共查询到20条相似文献,搜索用时 31 毫秒
1.
Yb 2O 3 stabilized ZrO 2 (YbSZ) doped with different TiO 2 contents were produced, and their phase structure, thermal conductivities and thermal expansion coefficients were investigated. A new solid-solution model is proposed, i.e. Ti 4+ would take the interstitial sites when its content is below a critical value (≤2.5 mol%) and then substitute for Zr 4+. The abnormal lattice volume and thermo-physical properties of 2.5 mol% TiO 2 doped YbSZ, and the positive effects of TiO 2 doping on the thermal conductivity at moderate doping level are consistent with the new defect model. However, monoclinic phase is formed when the TiO 2 content reaches to 10 mol% and its content increases with doping content, which have negative influence on the thermo-physical properties. Considering the comprehensive properties, 10 mol% TiO 2 doped YbSZ is considered as a promising thermal barrier coating ceramic. 相似文献
2.
Low-temperature electrocatalytic reduction of nitric oxide (NORR) is promising for the low-cost, high-efficiency removal and utilization of nitric oxide (NO), which couples the two crucial industrial processes of denitration and synthetic ammonia. We reported a binary catalyst of Cu/P–TiO 2 for NORR process, which took advantages of the Cu electrocatalysts and porous TiO 2. The increase of surface areas and channels can improve the adsorption of NO molecules. The decoration of the ultrafine Cu nanoparticles on the porous TiO 2 may prevent the agglomeration of ultrafine Cu nanoparticles. The as-prepared Cu/P–TiO 2 electrode exhibits excellent electrocatalytic activity with a Faraday efficiency of 86.49% and NH 3 yield of 3520.80 μg·h ?1·mg ?1 in 0.1 M K 2SO 4 at ?0.3 V vs. RHE. The mechanism of the NORR reaction process with Cu/P–TiO2 catalysts was also discussed. This research may broaden the application areas of TiO 2-based materials in the electrocatalysis and provide a new sight in the treatment of NO pollutants. 相似文献
3.
Despite a number of studies have been carried out on TiO 2 based materials as photocatalysts for water pollutant treatment, it still needs sustained effort to extend the optical range of the photocatalysts and inhibit the recombination of photo-induced carriers to improve their catalytic activities under solar light. In this work, a series of Sn-doped TiO 2 with different amounts of Sn doping (1, 5, 10 and 20 mol%) were biomimetically synthesized by a facile sol–gel method using cellulosic cotton as biotemplate. The Sn-doped TiO 2 materials possess a typical three-dimensional hierarchical structure of microtubes consisting of interwoven nanofibers. The photocatalytic performance was evaluated via the degradation of methylene blue (MB) (10.0 mg L ?1) under Xenon lamp simulated solar irradiation. The results show that Sn(5)-TiO 2 (5 mol% Sn doping) sample exhibits an outstanding photocatalytic capacity with a superior degradation rate of higher than 98% within 30 min and a good reusability without significant decrease of activity after reused for four cycles. The most significantly improved photocatalytic capacity of TiO 2 is ascribed to more extra surface hydroxyl groups and accessible active sites provided by the relatively high surface area, and a higher light capturing and utilization efficiency with less recombination of the photogenerated electron-hole pairs endowed by the good synergistic effect of the special hierarchically porous microstructure and the appropriate amount of Sn doping. Whereas, the excessive Sn doping reduces the photocatalytic activity obviously, resulting from the phase transformation of TiO 2 generating more rutile phase with less reactivity, the phase separation with clear grain boundary blocking the active sites, and the extra Sn 4+ acting as the recombination center. This research presents a facile biomimetic synthesis strategy combined with the traditional sol–gel method to develop various ion doped metal oxides as photocatalysts with enhanced activity. 相似文献
4.
