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1.
A TiO2 nanotube-based nanoreactor was designed and fabricated by facile two steps synthesis: firstly, hydrothermal synthesized SrTiO3 was deposited on TiO2 nanotubes (TiO2NTs). Secondly, the Au nanoparticles (NPs) were encapsulated inside the TiO2NTs followed by vacuum-assisted impregnation. The as-synthesized composites were characterized using Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Photoluminescence spectra (PL) and Ultraviolet–visible absorption spectroscopy (UV–vis). The photocatalytic performance was evaluated by the hydrogen evolution reaction. The results revealed that the SrTiO3 modified TiO2NTs confined Au NPs (STO-TiO2NTs@Au) achieved an enhanced hydrogen evolution rate at 7200 μmol h−1 g−1, which was 2.2 times higher than that of bald TiO2NTs@Au at 3300 μmol h−1 g−1. The improved photocatalytic activity could be attributed to the synergistic effect of the electron-donating of SrTiO3 and TiO2NTs confinement. The as-designed nanoreactor structure provides an example of efficient carriers' separation photocatalyst.  相似文献   

2.
A series of Au/TiO2 catalysts were prepared by photo-deposition (PD) method. Various preparation parameters, such as pH value, power of UV light and irradiation time on the characteristics of the catalysts were investigated. The catalysts were characterized by inductively-coupled plasma-mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The preferential oxidation of CO in H2 stream (PROX) on these catalysts was carried out in a fixed-bed micro reactor with a feed of CO: O2: H2: He = 1: 1: 49: 49 (volume ratios) and a space velocity of 30,000 ml/g h. Limited amount of O2 was used to investigate the selectivity of O2 reacting with CO or H2. Au/TiO2 catalysts prepared by PD method showed narrow particle size distribution of gold particles within few nanometers and were found to be 1.5 nm. The particle size of gold nanoparticles deposited on the support depends on irradiation time, UV light source and pH value of preparation. The electronic structure of Au was a function of particle size. The smaller the Au particle size was, the higher the concentration of Au cation was. Using weak power of UV light, appropriate irradiation time and suitable pH value, very fine gold particles on the support could be obtained even in the powder form. The samples prepared with PD method did not need heat treatment to reduce Au cation, UV irradiation could reduce it. Therefore it is easier to have smaller particle size. Au/TiO2 catalysts prepared by PD method were very active and selective in PROX reaction. In long time test, the catalysts were stable at 80 °C for more than 60 h.  相似文献   

3.
A series of Au/TiO2 photocatalysts was synthesized via the light assistance through the photo-deposition for H2 production by photocatalytic water splitting using ethanol as the hole scavenger. Effect of solution pH in the range of 3.2–10.0 on the morphology and photocatalytic activity for H2 production of the obtained Au/TiO2 photocatalysts was explored. It was found that all Au/TiO2 photocatalysts prepared in different solution pH exhibited comparable anatase fraction (~0.84–0.85) and crystallite size of TiO2 (21–22 nm), but showed different quantity of deposited Au nanoparticles (NPs) and other properties, particularly the particle size of the Au NPs. Among all prepared Au/TiO2 photocatalysts, the Au/TiO2 (10.0) photocatalyst exhibited the highest photocatalytic activity for H2 production, owning to its high metallic state and small size of Au NPs. Via this photocatalyst, the maximum H2 production of 296 μmol (~360 μmol/g?h) was gained at 240 min using the 30 vol% ethanol as the hole scavenger at the photocatalyst loading of 1.33 g/L under the UV light intensity of 0.24 mW/cm2 with the quantum efficiency of 61.2% at 254 nm. The loss of the photocatalytic activity of around 20% was observed after the 5th use.  相似文献   

4.
An effective improvement of hydrogen evolution from water splitting under solar light irradiation was investigated using quantum dots (QDs) compounds loaded onto a Au/TiO2 photocatalyst. First, Au/TiO2 was prepared by the deposition-precipitation method, and then sulfide QDs were loaded onto the as-prepared Au/TiO2 by a hydrothermal method. QDs were loaded onto Au/TiO2 to enhance the energy capture of visible light and near-infrared light of the solar spectrum. The results indicated that the as-prepared heterojunction photocatalysts absorbed the energy from the range of ultraviolet light to the near-infrared light region and effectively reduced the electron-hole pair recombination during the photocatalytic reaction. Using a hydrothermal temperature of 120 °C, the as-prepared (ZnS–PbS)/Au/TiO2 photocatalyst had a PbS QDs particle size of 5 nm, exhibited an energy gap of 0.92 eV, and demonstrated the best hydrogen production rate. Additionally, after adding 20 wt % methanol as a sacrificial reagent to photocatalyze for 5 h, the hydrogen production rate reached 5011 μmol g−1 h−1.  相似文献   

