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1.
An intense scientific activity was recorded during the last several years in the field of preparation, characterization and use of copper-based TiO2 photocatalysts for hydrogen generation through photocatalytic reforming of organics. Different copper species were used dissolved in aqueous solution or incorporated on the TiO2 surface as single co-catalyst or in the presence of a second catalyst (e.g., graphene, carbon fibers) to (1) effectively separate the electron–hole pairs, thus reducing the occurrence of the recombination reaction, and (2) extend the light absorption to the visible range of the solar spectrum. Many organic species (e.g., methanol, glycerol, formic acid) were proposed as sacrificial agents for hydrogen generation, although the prevailing idea is that of using organic compounds currently found in industrial wastewaters. The pH value was recognized as a fundamental variable in photocatalytic H2 generation via copper modified-TiO2 catalysts. A positive effect to promote hydrogen generation was associated to an increase in pH until moderate alkaline values. On the other hand, a release in the solution of cupric ions and a consequent decrease in photocatalytic activity were observed when decreasing pH. A relevant lack of information was recorded about the efficiencies of hydrogen generation which were reported only in few papers. Therefore, this critical literature review has been performed with the aim of providing a complete background to select the most efficient approaches and eventually promote new competitive systems for hydrogen generation via photoreforming for industrial applications.  相似文献   

2.
The photocatalytic removal of colour of a synthetic textile effluent, using TiO2 suspensions under solar radiation, has been studied at pilot plant scale. A synthetic dye solution was prepared by a mix of six commercial textile dyes. A photochemical reactor of parallel CPC reflectors with UV-transparent tubular receivers was used. The study of photodegradation was carried out using the Taguchi’s parameter design method. Following this methodology, the reaction was conducted under different flow conditions, pH and H2O2 concentrations. The results show that all dyes used in the experiences can be degraded successfully by photo-oxidation. The process shows a significant enhancement when it is carried out at high flows, alkaline media and high H2O2 concentration. Colour removal from the effluent was reached at 55 min operating time.  相似文献   

3.
A series of synthesised TiO2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 μmol h−1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.  相似文献   

4.
Chemically modified g-C3N4 for the photocatalytic H2 evolution from water was explored. Bulk g-C3N4 was treated in hot HNO3 aqueous solution to obtain the oxidized material (o-g-C3N4), tested in water containing glucose as model water-soluble sacrificial biomass, using Pt as co-catalyst, under simulated solar light. The behaviour of o-g-C3N4 was studied in relation with catalyst amount, Pt loading, glucose concentration. Results showed that H2 production is favoured by increasing glucose concentration up to 0.1 M and Pt loading up to 3 wt%, and it resulted strongly enhanced using small amount of o-g-C3N4 (0.25 g L?1). o-g-C3N4 possesses superior photocatalytic activity (~26-fold higher) compared to pristine g-C3N4, with H2 evolution further improved by ultrasound-assisted exfoliation and evolution rates up to ca. 1370 μmol h?1 per gram of catalyst, with excellent reproducibility (RSD < 6%, n = 3). Significant production was observed also in river water and seawater, with results far better (up to ca. 2500 μmol g?1 h?1) compared to commercial AEROXIDE® P25 TiO2 under natural solar light.  相似文献   

5.
An optimized Ru-doped LaFeO3 photocatalyst was coupled with magnetic Fe2O3 particles and was tested in the photocatalytic hydrogen production from glucose degradation under visible light irradiation. The catalysts were successfully synthesized by solution combustion synthesis using citric acid as organic fuel. Complete glucose degradation and hydrogen production of 5460 μmol/L was obtained after 4 h of irradiation using composite containing 67 wt% of Ru-doped LaFeO3. After seven cycles of reuse, the photocatalytic activity did not change, evidencing the high stability of the magnetic photocatalyst, which can be recovered from the photoreactor using an external magnetic force. The recyclable sample was finally tested in the treatment of real wastewater from cherries washing process, and a very high hydrogen production (12344 μmol/L) was achieved. Finally, the possibility to couple the photocatalytic process (used for the production of hydrogen) with a heterogeneous photo-Fenton process was investigated in order to mineralize the unconverted organics in the wastewater coming from the photoreactor.  相似文献   

