Cu(OH)<Subscript>2</Subscript> Nanostructures for Dynamic Photodegradation of Methyl Orange under Visible Light

new material of Cu(OH)₂ nanostructures was prepared using cupric nitrate and sodium hydroxide as raw materials by the chemical precipitation method. The Cu(OH)₂ nanostructures were characterized by scanning electron microscope, transmission electron microscopy, infrared spectrometer, and X-ray diffractometer. The results showed that the Cu(OH)₂ nanostructures exhibited excellent uniform and dispersion at 40°C. A series of factors was investigated to effect the photocatalytic efficiency of methyl orange (MO), such as the concentration of Cu(OH)₂ nanostructures, the reaction time of the Cu(OH)₂ nanostructures, the initial concentration of MO, and so on. As a result, the Cu(OH)₂ nanostructures exhibited excellent photocatalytic efficiency with the concentration of 20 mg L^–1 Cu(OH)₂ nanostructures, the initial concentration of MO was 15 mg L^–1 and the stirring time was 70 min.     

Enhancement of visible-light photocatalytic activity of Cu-doped TiO<Subscript>2</Subscript> nanoparticles

Bare TiO₂ and Cu-doped TiO₂ nanoparticles with different nominal doping amounts of Cu ranging from of 0.5 to 5.0 mol% were synthesized using the modified sol–gel method. The samples were physically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller-specific surface area, UV–Vis diffuse reflectance spectroscopy, zeta potential, X-ray photoelectron spectroscopy, inductively coupled plasma, and photoluminescence techniques. The Cu-doped TiO₂ exhibited good photocatalytic activity in mineralization of oxalic acid and formic acid under visible light irradiation. Photomineralization of oxalic and formic acids under visible light irradiation revealed greatly enhanced photoactivity exhibited by the 2.0 mol% Cu-doped TiO₂ photocatalyst compared to bare TiO₂ . The enhanced photocatalytic performance arises from copper ion doping in the TiO₂ structure, leading to an extended photoresponsive range, enhanced photogenerated charge separation, and transportation efficiency.     

Chitosan-modified TiO<Subscript>2</Subscript> as photocatalyst for ethanol reforming under visible light

This work reports the reforming of bio-ethanol on chitosan–TiO₂ hybrid photocatalysts at ambient temperature. The influence of chitosan composition on the photocatalytic performance of chitosan–TiO₂ hybrid was studied. The hybrids were characterized by CHN elemental analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the preparation variables used for the incorporation of chitosan on TiO₂ promoted changes in the morphology, superficial area, crystal size and porosity of the photocatalyst, affecting the band gap of this semiconductor and consequently the reactivity of the chitosan–TiO₂ hybrids. The catalysts were evaluated for hydrogen production from ethanol under visible light. It was demonstrated that the calcination temperature of 623 K and a chitosan content of 20% were the most appropriate preparation conditions and the resulting product displays a pore size of 1.9 nm, crystal size of 11.3 nm, BET area of 178 m² g^?1 and band gap of 2.92 eV. The calcination temperature of 623 K and incorporation of 20% of chitosan obtained the same results in the conversion rate of hydrogen in comparison to the pure TiO₂ P25.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

Preparation of ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles by mechanical alloying and annealing for sensitizing C-modified TiO<Subscript>2</Subscript> and acquirement of efficient photocatalyst

