共查询到20条相似文献,搜索用时 10 毫秒
1.
In this paper, a novel composite photocatalyst AgI/AgCl/TiO 2 was prepared by ion exchange method and characterized by XRD, SEM and UV-Vis spectrometry. The as-prepared AgI/AgCl/TiO 2 composites show much higher photocatalytic activity than AgCl/TiO 2 and AgI/TiO 2 under visible-light irradiation ( λ > 400 nm) in the process of methyl orange (MO) degradation. When the molar percentage of AgI to initial AgCl is 20% (sample SE-20%), the maximal degradation efficiency of MO has reached 85.8% after irradiation for 120 min. The enhancement of photocatalytic activity of the composite photocatalyst AgI/AgCl/TiO 2 will be attributed to its good absorption in the visible-light region, especially low recombination rate of the electron-hole pairs based on the photoluminescence (PL) spectra investigation of AgI/AgCl/TiO 2 and the matching band structures of AgI, AgCl and TiO 2. The detection of reactive species by radical scavengers displays that O 2− and H 2O 2 are the main reactive species for the degradation of MO under visible-light irradiation. Moreover, PL analysis by using terephthalic acid (TA) as a probe molecule further reveals that OH can be negligible for the degradation of MO. 相似文献
2.
Anatase TiO 2 was prepared by a facile sol-gel method at low temperature through tailoring the pH of sol-gel without calcination. As a control, anatase TiO 2 was also synthesized by the conventional sol-gel process, in which calcination at 500 °C was required to transform the amorphous oxide into highly crystalline anatase. As-prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). Their photocatalytic activities were evaluated by degradation of methyl orange under UV light irradiation. On the basis of experiment results, it could be concluded that TiO 2 prepared by low temperature route showed more advantages in small particle size, highly dispersion nature, abundance of surface hydroxyl groups, strong PL signal, and high photocatalytic activity over TiO 2 obtained by the conventional sol-gel process. Furthermore, the reason of the former possessing higher photocatalytic activity was discussed. 相似文献
3.
Catalytic ultrasonic degradation of aqueous methyl orange was studied in this paper. Heterogeneous catalyst MnO 2/CeO 2 was prepared by impregnation of manganese oxide on cerium oxide. Morphology and specific surface area of MnO 2/CeO 2 catalyst were characterized and its composition was determined. Results showed big differences between fresh and used catalyst. The removal efficiency of methyl orange by MnO 2/CeO 2 catalytic ultrasonic process was investigated. Results showed that ultrasonic process could remove 3.5% of methyl orange while catalytic ultrasonic process could remove 85% of methyl orange in 10 min. The effects of free radical scavengers were studied to determine the role of hydroxyl free radical in catalytic ultrasonic process. Results showed that methyl orange degradation efficiency declined after adding free radical scavengers, illustrating that hydroxyl free radical played an important role in degrading methyl orange. Theoretic analysis showed that the resonance size of cavitation bubbles was comparable with the size of catalyst particles. Thus, catalyst particles might act as cavitation nucleus and enhance ultrasonic cavitation effects. Measurement of H 2O 2 concentration in catalytic ultrasonic process confirmed this hypothesis. Effects of pre-adsorption on catalytic ultrasonic process were examined. Pre-adsorption significantly improved methyl orange removal. The potential explanation was that methyl orange molecules adsorbed on catalysts could enter cavitation bubbles and undergo stronger cavitation. 相似文献
4.
Pd-modified carbon fibers (CFs) are obtained by a facile oxidation-reduction method and then dip-coated in a sol-gel of titanium dioxide (TiO 2) to form supported TiO 2/Pd-CF photocatalysts. The morphology of the Pd-modified CFs and the amount Pd deposited are characterized by field emission scanning electron microscopy and atomic absorption spectrometry, respectively. X-ray diffraction is used to investigate the crystal structures of the TiO 2 photocatalyst. Acid orange II is used as a model contaminant to evaluate the photocatalytic properties of the photocatalyst under UV irradiation. TiO 2/Pd-CF exhibits higher catalytic activity than TiO 2/CF towards the degradation of acid orange II. Optimum photocatalytic performance and support properties are achieved when the Pd particle loading is about 10.8 mg/g. 相似文献
5.