6.
The main objective of the present study was to assess the photocatalytic degradation over TiO2 of an aqueous solution containing 20 mg L−1 of the antibiotic Oxytetracycline (OTC) using simulated solar radiation, seconded by a solar radiation experiment carried out in a pilot plant equipped with Compound Parabolic Collectors (CPCs) under the optimal conditions found in preliminary lab-scale experiments. These comprehended a set of 1 L aqueous experiments with TiO2 loads ranging from 0.1 to 0.5 g L−1 starting from different initial pH values. These experiments were carried out in a Solarbox equipped with a 1000 W Xe-OP lamp. OTC degradation was followed by HPLC-DAD, while its mineralization was followed by the removal of Total Organic Carbon.Results suggested that 0.5 g L−1 of TiO2 with no initial pH adjustment (pH ∼ 4.4) was the best combination for the removal of both OTC (100% after 40 min of irradiation; 7.5 kJ L−1 of UV dose) and TOC (>90% after 180 min of irradiation; 38.3 kJ L−1 of UV dose). Under these conditions, the BOD5/COD ratio rose from almost 0 to nearly 0.5, showing a remarkable improvement in biodegradability, while inhibition percentage of bioluminescence of Vibrio fischeri after 15 min of exposition measured by Microtox® decreased significantly from 35% down to 7%. A scheme of the OTC degradation pathway is proposed, based on the results obtained from this particular experiment.The solar photocatalytic experiment done under the same conditions was carried out in a solar pilot plant equipped with CPCs. OTC and TOC removal was followed as a function of accumulated UV energy entering the reactor. Results showed a 100% OTC and almost 80% TOC removal with 1.8 kJ L−1 and 11.3 kJ L−1 of photo treatment energy, respectively.  相似文献   

7.
Hydrogen production from ethanol solution (initial ethanol concentration of 50%) by pulsed discharge coupled with TiO2 is investigated in this work. Strong ultraviolet light is emitted by pulsed discharge in liquid, which makes photocatalysis have a great prospect in plasma reforming. Two kinds of TiO2 are attempted, containing non-metal ion doping and Ag deposition. The results show that the flow rate of hydrogen produced by pulsed discharge with TiO2 coated non-metal can be achieved 1.55 L/min, which is higher than with TiO2 coated Ag, but both two are higher than discharge without TiO2. From SEM analysis, it may be associated with the larger specific surface area of TiO2 coated non-metal. However, percentage concentration of hydrogen produced with TiO2 coated Ag is higher than others, which can be attained 78%. It may be due to the high work function of Ag. In addition, mechanism of hydrogen produced by pulsed discharge coupled with TiO2 is also analyzed. It demonstrates that the increase of ·H is the main reason for increased hydrogen yield.  相似文献   

8.
Photocatalytic degradation of acid orange 7 (AO7) in aqueous systems was successfully achieved by the combination of TiO2 with potassium persulphate under solar light using a photochemical reactor with recirculation. Degradation of AO7 involves color removal and mineralization. The employment of TiO2 removed 85% of color from the 0.2 mM AO7 aqueous solution under solar light; while, 66% of color was abated using the persulphate ion as oxidant in the absence of TiO2 under similar conditions in 2 h. However, over 90% of color removal was achieved by combining TiO2 and the persulphate ion for the same solution under similar conditions. Color removal was faster at pH 3. Mineralization of AO7 was followed by measuring chemical oxygen demand (COD). Negligible COD abatement of the textile dye was observed in the absence of persulphate ions (S2O82−) while over 70% of COD abatement was observed for the initial dye concentrations of 0.2–0.7 mM employing a mix of TiO2–S2O82− under solar light.  相似文献   

