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1.
The photocatalytic hydrogen production from aqueous methanol solution was investigated with ZnO/TiO2, SnO/TiO2, CuO/TiO2, Al2O3/TiO2 and CuO/Al2O3/TiO2 nanocomposites. A mechanical mixing method, followed by the solid-state reaction at elevated temperature, was used for the preparation of nanocomposite photocatalyst. Among these nanocomposite photocatalysts, the maximal photocatalytic hydrogen production was observed with CuO/Al2O3/TiO2 nanocomposites. A variety of components of CuO/Al2O3/TiO2 photocatalysts were tested for the enhancement of H2 formation. The optimal component was 0.2 wt% CuO/0.3 wt% Al2O3/TiO2. The activity exhibited approximately tenfold enhancement at the optimum loading, compared with that with pure P-25 TiO2. Nano-sized TiO2 photocatalytic hydrogen technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy.  相似文献   

2.
The In-doped HLaNb2O7 oxide semiconductors synthesized by solid-state reaction followed by an ion-exchange reaction were found to be a novel composite photocatalyst system with enhanced activity for water splitting. Pt was incorporated in the interlayer of In-doped HLaNb2O7 by the stepwise intercalation reaction. The In-doped HLaNb2O7 powder samples were characterized with X-ray diffraction (XRD) and UV-vis diffuse reflectance spectrometry. The photocatalytic activities of Pt-loaded In-doped HLaNb2O7 and individual precursor materials were evaluated by H2 evolution from aqueous CH3OH solution under UV light irradiation. It was found that the composite In-doped HLaNb2O7 showed a higher H2 evolution rate in comparison with individual materials. The hydrogen production activity of In-doped HLaNb2O7 was greatly enhanced by Pt co-incorporation. The In content in the In-doped HLaNb2O7 system was discussed in relation to the photophysical and photocatalytic properties. As In content equal 5 mol%, the HLaNb2O7:In/Pt showed a photocatalytic activity of 354 cm3 g−1 hydrogen evolution in 10 vol% methanol solution under irradiation from a 100 W mercury lamp at 333 K for 3 h.  相似文献   

3.
Photo-assisted hydrogen generation studies of platinum loaded titanium (IV) oxide nanotubes suspended in ethanol–water mixture were carried out at room temperature. The TiO2 nanotubes synthesized by rapid breakdown anodization technique were loaded with Pt nanoparticles by chemical reduction of aqueous chloroplatinic acid solution using sodium borohydride. The chemisorption (active) surface area of the synthesized nanocomposites for hydrogen was measured by pulse chemisorption method using temperature programmed desorption reduction oxidation equipment and found to decrease with increase in platinum loading in the range 1–10 wt%. The platinum supported nanotube composites were characterized for phase and morphology by XRD, TEM and SEM. The hydrogen generated by the photocatalytic reduction of water from water–ethanol mixture at different wavelengths of incident light, using the Pt-TiO2 nanocomposite photocatalyst, was determined by using a proton exchange membrane based hydrogen meter. The highest hydrogen generation efficiency was observed at 1–2.5 wt% of Pt loading. The maximum photocatalytic hydrogen generation of 0.03 mol/h/g of Pt-TiO2 was observed with a 64 W UV light source (λ = 254 nm). The photoluminescence property of the Pt loaded TiO2 has been correlated with the hydrogen generation efficiency and the reaction mechanism briefly discussed.  相似文献   

4.
In this study, various nanoscale metal oxide catalysts, such as CeO2, TiO2, Fe2O3, Co3O4, and SiO2, were added to the LiBH4/2LiNH2/MgH2 system by using high-energy ball milling. Temperature programmed desorption and MS results showed that the Li–Mg–B–N–H/oxide mixtures were able to dehydrogenate at much lower temperatures. The order of the catalytic effect of the studied oxides was Fe2O3 > Co3O4 > CeO2 > TiO2 > SiO2. The onset dehydrogenation temperature was below 70 °C for the samples doped with Fe2O3 and Co3O4 with 10 wt.%. More than 5.4 wt.% hydrogen was released at 140 °C. X-ray diffraction indicated that the addition of metal oxides inhibited the formation of Mg(NH2)2 during ball milling processes. It is thought that the changing of the ball milling products results from the interaction of oxide ions in metal oxide catalysts with hydrogen atoms in MgH2. The catalytic effect depends on the activation capability of oxygen species in metal oxides on hydrogen atoms in hydrides.  相似文献   

