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1.
TiO 2 microspheres were synthesized by hydrothermal reaction using Ti(OBu) 4 as the precursor. In order to enhance the efficiency of water splitting by the TiO 2 microspheres, Pt-modified TiO 2 microspheres were prepared by the impregnation-reduction method. The diameter of TiO 2 microspheres is around 5–10 μm. The photocatalytic performances of the catalysts were measured by hydrogen generation from a mixture of water and methanol under UV light irradiation. The photocatalytic activity of the TiO 2 microspheres was remarkably enhanced by loading Pt. The optimal Pt loading is 1.2 wt%. Pt/TiO 2 microspheres exhibit about 125 times greater H 2 production rate than the unmodified TiO 2 microspheres. The effect of calcination temperature on photocatalytic activity of the TiO 2 microspheres was also investigated. 相似文献
2.
One-step route based on the thermal decomposition of the double salt (NH 4) 2TiO(SO 4) 2 (ammonium titanyl sulfate, ATS) is presented to prepare size-defined aggregates of Ti-based nanoparticles with structural hierarchy. The component of Ti-based networks is tunable from anatase/rutile TiO 2, nitrogen-doped TiO 2, TiN xO 1−x, to TiN depending on the atmospheres and reaction temperatures. The as-prepared Ti-based powders were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS), and BET surface area techniques. It is found that TiO 2 in the predominant rutile phase could be achieved by the thermal decomposition of ATS in flowing Ar gas. Furthermore, the nitrogen-doped TiO 2, TiN xO 1−x solid solution and TiN were prepared by the thermal decomposition of ATS in flowing NH 3 gas by varying the temperatures. The network of anatase TiO 2 with a specific surface area up to 64 m 2 g −1 contains large mesopores with a mean diameter of ca. 15 nm, and the large pore size allows more accessible surface and interface available for the photocatalytic degradation of large-molecule dyes. The photocatalytic activity of the prepared TiO 2 and nitrogen-doped TiO 2 under UV–vis light irradiation is compared to Degussa P-25 using the photocatalytic degradation of methylene blue (MB) as a model reaction. The anatase TiO 2 nanoparticles derived from one-step route show the highly efficient photocatalytic activity for the degradation of MB in comparison with Degussa P-25. The presence of large-sized rutile in the TiO 2 powder decreases the specific surface area and thus the powder exhibits a lower photocatalytic activity. 相似文献
3.
Aluminum (Al) nanoparticles (NPs) patterned Erbium-doped Titanium dioxide (Er:TiO 2) thin films (TFs) were synthesized by the combination of sol-gel and glancing angle deposition (GLAD) technique inside the thermal evaporation system. Effects of Al NPs on electrical and optical properties of the Er:TiO 2 TF were experimented and systematically analyzed. Size of NPs was estimated from the field emission scanning electron microscopy (FESEM) image. Diameter of the maximum number of Al NPs was determined to be ~13 nm. The presence of Al was confirmed from the energy dispersive X-ray (EDX) spectra. The optical absorption at around 315 nm revealed the plasmonic resonance of Al NPs. The Au/Er:TiO 2/Al NPs/Er:TiO 2/p-Si Schottky contact-based plasmonic photodetector (PD) was fabricated, which showed excellent photosensitivity under both forward and reverse bias conditions. The responsivity was calculated at an applied voltage of 1 V, which exhibited a high response in the UV region with peak responsivity at 330 nm and 380 nm. The device showed fast switching behaviors under the illumination of 350 nm with a rise time of ~0.55 s and fall time of ~0.13 s. A simple theoretical approach was adopted to evaluate some important parameters of the plasmonic device like photoconductive gain, transit time, and mobility of electrons. Detectivity (1.13 × 10 12 Jones) and noise equivalent power (NEP) (2.46 × 10 ?14 W) at 330 nm indicate the suitability of the device as a sensitive UV PD. Hence, the embedded plasmonic Al NPs on Er:TiO 2 TF-based devices can commercially emerge as an efficient and cost-effective UV photodetector. 相似文献
4.