9.
L.S. Yoong  F.K. Chong  Binay K. Dutta   《Energy》2009,34(10):1652
The advantage of copper doping onto TiO2 semiconductor photocatalyst for enhanced hydrogen generation under irradiation at the visible range of the electromagnetic spectrum has been investigated. Two methods of preparation for the copper-doped catalyst were selected – complex precipitation and wet impregnation methods – using copper nitrate trihydrate as the starting material. The dopant loading varied from 2 to 15%. Characterization of the photocatalysts was done by thermogravimetric analysis (TGA), temperature programmed reduction (TPR), diffuse reflectance UV-Vis (DR-UV-Vis), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Photocatalytic activity towards hydrogen generation from water was investigated using a multiport photocatalytic reactor under visible light illumination with methanol added as a hole scavenger. Three calcination temperatures were selected – 300, 400 and 500 °C. It was found that 10 wt.% Cu/TiO2 calcined at 300 °C for 30 min yielded the maximum quantity of hydrogen. The reduction of band gap as a result of doping was estimated and the influence of the process parameters on catalytic activity is explained.  相似文献   

10.
1-D mesoporous TiO2 nanotube (TNT) with large BET surface area was successfully synthesized by a hydrothermal-calcination process, and employed for simultaneous photocatalytic H2 production and Cu2+ removal from water. Cu2+, across a wide concentration range of 8-800 ppm, was removed rapidly from water under irradiation. The removed Cu2+ then combined with TNT to produce efficient Cu incorporated TNT (Cu-TNT) photocatalyst for H2 production. Average H2 generation rate recorded across a 4 h reaction was between 15.7 and 40.2 mmol h−1 g−1catalyst, depending on initial Cu2+/Ti ratio in solution, which was optimized at 10 atom%. In addition, reduction process of Cu2+ was also a critical factor in governing H2 evolution. In comparison with P25, its large surface area and 1-D tubular structure endowed TNT with higher photocatalytic activity in both Cu2+ removal and H2 production.  相似文献   

11.
Nanostructured CuOx/TiO2 (a mixture of Cu/Cu2O/CuO) was prepared by impregnation for enhancing photocatalytic hydrogen generation from an aqueous solution containing 10 v/v% methanol. At an optimum Cu loading of 0.5 wt% and a calcination temperature of 500 °C, the CuOx was present as relatively highly dispersed (0.90), fine deposits. At Cu loadings beyond 0.5 wt% a bimodal distribution of CuOx deposits appeared with the prevalence of larger Cu deposits increasing with increasing Cu content. A corresponding decrease in H2 generation was observed as Cu loading increased which was attributed to the increasing presence of the larger CuOx deposits. The particle calcination temperature (in air) was also found to affect CuOx/TiO2 activity with an optimum performance achieved at a temperature of 300 °C. Calcining the CuOx/TiO2 at 500 °C led to greater oxidation of the CuOx deposits (∼40%) to form more Cu2+ which corresponded to an almost proportional (42%) decrease in H2 generation. The findings demonstrate the importance of Cu dispersion and oxidation state in governing photocatalytic H2 generation by CuOx/TiO2.  相似文献   

12.
Simultaneous photocatalytic hydrogen production and CO2 reduction (to form CO and CH4) from water using methanol as a hole scavenger were investigated using silver-modified TiO2 (Ag/TiO2) nanocomposite catalysts. A simple ultrasonic spray pyrolysis (SP) method was used to prepare mesoporous Ag/TiO2 composite particles using TiO2 (P25) and AgNO3 as the precursors. The material properties and photocatalytic activities were compared with those prepared by a conventional wet-impregnation (WI) method. It was found that the samples prepared by the SP method had a larger specific surface area and a better dispersion of Ag nanoparticles on TiO2 than those prepared by the WI method, and as a result, the SP samples showed much higher photocatalytic activities toward H2 production and CO2 reduction. The optimal Ag concentration on TiO2 was found to be 2 wt%. The H2 production rate of the 2% Ag/TiO2–SP sample exhibited a six-fold enhancement compared with the 2% Ag/TiO2–WI sample and a sixty-fold enhancement compared with bare TiO2. The molar ratio of H2 and CO in the final products can be tuned in the range from 2 to 10 by varying the reaction gas composition, suggesting a viable way of producing syngas (a mixture of H2 and CO) from CO2 and water using the prepared Ag/TiO2 catalysts with energy input from the sun.  相似文献   

