共查询到20条相似文献,搜索用时 31 毫秒
1.
A novel rice spike-like g-C 3N 4/TiO 2 nanowire heterojunctions are fabricated by hydrothermal treating Na 2Ti 3O 7 ultralong nanotubes in the presence of g-C 3N 4. The presence of g-C 3N 4 promotes the hydrolysis of Na 2Ti 3O 7 ultralong nanotubes. The partially replaced O of TiO 2 by N from g-C 3N 4 leads to the formation of a tight-binding interface between one dimensional TiO 2 and two dimensional g-C 3N 4, which is crucial for fast and effective transfer of photogenerated electrons in heterostructured photocatalysts. As a result, the g-C 3N 4/TiO 2 nanowire heterojunctions exhibit excellent visible-light photocatalytic activity. The kinetic constant (k) of g-C 3N 4/TiO 2 (0.024?min ?1) for degradation of methylene blue under visible light irradiation is 1.85 and 4 times than that of pure g-C 3N 4 and P25, respectively. 相似文献
2.
The solar light sensitive g-C 3N 4/TiO 2 heterojunction photocatalysts containing 20, 50, 80, and 90 wt% graphitic carbon nitride (g-C 3N 4) were prepared by growing Titania (TiO 2) nanoparticles on the surfaces of g-C 3N 4 particles via one step hydrothermal process. The hydrothermal reactions were allowed to take place at 110 °C at autogenous pressure for 1 h. Raman spectroscopy analyses confirmed that an interface developed between the surfaces of TiO 2 and g-C 3N 4 nanoparticles. The photocatalyst containing 80 wt% g-C 3N 4 was subsequently heat treated 1 h at temperatures between 350 and 500 °C to improve the photocatalytic efficiency. Structural and optical properties of the prepared g-C 3N 4/TiO 2 heterojunction nanocomposites were compared with those of the pristine TiO 2 and pristine g-C 3N 4 powders. Photocatalytic activity of all the nanocomposites and the pristine TiO 2 and g-C 3N 4 powders were assessed by the Methylene Blue (MB) degradation test under solar light illumination. g-C 3N 4/TiO 2 heterojunction photocatalysts exhibited better photocatalytic activity for the degradation of MB than both pristine TiO 2 and g-C 3N 4. The photocatalytic efficiency of the g-C 3N 4/TiO 2 heterojunction photocatalyst heat treated at 400 °C for 1 h is 1.45 times better than that of the pristine TiO 2 powder, 2.20 times better than that of the pristine g-C 3N 4 powder, and 1.24 times better than that of the commercially available TiO 2 powder (Degussa P25). The improvement in photocatalytic efficiency was related to i) the generation of reactive oxidation species induced by photogenerated electrons, ii) the reduced recombination rate for electron-hole pairs, and iii) large specific surface area. 相似文献
3.
Dendritic growth of bismuth oxide nanostructured films was accomplished by reactive magnetron sputtering. The deposition of the Bi 2O 3 template layers was adapted to abide a vapour-liquid-solid mechanism in order to develop a 3D growth morphology with high surface area templates for photocatalytic applications. TiO 2 photocatalytic thin films were deposited at a later stage onto Bi 2O 3 layers. The obtained heterostructured films were characterized by scanning electron microscopy, X-ray diffraction and atomic force microscopy. Additionally, the photocatalytic efficiency was assessed by conducting an assay using methylene blue dye as testing pollutant under a UV-A illumination. The photocatalytic tests revealed that the Bi 2O 3 layers functionalized with TiO 2 thin films are more efficient at degrading the pollutant, by a factor of 6, when compared with the individual layered films. 相似文献
4.