A novel strategy involving the combination of soft-templating and solid–liquid method (CSSL) is presented to synthesize mesoporous
nanocrystalline zirconia with high specific surface area, that is, the mesostructured zirconia hybrid is firstly synthesized via cooperative assembly between zirconium sulphate as inorganic
precursor and 1-hexadecyl-3-methylimidazolium bromide (C 16mim +Br −) as the structure-directing agent, and subsequently ground with solid magnesium nitrate salt followed by heat-treatment in
air. The resulting zirconia material after calcination at 600 °C possesses a wormlike arrangement of mesopores surrounded
by tetragonal ZrO 2 nanocrystallites of ca. 2.3 nm. The BET surface area is 255 m 2/g and the pore size is ca. 4.3 nm. However, no mesoporous structure exists in the obtained zirconia material via the simple soft-templating method at
the same calcination temperature. Photoluminescence (PL) spectra of the obtained mesoporous nanocrystalline ZrO 2 show a strong emission peak at ca. 394 nm under UV excitation of 250 nm wavelength. 相似文献
5.
Mesoporous TiO 2 microspheres were successfully synthesized by a facile hydrothermal process and the obtained product was sintered at 450 °C. The sintered TiO 2 powder was characterised by powder X-ray diffraction pattern and the result shows pure anatase phase with good crystalline nature. The morphological image of field emission scanning electron microscopy and high resolution transmission electron microscopy shows spherical shape and size of the particles is around 100 to 300 nm. The Brunauer–Emmett–Teller surface area of synthesized TiO 2 material was 56.32 m 2 g ?1 and average pore width of synthesized materials was 7.1 and 9.3 nm. Bimodal pore structure of TiO 2 microspheres has been very effective for electrolyte diffusion into photoanode in dye sensitized solar cells. The synthesized anatase TiO 2 microsphere based dye sensitized solar cells have high surface area with light scattering effect to enhance the photocurrent and conversion efficiency than the commercial P25 photoanode material. The power conversion efficiency of synthesized mesoporous TiO 2 microspheres and commercial P25 material is 4.2 and 2.7 % respectively. Therefore bimodal mesoporous anatase TiO 2 microsphere appears to be a promising and potential candidate for dye sensitized solar cells (DSSC) application. 相似文献
6.
Templated by TiO 2 microspheres , litchi-like SrTiO 3 crystals with a narrow size distribution and monodispersity were synthesized through the combination of regulating the ethylene glycol concentration during the hydrothermal process and the post heat treatment. The results show that when the volume ratio of water and ethylene glycol reached 10:70, microsized SrCO 3 was firstly formed under the hydrothermal process, and then the litchi-like SrTiO 3 powder was obtained after the postheat treatment at 700°C for 4 hours, which shows a large specific surface area of 37.41 m 2/g. It is found that the concentration of ethylene glycol aqueous solution plays an important role on the morphology of the SrTiO 3 crystals, and the slightly higher viscosity and proper amount of OH hydroxyl groups facilitate the formation of the micrometer spherical hierarchical surface. 相似文献
7.
Undoped and metal doped nanocrystalline TiO 2 transparent thin films were synthesized on glass substrates via sol-gel/dip-coating method. TiO 2 thin film coatings can be applied to the surfaces of solar panels to impart self-cleaning properties to them. The structural and optical properties of few nanometer-thick films were characterized by XRD, SEM, CA, AFM, XPS, and UV–Vis spectrophotometry techniques. The stoichiometric TiO 2 films crystallized in anatase phase, with a particle size of ~100 nm, which were uniformly distributed on the surface. The prepared films with a roughness of ~1–5 nm, increased the hydrophilicity of the glass surface. Reducing the amount of Ti precursor (X) favored the improvement of film quality. To improve the photocatalytic activity of the TiO 2 thin film, it was doped with Ni, Cd, Mo, Bi and Sr metal ions. The effect of metal doping on the photocatalytic activity of the films was investigated using the degradation process of methylene blue (MB) dye as the model contaminant. Among the prepared coatings, the Sr–TiO 2 film showed the highest efficiency for MB degradation. It increased the dye degradation efficiency of the films under both UV and Vis lights. The kinetic investigations also showed that the degradation of MB by TiO 2 and M ? TiO 2 films obeyed the pseudo-first order kinetics. 相似文献
8.
The titanate nanostructures with high UV absorption characteristics could be fabricated by hydrothermal method within a temperature range of 90–150 °C. TEM, XRD, BET analyses, and UV–vis spectroscopy were employed to elucidate the synthesized titanate nanostructure characteristics which were microstructure, phase transformation, specific surface area, and band gap energy, respectively. With an increase in the hydrothermal treating temperature from 90 to 120 °C, the specific surface area of titanate nanostructures was increased from 83 to 258 m 2/g, while the band gap energy of titanate nanostructures was increased from 3.44 to 3.84 eV and then slightly decreased to 3.81 eV at 150 °C. The fabricated titanate nanostructures could exhibit higher UV adsorption capability but lower photocatalytic activity when compared with that of commercial TiO 2 powders. 相似文献
9.