5.
The application of hydrogen energy potentially addresses energy and environmental problems. In order to improve the photocatalytic efficiency, nanocomposite of N-doped TiO2 with graphene oxide (NTG) is prepared and characterized with Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), photoluminescent spectra. The application of NTG to hydrogen evolution exhibits high photocatalytic efficiency of 716.0 or 112.0 μmol h−1 g−1 under high-pressure Hg or Xenon lamp, which is about 9.2 or 13.6 times higher than P25 photocatalyst. This is mainly attributed to the N-doping of TiO2 and the incorporation of graphene oxide resulting in narrow band gap, together with the synergistic effect of fast electron-transporting of photogenerated electrons and the efficient electron-collecting of graphene oxide retarding charge recombination. These results provide a significant theoretical foundation for the potential application of N-doping photocatalysts to hydrogen evolution.  相似文献   

6.
Photocatalysis is an effective way to utilize solar energy to produce hydrogen from water. Au/TiO2 nanoparticles (NPs) have a better performance in photocatalytic hydrogen generation because of the localized surface plasmon resonance (LSPR) effect of Au/TiO2 NPs. In the photocatalytic hydrogen generation experiments, it was found that light intensity plays a key role in the photocatalytic reaction rate of Au/TiO2 NPs. At a light intensity of 0–7 kW/m2, the reaction rate has a super-linear law dependence on the light intensity (Rate ∝ Intensityn, with n > 1). However, at a light intensity of 7–9 kW/m2, the dependency becomes sub-linear (n < 1). This means that the increase rate of photocatalytic rate is smaller than that of light intensity when the light intensity exceeds 7 kW/m2. In addition, the finite element method (FEM) was utilized to further elucidate the role of light intensity by calculating the absorption power and nearfield intensity mapping of a Au/TiO2 nanoparticle. The variation trend of the calculated total absorption power agrees with the photocatalytic experimental results for different light intensities. These results shed light on the utilization of concentrated solar photocatalysis to increase the solar-to-hydrogen performance of Au/TiO2 NPs.  相似文献   

7.
Cheap and efficient photocatalysts were fabricated by simply mixing TiO2 nanoparticles (NPs) and CuO NPs. The two NPs combined with each other to form TiO2/CuO mixture in an aqueous solution due to the opposite surface charge. The TiO2/CuO mixture exhibited photocatalytic hydrogen production rate of up to 8.23 mmol h−1 g−1 under Xe lamp irradiation when the weight ratio of P25 to CuO was optimized to 10. Although the conduction band edge position of CuO NPs is more positive than normal hydrogen electrode, the TiO2/CuO mixture exhibited good photocatalytic hydrogen production performance because of the inter-particle charge transfer between the two NPs. The detailed mechanism of the photocatalytic hydrogen production is discussed. This mixing method does not require a complicated chemical process and allows mass production of the photocatalysts.  相似文献   

8.
A novel three-dimensional (3D) core-shell nanostructure decorated with plasmonic Au nanoparticles (NPs) was prepared for photoelectrochemical water splitting. In the new nanostructure, ZnO nanorods (NRs) are perpendicular to ZnO nanosheets (NSs), and the ZnO NSs-NRs are coated with a thin TiO2 shell formed by liquid phase deposition. The plasmonic Au NPs were formed in situ on the surface of ZnO NSs-NRs@TiO2 by thermal reduction. A thin TiO2 shell and uniformly distributed Au NPs were successfully obtained. The photoconversion efficiency and photocurrent density of the 3D ZnO NSs-NRs@TiO2-Au nanostructure respectively reached 0.48% and 1.73 mA cm−2 at 1.23 V vs. reversible hydrogen electrode, 4.80 and 4.33 times higher than those of ZnO NSs, respectively. The thin TiO2 shell effectively promoted charge separation, while the surface plasmon resonance effects of the Au NPs improved the photocurrent density. The findings suggest that the 3D ZnO NSs-NRs@TiO2-Au nanostructure is a promising photoanode for photoelectrochemical water splitting.  相似文献   