Z-scheme anatase/rutile TiO 2/g-C 3N 4 hybrids (denoted as LTARCN-x, x represents calcination temperature) were designed and synthesized by growing TiO 2 nanorods on the surface of g-C 3N 4 utilizing impregnation-calcination method. Furthermore, through the etched effect of hydrochloric acid and calcination treatment, the as-prepared LTARCN-x possessed abundant pore structure and larger surface area, and the surface area of LTARCN-425 was 8.5 times than that of bulk g-C 3N 4. Meanwhile, the g-C 3N 4 would play a role of carrier to prevent from the aggregation of TiO 2 nanorods. In addition, under visible light irradiation, the Z-scheme heterostructure would be constructed between the rutile TiO 2 nanorod and g-C 3N 4 nanosheet, respectively. The optimized photocatalyst LTARCN-425 exhibited a preferable activity, the photocatalytic hydrogen production rate of LTARCN-425 was about 1031 μmol g ?1 h ?1, and it was about 6.3 and 13.6 times than that of g-C 3N 4 and TiO 2, respectively. Moreover, the photocatalytic mechanism of the hydrogen production was studied intensively via designing fluorescent probe, Pt and PbO 2 deposition experiment, and the characterizations of EPR, TEM, HRTEM and XPS. 相似文献
5.
2D heterojunction based on g-C 3N 4 nanosheets with other semiconductor nanosheets is a promising way to improve photocatalytic hydrogen evolution (PHE) activity over g-C 3N 4. However, current 2D heterojunction based on g-C 3N 4 are unsatisfactory due to their insufficient absorption of visible light and inefficient charge separation. In this work, Ag/TiO 2/g-C 3N 4 nanocomposites based on 2D heterojunction coupling with Ag surface plasmon resonance (SPR) were synthesized by a method combining facile wetness impregnation calcination. The PHE activity of Ag/TiO 2/g-C 3N 4 nanocomposites is attributed to the TiO 2/g-C 3N 4 2D heterojunction and bare g-C 3N 4 nanosheet under visible light irradiation, indicating a cooperative effect between Ag and TiO 2/g-C 3N 4 2D heterojunction. As a result of SPR effect, the composites strongly absorb visible light. In addition, the oscillating hot electrons from Ag can easily transfer to 2D heterojunction. This synergistic effect lead to sufficient visible light absorption and efficient charge separation of 2D heterojunction, which improved the PHE activity of g-C 3N 4. This work indicates that loading metal nanoparticles on 2D heterojunction as metal SPR-2D heterojunction nanocomposites may be a potential method for harvesting visible light for PHE. 相似文献
6.
TiO 2 photocatalyst loaded on Si 3N 4 (TiO 2/Si 3N 4) was prepared by a conventional impregnation method and its photocatalytic performance for the degradation of organics (2-propanol) diluted in water was compared with that of TiO 2 photocatalysts (TiO 2/SiO 2, TiO 2/Al 2O 3, and TiO 2/SiC) loaded on various types of supports (SiO 2, Al 2O 3, and SiC). The formation of the well-crystallized anatase phase of TiO 2 was observed on the calcined TiO 2/Si 3N 4 photocatalyst, while a small anatase phase of TiO 2 was observed on the TiO 2/SiC photocatalyst and amorphous TiO 2 species was the main component on the TiO 2/SiO 2 and TiO 2/Al 2O 3 photocatalysts. The measurements of the water adsorption ability of photocatalysts indicated that the TiO 2/Si 3N 4 photocatalyst exhibited more hydrophobic surface properties in comparison to other support photocatalysts. Under UV-light irradiation, the TiO 2/Si 3N 4 photocatalyst decomposed 2-propanol diluted in water into acetone, CO 2, and H 2O, and finally, acetone was also decomposed into CO 2 and H 2O. The TiO 2/Si 3N 4 photocatalyst showed higher photocatalytic activity than TiO 2 photocatalyst loaded on other supports. The well-crystallized TiO 2 phase deposited on Si 3N 4 and the hydrophobic surface of Si 3N 4 support are important factors for the enhancement of photocatalytic activity for the degradation of organic compounds in liquid-phase reactions. 相似文献
7.
