锐钛矿/TiOz(B)异质纳米线制备、表征及其光催化性能研究

通过简单的水热反应,和后续的退火处理得到锐钛矿/TiO2(B)异质结构纳米线.通过XRD、SEM和TEM对其进行表征.并对锐钛矿/TiO2 (B)进行甲基橙紫外光降解性能测试,探究和讨论了H2O2对其光催化性能的影响,实验表明当加入1.6mL H2O2时对体系光催化促进效果最优,只需要8min分解率达到99％,降解时间只为无H2O2时的1/5.     

Controlled synthesis of anatase TiO2 octahedra with enhanced photocatalytic activity

Titanium dioxide (TiO₂) nanocrystals with specific exposed crystal facet have attracted considerable interest due to their promising applications in the fields of energy and environment. In this paper, we report on a simple solvothermal approach for the synthesis of anatase TiO₂ octahedra with high yield, using titanium(IV) sulfate and hydrazine hydrate as the starting materials. The formation mechanism of anatase TiO₂ octahedra is suggested. The samples were characterized with XRD, Raman, SEM, TEM, FTIR, XPS, and UV/vis techniques, and further tested as a candidate in photocatalysis to decompose methyl orange in aqueous solution at room temperature. The results show that SO₄²⁻ ions not only benefit the formation of octahedral nanocrystals, but also inhibit nitrogen doping into TiO₂ matrix. More importantly, it is found that the octahedral TiO₂ nanocrystals show enhanced photocatalytic activity compared to TiO₂ P25 and anatase TiO₂ counterparts.     

Hydrothermal synthesis and photocatalytic activity of anatase TiO2 nanofiber

TiO2 nanofiber consisting of 15 +/- 5 nm anatase grains was synthesized by hydrothermal treatment of fibrous hydrogen titanate precursor at 180 degrees C for 20 h. The hydrogen titanate precursor was synthesized by hydrothermal treatment of commercial P25 TiO2 powder in 10 M NaOH at 200 degrees C for 20 h followed by soaking in 0.1 M HNO3 to perform ion exchange between the as-synthesized Na titanate and H. By controlling pH of the solution during hydrothermal treatment of the hydrogen titanate precursor, pure anatase TiO2 nanofiber was obtained. Its band-gap energy determined from the onset of diffused reflectance spectrum was 3.19 eV which is equal to that of anatase TiO2 powder. The TiO2 nanofiber showed higher photodecomposition efficiency than the Cotiox KA-100 TiO2 but lower than the P25 TiO2. Photodegradation is the predominant process for 'Reactive blue 171' removal.     

H(2)O(2)-sensitized TiO(2)/SiO(2) composites with high photocatalytic activity under visible irradiation

TiO(2)/SiO(2) composite photocatalysts were prepared by depositing of TiO(2) onto nano-SiO(2) particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO(2)/SiO(2) composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO(2). Increases in the amount of TiO(2) would decrease the dispersion in the composites. H(2)O(2)-sensitized TiO(2)/SiO(2) composite photocatalysts could absorb visible light at wavelength below 550 nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO(2) exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO(2) content over 30% decreased with increasing of TiO(2) content. Increases in the calcination temperature and TiO(2) content promote the formation of bulk TiO(2) and result in a decrease in activity.     

Multi-modal mesoporous TiO(2)-ZrO(2) composites with high photocatalytic activity and hydrophilicity

Utilizing the amphiphilic triblock copolymer Pluronic P123 as the surfactant, and Ti(O(n)Bu)(4) and ZrOCl(2)·8H(2)O as the inorganic sources, a series of multi-modal mesoporous TiO(2)-ZrO(2) composites have been successfully synthesized through a one-step method. The resultant materials were characterized in detail by x-ray diffraction, atomic force microscopy, high resolution scanning electron microscopy, transmission electron microscopy, N(2) adsorption and water contact angle measurements. The effect of calcination temperatures on the physical parameters, hydrophilicity and photocatalytic activity of the obtained mesoporous TiO(2)-ZrO(2) composites was also investigated in this paper.     