5.
TiO2 photocatalyst with deposited CuO (CuO-TiO2) was synthesized by the impregnation method using P25 (Degussa) as support, and exhibited high photocatalytic hydrogen generation activity from methanol/water solution. A substantial hydrogen evolution rate of 10.2 ml min−1 (18,500 μmol h−1 g−1catalyst) was observed over this efficient CuO-TiO2 with optimal Cu content of 9.1 mol% from an aqueous solution containing 10 vol% methanol; this improved hydrogen generation rate is significantly higher than the reported Cu-containing TiO2, including some Pt and Pd loaded TiO2. Optimal Cu content of 9.1 mol% provided maximum active sites and allowed good light penetration in TiO2. Over this efficient CuO-TiO2, the hydrogen generation rate was accelerated by increasing the methanol concentration according to Freundlich adsorption isotherm. However, the photocatalytic hydrogen generation rate was suppressed under long time irradiation mainly due to accumulation of by-products, reduction of CuO and copper leaching, which requires further investigation.  相似文献   

6.
Nitrogen and sulfur co-doped and N-doped TiO2 anatase TKP 102 (Tayca) were prepared by manual grinding with thiourea and urea, respectively, and annealing at 400 °C. Both materials showed visible-light absorption as measured by Diffuse Reflectance Spectroscopy (DRS). Interstitial N-doping, anionic and cationic S-doping was found when the TiO2 was doped with thiourea while TiO2 doped with urea showed only the presence of interstitial N-doping as measured by X-ray Photo-electron Spectroscopy (XPS). The N content on the surface of N-doped TKP 102 photocatalyst was 2.85 at.% and higher than the N content in the N, S co-doped TiO2 photocatalyst (0.6 at.%).The photocatalytic activity of the doped catalysts was tested using phenol and Escherichia coli as chemical and biological targets, respectively, using N, S co-doped, N-doped TiO2, undoped Degussa P-25 and undoped TKP 102 powders under simulated solar light. It was found that undoped Degussa P-25 was the photocatalyst with the highest photocatalytic activity towards phenol oxidation and E. coli inactivation. N, S co-doped powders showed almost the same photocatalytic activity as undoped TKP 102 while N-doped TKP 102 was the less active photocatalyst probably due the N impurities on the TiO2 acting as recombination centers.  相似文献   

7.
Efficient Cu incorporated TiO2 (Cu–TiO2) photocatalysts for hydrogen generation were fabricated by four methods: in situ sol–gel, wet impregnation, chemical reduction of Cu salt, and in situ photo-deposition. All prepared samples are characterized by good dispersion of Cu components, and excellent light absorption ability. Depending on the preparation process, hydrogen generation rates of the as-prepared Cu–TiO2 were recorded in the range of 9–20 mmol h−1 gcatalyst−1, which were even more superior to some noble metal (Pt/Au) loaded TiO2. The various fabrication methods led to different chemical states of Cu, as well as different distribution ratio of Cu between surface and bulk phases of the photocatalyst. Both factors have been proven to influence photocatalytic hydrogen generation. In addition, the Cu content in the photocatalyst played a significant role in hydrogen generation. Among the four photocatalysts, the sample that was synthesized by in situ sol–gel method exhibited the highest stability. High efficiency, low cost, good stability are some of the merits that underline the promising potential of Cu–TiO2 in photocatalytic hydrogen generation.  相似文献   