ZnFe₂O₄ nanoparticles sensitized by C-modified TiO₂ hybrids (ZnFe₂O₄–TiO₂/C) were successfully prepared by a feasible method. The ZnFe₂O₄ nanoparticles were prepared by mechanical alloying and annealing. The residual organic compounds in the synthetic process of TiO₂ were selected as the carbon source. The as-prepared composites were characterized by X-ray diffraction, Raman spectroscopy, X-ray fluorescence, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible light diffuse reflectance spectroscopy (UV–Vis) and N₂ adsorption–desorption analysis. The photocatalytic activity of the photocatalysts was measured by degradation of methyl orange under ultraviolet (UV) light and simulated solar irradiation, respectively. The results show that the carbon did not enter the TiO₂ lattice but adhered to the surface of TiO₂. The photocatalytic activity of the as-prepared C-modified TiO₂ (TiO₂/C) improved both under UV and simulated solar light irradiation, but the improvement was not dramatic. Introduction of ZnFe₂O₄ into the TiO₂/C could enhance the absorption spectrum range. The ZnFe₂O₄–TiO₂/C hybrids exhibited a higher photocatalytic activity both than that of the pure TiO₂ and TiO₂/C under either UV or simulated solar light irradiation. The complex synergistic effect plays an important role in improving the photocatalytic performance of ZnFe₂O₄–TiO₂/C composites. The optimum photocatalytic performance was obtained from the ZnFe₂O₄(0.8 wt%)–TiO₂/C sample.     

Solvothermal preparation of copper(II) porphyrin-sensitized mesoporous TiO<Subscript>2</Subscript> composites: enhanced photocatalytic activity and stability in degradation of 4-nitrophenol

Four new copper(II) porphyrins CuPp(1, 2, 3, 4) with a different number of peripheral ester groups were synthesized and used to sensitize the mesoporous TiO₂ under solvothermal condition, and accordingly, four mesoporous CuPp(1, 2, 3, 4)/TiO₂ composites were obtained. These composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, BET nitrogen adsorption–desorption isotherms (BET), UV–vis diffuse reflectance spectroscopy (UV–vis-DRS), and Fourier-transform infrared spectroscopy (FT-IR). The results showed the crystal structure and morphology of mesoporous TiO₂ were not affected by the porphyrin existence on its surface. The photocatalysis properties of mesoporous TiO₂ and CuPp(1, 2, 3, 4)/TiO₂ have been evaluated by conducting the photocatalytic degradation of 4-nitrophenol (4-NP) under visible-light irradiation, and the result showed their higher photocatalytic activities and the order is: CuPp(4)/TiO₂ > CuPp(3)/TiO₂ > CuPp(2)/TiO₂ > CuPp(1)/TiO₂ ? TiO₂. The probable reasons are their large surface area and different number of peripheral groups in CuPp, which separate electron–hole pairs efficiently. The repetition test of CuPp(1, 2, 3, 4)/TiO₂ composites demonstrated that they still maintained superior photocatalytic activity over six recycles.     

Synthesis,Characterization and Photocatalytic Application of TiO<Subscript>2</Subscript>/SnO<Subscript>2</Subscript> Nanocomposite Obtained Under Non-thermal Plasma Condition at Atmospheric Pressure

A plasma-assisted synthesis of TiO₂/SnO₂ nanocomposite is described. In this approach, a precursor containing a mixture of [TiCl₃ and SnCl₂] exposed to electric discharge was oxidized by plasma-generated reactive species (HO^·/H₂O = 2.85 eV/SHE). SnO₂ microstructures with a diameter of 10–40 µm were coated by thin layers TiO₂ nanorods with mean diameter of 6–8 nm. The obtained TiO₂/SnO₂ nanocomposite was characterized by transmission and scanning electron microscopy, X-ray diffraction and Fourier transform infrared. TiO₂/SnO₂ nanocomposite was found to be a promising new material for the photocatalytic discoloration of aqueous Remazol Brilliant Blue-R dye under daylight and UVA light sources, due to the combined effects of large specific surface area and heterojunction which efficiently separates the electron–hole pairs delaying the charge recombination. The leaching test indicated that the nanocomposite is stable easily reusable.     