The acceptor-doped rutile TiO 2 ceramics, x mol% M 2O 3-(1- x) mol% TiO 2 (M = Al 3+, Ga 3+, and In 3+), were prepared by solid state reaction method. The influence of Ar/H 2 annealing on the structural and dielectric properties of the ceramics were systematically investigated. Our results reveal that the dielectric properties of the ceramics can be significantly improved by the Ar/H 2 annealing. Ga 3+ is found to be the most suitable dopant with the best doping level of 5 mol%. Excellent dielectric properties of colossal and flat dielectric permittivity (~1.2 × 10 5 (@1 kHz and 25 °C), low dielectric loss (~0.1), and good frequency stability were achieved over the temperature range of -70–150 °C in the Ar/H 2-annealed 5 mol% Ga 2O 3-95 mol% TiO 2 ceramic. This approach of acceptor-doping and Ar/H 2 annealing leads to two thermally activated relaxations in the sample. The low-temperature relaxation is argued to be a Maxwell-Wagner relaxation caused by frozen electrons, while the high-temperature relaxation is a glass-transition-like relaxation associated with the freezing process of the electrons. This work highlights that engineering low-temperature Maxwell-Wagner relaxation paves a new way other than the frequently used acceptor-donor dual doping to design superior dielectric properties in the TiO 2 system. 相似文献
5.
Stability of suspensions of TiO 2 nanoparticles synthesized by the flame aerosol reactor (FLAR) could be altered by doping TiO 2 nanoparticles with Pt, Pd, or Pt–Pd dopants. It was found that doping of TiO 2 with Pd or Pt could contribute to the control of the agglomeration of TiO 2 suspended in water. With the change of doping content, the isoelectric point (IEP) of stable TiO 2 suspension decreased gradually from 5 to 3.6 while the specific surface area was increased from 43.27 to 60.84 m 2/g. With pH > 6.0, 2 wt% Pt–Pd/TiO 2 suspension exhibited the lowest agglomeration behavior. The plausible intrinsic structures of Pt, Pd, and Pt–Pd doped TiO 2 nanoparticles were proposed and discussed with respect to their IEP based on the DLVO theory. 相似文献
6.
Dye sensitized solar cell (DSSC) is an emerging energy harvesting tool which converts direct sunlight into electrical energy. These cells have much better properties in contrast with silicon based solar cells because of their flexible nature, light weight, low cost, environment friendly nature, and involvement of a simple manufacturing process. Since, a photoanode is the backbone of DSSC, we synthesized a pure and 1% manganese (Mn) doped titanium dioxide (TiO 2) films by sol-gel method which are irradiated with silver (Ag) ions at two different concentrations (2 × 10 14 and 4 × 10 14) ions-cm ?2. X-ray diffraction revealed that Mn doping followed by Ag irradiation transformed TiO 2 from pure anatase to rutile phase. Ultraviolet–visible spectroscopy exposed the reduction in band gap of TiO 2 film during this doping and irradiation process. Therefore, absorption is enhanced with red shift in UV-range. When these films are used as a photoanode in DSSC, 1% Mn doped TiO 2 film exposed with Ag at the concentration of (2 × 10 14) ions-cm ?2 exhibited maximum efficiency of 2.40%. 相似文献
7.
The structural and optical properties of ZnO nanoparticles doped simultaneously with Mg and Al were investigated. XRD results revealed the hexagonal wurtzite crystalline structure of ZnO. The FE-SEM study confirmed the formation of nano-sized homogeneous grains whose sizes decreased monotonously with increasing doping concentrations of Mg and Al. The absorption spectra showed that band gap increased from 3.20 to 3.31 eV with Mg doping. As the Al concentration changed from x=0.01 to x=0.06 mol% at constant Mg concentration the band gap observed to be decreased. Particle sizes estimated from effective mass approximation using absorption data and these values are in good agreement with the crystallite sizes calculated from XRD data. Raman spectra of ZnO showed a characteristic peak at 436 cm −1 correspond to a non-polar optical phonon E 2 (high). With increase of the Al doping concentrations, E 2 (high) phonon frequency shifted to 439 cm −1 from to 436 cm −1. The origin of E 2 (high) peak shift in ZnO nanoparticles is attributed to optical phonon confinement effects or the presence of intrinsic defects on the nanoparticles. PL spectra indicated that with increase of Al co-doping along with Mg into ZnO, intensity of the peak positioned at 395 nm was initially increased at x=0 and then decreased with increase of the Al concentrations from x=0.01 to x=0.06 mol%. 相似文献
8.
