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1.
Electron beam lithography was used to fabricate platinum μ-contacts over tungsten oxide nanorods formed on a mica substrate. This made possible the measurement of sensorial response of these self-assembled tungsten oxide nanorods to hydrogen gas for the first time. The nanorods were prepared by thermal evaporation from an oxide source. Consequently, two types of conductometric sensors were assembled: a) percolating network of nanorods and b) set of individually contacted WO3 nanorods. The preparation procedures are described in detail and the comparison of response of both types of assemblies is given. The first sensorial measurements revealed a good response of the b) type of sensor and the minimum repeatedly detected concentration of H2 was 50 ppm.  相似文献   

2.
In this research, the effect of using aluminum oxide nanofluid (pure water mixed with Al2O3 nanoparticle with 35 nm diameter) on the thermal efficiency enhancement of a heat pipe on the different operating state was investigated.  相似文献   

3.
Single crystalline TiO2 nanorods and polycrystalline nanotubes were fabricated with same length to investigate the effects of their nanostructures on photocatalytic properties for splitting water. In order to enhance the visible light absorbance, TiO2 nanorods and nanotubes were sensitized with semiconductor nanoparticles such as CdS, CdSe, and CdS/CdSe, and compared in viewpoint of solar hydrogen generation. It was observed that single-crystalline nanorods showed superior photocatalytic properties to polycrystalline nanotubes, and also the potential level of the nanorods with rutile phase was measured as lower than that of the nanotubes with mixture of anatase and rutile. Further improvement of photo-conversion efficiency was obtained by subsequent heat treatments of the sensitized photoelectrodes. It turns out that the improvement is attributed to the improved crystallinity and the increased size of the nanoparticles during the post-annealing treatments. It was demonstrated that TiO2 nanorods with lower potential level and a single crystalline phase on FTO glass were advantageous for effective charge injection from the sensitized nanoparticles and transport without recombination lost at grain boundaries.  相似文献   

4.
Here we develop photoanodes based on hierarchical zinc oxide (ZnO) nanostructures such as vertically aligned nanorods (NR), nanorods interconnected by thin nanosheets (NR@TN) and nanorods interconnected by dense nanosheets (NR@DN). The morphological variations were successfully controlled by secondary growth time and the plausible formation mechanisms of these hierarchical ZnO architectures were explained based on the experiment analysis. Under simulated light illumination (AM 1.5, 100 mW cm?2), NR@TN produced a photocurrent density of 0.62 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (vs. RHE). Importantly, 35% enrichment in photoconversion efficiency was observed for NR@TN at much lower bias potential (0.77 V vs. RHE) compared with NR (0.135%) and NR@DN (0.13% at 0.82 V vs. RHE). Key to the improved performance is believed to be synergetic effects of excellent light-trapping characteristics and the large surface-to-volume ratios due to the nanosheet structures. The nanorod connected with thin nanosheet structures improved the efficiency by means of improved charge transfer across the nanostructure/electrolyte interfaces, and efficient charge transport within the material. We believe that the hierarchical ZnO structures can be used in conjunction with doping and/or sensitization to promote the photoelectrochemical (PEC) performance. Further, the ZnO nanorod interconnected with nanosheets morphology presented in this article is extendable to other metal oxide semiconductors to establish a universal protocol for the development of high performance photoanodes in the field of PEC water splitting.  相似文献   

5.
In this study, an attempt was made to reduce the higher oxides of nitrogen (NOx) emission of a crude rice bran oil methyl ester (CRBME) blend through modification of combustion process by retarding fuel injection timing and exhaust gas recirculation at an increased fuel injection pressure. At modified condition, delay period and peak pressure of CRBME blend were lower than those at normal condition. The occurrence of maximum heat release rate retarded with a higher magnitude when compared with normal condition. Experimental results show that as a result of combustion modification, NOx and carbon monoxide emissions were reduced significantly with marginal increase in smoke density. Brake thermal efficiency and unburnt hydrocarbon emissions of the engine were increased significantly as a result of this modification process. This investigation shows that the NOx emission of a biodiesel blend can be reduced with less sacrifice on smoke density and increase in the brake thermal efficiency by modifying the combustion process.  相似文献   