Electrodeposition of CuGaSe<Subscript>2</Subscript> and CuGaS<Subscript>2</Subscript> thin films for photovoltaic applications

CuGaSe₂ and CuGaS₂ polycrystalline thin film absorbers were prepared by one-step electrodeposition from an aqueous electrolyte containing CuCl₂, GaCl₃ and H₂SeO₃. The pH of the solution was adjusted to 2.3 by adding HCl and KOH. Annealing improved crystallinity of CuGaSe₂ and further annealing in sulphur atmosphere was required to obtain CuGaS₂ layers. The morphology, topography, chemical composition and crystal structure of the deposited thin films were analysed by scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy and X-ray diffraction, respectively. X-Ray diffraction showed that the as-deposited CuGaSe₂ film exhibited poor crystallinity, but which improved dramatically when the layers were annealed in forming gas atmosphere for 40 min. Subsequent sulphurization of CuGaSe₂ films was performed at 400 °C for 10 min in presence of molecular sulphur and under forming gas atmosphere. The effect of sulphurization was the conversion of CuGaSe₂ into CuGaS₂. The formation of CuGaS₂ thin films was evidenced by the shift observed in the X-ray diffraction pattern and by the blue shift of the optical bandgap. The bandgap of CuGaSe₂ was found to be 1.66 eV, while for CuGaS₂ it raised up to 2.2 eV. A broad intermediate absorption band associated to Cr and centred at 1.63 eV was observed in Cr-doped CuGaS₂ films.     

Hierarchically nanostructured porous TiO<Subscript>2</Subscript>(B) with superior photocatalytic CO<Subscript>2</Subscript> reduction activity

Hierarchically nanostructured, porous TiO₂(B) microspheres were synthesized by a microwave-assisted solvothermal method combined with subsequent heat treatment in air. The materials were carefully characterized by scanning and transmission electron microscopy, X-ray diffraction, CO₂ adsorption, and a range of spectroscopies, including Raman, infrared, X-ray photoelectron and UV-Vis spectroscopy. The hierarchical TiO₂(B) particles are constructed by ultrathin nanosheets and possess large specific surface area, which provided many active sites for CO₂ adsorption as well as CO₂ conversion. The TiO₂(B) nanostructures exhibited marked photocatalytic activity for CO₂ reduction to methane and methanol. Anatase TiO₂ and P₂5 were used as the reference photocatalysts. Transient photocurrent measurement also proved the higher photoactivity of TiO₂(B) than that of anatase TiO₂. In-situ infrared spectrum was measured to identify the intermediates and deduce the conversion process of CO₂ under illumination over TiO₂(B) photocatalyst.     

Synthesis and Characterization of CdS Nanoparticles via Cyclic Microwave from Cadmium Oxalate

The present study reports synthesis and characterization of CdS nanoparticles prepared by cyclic microwave route with the use of [Cd(C₂O₄)·3H₂O] powder as a precursor. The products, with an average size ~15 nm, were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, thermogravimetric analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. Optical property of obtained product was investigated by photoluminescence spectroscopy. The prepared nanostructures displayed a very strong luminescence at 528 nm (2.34 eV) at room temperature.     

Freeze-drying synthesis and characterisation of Na composites of ZnO,TiO<Subscript>2</Subscript> and ZnTiO<Subscript>3</Subscript> semiconductor oxides

The freeze-drying method of metal oxides synthesis has a number of advantages such as high homogeneity, varying porous structures, morphologies and uniform particle size distribution, etc. Because of these advantages, the binary metal oxides ZnO, TiO₂ and ternary metal oxide ZnTiO₃ were synthesised by the freeze-drying method. The synthesised materials were characterised by X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FT-IR), UV-VIS spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The as-synthesised metal oxides were calcined at different temperatures to study the phase evolution and morphological changes. The crystalline cubic-phase ZnTiO₃ (a = 8.3948 Å) was obtained on calcination of the precursor at 600°C, and decomposed to the cubic phase Zn₂TiO₄ (a = 8.4580 Å) and rutile TiO₂ (a = 4.5955 Å and c = 2.9593 Å) at 1000°C. The band gap of ZnO (3.28?3.10 eV), TiO₂ (3.37?2.97 eV) and ZnTiO₃ (3.92?3.80 eV) calculated using Tauc’s relation was found to vary inversely with calcination temperature and phase transition.     