8.
Hydrogen production from the photocatalytic water splitting reaction is very attractive because it is an environmentally friendly process, where hydrogen is produced from two abundantly renewable sources, i.e. water and solar energy, with the aid of photocatalysts. TiO2 is the most widely investigated photocatalyst; however, it alone still exhibits low performance to photocatalytically produce hydrogen. Hence, the aim of this work focused on the enhanced photocatalytic hydrogen production over Ag-loaded mesoporous-assembled TiO2-ZrO2 mixed oxide nanocrystal photocatalysts under UV light irradiation. The TiO2-ZrO2 mixed oxides with various TiO2-to-ZrO2 molar ratios were synthesized by a sol-gel process with the aid of a structure-directing surfactant, followed by Ag loading via a photochemical deposition method. The influences of photocatalyst preparation parameters, i.e. calcination temperature, phase composition, and Ag loading, were studied. The results revealed that the mesoporous-assembled TiO2-ZrO2 mixed oxide nanocrystal photocatalyst with a TiO2-to-ZrO2 molar ratio of 93:7 calcined at 500 °C exhibited the highest photocatalytic hydrogen production activity, and the Ag loading of 0.5 wt.% further greatly enhanced the photocatalytic activity of such TiO2-ZrO2 mixed oxide photocatalyst.  相似文献   

9.
A novel perovskite intercalated nanomaterial HLaNb2O7/(Pt, TiO2) is fabricated by successive intercalated reaction of HLaNb2O7 with [Pt(NH3)4]Cl2 aqueous solution, n-C6H13NH2/C2H5OH organic solution and acidic TiO2 colloid solution, followed by ultraviolet light irradiation. The gallery height and the band gap energy of HLaNb2O7/(Pt, TiO2) is less than 0.6 nm and 3.14 eV, respectively. The photocatalytic activity of HLaNb2O7/TiO2 is superior to that of unsupported TiO2 and is enhanced by the co-incorporation of Pt. The photocatalytic hydrogen evolution based on HLaNb2O7/(Pt, TiO2) is 240 cm3 h−1 g−1 using methanol as a sacrificial agent under irradiation with wavelength more than 290 nm from a 100-W mercury lamp. High photocatalytic activity of HLaNb2O7/(Pt, TiO2) may be due to the host with rare earth La element and perovskite structure, the quantum size effect of intercalated semiconductor and the coupling effect between host and guest.  相似文献   

10.
The physical properties and photoelectrochemical characterization of the spinel ZnFe2O4, elaborated by chemical route, have been investigated for the hydrogen production under visible light. The forbidden band is found to be 1.92 eV and the transition is indirectly allowed. The electrical conduction occurs by small polaron hopping with activation energy of 0.20 eV. p-type conductivity is evidenced from positive thermopower and cathodic photocurrent. The flat band potential (0.18 VSCE) determined from the capacitance measurements is suitably positioned with respect to H2O/H2 level (−0.85 VSCE). Hence, ZnFe2O4 is found to be an efficient photocatalyst for hydrogen generation under visible light. The photoactivity increases significantly when the spinel is combined with a wide band gap semiconductor. The best performance with a hydrogen rate evolution of 9.2 cm3 h−1 (mg catalyst)−1 occurs over the new hetero-system ZnFe2O4/SrTiO3 in Na2S2O3 (0.025 M) solution.  相似文献   

11.
A series of ZnIn2S4 photocatalysts was synthesized via a cetyltrimethylammoniumbromide (CTAB)-assisted hydrothermal method. These ZnIn2S4 products were characterized by X-ray diffraction (XRD), UV–visible absorption spectra (UV–vis) and scanning electron microscopy (FESEM). The effects of hydrothermal time and CTAB on the crystal structures, morphologies and optical properties of ZnIn2S4 products were discussed in detail. The photocatalytic activities of the as-prepared samples were evaluated by photocatalytic hydrogen production from water under visible-light irradiation. It was found that the photocatalytic activities of these ZnIn2S4 products decreased with the hydrothermal time prolonging while increased with the amount of CTAB increasing. The highest quantum yield at 420 nm of ZnIn2S4 photocatalyst, which was prepared through the CTAB (9.6 mmol)-assisted hydrothermal procedure for 1 h, was determined to be 18.4%. The optimum amount of Pt loaded for the ZnIn2S4 photocatalyst was about 1.0 wt%, under the present photocatalytic system.  相似文献   