Nanopowders of TiO 2–SnO 2 over a full composition range extending from 100 mol% TiO 2 to 100 mol% SnO 2 are obtained by the sol–gel method from TTIP and SnCl 2·5H 2O precursors of Ti and Sn, respectively followed by calcination at 400 °C. The samples are characterized by means of BET, XRD and TEM. Optical properties of the prepared nanomaterials are studied as well. TEM images indicate that the nanoparticles are regular in shape. The specific surface area, SSA of TiO 2 is 95 m 2/g while that of SnO 2 amounts to 129 m 2/g. The highest SSA of 156 m 2/g is achieved at 20 mol% of TiO 2. Occurrence of rutile, anatase and brookite polymorphic forms depends on the chemical composition of nanopowders. Formation of rutile-type solid solution of TiO 2–SnO 2 over the range of 0–80 mol% TiO 2 is confirmed by Vegard rule applied to lattice constants. Electronic band gap decreases with Ti content from 3.84 eV (100 mol% SnO 2) to 3.18 eV (100 mol% TiO 2). 相似文献
9.
The plasmonic effects of infiltrated silver (Ag) nanoparticles, with different contents, inside a nanostructured TiO 2 film on the photovoltaic performance of dye‐sensitized solar cells (DSSCs) are explored. The synthesized Ag nanoparticles are immobilized onto deposited TiO 2 nanoparticles by a new strategy using 3‐mercaptopropionic acid (MPA), a bifunctional linker molecule. Transmission electron microscope (TEM) images show that monodispersed Ag and polydispersed TiO 2 nanoparticles have an average diameter of 12 ± 3 nm and 5 ± 1 nm, respectively. Moreover, Fourier transform infrared spectroscopy (FTIR) analysis reveals that Ag nanoparticles were successfully functionalized and capped with MPA. Optical studies on the MPA‐capped Ag nanoparticles inside TiO 2 film show an increase in the total absorbance of the electrode. Moreover, EIS measurements confirm that MPA‐capped Ag nanoparticles inhibit the charge recombination and improve the stability of nanoparticles in I3?/ I? electrolyte. The DSSC assembled with optimal content of MPA‐capped Ag nanoparticles demonstrated an enhanced power conversion efficiency (8.82% ± 0.07%) compared with the pure TiO 2 (7.30% ± 0.05%). The increase in cell efficiency was attributed to the enhanced dye light absorption in strength and spectral range due to the surface plasmon resonance of MPA‐capped Ag nanoparticles in the photoanode. 相似文献
10.
Porous TiO 2 thin films were prepared on the Si substrate by hydrothermal method, and used as the Pt electrocatalyst support for methanol oxidation study. Well-dispersed Pt nanoparticles with a particle size of 5–7 nm were pulse-electrodeposited on the porous TiO 2 support, which was mainly composed of the anatase phase after an annealing at 600 °C in vacuum. Cyclic voltammetry (CV) and CO stripping measurements showed that the Pt/TiO 2 electrode had a high electrocatalytic activity toward methanol oxidation and an excellent CO tolerance. The excellent electrocatalytic performance of the electrode is ascribed to the synergistic effect of Pt nanoparticles and the porous TiO 2 support on CO oxidation. The strong electronic interaction between Pt and the TiO 2 support may modify CO chemisorption properties on Pt nanoparticles, thereby facilitating CO oxidation on Pt nanoparticles via the bifunctional mechanism and thus improving the electrocatalytic activity of the Pt catalyst toward methanol oxidation. 相似文献
11.
Titanium dioxide (TiO 2) is a well-known photocatalyst that has been used in photocatalysis and has been studied as an alternative for artificial photosynthesis cells. Many works have tried doping this material with different elements to increase its photoactivity; however, a consequence of doping that has not received much attention is the segregation at the nanoparticle interfaces, such as the surface and the grain boundary (GB). In this study, Sb-doped TiO 2 nanoparticles have been produced by the polymeric precursor method, with the compositional range varying from 0 to 2 mol% Sb. The surface excess was measured by the surface lixiviation method, and the GB excess was calculated considering the total amount of Sb and its solubility in the TiO 2 bulk. The results showed that Sb interfacial segregation at both surface and GB increased the specific surface areas, reduced the crystallite sizes, increased the presence of the rutile phase, and changed the CO 2 adsorption, evidenced by DRIFT spectroscopy. The photoactivity was tested by the degradation of acetaminophen (ACT) under UV irradiation, revealing an increase of ~53% of activity for 0.05 mol% Sb-doped TiO 2 compared to undoped TiO 2. 相似文献
12.