Imprinted Azorubine electrochemical sensor based upon composition of MnO<Subscript>2</Subscript> and 1-naphthylamine on graphite nanopowder

A new sensitive and selective molecularly imprinted electrochemical sensor was developed for Azorubine determination. This sensor was based on molecularly imprinted polymer composed of poly(1-naphthylamine), triphenylamine (as cross-linkers) and dispersed MnO₂ nanorod particles on graphite nanopowders. The structure of the prepared nanocomposite was characterized by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. Calibration curve of the imprinted sensor was linear in the concentration range 1–12 mg L^??1 with a detection limit of 0.57 mg L^??1. The application of the sensor was checked by the determination of Azorubine in a water sample.     

Chemical synthesis of Ni/TiO<Subscript>2</Subscript> nanophotocatalyst for UV/visible light assisted degradation of organic dye in aqueous solution

The Ni/TiO₂ nanoparticles with different Ni dopant content were prepared by a modified sol–gel method. The structure and photoinduced charge properties of the as-prepared catalysts were determined using X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy techniques, and the photocatalytic efficiency of these catalysts was tested using an organic dye. It was shown that Ni modification could greatly enhance the photocatalytic efficiency of these nanocomposite catalysts by taking the photodegradation of methyl orange as a model reaction. With appropriate ratio of Ni and TiO₂, Ni/TiO₂ nanocomposites showed the superior photocatalytic activity than the single TiO₂ nanoparticles. Surface photovoltage spectra demonstrated that Ni modification could effectively inhibit the recombination of the photoinduced electron and holes of TiO₂. This electron–hole pair separation conditions are responsible for the higher photocatalytic performance of Ni/TiO₂ nanocomposites in the visible region of electromagnetic spectrum.     

A Novel NiWS-TiO<Subscript>2</Subscript>(w) Catalyst Using NiWO<Subscript>4</Subscript> Nanoparticles as Precursor with Enhanced Hydrodesulfurization Activity

In this work, NiWO₄ nanoparticles were prepared by a novel simple method and loading on the mesoporous TiO₂ whiskers (TiO₂(w)) carrier as the precursor of NiWS. In addition, the NiWS-TiO₂(w) catalysts showing high hydrodesulfurization (HDS) activity is described. The structure and chemical composition of the as-prepared samples were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, NH₃-temperature programmed desorption and transmission electron microscopy, respectively. Results indicate that smaller crystallite size and better dispersion of active NiWO₄ particles could be achieved by using TiO₂(w) as the support to disperse NiWO₄ nanoparticles. TiO₂(w) can also decrease the reduction temperature of Ni–W metal oxide and promote a highly sulfidation degree of Ni and W active sites. The obtained NiWS-TiO₂(w) catalysts show much higher dibenzothiop HDS activity than the unsupported NiWS catalyst, and the sulphur content of desulfurated oil can reach 20 ppm at the mild condition of 260 °C and 2 Mpa.     

A Simple Thermal Decomposition Method for Synthesis of ZrO<Subscript>2</Subscript>/GrO Nanolayer

This paper reports on a novel processing route for producing ZrO₂/GrO nanocomposites by solid-state thermal decomposition of zirconium acetate nanostructures and graphene as starting reagents, powders were carried out in the temperature 200 °C for 2 h. In addition, nanocomposites of ZrO₂/GrO were obtained by solid-state thermal decomposition of the as-synthesized graphene oxide and Zr(CH₃COO)₂·4H₂O. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, atomic force microscope, photoluminescence spectroscopy and Thermogravimetric analysis. The sublimation process of the Zr(OAc)₂ and GrO powder were carried out within the range of 210, 220 and 230 °C. The XRD studies indicated the production of pure ZrO₂/GrO nanocomposites after thermal decomposition.     