6.
The wide range of hydrogen's flammable limits enables ultra-lean combustion. A lean burn reduces the combustion temperature, increases thermal efficiency, and reduces knock, which is a serious problem in a spark ignition (SI) engine. The anti-knock improvement from hydrogen addition makes it feasible to increase the compression ratio (CR) and further improve the thermal efficiency. Herein, the effects of the CR on performance and emission characteristics were investigated using an 11-L heavy-duty SI engine fuelled with HCNG30 (CNG 70 vol%, hydrogen 30 vol%) and CNG. These fuels were used to operate an engine with CRs of 10.5 and 11.5. The results showed that thermal efficiency improved with an increased CR, which significantly decreased CO2 emission. On the other hand, the NOx emission was largely increased. Nevertheless, for HCNG30, a CR of 11.5 improved thermal efficiency by 6.5% and decreased NOx emission by over 75%, as compared to a conventional CNG engine.  相似文献   

7.
The morphological evolution of specimen taken out after the different duration in TiCl3 solution was investigated by field emission scanning electron microscopy (FE-SEM). The rutile TiO2 splitting microspheres may be formed by the splitting crystal growth mechanism through the multistep process. The microsphere composed of the 20 nm width nanorods was in the range of 1.5–2.5 μm in the diameter. The dye-sensitized solar cell (DSC) based on the microspheres received 3.57% conversion efficiency under simulated AM 1.5 (100 mW/cm2) solar illumination, which exhibited remarkably higher charge collection efficiency and light scattering compared to that of P25. Electrochemical impedance spectroscopy (EIS) measurement revealed that impedance resistance at the surface of single-crystalline rutile TiO2 splitting microspheres was 6 times larger than that of P25 nanoparticles, indicating electron recombination was significantly retarded.  相似文献   

8.
Abstract

SnO2 nanorods and hollow spheres were conducted via a surfactant assisted hydrothermal reaction with the hydrothermal temperature. The crystalline structure and morphologies of the as prepared samples were characterised by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that the products are hollow spheres with diameters of approximately 400–800 nm and shell thicknesses of 60–70 nm via hydrothermal treating at 160°C for 42 h and rod-like nanostructures with diameters of ~30 nm and lengths of 100–300 nm via hydrothermal treating at 200°C for 42 h respectively. The as prepared samples were used as anode materials for lithium ion battery, whose charge–discharge properties and cycle performance were examined. The results show that the initial discharge capacities of SnO2 hollow spheres and SnO2 nanorods samples are 1303 and 1426 mA h g?1 at 0·2C rate, and still retain charge capacities of 518 and 578 mA h g?1 respectively. Its good cycling behaviour and charge capacities make it a promising cathode material for advanced electrochemical devices for lithium ion batteries.  相似文献   

9.
In this study, the hydrogen (H2) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H2 sensor performance, the nanorods were heated at 500 °C in dry air. H2 sensing measurements were done in the temperature range of 25–200 °C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the un-coated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure.  相似文献   

10.
In this work, a novel hybrid structure of tungsten nitride nanorods upon graphene nanosheets was obtained by synthesizing WOx nanorods/graphene oxide (GO) nanosheets followed by hydrogenation and nitridization treatment. Electron microscopy and X-ray diffraction results indicated that the hybrid was composed of W2N nanorods and reduced graphene oxide nanosheets. Surface chemical characteristics of the hybrid were characterized by X-ray photoelectron spectroscopy (XPS) and its electrocatalytic activities were evaluated using a rotating disk electrode measurement system. Compared to the WO3 nanorods-GO hybrid, onset potential of the W2N nanorods-rGO hybrid for oxygen reduction reaction (ORR) was shifted from 0.6 V to 0.71 V, and the limiting current density increased by 1.4 times, exhibiting significantly enhanced electrocatalytic performance, which rendered the W2N-rGO hybrid as a potential non-precious-metal ORR catalyst in fuel cells and metal air battery applications.  相似文献   

11.
We conducted an extensive study on poly(3-hexylthiophene) (P3HT) in combination with titanium dioxide (TiO2) nanorods hybrid material for polymer solar cell applications. The device performance critically depends on the morphology of the hybrid film that will be determined by the molecular weight of P3HT, the solvent type, the hybrid compositions, the surface ligand on the TiO2 nanorods, film thickness, process conditions, and so on. The current–voltage characteristic of the device fabricated in air has shown a power conversion efficiency of 0.83% under air mass (AM) 1.5 illumination using high molecular weight (65,000 D) P3HT, high boiling point solvent trichlorobenzene, and pyridine-modified TiO2 nanorods with a film thickness of about 100 nm. The Kelvin probe force microscopy (KPFM) study of hybrid films shows large-scale phase separation with domain size greater than 10 nm, which may be the main factor limiting device performance.  相似文献   