13.
Mesoporous-assembled TiO2 nanocrystals with very high photocatalytic H2 production activity were synthesized through a modified sol-gel process with the aid of urea as mesopore-directing agent, heat-treated under various calcination temperatures, and assessed for their photocatalytic H2 production activity via water splitting reaction. The resulting mesoporous-assembled TiO2 nanocrystals were systematically characterized by N2 adsorption-desorption analysis, surface area and pore size distribution analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results showed that the photocatalytic H2 production activity of the synthesized mesoporous-assembled TiO2 nanocrystal calcined at 500 °C, which possessed very narrow pore size distribution, was extraordinarily higher than that of the commercially available P-25 TiO2 and ST-01 TiO2 powders.  相似文献   

14.
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   

15.
CuO was introduced into porous TiO2 nanorod through impregnation method. Before the impregnation step, TiO2 nanorod was hydrothermally synthesized from TiO2 powder in aqueous NaOH solution and followed by thermal treatment at 450 °C. The structures and properties of impregnated samples were characterized using various techniques, including XRD, BET, XAS, TEM, and UV-DRS. Their photocatalytic performance on simultaneous hydrogen production from pure water and aqueous methanol solution was also investigated under solar light. It was found that CuO/TiO2 nanorod possessed a high surface area, good photocatalytic property and excellent hydrogen generation activity. Incorporation of Cu ions into the lattice framework of anatase TiO2 nanorod enhanced the efficiency in visible region at 438–730 nm. Moreover, the XAS results showed that some Cu ions formed solid solution in the TiO2 nanorod (CuxT1−xO2). However, the excessive incorporation of Cu ions did not improve any ability of anatase TiO2 nanorod for production of hydrogen from pure water splitting. This could be due to the excessive CuO agglomeration at outside-pores which blocked the sensitization of TiO2 nanorod. Only 1% Cu/TiO2 nanorod was found to be a remarkable and an efficient photocatalyst for hydrogen production under solar light from both pure water and sacrificial methanol splitting. The highest rate of hydrogen production of 139.03 μmol h−1 gcatalyst−1 was found in sacrificial methanol which was 3.24% higher than in pure water.  相似文献   

16.
The photocatalytic production of H2 using carbon-doped TiO2 (CTiO2) nanoparticles has been investigated in single or mixed systems of organic fatty acids (OFAs) under visible light irradiation, including acetic acid, propionate acid, butyric acid and lactic acid. When OFAs were applied at the same electron density (10 e-eq L?1), the H2 evolution rates followed the order of propionic acid > butyric acid ≈ acetic acid > lactic acid, whereas at the same molar concentration (0.5 mol L?1), that order changed to lactic acid > acetic acid > butyric acid ≈ propionic acid. This result implied that the electron transfer efficiency differed from four OFAs, probably due to their different affinity with CTiO2. O2?? and CH3? partially contributed to OFAs degradation and H2 production. The quantum dynamics simulations of electron transfer revealed that the dominant mechanism of H2 production was direct electron transfer from adsorbed OFAs to CTiO2. This work aims to pursue the synergy of solar energy utilization and conversion of OFAs into H2.  相似文献   

17.
The CdS/TiO2 composites were synthesized using titanate nanotubes (TiO2NTs) with different pore diameters as the precursor by simple ion change and followed by sulfurization process at a moderate temperature. Some of results obtained from XRD, TEM, BET, UV–vis and PL analysis confirmed that cadmium sulfide nanoparticles (CdSNPs) incorporated into the titanium dioxide nanotubes. The photocatalytic production of H2 was remarkably enhanced when CdS nanoparticles was incorporated into TiO2NTs. The apparent quantum yield for hydrogen production reached about 43.4% under visible light around λ = 420 nm. The high activity might be attributed to the following reasons: (1) the quantum size effect and homogeneous distribution of CdSNPs; (2) the synergetic effects between CdS particles and TiO2NTs, viz., the potential gradient at the interface between CdSNPs and TiO2NTs.  相似文献   