Synthesis and photocatalytic activity of sea urchin-shaped rutile TiO2 nanocrystals

Sea urchin-shaped rutile nanostructures (SUR NSs) with abundant {110} surfaces are synthesized at 60 °C under atmospheric pressure. The SUR NSs were ~ 420 nm in diameter and contain a number of needle-like rutile single crystals grown parallel to the (110) face from a single nucleus in a radial fashion. The photocatalytic activity of the SUR NSs is significantly higher than that of commercial rutile nanoparticles with the same specific surface area. This demonstrates that {110} facets are effective in enhancing photoactivity.     

Low-temperature fabrication of porous anatase TiO2 film with tiny slots and its photocatalytic activity

The films consisting of 4,4′-dihydroxydiphenyl propane (BPA) and anatase TiO₂ colloidal particles were prepared by a dip-coating method. The BPA in the films was preferentially dissolved in anhydrous ethanol and thus eliminated from the films, so the porous anatase TiO₂ films were obtained. The surface morphology and the properties of the films were studied. The results show that the co-continuous morphology of the blends is favorable to the formation of porous surface structure with homogeneous and continuous tiny slots. The porosity induces the effective adsorption of Rhodamine B (RB) on the catalyst surface, and thus the photocatalytic activity is enhanced.     

A facile decoration of anatase Fe3O4/TiO2 nanocomposite with graphene quantum dots: Synthesis,characterization, and photocatalytic activity

A combination of electron-rich graphene quantum dots (GQDs) with Fe₃O₄/TiO₂ nanocomposites may develop an efficient electron transfer for enhanced photocatalytic activity. In this report, a facile decoration of GQDs with maltose precursor was synthesized and loaded onto magnetic anatase TiO₂ nanocomposites under hydrothermal methods. The as-synthetized magnetic TiO₂/GQDs nanocomposite resulted in a specific surface area of 38.00 m²/g and a total pore volume of 0.186 cm³/g. The HRTEM images showed a lattice plane distance of 0.350 nm related to the interplanar spacing of the anatase TiO₂ (1 0 1) plane and that of 0.299 nm observed for the in-plane lattice part of GQDs. The effects of magnetic loading ratio and GQDs loading onto TiO₂, pH, photocatalyst dosage, and methylene blue (MB) concentration were thoroughly evaluated to find the optimum conditions of mineralization MB for getting the highest photocatalytic efficiency. The removal efficiency of around 86.08 ± 3.62% was obtained at pH11, photocatalytic dose 400 mg/100 mL, and MB concentration 10 mg/L. Moreover, the photogenerated electron transfers and MB degradation mechanism by the resulting Fe₃O₄/TiO₂/GQD_S under irradiation of UVA light are proposed. The as-synthesized material improved meaningfully greater photocatalytic efficiency for degrading MB under UVA light irradiation than merely pure anatase TiO₂. Also, the predominant mechanism of MB degradation was direct oxidative decomposition through the photogenerated holes. The photocatalytic destruction of MB complied with the apparent first-order models under UVA light irradiation.     

Preparation of Ti3+/N-co-doped TiO2 by one-step hydrothermal synthesis method with high photocatalytic degradation performance under visible light

Journal of Materials Science: Materials in Electronics - Ti3+/N-co-doped TiO2 was successfully synthesized in situ by one-step hydrothermal method using tetrabutyl titanate (TBOT) as the titanium...     