This study aimed to enhance the visible light photosensitivity of TiO 2 nanoparticles for self-cleaning applications by doping with Fe 3+. Nanocrystalline undoped and Fe-doped TiO 2 (Ti 1 − xFe xO 2, x = .01–.04) were synthesized via sol–gel method. The results demonstrated that Fe-doped TiO 2 nanoparticles exhibited visible light sensitivity and self-cleaning properties. An increased Fe concentration resulted in a red shift in the absorption band edge. Fe 0.03-doped TiO 2 with an average particle size of ∼21 nm, a crystallite size of ∼12 nm, and a band gap of ∼2.86 eV showed the highest photocatalytic activity (60% methylene blue degradation) and super-hydrophilicity (water droplet contact angle 9°) under visible light radiation. These findings highlight the potential of Fe-doped TiO 2 nanoparticles as a promising material for self-cleaning applications. 相似文献
13.
The structural and luminescent properties of Eu 3+ doped TiO 2 nanophosphors synthesized by low cost combustion method were investigated. The X-ray diffraction analysis revealed that crystallite size decreases with doping concentration. Lattice volume expansion occurred due to the substitution of Ti 4+ ions by larger ionic radii ions Eu 3+. FESEM images showed prepared phosphors to be nano size spherical shaped particles. Energy band gap of 3 mol% Eu 3+ doped samples decreased to 3.15 eV due to doping effect. The Eu 3+ doped TiO 2 nanophosphors exhibited main red emission peak centered at 616 nm under 395 nm UV light excitation. Concentration quenching was observed at 3 mol% doping, that has been ascribed to dipole-dipole interaction. The covalent nature of Eu-O bond and environment around Eu 3+ ions were discussed using Judd-Ofelt (J-O) intensity parameters. Internal quantum efficiency was calculated using excited state lifetime 5D 0 state of Eu 3+ ion and J-O theory. The CIE colour coordinates and colour purity were calculated using the spectral energy distribution function. Low excited state life time indicated that Eu 3+ doped TiO 2 can be used as red emitting phosphor for white light emitting diode applications. 相似文献
14.
The effect of substituting SnO 2 for TiO 2 in RuO 2+TiO 2 electrodes has been studied by varying the SnO 2 content systematically in a series of oxides of general composition 30 mol% RuO 2+ x mol% SnO 2+(70- x) mol% TiO 2. The surface properties have been investigated by voltammetric curves, the electrocatalytic activity by using O 2 evolution from 1 mol dm –3 HClO 4 solutions as a test reaction. It has been observed that only the surface area changes at intermediate compositions as a result of morphological modifications, while the electrocatalytic activity increases dramatically as the substitution of SnO 2 for TiO 2 becomes complete. Reasons for that are discussed. The present results do not support the claim that SnO 2 depresses the electrocatalytic activity of oxide electrodes for oxygen evolution.Dedicated to Professor Dr Fritz Beck on the occasion of his 60th birthday. 相似文献
15.
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
16.
The TiO 2/SiO 2/Ni–Cu–Zn ferrite composite for magnetic photocatalysts with high photocatalytic activity is successfully prepared in this study. The composite are composed of spherical or elliptical Ni–Cu–Zn ferrite nanoparticles about 20–60 nm as magnetic cores, silica as barrier layers with thickness of 15 nm between the magnetic cores and titania shells with thickness approximately 1.5 nm. Photodegradation examination of TiO 2/SiO 2/ Ni–Cu–Zn ferrite composite was carried out in methylene blue (MB) solutions illuminated under a Xe arc lamp with 35 W and color temperature of 6000 K. The results indicated that about 47.1% of MB molecules adsorbed on the TiO 2/SiO 2/Ni–Cu–Zn ferrite composite within 30 min mixing due to it higher pore volume of 0.034 cm 3/g, and after 6 h Xe lamp irradiation, 83.9% of MB 16.1% was photodegraded. Compared with the TiO 2 /Ni–Cu–Zn ferrite composite, the TiO 2/SiO 2/Ni–Cu–Zn ferrite composite with silica barrier layer prohibited the photodissolution and enhanced the photocatalytic ability. The magnetic photocatalyst shows high photocatalytic efficiency that the apparent first‐order rate constant kobs is 0.18427 h ?1, and good magnetic property that the saturation magnetization ( Ms) of is 37.45 emu/g, suggesting the magnetic photocatalyst can be easily recovered by the application of an external magnetic field. 相似文献
17.