Tin dioxide nanoparticles were prepared in the presence of graphitized carbon nitride (g-C 3N 4) forming nanocomposites with different contents of SnO 2 up to 40 %. G-C 3N 4 was synthetized by heating of melamine at 550 °C in the open air and Sn 2+ ions were precipitated by sodium hydroxide in g-C 3N 4 aqueous dispersions. Resulting mixtures were dried by freezing at ?20 °C and calcined at 450 °C to obtain SnO 2/g-C 3N 4 nanocomposites.The nanocomposites were characterized by common characterization methods in solid state and in their aqueous dispersions using dynamic light scattering (DLS) analysis and photocatalysis. SnO 2 nanoparticles in the nanocomposites were found to have an average size of 4 nm, however, those precipitated without g-C 3N 4 had an average size of 14 nm. Separation of photoinduced electron and holes via heterojunction between SnO 2 and g-C 3N 4 was demonstrated by photocatalytic decomposition of Rhodamine B (RhB) under LED visible irradiation (416 nm) and photocurrent measurements. The most photocatalytically active nanocomposite contained 10 % of SnO 2. Graphitized carbon nitride was assumed to serve as a template structure for the preparation of SnO 2 nanoparticles with a narrow size distribution without using any stabilizing additives. 相似文献
8.
A novel multi-dimensional through-holes structure of g-C 3N 4 with adjustable pore size was prepared by controlling the mass ratio of oxamide (OA, structure guiding agent) to urea during one-step calcination process, and a break-rearrangement mechanism was explored. Then, a series of porous g-C 3N 4/TiO 2 (CT) composites with uniformly deposited TiO 2 nanoparticles were prepared based on the multi-dimensional framework by a facile hydrothermal method. The results show that a new S-scheme heterojunction with multi-dimensional through-channel structure was obtained, which is particularly desired for enhancing the visible-light utilization, reducing the carrier recombination rate and enhancing redox capacity. The CT composite obtained at hydrothermal treatment time of 2 h has a specific surface area of 180.15 m 2 g -1, which shows high degradation capability (99.99%) for tetracycline hydrochloride (TC·HCl) under 350 W Xe lamp irradiation for 90 min. In addition, CT nanostructures was in-situ growth on carbon fiber (CFs), the degradation rate constant is 0.1566 min -1, and 90% of the degradation efficiency can be maintained even after 5 consecutive cycles. It is expected to provide an effective reference for solving the problems of recovery difficulty and low reuse rate of powder photocatalytic materials. 相似文献
9.
In this study, the multifunctional carbon nitride based composite graphitic-C 3N 4 (g-C 3N 4)/TiO 2/Ag was prepared through a simple and efficient vacuum freeze-drying route. TiO 2 and Ag nanoparticles were demonstrated to decorate onto the surface of g-C 3N 4 sheet. In the ultraviolet–visible absorption test, a narrower band gap and red-shift of light absorption edge were observed for g-C 3N 4/TiO 2/Ag compared to pristine g-C 3N 4 and single-component modified g-C 3N 4/TiO 2. The photodegradation property of g-C 3N 4/TiO 2/Ag was investigated toward the degradation of methylene blue (abbreviated as MB) under the irradiation of visible light. These results indicated that the degradation performance of organic dyes for g-C 3N 4/TiO 2/Ag was obviously improved compared with g-C 3N 4/TiO 2 and g-C 3N 4. The reaction rate constant of MB degradation for g-C 3N 4/TiO 2/Ag was 4.24 times higher than that of pristine g-C 3N 4. In addition, such rationally constructed nanocomposite presented evidently enhanced antibacterial performance against the Gram-negative Escherichia coli. Concentration dependent antibacterial performance was systematically investigated. And 84% bacterial cell viability loss had been observed at 500 μg/mL g-C 3N 4/TiO 2/Ag within 2 h visible light irradiation. 相似文献
10.