Synthesis and photocatalytic activity of stable nanocrystalline TiO(2) with high crystallinity and large surface area

Superior photoactive TiO(2) nanopowders with high crystallinity and large surface area were synthesized by a hydrothermal process in the presence of cetyltrimethylammonium bromide and a post-treatment with ammonia. The prepared photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, N(2) adsorption-desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectra (DRS) and surface photovoltage spectroscopy (SPS). The prepared nanocrystallites were highly resistant to thermal sintering, and the calcinations up to 900 degrees C were shown to enhance the crystallinity of the anatase phase without any rutile phase and the separation rate of photoinduced charges of TiO(2) particles. It remained as large as 196 and 125 m(2)/g even after calcinations at 700 and 800 degrees C, respectively. The photocatalytic activity of prepared photocatalysts was obviously higher than that of commercial Degussa P25 on the photodegradation of methylene blue and phenol in water under ultraviolet-light irradiation, and the sample calcined at 800 degrees C afforded the highest photocatalytic activity.     

MgTiO3/MgTi2O5/TiO2 heterogeneous belt-junctions with high photocatalytic hydrogen production activity

An effective photocatalytic hydrogen production catalyst comprising MgTiO₃/MgTi₂O₅/TiO₂ heterogeneous belt-junctions was prepared using magnesium ions by a thermally driven doping method. The tri-phase heterogeneous junction was confirmed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The as-prepared MgTiO₃/MgTi₂O₅/TiO₂ heterojunctions exhibited a very high photocatalytic hydrogen production activity (356.1 mol·g_0.1gcat·h^-1) and an apparent quantum efficiency (50.69% at 365 nm) that is about twice of that of bare TiO² nanobelts (189.4 mol·g_0.1gcat·h^-1). Linear sweep voltage and transient photocurrent characterization as well as analysis of the electrochemical impedance spectra and Mott–Schottky plots revealed that the high photocatalytic performance is caused by the one-dimensional structure, which imparts excellent charge transportation characteristic, and the MgTiO₃/MgTi₂O₅/TiO₂ tri-phase heterojunction, which effectively drives the charge separation through the inherent electric field. This titanate-based tri-phase heterogeneous junction photocatalyst further enriches the catalyst system for photocatalytic hydrogen production.

     

A general aqueous sol-gel route to Ln(2)Sn(2)O(7) nanocrystals

This paper describes a general aqueous sol-gel route for the synthesis of a series of rare earth stannates, Ln(2)Sn(2)O(7) (Ln = Y, La, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Lu), with pure pyrochlore phase via the assistance of a cetyltrimethyl ammonium bromide (CTAB) surfactant. The route involves first the formation of CTAB-inorganic lamellar structures and then their thermal decomposition at 800?°C to yield the pyrochlore Ln(2)Sn(2)O(7) nanocrystals. Techniques using a thermo-gravimetric/differential thermal analyzer (TG-DTA), x-ray diffraction (XRD) and transmission electron microscopy (TEM) as well as selected-area electron diffraction (SAED) have been employed to characterize the as-synthesized Ln(2)Sn(2)O(7) nanocrystals. Furthermore, photoluminescence (PL) of the 5% Eu(3+) activated Ln(2)Sn(2)O(7) nanocrystals and carbon monoxide catalytic oxidation over the as-obtained Ln(2)Sn(2)O(7) nanocrystals were investigated. The results indicate that the PL properties as well as the catalytic activity changes significantly with the ionic radii of the rare earth elements.     

Enhanced photocatalytic activity of (Zn,N)-codoped TiO2 nanoparticles

(Zn, N)-codoped TiO₂ nanoparticles were prepared by the sol–gel method. X-ray diffraction (XRD) results testified that anatase samples were obtained. Transmission electron microscopy (TEM) patterns revealed that the average grain size of all the samples is about 15 nm and the Zn doping caused obvious particle aggregation. The Brunauer–Emmett–Teller (BET) surface areas of the samples were measured to testify the aggregation. The Zn doping caused slight blue-shift of absorption edge by the ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) measurements. The photocatalytic activity for the degradation of methylene blue (MB) solution was best enhanced in the (Zn, N)-codoped TiO₂ with 1 at.% Zn doping level. Photoluminescence (PL) emission spectra of the samples were also investigated, which revealed that the oxygen vacancy and isolated N 2p states played important roles in the photo-generated charge carrier recombination in the (Zn, N)-codoped TiO₂. It was suggested that the doping induced oxygen vacancies could promote the photocatalytic oxidation processes.     