The visible-light photocatalytic behavior of two different N-doped TiO 2 correlated with their physicochemical properties was investigated. The results show that N-TiO 2-1, prepared by a novel TiO 2 with unique defect structure, is more active in visible-light photocatalytic oxidation of C 3H 6 than N-TiO 2-2, prepared by standard P25-TiO 2 (Degussa). The specific rate constant of the former is ca. 5 times that of the latter. One model of photoactive center (V o-NO-Ti) in anatase phase responsible for the visible-light photocatalytic activity is proposed. The higher the V o-NO-Ti concentration is, the better the visible-light photocatalytic activity is. 相似文献
6.
TiO 2 micro/nanospheres were synthesized by a combination process contains hydrolysis of titanium tetra-n-butyl in mixed solution of anhydrous ethanol/ammonia and the subsequent calcination under 550 °C for 7 h. The pH values of the mixed solution were tuned to be 10.4, 11.0 and 11.6, respectively, by adding different amounts of ammonia. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the morphologies and the crystallinity. X-ray diffraction (XRD) patterns indicated that pH value of the precursors has an important effect on the crystal phase composition. UV-vis diffuse reflectance spectrum was applied to characterize the optical properties of samples. Degradation of methylene blue under the irradiation of 300 W Hg lamp confirmed the enhanced photocatalytic activity of TiO 2 micro/nanospheres. In addition, the formation mechanism was proposed. 相似文献
7.
Semiconductor loaded mesoporous materials in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Ag 2S/MCM-41 photocatalysts were prepared by ion exchange method and used for the photocatalytic degradation of methylene blue. The materials were characterized by different analytical techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and BET (Brunauer-Emmert-Teller) experiments. The effect of Ag 2S, MCM-41 support and different wt% of Ag 2S over the support on the photocatalytic degradation and influence of parameters such as Ag 2S loading, catalyst a mount, pH and initial concentration of dye on degradation are evaluated. The degradation reaction follows pseudo-first order kinetics. It was seen that 0.6 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. The degradation efficiency was decreased in dye concentration above 3.2 ppm for dye. 相似文献
8.
A series of photocatalysts TiO 2/CFA were prepared using coal fly ash (CFA), waste discharged from coal-fired power plant, as substrate, and then these photocatalysts were characterized by scanning electron microscope, X-ray diffraction analysis, nitrogen adsorption test and ultraviolet-visible absorption analysis. The effects of loading percent of TiO 2 on the photocatalytic activity and re-use property of TiO 2/CFA were evaluated by the photocatalytic decoloration and mineralization of methyl orange solution. The results show that the pore volume and the specific surface area of the TiO 2/CFA both increased with the increase in the loading percent of TiO 2, which improved the photocatalytic activity of TiO 2/CFA. However, when the loading percent of TiO 2 was too high (up to 54.51%), superfluous TiO 2 was easy to break away from CFA in the course of water treatment, which was disadvantaged to the recycling property of TiO 2/CFA. In this study, the optimal loading percent of TiO 2 was 49.97%, and the efficiencies of photocatalytic decoloration and mineralization could be maintained above 99% and 90%, respectively, when the photocatalyst was used repeatedly, without any decline, even at the sixth cycle. 相似文献
9.
Two kinds of vanadium-doped TiO 2 powders photocatalysts were prepared by sol-gel method in even doping and uneven doping modes, and were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of TiO 2 photocatalysts doped by vanadium evenly with lower dopant level up to 0.002 mol.% is better than that of undoped TiO 2, while with higher dopant level the activity is worse. TiO 2 photocatalysts doped by vanadium unevenly with a p-n junction semiconductor structure, was shown to have a much higher photocatalytic destruction rate than that of TiO 2 photocatalysts doped by vanadium evenly and undoped TiO 2, which is ascribed mainly to the electrostatic-field-driven electron-hole separation in TiO 2 particles doped by vanadium unevenly. 相似文献
10.
X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide–poly(vinylidenefluoride) (TiO 2–PVDF) films developed for applications in the photocatalytic degradation of pollutants. The composites were deposited on glass substrates by casting or spin coating from TiO2–PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO2–PVDF surface composition were used to optimize preparation conditions (composition of the TiO2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability. The use of spin-coating deposition and the increase of TiO2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO2/PVDF ratios led to film instability. PVDF–TiO2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO2 and the role played by the PVDF film during the degradation process. 相似文献
11.