Titania (TiO 2) nanoparticles have been synthesized using organic precursor technique. The titania nanoparticles were characterized. The results indicated that the prepared titanium oxalate and citrate precursors were transformed to anatase TiO 2 phase at temperature 400 °C for 2 h. Dye-sensitized solar cells were assembled using the prepared nanocrystalline TiO 2 with large surface area. The specific surface area S BET was 80.9 and 78.6 m 2/g using oxalic and citric acids, respectively. The power efficiency was 3.5 and 2.4%. A brief discussion on the possible reasons behind the low power conversion efficiency observed for these type of solar cells was reported. 相似文献
10.
Multifunctional materials have received considerable attention as they could integrate different functional components in one-single platform. In this study, novel chitosan/Fe 3O 4/TiO 2@TiO 2 nanowire (NW) microspheres having extracellular matrix-like fibrous surface and photothermal antibacterial property were synthesized through in situ hydrothermal growth of TiO 2 NWs on chitosan/Fe 3O 4/TiO 2 microspheres. It is found that the microspheres were spherical in morphology with a diameter of 100–300 µm and exhibited a hierarchical and nanofibrous feature. Their surface was mainly constructed by numerous TiO 2 NWs with a diameter of 20– 30nm. In vitro biological evaluation indicates that the chitosan/Fe 3O 4/TiO 2@TiO 2 NW microspheres significantly enhanced attachment and proliferation of human umbilical vein endothelial cells compared with chitosan/Fe 3O 4/TiO 2 nanocomposite microspheres due to the presence of nanofibrous surface. Moreover, the microspheres showed photothermal antibacterial property to inhibit the growth of bacteria due to the presence of Fe 3O 4 component. 相似文献
11.
One of the important ways to improve photocatalytic efficiency is to prepare catalyst with enhanced surface area. In this work, titanium dioxide (TiO 2) nanoparticles having enhanced surface area were synthesized under the interference of SiO 2. The mixed oxide, SiO 2-TiO 2 (10% mol% Si), was prepared by a sol-gel procedure using titanium tetra-n-butoxide as Ti-precursor. The commercial SiO 2 nanoparticles were added into the TiO 2 sols after hydrolysis. After condensation and calcination heat treatment, the SiO 2-TiO 2 nanoparticles were obtained. To achieve the purpose of obtaining the high-surface-area TiO 2, the SiO 2 was removed subsequently by aqueous NaOH solution. The TiO 2 products were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA), and by N 2 adsorption-desorption isotherm. A fine mesoporous structure was formed for as-prepared TiO 2 after calcination at 400 °C and the average pore diameter was about 7 nm. The porous TiO 2 products possess mixing phases of anatase and rutile. Phase transformation from anatase to rutile occurred when the samples were calcined. The phase transition temperature is sensitive to the silicon content. The particle size of ~43 nm remained constant upon calcinations from 500 to 700 °C. The specific surface area was increased up to 66% compared to regular TiO 2 samples that were prepared by the similar sol-gel procedure. The porous TiO 2 nanostructures exhibited enhanced photocatalytic performance to decompose methylene blue under UV irradiation. 相似文献
12.
The combination of porous carbon matrix and metal oxide is trending for capacitive deionization (CDI) due to their synergistic electrochemical behaviour and properties. In this research, a flexible electrode based on electrospun porous carbon nanofibers and TiO 2 nanoparticles (particle size ~7 nm) i.e., PCNFs/TiO 2 composite coated over carbon cloth is developed. A facile in-situ activation procedure using sacrificial polymer is adopted over typical chemical activation treatment to synthesize PCNFs/TiO 2 composite. PCNFs/TiO 2 composite is prepared in two steps, possessing a high specific surface area of ~343 m 2 g ?1 and pore volume of 0.038 cm 3 g ?1. Interestingly, CDI unit assembled with PCNFs/TiO 2 composite based flexible electrodes delivers the large salt electrosorption capacity of 204.8 mg g ?1 at voltage 1.2 V in a salt solution of concentration 500 ppm and conductivity 880 μS cm ?1. The excellent adsorption capacity retention of 96.4% up to ten adsorption-regeneration cycles can be a tempting option for future flexible CDI applications. 相似文献
13.
