 mg L(-1), 100 mL) and PW(12)/TiO(2)-19.8 (100 mg) for 90 min. In addition, nearly total mineralization of DBP and DEP was realized by further increasing light irradiation time to 12h. Based on the intermediates identified in the reaction system, the photocatalytic degradation pathway of PAEs was put forward.

Visible light-driven degradation of tetrabromobisphenol A over heterostructured Ag/Bi5Nb3O15 materials

A mild wet chemical synthesis route, hydrothermal treatment–photodeposition, was developed to obtain a series of heterostructured metallic silver/bismuth niobate (Ag/Bi5Nb3O15) hybrid materials with a single-crystalline orthorhombic layered structure and photoresponse in both the UV and visible light region. As a novel alternative photocatalyst to TiO2, the photocatalytic activity of as-prepared Ag/Bi5Nb3O15 was evaluated by the degradation of an aqueous tetrabromobisphenol A (TBBPA, a member of thebrominated flame retardant family) under visible light irradiation (400 nm < λ < 680 nm and 420 nm < λ < 680 nm). Additionally, the influence of initial pH in the reaction system on TBBPA degradation was investigated. The excellent photocatalytic activity of the Ag/Bi5Nb3O15 materials was explained, and the degradation pathway of an aqueous TBBPA catalyzed by the Ag/Bi5Nb3O15 under the visible light irradiation was proposed.

Template-free and morphology-controlled hydrothermal growth of single-crystalline Bi12TiO20 with excellent simulated sunlight photocatalytic activity

Single-crystalline bismuth titanates (Bi12TiO20) with the cubic phase and various morphologies (flower-, belt-, tetrahedral-like) were controllably fabricated by using a mild template-free hydrothermal process. The samples were fully characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM, nitrogen porosimetry measurement, UV-vis diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). The influence of the solvent and the concentration of NO3− in the reaction system on the crystallinity and morphology of the Bi12TiO20 samples was investigated in detail. Bi12TiO20 crystals were used as the sunlight-driven photocatalysts to degrade aqueous dye methyl orange (MO) and p-nitrophenol (PNP), and the influence of Bi12TiO20 morphology on the photocatalytic activity was discussed. Finally, the recyclability of Bi12TiO20 was evaluated through three consecutive runs.

Morphology-controlled preparation and enhanced simulated sunlight and visible-light photocatalytic activity of Pt/Bi5Nb3O15 heterostructures

Plate- and octahedron-like Pt/Bi5Nb3O15 heterostructures are controllably prepared by a hydrothermal treatment method combined with photodeposition in the presence of different surfactants, i.e., cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP). The composition, structure, morphology, optical absorption properties, and textural properties of as-prepared Pt/Bi5Nb3O15 are well-characterized, and their simulated sunlight and visible-light photocatalytic activity is evaluated by the degradation of two typical organic pollutants, i.e., methyl orange (MO) and p-nitrophenol (PNP). Special attention is paid to investigate and explain the influence of the morphologies on the photocatalytic activity of the heterostructured Pt/Bi5Nb3O15.