12.
ABSTRACT

Optimal energy renovations of apartment buildings in Finland have a great impact on annual energy demand. However, reduction of energy demand does not necessarily translate into similar changes in peak power demand. Four different types of apartment buildings, representing the Finnish apartment building stock, were examined after optimal energy retrofits to see the influence of retrofitting on hourly power demand. Switching from district heating to ground-source heat pumps reduced emissions significantly under current energy mix. However, the use of ground-source heat pumps increased hourly peak electricity demand by 46–153%, compared to district heated apartment buildings. The corresponding increase in electrical energy demand was 30–108% in the peak month of January. This could increase the use of high emission peak power plants and negate some of the emission benefits. Solar thermal collectors and heat recovery systems could reduce purchased heating energy to zero in summer. Solar electricity could reduce median power demand in summer, but had only a little effect on peak power demand. The reduction in peak power demand after energy retrofits was less than the reduction in energy demand.  相似文献   

13.
This study demonstrates a high-performance visible-light-driven photocatalyst for water splitting H2 production. CdS nanorods (30 nm in diameters) with shorter radial transfer paths and fewer defects were prepared by a solvothermal method. To mitigate the recombination of electrons and holes, MoS2 nanosheets with rich active sites were modified on the surface of CdS nanorods by a room-temperature sonication treatment. The photocatalytic water splitting tests show that the MoS2/CdS nanocomposites exhibit excellent H2 evolution rates. The highest H2 evolution rates (63.71 and 71.24 mmol g?1h?1 in visible light and simulated solar light irradiation) was found at the 6% MoS2/CdS nanocomposites, which was 14.61 times and 13.39 times higher than those of the corresponding pristine CdS nanorods in visible light and simulate solar light irradiation, respectively. The apparent quantum efficiency (AQE) of the 6% MoS2/CdS nanocomposites at 420 nm was calculated to be 33.62%. The electrochemistry tests reveal that the enhanced photocatalytic activity is a result of extra photogenerated charge carries, greatly enhanced charge separation and transfer ability of the MoS2/CdS composites. This study may give new insights for the rational design and facile synthesis of high-performance and cost-effective bimetallic sulfide photocatalysts for solar-hydrogen energy conversion.  相似文献   

14.
Solid biomass materials are an important industrial fuel in many developing countries and also show good potential for usage in Europe within a future mix of renewable energy resources. The sustainable use of wood fuels for combustion relies on operation of plant with acceptable thermal efficiency. There is a clear link between plant efficiency and environmental impacts due to air pollution and deforestation. To supplement a somewhat sparse literature on thermal efficiencies and nitrogen oxide emissions from biomass-fuelled plants in developing countries, this paper presents results for tests carried out on 14 combustion units obtained during field trials in Sri Lanka. The plants tested comprised steam boilers and process air heaters. Biomass fuels included: rubber-wood, fuelwood from natural forests; coconut shells; rice husks; and sugar cane bagasse. Average NOx (NO and NO2) emissions for the plants were found to be 47 gNO2 GJ−1 with 18% conversion of fuel nitrogen. The former value is the range of NOx emission values quoted for combustion of coal in grate-fired systems; some oil-fired systems and systems operating on natural gas, but is less than the emission levels for the combustion of pulverized fuel and heavy fuel oil. This value is significantly within current European standards for NOx emission from large combustion plants. Average thermal efficiency of the plants was found to be 50%. Observations made on operational practices demonstrated that there is considerable scope for the improvement of this thermal efficiency value by plant supervisor training, drying of fuelwood and the use of simple instruments for monitoring plant performance.  相似文献   

15.
Fluorine-doped indium oxide thin films, F-In2O3, prepared by the spray pyrolysis technique on glass substrates have been studied using cathodoluminescence spectroscopy, X-ray diffraction and spectrophotometry. These films, deposited at the optimal substrate temperature (Ts=450 °C), crystallize in a cubic structure with a preferential orientation along the (4 0 0) direction. For this temperature, the electrical resistivity is in the order of 6×10−3 Ω cm and the average optical transmission in the visible region is larger than 95%. At room temperature, the cathodoluminescence spectra of F-In2O3 present two emission peaks: blue indirect band gap peak at 410 nm and a red emission at 650 nm.  相似文献   

