Photocatalytic Activity Of As-prepared Samples Research Articles

Urchin-like m-LaVO4 and m-LaVO4/Ag microspheres: Synthesis and characterization

The semiconductor nanostructures decorated with noble metals have attracted increasing attention due to their interesting physical and chemical properties. In this work, urchin-like monoclinic (m-) LaVO4 microspheres were prepared by a hydrothermal method and used as a template to fabricate Ag nanoparticle-decorated m-LaVO4 composites. The morphology and structure were characterized by transmission electron microscope, high-resolution transmission electron microscope, scanning electron microscope, and energy-dispersive X-ray. It was found that Ag nanoparticles with narrow size distribution were uniformly loaded on urchin-like m-LaVO4 microspheres, and the resulted composite microspheres showed distinct surface plasmon absorption band compared to pure m-LaVO4 microspheres. Photocatalytic activities of as-prepared samples were examined by studying the degradation of methyl orange solutions under visible-light irradiation (>400nm). Results clearly showed that urchin-like m-LaVO4/Ag microspheres possess much higher photocatalytic activity than pure m-LaVO4 microspheres and P25.

Enhanced visible light photocatalytic activity of TiO2 nanotube arrays modified with CdSe nanoparticles by electrodeposition method

Highly ordered TiO2 nanotube arrays (NTAs) were fabricated on titanium substrate via electrochemical anodization method. CdSe nanoparticles were deposited on the TiO2 NTAs through the electrodeposition process. The influence of electrolyte concentration and deposition time on the visible light photocatalytic performance of CdSe/TiO2 NTAs was studied systematically. The photocatalytic activity of as-prepared samples was evaluated by degradation of methyl orange under visible light irradiation. The results indicated that the CdSe nanoparticles distributed uniformly on the surface of TiO2 NTAs when deposited in the electrolyte containing 0.02M CdCl2, 2mM SeO2 and 0.02M Na2SO4 with time of 600s. After irradiation under visible light for 2h, the degradation rate of CdSe/TiO2 NTAs composite material reached 94.4%, while the degradation rate of unmodified TiO2 NTAs was only 6.2 % under the same condition, demonstrating that the CdSe/TiO2 NTAs exhibited higher photocatalytic activity in visible light region. In addition, a reasonable degradation rate of 80.96% was achieved even after being used for 5 times.

Solvent-controlled preparation and photocatalytic properties of nanostructured TiO2 thin films with different morphologies

A low-temperature growth method of nanostructured TiO2 thin films with different morphologies was reported. Rod-like, grass-like and nanosheet structured films have been successfully fabricated just by adjusting the ratio of different solvents. The effects of the solvent on the morphologies of the TiO2 nanostructures were investigated. The formation mechanism of different morphologies was proposed based on the experiment results. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The photocatalytic activity of as-prepared samples for the degradation of methylene blue (MB) in water was evaluated under UV illumination. Results showed that the solvents exhibited important effect on the morphologies and photocatalytic activity of as-prepared nanostructured titania films.

Preparation of N-doped TiO2 by oxidizing TiN and its application on phenol degradation

Incomplete oxidation of titanium nitride (TiN) to prepare nitrogen-doped TiO2 was verified by calcining TiN at different temperatures in air for 30 min. The as-prepared samples were characterized by X-ray diffraction, UV-Vis diffuse reflectance spectra and X-ray photoelectron spectroscopy. The results confirmed that oxidizing TiN incompletely is an effective and simple method to prepare nitrogen-doped TiO2. Photocatalytic degradation of phenol was conducted to evaluate the photocatalytic activity of as-prepared samples. The results showed that phenol can be degraded efficiently by the as-prepared samples under visible light; low phenol concentration was conducive to degradation; the optimum calcination temperature and photocatalyst dosage are 650 °C and 0.5 g/L, respectively. The effects of different light sources on phenol degradation were compared. The reusability of nitrogen-doped TiO2 was tested and the results indicated a relatively good reusability under laboratory conditions.

A simple method for the preparation of Bi2WO6-reduced graphene oxide with enhanced photocatalytic activity under visible light irradiation

Reduced graphene oxide/Bi2WO6 (RGO–Bi2WO6) composite photocatalysts were prepared by a simple one-pot method. Namely, the reduction of graphene oxide and the growth of Bi2WO6 crystal occurred simultaneously in one single process. The obtained samples were characterized by XRD, SEM, and DRS. The photocatalytic activities of as-prepared samples was investigated by degradation of MB under visible light irradiation. An enhancement in photocatalytic activities were observed in RGO–Bi2WO6 composites compared with pure Bi2WO6. We also investigated the effect of graphene amount on the photocatalytic activity of the as-prepared composite photocatalysts. Results showed that there was an optimal amount of 2.5%.

Effects of N Precursor on the Agglomeration and Visible Light Photocatalytic Activity of N-Doped TiO<SUB>2</SUB> Nanocrystalline Powder

N-doped TiO2 nanocrystalline powders were prepared by the sol-gel method using various N precursors, including triethylamine, hydrazine hydrate, ethylenediamine, ammonium hydroxide, and urea. The samples were characterized by X-ray diffraction, N2 adsorption isotherms, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of as-prepared samples under irradiation of visible light (lambda > 405 nm) were evaluated by photodecomposition of methyl orange. The alkalinity of N precursor was found to play a key role in the gel process. The N precursor with moderate alkalinity causes TiO2 nanoparticles to be sol-transformed into a loosely agglomerated gel. This transformation facilitates the preparation of an N-doped TiO2 powder with small nanocrystal size, large specific surface area, and high N doping level and results in high visible light photocatalytic activity. The N in TiO2 with N is binding energy at 399-400 eV may be assigned to the N-H species located in interstitial sites of TiO2 lattice which is the active N species responsible for the visible light photocatalytic activity. The N species of N 1s peak at 402 and 405 eV are ineffective to the visible light photocatalytic activity and may inhibit the photocatalytic activity. Moreover, a TiO2 nanoparticle powder with large specific area can be achieved by using urea as a template and then by using ammonium hydroxide to transform the sol into gel.

H 2O 2 modified surface of TiO 2/fly-ash cenospheres and enhanced photocatalytic activity on methylene blue

In this study, the TiO 2/fly-ash cenospheres were prepared via sol–gel method, and the surface of TiO 2/fly-ash cenospheres was further modified by hydrogen peroxide (H 2O 2). Scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) were applied to characterize structure, performance and chemical composition of as-prepared samples. The photocatalytic activity of as-prepared samples was evaluated by degradation of methylene blue under visible light irradiation. The results indicate that the modified phototcatalyst of TiO 2/fly-ash cenospheres is effectively improved the absorption of light. The photocatalytic degradation of methylene blue is enhanced under visible light irradiation, which the degradation rate is higher 42.5% than the untreated TiO 2/fly-ash cenospheres with H 2O 2. Moreover, the simple way to modified TiO 2/fly-ash cenospheres and enhancing the photocatalytic activity is better for practical application.

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible-light-driven plasmonic photocatalyst Ag-TiO(2) nanocomposite hollow spheres are prepared by a template-free chemically-induced self-transformation strategy under microwave-hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of .OH radicals on the surface of visible-light illuminated TiO(2) was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible-light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO(2) hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag-TiO(2) nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible-light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO(2) and commercial Degussa P25 (P25) powders. Especially, the as-prepared Ag-TiO(2) nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium (R) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.