9.
Photo-induced reforming of methanol, ethanol, glycerol and phenol at room temperature for hydrogen production was investigated with the use of ultra-small Pt nanoparticles (NPs) loaded on TiO2 nanotubes (NTs). The Pt NPs with diameters between 1.1 and 1.3 nm were deposited on TiO2 NTs by DC-magnetron sputtering (DC-MS) technique. The photocatalytic hydrogen rate achieved an optimum value for a loading of about 1 wt% of Pt. Apparent quantum yield for hydrogen generation was measured for methanol and ethanol water solutions reaching a maximum of 16% under irradiation with a wavelength of 313 nm in methanol/water solution (1/8 v/v). Pt NPs loaded on TiO2 NTs represented also a true water splitting catalyst under UV irradiation and pure distilled water. DC-MS method appears to be a technologically simple, ecologically benign and potentially low-cost process for production of an efficient photocatalyst loaded with ultra-small NPs with precise size control.  相似文献   

10.
One-dimensional (1D) Pt/TiO2 hybrid nanofibers (HNFs) with different concentrations of Pt were fabricated by a facile two-step synthesis route combining an electrospinning technique and calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) results showed that the Pt nanoparticles (NPs) with the size of 5–10 nm were well dispersed in the TiO2 nanofibers (NFs). Further investigations from the UV–Vis diffuse reflectance (DR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that some Pt ions were incorporated into the TiO2 lattice as Pt4+ state, which contributed to the visible light absorption of TiO2 NFs. Meanwhile, the Pt2+ ions existing on the surface of Pt NPs resulted in the formation of Pt–O–Ti bond at Pt NPs/TiO2 NFs interfaces that might serve as an effective channel for improving the charge transfer. The as-electrospun Pt/TiO2 HNFs exhibited remarkable activities for photocatalytic H2 evolution under visible light irradiation in the presence of l-ascorbic acid as the sacrificial agent. In particular, the optimal HNFs containing 1.0 at% Pt showed the H2 evolution rate of 2.91 μmol h−1 and apparent quantum efficiency of 0.04% at 420 nm by using only 5 mg of photocatalysts. The higher photocatalytic activity could be ascribed to the appropriate amount of Pt ions doping and excellent electron-sink effect of Pt NPs co-catalysts.  相似文献   

11.
TiO2(B)/CdS/Au and TiO2(B)/Au/CdS heterostructures were synthesized to investigate the effect of the selected deposition of CdS and Au nanoparticles (NPs) on H2 generation. TiO2(B) spheres (phase B) consisted of nanosheets were synthesized via a hydrothermal reaction. The deposition of CdS and Au NPs were carried out using wet-chemical method and a reduction reaction, respectively. The size and amount of Au and CdS NPs were adjusted to optimize the resulting properties and discuss the change of band gap. Two kinds of heterogeneous revealed different photocatalytic hydrogen generation which indicated the position of Au NPs affect the transfer of photogenerated carriers. The hydrogen production rate of TiO2(B)/CdS/Au heterostructures reached up to 12100 μmol g−1 h−1, which is about 3.8 times of that of pure TiO2(B) spheres. This is ascribed to the structure of heterostructures. CdS NPs increase the separation of photogenerated electrons and Au NPs accelerated the transfer of the electrons. The result provided a utilizable strategy for efficient photocatalysis H2 generation.  相似文献   

12.
Deposition of Pt NPs with preferred dispersion and morphologies on TiO2 have been the focus of studies in photocatalytic and photoelectrochemical hydrogen production. Green synthesis of TiO2/Pt NPs nanocomposites with narrow size distribution of Pt NPs still remain a challenge. Herein, we report that sucrose is highly efficient for the preparation of well-dispersed TiO2/Pt NPs photocatalysts. Moreover, the sucrose could act as an electron donor, showing higher hydrogen production activity under simulated sunlight than pure water. The as-synthesized photocatalysts have been characterized by techniques of transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDX), and diffuse reflectance spectroscopy (DRS). Compared with TiO2/Pt NPs photocatalysts prepared through conventional photodeposition, the photocatalysts as prepared showed higher photocatalytic efficiency. Moreover, the catalyst could be reused easily without apparent degradation of their original photocatalytic activities. This approach presents a promising and low-cost strategy to improve the photocatalytic performance of TiO2 from biomass.  相似文献   