CdS/TiO 2 nanocomposites were prepared via a simple wet chemical method, and characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their ability to degrade Acid Rhodamine B was investigated under visible light irradiation. The results indicate that CdS/TiO 2 nanocomposite with a mass ratio of 4:1(TiO 2:CdS) showed high photocatalytic activity and the CdS loaded on TiO 2 nanotube surface exhibited a hexagonal phase. The dispersion of CdS on TiO 2 nanotube surface had an important effect on the degradation efficiency of pollutant, which provides a strategy for practical industry application. 相似文献
12.
Activated carbon (AC) supported Zn 2+–TiO 2 photocatalyst was prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction, scanning electron micrograph, nitrogen absorption, diffuse reflectance UV/VIS and X-ray photoelectron spectroscopy. Using toluene as a pollution target, the photocatalytic activity of photocatalyst was evaluated. The results showed that prepared photocatalyst was obviously helpful for the removal of toluene in air. The photocatalytic degradation of toluene by Zn 2+–TiO 2/AC reached 100% for 40 min and remained 75% after 160 min, while degradation by TiO 2 was only 30%. It indicated that the photocatalytic activity of prepared photocatalyst was enhanced. It is due to Zn 2+-doping increased the oxidation and reduction of hole–electron pairs, which was the important factor in heterogeneous photocatalysis. 相似文献
13.
In this study, new nanoscale photocatalyst based on silver and CNTs/TiO 2 was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO 2 was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO 2 increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO 2 for dye degradation was nearly 1.2 times than that of CNTs/TiO 2, which indicated decorating Ag nanoparticles on CNTs/TiO 2 could enhance the photocatalytic ability. 相似文献
14.
TiO 2 sol-gels with various Ag/TiO 2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO 2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO 2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO 2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO 2 sol-gel, four types of the TiO 2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO 2), TA (bottom layer was pure TiO 2, surface layer was Ag modified), TT (pure TiO 2 thin film) and AA (TiO 2 thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent ( Iph). LSV confirmed the existence of Ag 0 state in the TiO 2 thin film. SEM and XRD experiments indicated that the sizes of the TiO 2 nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO 2 thin film. 相似文献
15.
Solid-phase photocatalytic degradation of polyethylene (PE) plastic, one of the most common commercial plastic, over copper phthalocyanine (CuPc) modified TiO 2 (TiO 2/CuPc) photocatalyst was investigated in the ambient air under solar light irradiation. Higher PE weight loss rate, greater texture change; more amount of generated CO 2, which is the main product of the photocatalytic degradation of the composite PEC plastic can be achieved in the system of PE-(TiO 2/CuPc) in comparison with PE-TiO 2 system. The CuPc promoted charge separation of TiO 2 and enhanced the photocatalytic degradation of PE based on the analysis of surface photovoltage spectroscopy (SPS). During the photodegradation of PE plastic, the reactive oxygen species generated on TiO 2 or TiO 2/CuPc particle surfaces play important roles. The present study demonstrates that the combination of polymer plastic with TiO 2/CuPc composite photocatalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants under solar light irradiation. 相似文献
16.
Titanium dioxide (TiO 2) nanoparticles co-doped with N and Fe were prepared via modified sol-gel process. The products were characterized by transmission electron microscopy (TEM), N 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). It is shown that the prepared TiO 2 particles were less than 10 nm with narrow particle size distribution. The addition of MCM-41 caused the formation of Ti-O-Si bond which fixed the TiO 2 on MCM-41 surface, thus restricted the agglomeration and growth of TiO 2 particles. The photocatalytic performance in the degradation of methylene blue showed that N, Fe co-doped TiO 2 exhibited much higher photocatalytic activity than doped sample with nitrogen or Fe 3+ alone under both UV and visible light. N, Fe co-doping decreased the loss of doping N during the degradation reaction, thus increased the photocatalytic stability. It was also found that the nitridation time had significant influence on the photocatalytic activity of prepared TiO 2 catalysts. 相似文献
17.
A new mono-functionalized porphyrin derivative, 5-mono-[4-(2-(4-hydroxy)-phenoxy)ethoxy]-10,15,20-triphenylporphyrin ( 3) and its Cu(II) ( 3a), Zn(II) ( 3b) and Ni(II) ( 3c) metalloporphyrins were synthesized and characterized by using various spectroscopic techniques. The corresponding 3a, 3b, 3c-TiO 2 photocatalysts were then prepared and characterized by means of FT-IR and diffused reflectance spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activities of 3a, 3b, 3c-TiO 2 were investigated by testing the photodegradation of 4-nitrophenol (4-NP) in aqueous solution under the halogen lamp irradiation. The results indicated that all the 3a, 3b, 3c enhanced the photocatalytic efficiency of bare TiO 2 in photodegrading the 4-NP, and 3a-TiO 2 exhibited the highest photocatalytic activity. The result is considered a combined action of potential match of 3a with TiO 2 CB and effective impregnated of 3a onto the surface of TiO 2. 相似文献
18.