12.
The main objective of this work was to investigate the different effects of transition metals (TiO2, VCl3, HfCl4) on the hydrogen desorption/absorption of NaAlH4. The HfCl4 doped NaAlH4 showed the lowest temperature of the first desorption at 85 °C, while the one doped with VCl3 or TiO2 desorbed at 135 °C and 155 °C, respectively. Interestingly, the temperature of desorption in subsequent cycles of the NaAlH4 doped with TiO2 reduced to 140 °C. On the contrary, in the case of NaAlH4 doped with HfCl4 or VCl3, the temperature of desorption increased to 150 °C and 175 °C, respectively. This may be because Ti can disperse in NaAlH4 better than Hf and V; therefore, this affected segregation of the sample after the desorption. The maximum hydrogen absorption capacity can be restored up to 3.5 wt% by doping with TiO2, while the amount of restored hydrogen was lower for HfCl4 and VCl3 doped samples. XRD analysis demonstrated that no Ti-compound was observed for the TiO2 doped samples. In contrast, there was evidence of Al–V alloy in the VCl3 doped sample and Al–Hf alloy in the HfCl4 doped sample after subsequent desorption/absorption. As a result, the V- or Hf-doped NaAlH4 showed the lower ability to reabsorb hydrogen and required higher temperature in the subsequent desorptions.  相似文献   

13.
Bilayer photoanodes were prepared onto glass substrates (FTO) in order to improve generated photocurrents using UV-vis light by water splitting process. A comparative study of photocatalytic was performed over the films surface using Fe2O3, WO3 and mixture of bicomponents (Fe2O3:WO3). Different types of films were prepared using Fe2O3, WO3 and bicomponents (mixture) on FTO substrates. The films were grown by sol gel method with the PEG-300 as the structure-directing agent. The photo-generated of the samples were determined by measuring the currents and voltages under illumination of UV-vis light. The morphology, structure and related composition distribution of the films have been characterized by SEM, XRD and EDX respectively. Photocurrent measurements indicated surface roughness as the effective parameter in this study. The deposited surfaces by bicomponents or mixture are flat without any feature on the surface while the deposited surfaces by WO3 appears rough surface as small round (egg-shaped particles) and cauliflower-like. The surface deposited by Fe2O3 show rough no as well as WO3 surface. The deposited surfaces by WO3 reveal the higher value of photocurrent measurement due to surface roughness. Indeed, the roughness can be effective in increasing contact surface area between film and electrolyte and diffuse reflection (light scattering effect). The solution (Fe2O3:WO3) shows the low photocurrent value in compare to WO3 and Fe2O3 hat it may be due to decomposition the compound at 450 ± 1 °C to iron-tungstate Fe2(WO4)3.  相似文献   

14.
The present work deals with the photoelectrochemical hydrogen production over the spinel ZnCr2O4. The photoactivity is dependent on the synthesis conditions and the oxide has been prepared by nitrate way in order to produce homogeneous powder with large active surface. The transport properties indicate p-type conductivity with activation energy of 0.21 eV. A corrosion potential of 0.404 VSCE and an exchange current density of 50 μA cm−2 have been determined from the semi logarithm plot. The photocurrent onset potential, assimilated to the flat band potential, was found to be −0.39 VSCE. ZnCr2O4/S2O32− is a self driven system where absorption of light promotes electrons into the conduction band with a potential (−1 V) sufficient to reduce water into hydrogen. The activity shows a tendency toward saturation whose deceleration is the result of the competitive reductions of end products namely S2O62− and S2O42− with water. A comparative study with CuCr2O4 is reported.  相似文献   

15.
A novel visible-light-driven photocatalyst CaIn2S4 was synthesized using a facile hydrothermal method followed by a post-calcination process. The influence of the calcination temperature and time on the activities of the photocatalyst was investigated. CaIn2S4 exhibits optical absorption predominantly in visible region with an optical band gap of 1.76 eV. Considerable activity for hydrogen evolution from pure water was observed without any sacrificial agents or cocatalysts under visible light irradiation. The maximum hydrogen evolution rate achieved was 30.92 μmol g−1 h−1 without obvious deactivation of the photocatalytic activity for four consecutive runs of 32 h.  相似文献   