13.
In this report, the preparation of an ensemble of hydrothermally synthesized TiO2 nanosheets with Au nanoparticles (TiO2 NSs-Au NPs) and their photoelectrocatalytic methanol oxidation behavior are accounted. The absorption spectral studies confirmed the successful emergence of Au NPs on TiO2 NSs ensemble and the existence of Au NPs broadened the light absorption to the visible light spectrum. The crystalline and structural complexity analysis confirms the anatase TiO2 as a major product in this synthesis. Morphology studies revealed the formation of 2 dimensional TiO2 NSs with chemically deposited Au NPs at the TiO2 surface and it was further confirmed by STEM-HAADF-EDS mapping studies. The ITO/TiO2 NSs-Au modified photoelectrode showed a synergistic catalytic response towards photoelectrocatalytic methanol oxidation than the ITO/TiO2 NSs electrode. Among them, TiO2 NSs with 1 mM Au NPs deposited composite (TiO2 NSs-Au (1)) showed 2-fold higher photocurrent for methanol oxidation than their pristine TiO2 NSs. The deposited of Au NPs in TiO2 NSs-Au nanocomposites facilitates the photoinduced charge separation and charge migration processes. Coherently the charge recombination process diminished in the TiO2 NSs-Au nanocomposite materials. The best synergistic photoelectrocatalytic methanol oxidation reaction at the ITO/TiO2 NSs-Au (1) modified electrode was achieved via extended visible light absorption with Schottky barrier induced enhancement of interfacial electron transfer process.  相似文献   

14.
In this present paper, cobalt oxide (CoOx) is studied as an effective cocatalyst in a photocatalytic hydrogen production system. CoOx-loaded titanium dioxide/cadmium sulfide (TiO2/CdS) semiconductor composites were prepared by a simple solvothermal method and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and X-ray photoelectron spectroscopy (XPS). Photocatalytic hydrogen production was studied using the as-synthesized photocatalysts in aqueous solution containing sodium sulfide (Na2S)/sodium sulfite (Na2SO3) as hole scavengers under visible light irradiation (λ > 400 nm). The optimal cobalt content in CoOx-loaded TiO2/CdS composite is determined to be 2.1 wt% and the corresponding rate of hydrogen evolution is 660 μmol g−1 h−1, which is about 7 times higher than TiO2/CdS and CdS photocatalysts under the same condition. Visible light-driven photocurrents of the semiconductor composites were further measured on a photoelectrochemical electrode, revealing that the photocorrosion of CdS can be prevented due to the presence of TiO2–CoOx.  相似文献   

15.
We report a facile method for the synthesis of TiO2 aerogels by a single step high temperature supercritical drying (HTSCD) of sol–gel derived TiO2. The morphological and structural features of the resultant materials were determined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Diffuse Reflectance (DR) spectra, and Fourier Transform infra-Red spectroscopy (FT-IR) measurements. The materials exhibited enhanced solar hydrogen production from water using methanol as sacrificial reagent under Ultra-Violet (UV) light in the absence of Pt as a co-catalyst. Among the TiO2 aerogel samples synthesized, TiO2-M-6h evolved 390 μmol g−1 of H2 after 4 h of irradiation, whereas TiO2-M-2h produced 217 μmol g−1 of H2 after 4 h of irradiation under identical conditions, indicating the importance of aging the gels prior to HTSCD step. The enhancement was credited to increase in surface area, and decrease in particle size in TiO2-M-6h as evidenced from N2-sorption and DRS studies respectively. Upon comparison with a room temperature synthesized TiO2-xerogel, the aerogel materials exhibited enhanced hydrogen production. The results validate the superior performance of TiO2 aerogel materials over TiO2 xerogels and indicate the potential of HTSCD method for the preparation of titania aerogels for solar energy applications.  相似文献   

16.
In this work, the catalytic performance of hardystonite/palladium nanocomposite (HT/Pd) for hydrogen evolution reaction (HER) and reduction of organic pollutants in water has been studied. For this purpose, palladium nanoparticles (Pd NPs) were synthesized by laser ablation in liquid (LAL) method in different concentrations and decorated on hardystonite substrate using a simple method. HT/Pd nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) analyses. The prepared nanocomposites were coated on a stainless steel mesh and their HER activity was investigated using cyclic voltammetry (CV). The results indicated that HT/Pd catalyst had good HER performance and capability of hydrogen storage. Moreover, HT/Pd nanocomposite with high surface area exhibited excellent catalytic activity in Cr(VI) reduction within 2.5 min.  相似文献   