Titanium dioxide (TiO 2) films are deposited by codoping nitrogen and carbon on indium tin oxide-coated substrates as visible light (Vis)-enabled catalysts. The X-ray diffraction peak intensity of the preferential orientation in (2 1 1) plane declines when the topmost 1.0 μm layer of the film is ground off. The decrease in the crystallite size and the crystallinity of anatase TiO 2 film is also evidenced by a shift towards the high wave number and broadening of the Raman spectra. Low doping concentrations of N (1.3%) and C (1.8%) are estimated by X-ray photoelectron spectroscopy (XPS) which displays an N 1 s peak at 396.8 eV and a C 1 s peak at 282.1 eV, respectively. This is attributed to the substitution of the oxygen sites with nitrogen and carbon, which is believed to be responsible for the Vis photocatalytic activity into a wavelength of >500 nm. The cross-sectional transmission electron microscopy images show larger pores at the grain boundaries and in larger columnar crystals than in the undoped TiO 2 film. All of these results indicate that porosity, crystallinity and shift in the preferential orientation are more pronounced close to the surface than close to the bottom of the sample. Wettability upon measurement of the water contact angle, methylene blue degradation and radical formation tests under both ultraviolet and Vis irradiation demonstrate that the topmost surface renders not only a larger reactive surface area but also a better carrier transport route than the rest of the film, improving its photocatalytic activity. These results show that surface porosity of the film is dominant than the tailoring of the photocatalytic activities of N,C-codoped TiO 2 catalysts. 相似文献
19.
A series of Nd-TiO 2 powders have been prepared by the sol-gel technique with neodymium nitrate and tetra- n-butyl titanium as raw materials, and then Nd-TiO 2 nanotubes were fabricated by the hydrothermal method with a 10 mol l −1 NaOH solution. The as-prepared Nd-TiO 2 nanotubes were characterized by TEM, XRD, DRS, and XPS, and their photocatalytic activity was also tested in the case of the degradation of methyl orange in water. TEM photograph showed that Nd-TiO 2 nanotubes were about 10-20 nm in diameter, with the lengths range from 100 to 300 nm. TiO 2 nanotubes contained anatase and rutile crystallites. However, 0.3% Nd-TiO 2 nanotubes contained anatase crystallites, and only little rutile crystallites, so it is shown that neodymium doping hindered the phase transformation from anatase into rutile. Nd doping increased the visible-light absorption ability of Nd-TiO 2 nanotubes, and a red shift for Nd-TiO 2 nanotubes appeared when compared to TiO 2 nanotubes. XPS analysis showed that two types of oxygen existed on the photocatalyst surface, including metal-O and hydroxyl group, and more hydroxyl group was on the surface of 2% Nd-TiO 2 nanotubes than on the surface of TiO 2 nanotubes. Nd doping enhanced the photocatalytic activities of Nd-TiO 2 nanotubes, and 0.3% Nd-TiO 2 nanotubes exhibited the highest photocatalytic activity. 相似文献
20.
In order to get photocatalysts with desired morphologies and enhanced visible light responses, the Fe-doped TiO 2 nanorod clusters and monodispersed nanoparticles were prepared by modified hydrothermal and solvothermal method, respectively. The microstructures and morphologies of TiO 2 crystals can be controlled by restraining the hydrolytic reaction rates. The Fe-doped photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy (UV-vis), N 2 adsorption-desorption measurement (BET), and photoluminescence spectroscopy (PL). The refinements of the microstructures and morphologies result in the enhancement of the specific surface areas. The Fe 3+-dopants in TiO 2 lattices not only lead to the significantly extending of the optical responses from UV to visible region but also diminish the recombination rates of the electrons and holes. The photocatalytic activities were evaluated by photocatalytic decomposition of formaldehyde in air under visible light illumination. Compared with P25 (TiO 2) and N-doped TiO 2 nanoparticles, the Fe-doped photocatalysts show high photocatalytic activities under visible light. 相似文献
|