Immobilization of TiO2 nanoparticles on Fe-filled carbon nanocapsules for photocatalytic applications

Using a simple sol-gel method, a novel magnetic photocatalyst was produced by immobilization of TiO₂ nano-crystal on Fe-filled carbon nanocapsules (Fe-CNC). High resolution TEM images indicated that the immobilization of TiO₂ on Fe-CNC was driven primarily by heterogeneous coagulation, whereas surface nucleation and growth was the dominant mechanism for immobilizing TiO₂ on acid-functionalized hollow CNC. The TiO₂ immobilized on Fe-CNC exhibited the anatase phase as revealed by the X-ray diffraction (XRD) patterns. In comparison with free TiO₂ and TiO₂-coated CNC, TiO₂-coated Fe-CNC displayed good performance in the removal of NO gas under UV exposure. Due to the advantages of easy recycling and good photocatalytic efficiency, the novel magnetic photocatalyst developed here has potential use in photocatalytic applications for pollution prevention.     

Low temperature synthesis of crystalline mesoporous titania with high photocatalytic activity by post-treatment in nitric acid ethanol solution

Mesoporous titania powder with a bicrystalline (anatase and brookite) framework was prepared by modified sol-gel method using dodecylamine as template. The template could be easily removed by refluxing the powder in nitric acid ethanol solution. The effects of the acid treatment on the stability of inorganic framework were investigated. The samples were characterized by FT-IR, XRD, N₂ adsorption-desorption isotherms and HRTEM. The result showed that all of the as-prepared samples were wormhole-like mesoporous structure. The as-prepared sample showed a high photocatalytic activity to degrade Rhodamine B under UV-light irradiation, which was attributed to the porous structure, large BET surface area, bicrystalline, and small crystallite size.     

Poly(vinyl alcohol)/poly(acrylic acid)/TiO2/graphene oxide nanocomposite hydrogels for pH-sensitive photocatalytic degradation of organic pollutants

Poly(vinyl alcohol)/poly(acrylic acid)/TiO₂/graphene oxide nanocomposite hydrogels were prepared using radical polymerization and condensation reaction for the photocatalytic treatment of waste water. Graphene oxide was used as an additive to improve the photocatalytic activity of poly(vinyl alcohol)/poly(acrylic acid)/TiO₂ nanocomposite hydrogels. Both TiO₂ and graphene oxide were immobilized in poly(vinyl alcohol)/poly(acrylic acid) hydrogel matrix for an easier recovery after the waste water treatment. The photocatalytic activity of poly(vinyl alcohol)/poly(acrylic acid)/TiO₂/graphene oxide nanocomposite hydrogels was evaluated on the base of the degradation of pollutants by using UV spectrometer. The improved removal of pollutants was due to the two-step mechanism based on the adsorption of pollutants by nanocomposite hydrogel and the effective decomposition of pollutants by TiO₂ and graphene oxide. The highest swelling of nanocomposite hydrogel was observed at pH 10 indicating that poly(vinyl alcohol)/poly(acrylic acid)/TiO₂/graphene oxide nanocomposite hydrogels were suitable as a promising system for the treatment of basic waste water.     

Solution- and air-recoverable photocatalytic nanofibers by facile and cost-effective electrospinning and co-precipitation processes

While nanostructured materials are of particular academic and practical interest, their recoverability and recyclability have been of paramount industrial and environmental concerns. In the present contribution, co-precipitation was demonstrated as a facile and cost-effective approach to incorporate magnetic sensitivity and enhance the recoverability of nanofibrous materials which were frequently utilized in catalysis, energy and medical applications, etc. In particular, reusable magnetic and photocatalytic hybrid nanofibers were generated by electrospinning and co-precipitation method. First, TiO₂ nanofibers were prepared through sol-gel reaction and electrospinning process. To improve their recoverability, CoFe₂O₄ nanoparticles were decorated onto the nanofibers' surfaces via co-precipitation of cobalt and iron ions in the presence of the nanofibers suspension. Furthermore, the resulting CoFe₂O₄-decorated TiO₂ nanofibers maintained their photocatalytic activity after the modification. When suspended in a solution or spread on a dried surfaces, these nanofibers could be recollected with a magnet. These findings suggested that incorporation of ferromagnetic into the nanofibers maintained their photocatalytic performance and reduced production cost as well as the risk of human and environmental exposure through solution and air.     

Photocatalytical water decomposition on visible light-driven solid-solution compounds K4Ce2Ta10−xNbxO30 (x = 0-10)

A series of single phase solid-solution K₄Ce₂Ta_10−xNb_xO₃₀ (x = 0-10) photocatalysts were synthesized by conventional high temperature solid state reaction. Their UV-vis diffuse reflectance spectra showed their absorbance edges shifted to long wavelength zone consistently with the increase of the amount of Nb for substituting Ta in these compounds, and the onsets of absorbance edges ranging from about 540 nm to 690 nm, corresponding to bandgap energy of 1.8-2.3 eV. These series of photocatalysts possess appropriate band gap (ca. 1.8-2.3 eV) and chemical level to use solar energy to decompose water into H₂, and the photocatalytical activities under visible light (λ > 420 nm) demonstrated that the activities decreased correspondingly with the increase of the amount of Nb in these compounds, which is regarded as the result of the differences of their band structures. Furthermore, the photocatalytical activities and the photophysical properties of these visible light-driven photocatalysts K₄Ce₂Ta_10−xNb_xO₃₀ (x = 0-10) were bridged by the first principle calculation based on Density Functional Theory with General Gradient Approximation and Plane-wave Pseudopotential methods.     