Preparation and photocatalytic activity of anatase TiO2 nanocrystallites with high thermal stability

Anatase TiO₂ nanocrystallites were prepared from TiCl₄ with addition of aqueous ammonia by changing Ti(OH)₄ hydrogel into its corresponding alcogel followed by supercritical drying in ethanol medium. The as-prepared TiO₂ was characterized by XRD, TG and BET. The results show that the prepared anatase TiO₂ has remarkable high thermal stability. The anatase structure of the prepared TiO₂ is maintained even after calcination up to temperatures as high as 800 °C. The photocatalytic activity of the prepared TiO₂ calcined at 800 °C in degradation of reactive brilliant red X-3B is comparable to commercially available nanosized P25 TiO₂.     

Synthesis, characterization, and photocatalytic activity of TiO(2-x)N(x) nanocatalyst

Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2).     

Phase-pure TiO(2) nanoparticles: anatase, brookite and rutile

We report on the synthesis of phase-pure TiO(2) nanoparticles in anatase, rutile and brookite structures, using amorphous titania as a common starting material. Phase formation was achieved by hydrothermal treatment at elevated temperatures with the appropriate reactants. Anatase nanoparticles were obtained using acetic acid, while phase-pure rutile and brookite nanoparticles were obtained with hydrochloric acid at a different concentration. The nanomaterials were characterized using x-ray diffraction, UV-visible reflectance spectroscopy, dynamic light scattering, and transmission electron microscopy. We propose that anatase formation is dominated by surface energy effects, and that rutile and brookite formation follows a dissolution-precipitation mechanism, where chains of sixfold-coordinated titanium complexes arrange into different crystal structures depending on the reactant chemistry. The particle growth kinetics under hydrothermal conditions are determined by coarsening and aggregation-recrystallization processes, allowing control over the average nanoparticle size.     

Microwave-assisted synthesis of anatase TiO(2) nanorods with mesopores

Pure anatase TiO(2) nanorods with mesopores were synthesized by a simple and low cost microwave-assisted method when tri-block copolymer was used as a structure stabilization agent and TiCl(4) as metal precursor. TEM investigation showed that larger nanorods were assembled by pearl-necklace-shaped nanorods following an oriented attachment mechanism in a specific direction. A proposed hypothetical scheme showed that the formation of lyotropic titania liquid crystal (TLC) serves a key role in the stabilization of nanorods, and the mesopores on nanorods are derived from the vacancy of inter-particles of nanorods and regions lacking inorganic precursors in the TLC structure. Control experiments showed that microwave treatment plays a key role in the maintenance of original morphologies and mesostructures free from destruction even under high temperature calcinations.     

Facile synthesis of defected TiO2-x (B) nanosheet/graphene oxide hybrids with high photocatalytic activity

TiO2 (B) nanosheets/GO (graphene oxide) hybrids are considered to be outstanding performance pho-tocatalysts for high efficiency of H2 evolution.However,they still suffer severe challenges during the synthetic processes,such as a large amount of the capping agents adhering on the surface and easy occurrence of aggregation.To figure out these obstacles,Ar plasma treatment as a modified method in this study not only enable the TiO2 (B) nanosheets distributed uniformly on the GO sheets but also engi-neer defects within TiO2 (B) nanosheetsto significantly improve the photocatalytic activity for the water splitting.The hydrogen evolution rate of the TiO2-x (B)/GO sheets is 1.4 times higher compared with that of original TiO2 (B)/GO sheets without Ar plasma treatment.The improved photocatalytic proper-ties were owing to the synergetic effects of oxygen vacancies and the heterojunction between GO and TiO2 (B),which can promote the visible light utilization and accelerate separation and transportation of photogenerated electron-holes.This study can provide a facile pathway to prepare the two-dimensional hybrid photocatalysts with high photocatalytic H2 activity.