In this paper, Cu 2O/TiO 2 composite porous microspheres were prepared in the absence of templates and additives by a simple hydrothermal method using Cu(CH 3COO) 2·H 2O and (NH 4) 2TiF 6 as precursors. The photocatalytic activity of the samples was evaluated by the photo-degradation of methylene blue (MB) aqueous solution under the visible-light illumination. To the best of our knowledge, this is the first report on the preparation and photocatalytic activity of Cu 2O/TiO 2 composite porous microspheres with a template-free hydrothermal method. This work may provide new insights into preparing other inorganic porous microspheres. 相似文献
11.
High performance-anatase TiO 2 films were successfully formed on metallic titanium by anodization in an acidic electrolyte composed of H 2SO 4, H 3PO 4 and H 2O 2 subsequent to pre-nitridation treatment. The pre-nitridation treatment was carried out by pre-annealing metallic titanium under a nitrogen atmosphere of 0.1 MPa. The anodized films showed photocatalytic activity in photooxidization of the iodide anion into the tri-iodide anion. The nitridation treatment had a significant effect not only on the formation of anatase TiO 2 films but also on the photocatalytic activity of the anodized films. 相似文献
12.
TiO 2, TiO 2/Ag and TiO 2/Au photocatalysts exhibiting a hollow spherical morphology were prepared by spray pyrolysis of aqueous solutions of titanium citrate complex and titanium oxalate precursors in one-step. Effects of precursor concentration and spray pyrolysis temperature were investigated. By subsequent heat treatment, photocatalysts with phase compositions from 10 to 100% rutile and crystallite sizes from 12 to 120 nm were obtained. A correlation between precursor concentration and size of the hollow spherical agglomerates obtained during spray pyrolysis was established. The anatase to rutile transformation was enhanced with metal incorporations and increased precursor concentration. The photocatalytic activity was evaluated by oxidation of methylene blue under UV-irradiation. As-prepared TiO 2 particles with large amounts of amorphous phase and organic residuals showed similar photocatalytic activity as the commercial Degussa P25. The metal incorporated samples showed comparable photocatalytic activity to the pure TiO 2 photocatalysts. 相似文献
13.
In this paper, a novel g-C 3N 4/2 wt% SnS 2 nanocomposite was successfully synthesized using an in-situ growth of SnS 2 on g-C 3N 4. X-ray diffraction (XRD), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET) method, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectrometer were used to characterize the photocatalysts. Exploring adsorption behavior, as an importatnt stage during photocatalytic reactions, is of great importance. Hence, both adsorption and photocatalytic performance of the synthesized photocatalysts have been investigated in detail. The adsorption isotherm fittings exhibited that Freundlich and Langmuir-Freundlich models can be applied to the methylene blue (MB) adsorption on the photocatalysts, indicating surface heterogeneity should be considered. A pseudo-second-order model was fitted to explore the adsorption kinetics. According to the observed redshift in the Fourier transform infrared spectroscopy (FTIR) result of g-C 3N 4/SnS 2 nanocomposite, π-π interaction was dominant during MB adsorption. Also, a slight redshift and significant PL intensity reduction in g-C 3N 4/SnS 2 nanocomposite led to 96% photocatalytic efficiency after 180 min under visible light radiation. The kinetics of photodegradation over g-C 3N 4/SnS 2 was about 9 and 3 times higher than those of g-C 3N 4 and SnS 2 photocatalysts, respectively. The superoxide and hydroxyl radicals were the main reactive species in the photocatalytic degradation with a Z-scheme charge transfer mechanism. The g-C 3N 4/SnS 2 nanocomposite was found to be remarkably stable after three consecutive cycles of MB degradation. 相似文献
14.