Preparation of high surface area LaTiO2N photocatalyst

Nanocrystalline LaTiO₂N with a surface area of 27.5 m²/g was synthesized by nitridation of amorphous La₂O₃/TiO₂ composite powder at 900 °C for 8 h using NH₃ as the reactant gas. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the as-prepared LaTiO₂N nanocrystals had a mean diameter of about 30 nm. It was found that the absorption edge of the oxynitride is significantly red-shifted compared with that of La₂Ti₂O₇ as increasing the nitridation temperature. The UV–vis absorption spectra indicated that the synthesized oxynitrides displayed good light absorption properties not only in the ultraviolet light but also in the visible-light region.     

Photoactive TiO2/CuxO composite films for photocatalytic degradation of methylene blue pollutant molecules

Applying photocatalysts for utilizing solar energy is attractive because of its clean and limitless characteristics, but they have giant obstacles such as wide bandgaps, photocorrosion, and rapid charge recombinations to overcome for applications. In this study, the TiO₂/Cu_xO composite films are investigated as photoactive materials for the photodegradation ofmethylene blue (MB) pollutant molecules under standard sun light illumination. The TiO₂ layer is firstly fabricated on the FTO substrate by a doctor blade method, and then the second copper component is introduced by a spin-coating. Then, the composite films are thermally sintered to form cuprous and cupric oxides. This additional copper oxide phases plays a crucial role in achieving high photodegradation performance of MB under light irradiation. The best MB photodegradability from the TiO₂/Cu_xO composite films was achieved with the 3.6 wt% Cu_xO content case, and it is probably due to the effective charge separations with reduced recombinations in the copper oxide phases by the Z-scheme band arrangements between Cu₂O and CuO components. The composite films were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy for the film surface and cross-sectional morphology, crystalline structure, atomic binding energy, and light absorbance, respectively.     

Nitrogen-doped titanium dioxide photocatalysts for visible response prepared by using organic compounds

In order to utilize visible light in photocatalytic reactions, nitrogen atoms were doped in commercially available photocatalytic TiO₂ powders by using an organic compound such as urea and guanidine. Analysis by X-ray photoelectron spectroscopy (XPS) indicated that N atoms were incorporated into two different sites of the bulk phase of TiO₂. A significant shift of the absorption edge to a lower energy and a higher absorption in the visible light region were observed. These N-doped TiO₂ powders exhibited photocatalytic activity for the decomposition of 2-propanol in aqueous solution under visible light irradiation. The photocatalytic activity increased with the decrease of doped N atoms in O site, while decreased with decrease of the other sites. Degradation of photocatalytic activity based on the release of nitrogen atoms was observed for the reaction in the aqueous suspension system.     

Multifunctional dual Z-scheme heterostructured Sm2O3-WO3-La2O3 nanocomposite: Enhanced electrochemical,photocatalytic, and antibacterial properties

In this study, heterostructured dual Z-scheme Sm₂O₃-WO₃-La₂O₃ nanocomposite (NC) and bare Sm₂O₃, WO₃, and La₂O₃ nanostructured (NSs) were prepared using a co-precipitation approach. The comparative electrochemical, photocatalytic, and antimicrobial properties of NC and NSs were studied. The XRD spectrum exhibits the formation of bare NSs and NC having cubic-Sm₂O₃, monoclinic-WO₃, and hexagonal-La₂O₃ phases. FESEM results showed mesoporous morphology of NC. The higher electrical conductivity 261.33 mho-cm⁻¹ and lower optical energy bandgap 2.55 eV were obtained for NC. The photodegradation tests exhibited that NC photocatalyst has degraded 99% (methylene blue), 96% (Methyl orange), 99% (safranin-O), 48% (p-nitroaniline), and 98% (methyl red) dyes pollutants in 40 min sunlight radiation and showed strong inhibition activity against E. coli, K. pneumoniae, S. aureus, P. Vulgaris, and P. aeruginosa bacterial strains with zones of inhibition (ZOI) 31 mm, 30 mm, 30 mm, 28 mm, and 31 mm, respectively. Electrochemical studies revealed the excellent capacitive characteristics of NC with a specific capacitance 532F/g at a scan rate 5 mV/s, energy density 48.0278 W h Kg⁻¹, and power density 0.3782 KW Kg⁻¹ at 0.006 A/cm² current density. Furthermore, the present study revealed a novel composition for environmental remediation and energy storage applications.     

Photocatalytic effects for the TiO2-coated phosphor materials

This study investigated the photocatalytic behavior of the coupling of TiO₂ with phosphorescent materials. A TiO₂ thin film was deposited on CaAl₂O₄:Eu²⁺,Nd³⁺ phosphor particles by using atomic layer deposition (ALD), and its photocatalytic reaction was investigated by the photobleaching of an aqueous solution of methylene-blue (MB) under visible light irradiation. To clarify the mechanism of the TiO₂-phosphorescent materials, two different samples of TiO₂-coated phosphor and TiO₂–Al₂O₃-coated phosphor particles were prepared. The photocatalytic mechanisms of the ALD TiO₂-coated phosphor powders were different from those of the pure TiO₂ and TiO₂–Al₂O₃-coated phosphor. The absorbance in a solution of the ALD TiO₂-coated phosphor decreased much faster than that of pure TiO₂ under visible irradiation. In addition, the ALD TiO₂-coated phosphor showed moderately higher photocatalytic degradation of MB solution than the TiO₂–Al₂O₃-coated phosphor did. The TiO₂-coated phosphorescent materials were characterized by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photon spectroscopy (XPS).