Photocatalytic degradation using TiO2 is one of the most effective techniques for treating residual emerging compounds present in water. However, practical applications are limited since it only absorbs ultraviolet irradiation. Nitrogen and sulfur (N, S) co-doped TiO2 nanomaterials (N,S-TiO2) were prepared by a controlled sol–gel method; the characterization and photocatalytic activity have been studied for the removal of ciprofloxacin antibiotic under UV–Visible light. The interstitial doping of nitrogen and sulfur substitute oxygen and titanium into the TiO2 lattice, which increases the valence band and decreases the conduction band, respectively. The lowest value band-gap of 2.5 eV and the crystallite size of 5.13 nm compared to other available synthesis methods was observed on N,S-TiO2 which allowed to broaden the light absorption to the visible region. The low level electron and hole recombination was related by the N, S doping. The optimal ciprofloxacin removal was obtained at pH 5.5, a dosage of 0.05 g, initial concentration of 30 mg L?1 with a removal efficiency of 78.7%. A comparison of the effectiveness of antibiotic treatment of N,S-TiO2 with synthetic TiO2 and commercial TiO2 was also made, taking the potential for regeneration into account. The photocatalytic degradation of ciprofloxacin catalyzed by N,S-TiO2 was described by pseudo-first-order kinetics. 相似文献
18.
Multi-element doping is an effective method to suppress the leakage of BiFeO 3 (BFO). A systematic study on the effect of various elements (La, Er, Zn, Ti) doping on the leakage performance, mechanism and other electrical properties of BFO films was performed As the kinds of doping elements increases, the leakage current density of the BFO film gradually decreases. The leakage current density is gradually reduced from 5.78 × 10 ?2 A/cm 2 doped with one element (La) to 1.25 × 10 ?2 A/cm 2 doped with two elements (La, Ti), 4.13 × 10 ?3 A/cm 2 doped with three elements (La, Ti, Zn), and 4.53 × 10 ?4 A/cm 2 doped with four elements (La, Er, Zn, Ti). Finally, compared with pure BFO films, the leakage current density in doped BFO films is reduced by two orders of magnitude. Moreover, the conduction mechanism in doped BFO films is gradually changed from space charge limited current to ohmic conduction. This work provides an effective method to ameliorate the leakage of ferroelectric materials and lays a foundation for the practical application of BFO-based films. 相似文献
19.
Pd-doped anatase TiO 2 nanoparticles were synthesized by a modified sol–gel deposition technique. The synthetic strategy is applicable to other transition and post-transition metals to obtain phase-pure anatase titania nanoparticles. This is important in the sense that anatase titania forms the most hydroxyl radicals (compared to other polymorphs like rutile, brookite, etc.) for better photocatalytic performance. XRD and Raman data confirm the phase-pure anatase formation. Doping of Pd 2+ into Ti 4+ sites (for substitutional doping) or interstitial sites (for interstitial doping) creates strain within the nanoparticles and is reflected in the XRD peak broadening and Raman peak shifts. This is because of the ionic radii difference between Ti 4+(∼68 pm) and Pd 2+(∼86 pm). XPS data confirm the formation of high surface titanol groups at the nanoparticle surface and a large number of loosely bound Ti 3+–O bonds, both of which considerably enhance the photocatalytic activity of the doped nanoparticles. A comparative study with other metal doping (Ga) shows that TiO 2: Pd nanoparticles have more Ti 3+–O bonds, which enhance the charge transfer rate and hence improve the photocatalytic activity compared to other transition and post-transition metal-doped titania nanostructures. 相似文献
20.
This study focuses on the relationship between photo-catalytic performance and optical property over Si-incorporated TiO 2. The Si-incorporated TiO 2 particles exhibited a pure structure of anatase having a particle size of less than 20 nm and surface area of more than 190 m 2/g. The absorbance did not shift to a higher wavelength in spite of the incorporation of the Si ions, but the intensity of the photoluminescence (PL) curve was the smallest in the case of the 2.0 mol% Si-TiO 2, which was related to the recombination between the excited electrons and holes. Based on these results, the photodecomposition of methyl orange in the liquid reaction was enhanced over the 2.0 mol% Si-incorporated TiO 2 compared with that over pure TiO 2: Methyl orange at 10.0 ppm was completely decomposed after 100 min when 1.0 g of the 2.0 mol% Si-incorporated TiO 2 was used. 相似文献
|