TiO 2–Ag nanocomposite was prepared by the sol–gel method and an azeotropic distillation with benzene was used for dehydration of the gel. Because of gel dehydration by distillation method a nanopowder with a surface area of 230 m 2/g was produced which decreased to 80 m 2/g after calcination. TEM micrographs and XRD patterns showed that spherical nanosized Ag particles (≈ 10 nm) were deposited among TiO 2 particles. The antibacterial activity of calcined powder at 300 and 500 °C was studied in the presence and in the absence of UV irradiation against Escherichia coli as a model for Gram-negative bacteria. The antibacterial tests confirmed the powder calcined at 300 °C possessed more antibacterial activity than the pure TiO 2, amorphous powder and the powder calcined at 500 °C under UV irradiation. In the absence of UV, the reduction in viable cells was observed only with calcinated powder at 300 °C. 相似文献
14.
Micro-mesoporous TiO 2/SiO 2 nanocomposite powders have been successfully synthesized by the sol-gel process with different TiO 2/SiO 2 molar ratios and were applied in the UV-photodegradation of quinoline (λ = 254 nm). The structural, morphological, and textural characterization of the powders showed a homogeneous distribution of TiO2 nanoparticles within a porous amorphous SiO2 matrix. Due to the micro-mesoporous character of the materials, their textural characteristics were evaluated by the N2 adsorption method, by comparing BET, DR, Langmuir, and DFT theories. Si 60Ti 40 powders (60%SiO 2/40%TiO 2) presented the highest specific surface area (SSA) obtained from BET (SSA = 363 m 2g -1), DR (SSA = 482 m 2g -1), and Langmuir (SSA = 492 m 2g -1) due to the adequate particle size of TiO 2 and its high dispersion in the porous matrix. A higher degradation of quinoline in the presence of H 2O 2 (66%) was achieved using Si 80Ti 20 powders (80%SiO 2/20%TiO 2), as compared to pure sol-gel TiO 2 powders, (51%) under the same reaction conditions (1 UVC lamp - 250W, t = 180 min). The better performance of the Si 80Ti 20 nanocomposite could be attributed to the small TiO 2 anatase crystallite size (<5.7 nm), high dispersion of these crystallites in the SiO 2 matrix, great specific surface area (DR SSA = 342 m 2 g ?1), and the formation of Ti–O–Si bond, which is associated with new catalytic sites in TiO 2/SiO 2 composite. 相似文献
15.
Mesoporous titanium dioxide (TiO2) photocatalysts were synthesized via a solvothermal method using sodium dodecyl sulfate (SDS) as templates. The effect of the SDS concentration and solution pH value on the resulting TiO2 catalyst and its photocatalytic activity were studied. The photocatalytic activity was assessed by degradation methylene blue under low-power (8W?×?4) UV light irradiation. The best performance showed that over 95% of methylene blue was degraded in 120 min and in the presence of S20 (20 mmol SDS addition, pH?=?4). With the optimal addition of SDS, the crystal size was reduced, and the surface area was increased. In addition, some bidentate-sulfates (–SO42?) residues were observed within the prepared mesoporous TiO2. The Detail characterization of of the as-prepared TiO2 samples were conducted by X-ray diffraction, Ultraviolet–Visible Spectroscopy, Scanning electron microscope, Brunauer-Emmett-Teller analysis, and Fourier-transform infrared spectroscopy, respectively. 相似文献
16.
ZrO 2 microspheres are widely used as a simulant of UO 2 in the development of nuclear fuel. However, the cracking of ZrO 2 microspheres prepared by internal gelation is still a challenge during drying and sintering processes. To address this issue, we designed and optimized the washing process for obtaining crack-free ZrO 2 microspheres. Through thermogravimetric, infrared, Raman, BET, and SEM analysis, it is shown that the cracking of the microspheres is mainly related to the pores in microspheres. The washing solvent with low surface tension is used to reduce the effect of capillary force on pore shrinkage. Therefore, the optimal washing process was designed as trichloroethylene (TCE)—0.5 M NH 3.H 2O—Propylene glycol methyl ether (PM) and gel microspheres with a high specific surface area of 315.3 m 2/g and pore volume of 0.4125 cm 3/g were obtained. The characterizations also further showed that when the microspheres were dried and sintered, the water vapor and the decomposition gas of organic matter were completely released from the pores in the microspheres. Our new washing process could be directly extended for preparing crack-free ceramic microspheres by internal gelation. 相似文献
17.