Highly efficient visible-light-driven heterojunction photocatalysts, spindle-shaped nanoporous TiO 2 coupled with graphitic g-C 3N 4 nanosheets have been synthesized by a facile one-step solvothermal method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption-desorption analysis and UV–vis diffuse reflectance spectrometry (DRS), proving a successful modification of TiO 2 with g-C 3N 4. The results showed spindle-shaped nanoporous TiO 2 microspheres with a uniform diameter of about 200 nm dispersed uniformly on the surface of graphitic g-C 3N 4 nanosheets. The g-C 3N 4/TiO 2 hybrid materials exhibited higher photocatalytic activity than either pure g-C 3N 4 or nanoporous TiO 2 towards degradation of typical rhodamine B (RhB), methyl blue (MB) and methyl orange (MO) dyes under visible light (>420 nm), which can be largely ascribed to the increased light absorption, larger BET surface area and higher efficient separation of photogenerated electron–hole pairs due to the formation of heterostructure. In addition, the possible transferred and separated behavior of electron–hole pairs and photocatalytic mechanisms on basis of the experimental results are also proposed in detail. 相似文献
15.
In this study, graphitic carbon nitride (g-C 3N 4) was successfully coupled with TiO 2 using hydrothermal method, to develop an advanced heterojunction photocatalyst. The interaction between g-C 3N 4 and TiO 2 was confirmed through analysis of X-Ray spectroscopy (XPS) C 1s, N 1s, O 1s high resolution core level spectra of g-C 3N 4, TiO 2 and g–C 3N 4–TiO 2 heterojucntion. Further, through valence band spectra analysis, conduction band offset (0.12 eV) and valence band offset (0.28 eV) of g–C 3N 4–TiO 2 heterojunction were estimated. Also, composite material was identified as type II heterojunction between g-C 3N 4 and TiO 2. XRD, UV–vis, BET and HRTEM were employed to understand the changes in physicochemical properties. Photocatalytic hydrogen production rates were evaluated through water splitting experiments. Under visible light irradiation highest hydrogen production rate was achieved for g–C 3N 4–TiO 2 heterojunction sample with high content of TiO 2, and was about 1041 μmol/g.h. The improved photocatalytic activity of the heterojunction material was explained in detail. 相似文献
16.
Operando FTIR spectroscopy has been used to study the photocatalytic oxidation of acetone vapors over semiconductors films containing TiO 2 and ZrO 2. Preparation of these coatings was carried out by dipping a silicon wafer in stable sols containing particles of TiO 2, Ti 1−xZr xO 2, or a mixture of ZrO 2 and TiO 2. These differences in chemical composition and phase homogeneity were selected in order to determine their effect on the photocatalytic performance. A transmission cell specifically designed for in situ studies of photocatalytic coatings was utilized for the FTIR experiments under reaction conditions. In contrast with investigations with powdered photocatalysts, the use of thin films guarantees that the whole semiconductor is irradiated, and for that reason purely photochemical reactions are monitored. Acetone adsorption takes place molecularly and is higher on the Ti 1−xZr xO 2 coating. This fact is very likely related to the higher specific surface of the samples containing Zr. However, the maximum photocatalytic rate for acetone degradation corresponds to the films composed by a binary mixture of TiO 2 and ZrO 2. On the other hand, remarkable differences on the type and concentration of intermediates appearing as a result of the photocatalytic oxidation of acetone are found for the coatings studied. A simple kinetic model was applied to analyze the evolution of both gas phase and surface species. The parameters obtained indicate that each specific surface process is affected in a different way by the variation in the composition of the photoactive films. 相似文献
17.
Y 2O 3-doped TiO 2 films were prepared on glass substrates by means of pulsed DC reactive magnetron sputtering method using titanium and yttrium mixed target. XPS results showed that the films were composed of fully oxidation states of the two elements, Y 2O 3–TiO 2 composite oxides. The existence of yttrium inhibited the crystal growth of TiO 2 in the films and Y 2O 3 mainly presented in its amorphous state in the films. UV–vis transmittance of the films decreased whereas their reflectance increased slightly. Yttrium doping had detrimental effect on photocatalytic activity of the TiO 2 films. Photocatalytic degradation efficiency of methyl orange solution declined along with increasing yttrium concentration. 相似文献
18.