17.
Different amounts of Au NPs were deposited on a modified-TiO2 using the deposition-precipitation method with urea and used for hydrogen production via water splitting at room temperature and atmospheric pressure. Methanol and simultaneous UV and visible radiation were used as sacrificial reagent and excitation sources, respectively. Both modified-support and photocatalysts were characterized by XRD, HRTEM or STEM-HAADF, FE-SEM-EDS, N2 physisorption and UV–vis DRS. The emission spectra of the excitation sources were also obtained by spectrofluorometry. XRD, HRTEM and UV–vis DRS results showed that TiO2 anatase was the predominant crystalline phase, with a relative high specific surface area. STEM-HAADF and FE-SEM-EDS techniques revealed that the average Au NPs size was increased with Au loading from 3.2 to 14.9 nm and that the estimated Au contents were close to the expected theoretical values. On the other hand, the photo-generated hydrogen was significantly increased with Au NPs incorporation and it could be associated to a slightly decrease of the energy band gap and the intrinsic localized surface plasmon resonance that can suppress the high rate of electron-hole pair recombination. The photocatalytic performance also depended on multiples experimental factors, such as: stirring speed, amount and size of Au NPs, as well as the radiation source. The highest hydrogen production rate (2336 μmol-H2/gcat⋅h) was obtained using the Au/TiO2 photocatalyst with 0.5 wt% Au, a stirring speed of 800 rpm and purple lamp (13 W) simultaneously emitting UV (52%) and visible (48%) radiation.  相似文献   

18.
To overcome the global challenges of energy crises and environmental threats, urea oxidation is a hopeful route to utilize urea-rich wastewater as an energy source for hydrogen production. Herein, we report an inorganic/organic type of nano-heterostructure (NHs–Ni-TiO2/p-NDIHBT) as a photoanode with excellent urea oxidation efficiency driven by visible light. This heterostructured photoanode consists of nickel (Ni)-doped TiO2 nanorods (NRs) arrays as an inorganic part and a D-A-D type organic polymer i.e p-NDIHBT as an organic part. The as-prepared photoanode was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The morphological studies of TEM confirm the coating of p-NDIHBT on Ni–TiO2 NPs (~1 μm). The consequence of heterostructure formation on optical and photoelectrochemical (PEC) properties of photoanode were explored through photoelectrochemical responses under visible light irradiation. The photoelectrochemical activity of Ni–TiO2 and Ni–TiO2/p-NDIHBT photoanode from linear sweep voltammetry (LSV) shows the ultrahigh photocurrent density of 0.36 mA/cm2 and 2.21 mA/cm2, respectively measured at 1.965 VRHE. Electrochemical impedance spectroscopy (EIS) of both photoanodes shows a highly sensitive nature toward the urea oxidation reaction. The hybrid photoanode also exhibits high photostability, good solar-to-hydrogen conversion efficiency, and high faradaic efficiency for urea oxidation.  相似文献   

19.
We report on the design and synthesis of a novel Au/TiO2/Au heterostructure and its implementation as a photoanode for photoelectrochemical (PEC) application. The Au/TiO2/Au heterostructure was produced by assembling Au nanoparticles and TiO2 nanorods (NRs) onto FTO substrate, followed by electrodepositing Au nanoparticles on the TiO2NRs. Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical methods were adopted to characterize the prepared photoanodes. Compared to the system involving Au nanoparticles directly linked to TiO2, this Au/TiO2/Au heterostructure exhibits significant improved photoresponse as a photoanode, as demonstrated good performance in PECs. This study illustrates the importance of pre-deposited Au underlayers in influencing PEC properties of hybrid assembled nanostructures. As the Au/TiO2NRs/Au photoanodes are easily fabricated and highly stable, Au/TiO2NRs/Au can serve as a good substitution for TiO2 in a variety of solar energy driven applications including PEC water splitting, photocatalysis, and solar cells.  相似文献   

20.
The electrochemical hydrogen storage of expanded graphite (EG) decorated with TiO2 nanoparticles (NPs) calcined at different temperatures has been investigated with the galvanostatic charge and discharge method. The TiO2 NPs are deposited on and between the graphene-like nanosheets of EG by a sol-gel method. The morphology, structure, composition, and specific surface area of the samples were characterized. The electrochemical measurement reveals that the EG decorated with TiO2 NPs calcined at 500 °C has a discharge capacity of 373.5 mAh/g which is 20 times higher than that of pure EG and quite appealing for the battery applications. The mechanism of enhancement of the electrochemical activity for the TiO2-decorated EG could be attributed to the preferable redox ability and photocatalytic property of TiO2 NPs.  相似文献   

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