Rutile TiO 2 particles with specific exposed crystal faces were prepared by hydrothermal treatment of titanium trichloride (TiCl 3) solution with poly(vinyl pyrrolidone) (PVP) as a shape-control reagent. Crystal phase, shape, and size of TiO 2 particles were found to be greatly dependent on the concentration of PVP in the solution. The exposed crystal surface of TiO 2 was controlled by changing the concentration of PVP in TiCl 3 and NaCl solutions. The prepared TiO 2 particles were characterized by TEM, SEM, XRD, and specific surface area measurements. The photocatalytic activity of the synthesized TiO 2 particles was evaluated by decomposition of acetaldehyde and toluene in gas phase. The synthesized TiO 2 particles showed higher photocatalytic activity for degradation of acetaldehyde and toluene than did commercial TiO 2 particles (MT-600B). However, the tendency of photocatalytic activities of the synthesized TiO 2 particles for degradation of acetaldehyde in gas phase was different from that for degradation of toluene. From the photodeposition of Pt and PbO 2, we propose that the (1 1 0) face provides reductive sites and that the (1 1 1) face provides oxidative sites. The results suggest that the crystal faces facilitate the separation of electrons and holes, resulting in improvement in photocatalytic activity. 相似文献
18.
A porous carbon nanocomposite with embedded TiO 2 nanowires (NWs) was synthesized using a two-step synthetic method in which carbon matrix was obtained by carbonizing a vacuum dried gel. This unique structure in which TiO 2 nanowires uniformly distributed in and tightly bonded to the carbon matrix shortened the electron transport path and reduced the transmission resistance. Nanoporous structure ensured continuous transfer of Li +/Na + and supplied a large specific surface area of 280.82 m 2 g −1 to provide more active sites. Different from other existing works on TiO 2@C anode materials with TiO 2 loading higher than 60 wt%, the obtained very small amount of TiO 2 (~12 wt%) improved the electrochemical and long-cycle performance of carbon substrate with TiO 2 NWs embedded significantly, due to uniformly distributed TiO 2 NWs throughout the carbon matrix. These TiO 2@C composite anodes could deliver a specific capacity of 286 mA h g −1 at 0.3 C, 197 mA h g −1 at 0.15 C for lithium and sodium ion batteries, respectively. It maintained remarkably stable reversible capacities of 128 and 125 mA h g −1 for lithium and sodium ion batteries at 3 C during 2500 cycles, respectively. Smaller fluctuations and smoother curves demonstrated that sodium ion storage was more stable than lithium ion storage for the TiO 2@C composite anode. In addition, the capacitive contributions of TiO 2@C in both systems are quantified by kinetics analysis. 相似文献
19.
C-, S-, N-, and Fe-doped TiO 2 photocatalysts were synthesized by a facile sol–gel method. The structure and properties of catalysts were characterized by N 2 desorption–adsorption, X-ray diffraction (XRD), UV–vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results revealed that the surface area of the multi-doped TiO 2 was significantly increased and the crystallite size was smaller than the pure TiO 2 obtained by a similar route. Compared with TiO 2, the peak position in doped-TiO 2 XRD patterns was slightly shifted, which could be attributed to the distortion by the substitution of carbon, nitrogen, and sulfur dopants for some oxygen atoms and Fe 3+ for Ti 4+ in the lattice of TiO 2. These substitutions were confirmed by XPS. In addition, these dopants were responsible for narrowing the band gap of TiO 2 and shifting its optical response from ultraviolet (UV) to the visible-light region. The photocatalytic reactivities of these multi-doped TiO 2 catalysts were investigated by degrading Rhodamine B (RB) in aqueous solution under visible-light irradiation (λ > 420 nm). It was found out that the reactivity was significantly enhanced and the catalyst doped with nitrogen, carbon, sulfur, and 0.3 wt% iron had the highest photocatalytic activity. 相似文献
20.
A novel kind of nanowire sponges, namely Si 3N 4 nanowire-weaving microspheres, synthesized from a simple, convenient, high-efficient approach are proposed here. As the reverse template, three-dimensional foam skeleton structure with uniform pores and ultrathin pore walls is constructed via the effective particle-stabilized foam method, where the silica sol and carbon black are chosen as the raw materials, providing the sufficient space for the growth of nanowires during the carbothermal reduction reaction process. The formation mechanism of this novel sponge is studied via multiple characterization methods. Si 3N 4 nanowires formed microspheres possess uniform and curving morphology due to the stable environment for growing via vapor–solid mechanism, leading to the relatively high specific surface area of 86.77 m 2/g. Owing to in-situ oxidation process, micro-spherical SiO 2 nanowire sponges with similar morphology are synthesized, which present diameter in range of 20-40 nm and specific surface area of 50.47 m 2/g. This work provides insights for the design of high-performance nanowire sponges with promising applications in the filtration, thermal insulators, and catalyst supports fields. 相似文献
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