Hydrothermal synthesis,characterization, and photocatalytic performance of W-doped MoO<Subscript>3</Subscript> nanobelts

Orthorhombic MoO₃ and W-doped MoO₃ nanobelts were successfully synthesized by a hydrothermal method. The effect of W dopant on the photocatalytic performance of W-doped MoO₃ nanobelts was studied. The phase, morphology, and oxidation state of the products were characterized by X-ray diffraction analysis, Fourier-transform infrared and Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. In this research, MoO₃ and W-doped MoO₃ exhibited the same phase and morphology of orthorhombic nanobelts with growth along the [001] direction, including detection of Mo⁶⁺, O^2?, and W⁶⁺ in the 3 mol% W-doped MoO₃ sample. The photocatalytic performance of the as-synthesized MoO₃ and W-doped MoO₃ nanobelts was monitored through photodegradation of methylene blue (MB) under visible radiation. W-doped MoO₃ nanobelts showed better photocatalytic performance than pure MoO₃. The 3 mol% W-doped MoO₃ photocatalyst exhibited very good visible-light-driven activity for photodegradation of MB, as high as 99 % within 60 min.     

Visible-light-driven photocatalysis of heterostructure Ag/Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> nanocomposites and their photocatalytic degradation of dye under visible light irradiation

Ag/Bi₂WO₆ nanocomposites were successfully synthesized by a combination of hydrothermal method and ultrasonic vibration. The phases, vibration modes, constituents and morphologies were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The visible-light-driven photocatalytic activitiy of 0–10 wt% Ag/Bi₂WO₆ samples was studied by determining the photodegradation of rhodamine B under xenon lamp. In this research, 10 wt% Ag/Bi₂WO₆ nanocomposites exhibit the highest efficiency and have the promising photocatalytic properties for waste water treatment.     

Synthesis of TiO<Subscript>2</Subscript> nanotubes using different alkaline media and their applications in photocatalysis and DSSCs

TiO₂ nanotubes (TNTs) were successfully synthesized from different alkaline media (i.e., NaOH and KOH) by using a microwave hydrothermal process. The effects of different alkaline media on the formation of TiO₂ nanotubes and their physicochemical properties were investigated. The phases of different TiO₂ nanostructures were studied by using X-ray diffraction patterns. Morphologies of the nanostructures were observed with a transmission electron microscope. The optical properties of the nanostructures were evaluated through the absorption behavior using UV–Vis diffuse reflectance spectroscopy. The photocatalytic activities of the TiO₂ nanostructures were evaluated by the degradation of methylene blue aqueous dye solution under the simulated solar light irradiation. Similarly, the photovoltaic efficiencies of the prepared samples were investigated by making photo-anode layers in the Dye Sensitized Solar Cells (DSSCs). The results revealed that in comparison to the single layered TiO₂ nanostructures in the DSSC, creation of a double layer structure significantly enhanced the efficiency of DSSC.     

Plasma-Assisted Synthesis of TiO2 Nanorods by Gliding Arc Discharge Processing at Atmospheric Pressure for Photocatalytic Applications

The present study explores a new method of synthesis of TiO₂ nano-particles in an aqueous medium from TiCl₃ precursor by non-thermal plasma in humid air as feeding gas obtained at atmospheric pressure. The precursor solution, TiCl₃ is oxidized by strongly reactive species generated by gliding arc plasma (HO^· = 2.85 V/SHE) to produce titanium oxide powders. The synthesized powder was characterised by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, FTIR spectroscopy, nitrogen physisorption, and UV–Vis spectroscopy. The results obtained showed that the material consists of rod-shaped nanoparticles of rutile and anatase phases. The presence of TiO₂ phases was confirmed by FTIR spectrum and textural analyses showed that the material is mesoporous with specific surface area of 158 m² g^?1. UV–Visible spectrum of the plasma-synthesized TiO₂ sample showed that it absorbs in the UV–A region leading to effective use as a photocatalyst under visible light.     

Nanosized TiO<Subscript>2</Subscript> particles decorated on SiO<Subscript>2</Subscript> spheres (TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>): synthesis and photocatalytic activities

Nanosized TiO₂ and nano-anatase TiO₂ decorated on SiO₂ spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO₂ nano particle and TiO₂ grafted on SiO₂ sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy (TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated using methylene blue as a model pollutant. The synthesized TiO₂/SiO₂ particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO₂ particles.