This study elucidates how indium tin oxide (ITO) thin film affects the microstructural and photocatalytic properties of layered TiO 2/ITO films prepared by DC magnetron sputtering. Two ITO substrates, as-received ITO (aITO) and in situ sputtered ITO (sITO), are adopted herein. Photocatalytic measurements of methylene blue and dimethyl sulfoxide indicate that the layered TiO 2/sITO film has greater photocatalytic oxidation than the TiO 2/aITO catalyst. According to photoelectrochemical tests, the latter exhibits a completely opposite activity to that of the former. Secondary ion mass spectrometry elemental depth profiles reveal that tin atoms in the sITO film really permeate into the growing TiO 2 film and promote the formation of the crystalline Ti 1−xSn xO 2 layer. Additionally, cross-sectional transmission electron microscopy images and the selective area diffraction patterns show the difference between the diffusion of tin in the two catalysts. The photocatalytic oxidation capability is further enhanced in the layered TiO 2/sITO film because of an increase in the bandgap energy and a positive shift in the Fermi level energy of the Ti 1−xSn xO 2 layer. Conversely, tin diffusion is limited in the aITO substrate under controlled conditions, in such a manner that a Schottky barrier can form at the TiO 2/aITO interface. Therefore, photogenerated electrons can be efficiently transferred from the overlaid TiO 2 film to the aITO substrate, producing a remarkable photocurrent density under UV illumination. Microstructural measurements reveal that the growth of the reactive {0 0 1} facets and columnar porous structure are favored by the synergetic effect of ITO substrate and an extended period of deposition. Accordingly, the photocatalytic capabilities are further raised. 相似文献
19.
Magnetic/dielectric composites can offer good electromagnetic impendence. However, the strategy for embodying strong absorbing ability and broad effective absorption band simultaneously is a significant challenge. Therefore, assembled porous Fe 3O 4@g-C 3N 4 hybrid nanocomposites have been designed and synthesized, in which porous Fe 3O 4 nanospheres assembled by ~ 3?nm Fe 3O 4 nanoparticles are surrounded by g-C 3N 4. The introduction of g-C 3N 4 improves dielectric loss ability at 2–18?GHz and magnetic loss ability at 2–10?GHz, and enhances attenuation constant, and increases electromagnetic impedance degree. These merits ensure that assembled porous Fe 3O 4/g-C 3N 4 hybrid nanocomposites deliver superior microwave absorption performance, such as effective absorption bandwidth, fE, (reflection loss less ??10?dB) exceeding 5?GHz at 2.0–2.3?mm, the maximal fE of 5.76?GHz and minimal reflection loss of at least ??20?dB with thickness ranging from 2.3 to 10.0?mm, avoiding the sensitivity of absorption properties to absorbing layer thickness. Stable microwave absorbing performance originates from multi-interfacial polarization, multi-reflection, enhanced electromagnetic loss capability, and good electromagnetic impedance. Our study offers a new idea for stable microwave absorber at 2–18?GHz. 相似文献
20.
The g-C3N4 nanosheet was prepared by calcination method, the MoS2 nanosheet was prepared by hydrothermal method. The g-C3N4/MoS2 composites were prepared by ultrasonic composite in anhydrous ethanol. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence techniques were used to characterize the materials. The photocatalytic degradation of Rhodamine B (Rh B) by g-C3N4/MoS2 composites with different mass ratios was investigated under visible light. The results show that a small amount of MoS2 combined with g-C3N4 can significantly improve photocatalytic activity. The g-C3N4/MoS2 composite with a mass ratio of 1:8 has the highest photocatalytic activity, and the degradation rate of Rh B increases from 50 to 99.6%. The main reason is that MoS2 and g-C3N4 have a matching band structure. The separation rate of photogenerated electron–hole pairs is enhanced. So the g-C3N4/MoS2 composite can improve the photocatalytic activity. Through the active material capture experiment, it is found that the main active material in the photocatalytic reaction process is holes, followed by superoxide radicals. 相似文献
|