18.
In most current fossil-based hydrogen production methods, the thermal energy required by the endothermic processes of hydrogen production cycles is supplied by the combustion of a portion of the same fossil fuel feedstock. This increases the fossil fuel consumption and greenhouse gas emissions. This paper analyzes the thermodynamics of several typical fossil fuel-based hydrogen production methods such as steam methane reforming, coal gasification, methane dissociation, and off-gas reforming, to quantify the potential savings of fossil fuels and CO2 emissions associated with the thermal energy requirement. Then matching the heat quality and quantity by solar thermal energy for different processes is examined. It is concluded that steam generation and superheating by solar energy for the supply of gaseous reactants to the hydrogen production cycles is particularly attractive due to the engineering maturity and simplicity. It is also concluded that steam-methane reforming may have fewer engineering challenges because of its single-phase reaction, if the endothermic reaction enthalpy of syngas production step (CO and H2) of coal gasification and steam methane reforming is provided by solar thermal energy. Various solar thermal energy based reactors are discussed for different types of production cycles as well.  相似文献   

19.
Highly ordered TiO2 nanotube arrays generate a considerable interest for hydrogen generation by an electrochemical photocell, since ordered architecture of nanotube arrays provides a unidirectional electric channel for electron's transport. Here, we report the hydrogen generation by highly ordered TiO2 nanotube arrays under actual sunlight in KOH electrolyte. The two-electrode electrochemical cell included an adjustable anode compartment capable of tracing the trajectory of the sun and a set of alkaline batteries connected with a rheostat for application of external bias. The results showed that the photocurrent responses of nanotube arrays match well with the intensity of solar irradiance on a clear summer day. Addition of ethylene glycol into KOH electrolyte as a hole scavenger enhanced the rate of hydrogen generation. A maximum photocurrent density of 31 mA/cm2 was observed at 13:30 h, by focusing the sunlight with an intensity of 113 mW/cm2 on the surface of the TiO2 nanotube arrays in 1 M KOH electrolyte with 10 vol% ethylene glycol under an applied bias of 0.5 V. The observed hydrogen generation rate was 4.4 mL/h cm2 under the focalized solar irradiance with an intensity between 104 mW/cm2 and 115 mW/cm2 from 10:00 to 14:20 h.  相似文献   

20.
The catalytic dehydrogenation of formic acid (HCOOH) on heterogeneous catalysts in aqueous solution to produce CO-free H2 has received intense investigation due to its promising application in portable power devices. In this work, we present a study on the mechanism of HCOOH dehydrogenation on the PtRuBiOx catalyst using density functional theory (DFT) calculations supported by complementary experiments. The catalyst's activity at room temperature was clarified by investigating HCOOH dehydrogenation on PtRu alloy and Bi2O3 surface with a focus on the key reaction steps. The PtRu with different alloying degree was modeled by a four-layer p (2 × 2) unit cell with Pt-skin and leaving Ru atoms in the second and the third layer based on the surface energy and the formation energy. The Bi2O3 surface was represented by the most stable (111) surface of δ-Bi2O3. Based on the computational and experimental results, a reaction pathway for HCOOH dehydrogenation on the PtRuBiOx in aqueous solution was proposed. The results suggest that the promotion of HCOOH dissociation on the Bi2O3 surface and the ligand effect between Pt and Ru are responsible for the activity of PtRuBiOx toward HCOOH dehydrogenation in aqueous solution at room temperature. Furthermore, the PdBiOx system was also prepared and investigated as a catalyst for HCOOH decomposition at room temperature. The catalytic behavior of PdBiOx for HCOOH dehydrogenation in aqueous solution was compared with that of the PtRuBiOx.  相似文献   

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