16.
This study investigated the effect of Nd2O3 and Gd2O3 as catalyst on hydrogen desorption behavior of NaAlH4. Pressure-content-temperature (PCT) equipment measurement proved that both two oxides enhanced the dehydrogenation kinetics distinctly and increasing Nd2O3 and Gd2O3 from 0.5 mol% to 5 mol% caused a similar effect trend that the dehydrogenation amount and average dehydrogenation rate increased firstly and then decreased under the same conditions. 1 mol% Gd2O3–NaAlH4 presented the largest hydrogen desorption amount of 5.94 wt% while 1 mol% Nd2O3–NaAlH4 exerted the fastest dehydrogenation rate. Scanning Electron microscopy (SEM) analysis revealed that Gd2O3–NaAlH4 samples displayed uniform surface morphology that was bulky, uneven and flocculent. The difference of Nd2O3–NaAlH4 was that with the increasing of Nd2O3 content, the particles turned more and more big. Compared to dehydrogenation behavior, this phenomenon demonstrated that small particles structure were beneficial to hydrogen desorption. Besides, the further study found that different catalysts and addition amounts had different effects on the microstructure of NaAlH4.  相似文献   

17.
The monoclinic-type Li3V2(PO4)3 cathode material was synthesized via calcining amorphous Li3V2(PO4)3 obtained by chemical reduction and lithiation of V2O5 using oxalic acid as reducer and lithium carbonate as lithium source in alcohol solution. The amorphous Li3V2(PO4)3 precursor was characterized by using TG–DSC and XPS. The results showed that the V5+ was reduced to V3+ by oxalic acid at ambient temperature and pressure. The prepared Li3V2(PO4)3 was characterized by XRD and SEM. The results indicated the Li3V2(PO4)3 powder had good crystallinity and mesoporous morphology with an average diameter of about 30 nm. The pure Li3V2(PO4)3 exhibits a stable discharge capacity of 130.08 mAh g−1 at 0.1 C (14 mA g−1).  相似文献   

18.
The CuO/SnO2 composites have been prepared by the simple co-precipitation method and further characterized by the XRD, FESEM and Raman spectroscopy. The photocatalytic H2 production from acetic acid (HAc) solution over CuO/SnO2 photocatalyst has been investigated at room temperature under UV irradiation. Effects of CuO loading, photocatalyst concentration, acetic acid concentration and pH on H2 production have been systematically studied. Compared with pure SnO2, the 33.3 mol%CuO/SnO2 composite exhibited approximately twentyfold enhancement of H2 production. The H2 yield is about 0.66 mol-H2/mol-HAc obtained under irradiation for prolonged time. The Langmuir-type model is applied to study the dependence of hydrogen production rate on HAc concentration. A possible mechanism for photocatalytic degradation of acetic acid over CuO/SnO2 photocatalyst is proposed as well. Our results provide a method for pollutants removal with simultaneous hydrogen generation. Due to simple preparation, high H2 production activity and low cost, the CuO/SnO2 photocatalyst will find wide application in the coming future of hydrogen economy.  相似文献   

19.
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   

20.
An efficient visible-light active photocatalyst of multilayer-Eosin Y-sensitized TiO2 is prepared through linkage of Fe3+ between not only TiO2 and Eosin Y but also different Eosin Y molecules to form three-dimensional polymeric dye structure. The multilayer-dye-sensitized photocatalyst is found to have high light harvesting efficiency and photocatalytic activity for hydrogen evolution under visible light irradiation (λ > 420 nm). On the optimum conditions (1:1 initial molar ratio of Eosin Y to Fe(NO3)3, initial 10 × 10−3 M Eosin Y, and 1.0 wt% Pt deposited by in situ photoreduction), its maximal apparent quantum yield for hydrogen evolution is 19.1% from aqueous triethanolamine solution (TEOA aq). The present study highlights linking between dye molecules via metal ions as a general way to develop efficient visible-light photocatalyst.  相似文献   

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