16.
An investigation of the electrochemical oxidation of glycerol as alternative to hydrogen and methane in solid oxide fuel cells (SOFCs) based on a noble metal-free anode catalyst was carried out. The anode electrocatalyst consisted of a Ni-modified La0.6Sr0.4Fe0.8Co0.2O3 (LSFCO) perovskite. After thermal activation, air treatment at 1100 °C followed by reduction at 800 °C in H2, Ni was mainly present as ultrafine La2NiO4 particles homogeneously dispersed on the perovskite surface. The thermal activation also caused a modification of perovskite into a lanthanum depleted structure. The thermal reduction at 800 °C determined the occurrence of metallic Ni on the surface. These results were corroborated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). A suitable power density (327 mW cm−2) was achieved for the electrolyte supported SOFC fed with chemical-grade glycerol in almost dry condition, i.e. steam to carbon ratio (S/C) of 0.2. The highest electrical efficiency (voltage efficiency) approached 50% at the peak power under mild humidification (S/C = 0.2). Whereas an increase of water to glycerol ratio, caused a progressive decrease of voltage efficiency at the peak power down to 44% for S/C = 2.  相似文献   

17.
Abstract

Intriguing ZnO three-dimensional (3D) dendritic nanorods on silicon substrates have been successfully synthesised by thermal evaporation of pure zinc powder at a relative low temperature of 478°C without any metal catalyst. ZnO dendritic nanostructure exhibits unique shape and it is composed of stems and nanorod branches. It is found that the nanorods are single crystalline wurtzite structures, and each nanorod grows along the [0001] direction. At different growth temperatures, the shapes of ZnO nanostructures can be altered. System analysis reveals that the formation and morphology of ZnO dendritic nanostructures are sensitive to the growth temperature. Finally, room temperature photoluminescence spectrum is also investigated, revealing that the ZnO dendritic nanostructure could find application in UV optoelectronic devices; the nanostructure implies some potential applications for nanoscale functional devices.  相似文献   

18.
In this present work, novel MoSb2‐xCuxSe4 thin films were prepared for different copper concentrations (x = 0.0, 0.1, 0.2 and 0.3 M) by a simple chemical bath deposition method. XRD patterns revealed the phase conversion of orthorhombic Sb2Se3 into Cu3SbSe3 by the incorporation of copper content with successive peak shift towards higher angles. Average crystallite was found to be 8, 17 and 25 nm for 0.1, 0.2 and 0.3 M Cu content, respectively. Fourier transform infrared spectra witnessed the presence of functional groups in citric acid and metal oxide vibrations. Field emission scanning electron microscope analysis picturized the grain size growth with respect to Cu content. UV–Vis analysis showed higher absorption in the visible region, and band gap values were found to be 2.08 ? 1.69 eV. Hall effect studies confirm the p‐type nature of the material. The photocurrent analysis shows higher photoconversion efficiency of 1.196% for 0.3 M copper content. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

19.
Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH3 medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene.  相似文献   

20.
In this study, anatase TiO2 nanorods with exposed high-energy {100} and {001} facets and low-energy {101} facets were fabricated in the presence of surfactants cetyltrimethylammonium bromide, didecyldimethylammonium bromide, and ammonia via a facile hydrothermal method without the erosive reagent hydrofluoric acid. The particle size and morphology were mainly tuned by regulating the hydrothermal temperature. When the temperature was increased from 150 °C to 180 °C and 200 °C, the length of the nanorods decreased from 700-1000 nm to 400–500 nm and 100–200 nm, respectively. Concurrently, the edges and tops of the truncated tetragonal pyramid of the TiO2 nanorods became blurry and flattened. The synthesized typical TiO2 nanorods were then used as photocatalysts, and their performance during the direct generation of H2 from water was evaluated. The TiO2 nanorods obtained at 150 °C successfully produced high amounts of H2 evolution (281.36 μmol) in the presence of methanol as a sacrificial agent under ultraviolet light irradiation for 4 h. The outstanding photocatalytic activity of the nanorods was mainly ascribed to the formation of surface heterojunctions in the edges and corners between adjacent high-energy {001} or {100} facets and low-energy {101} facets. The formed heterojunctions could facilitate charge separation through preferential carrier flow toward the specific facets.  相似文献   

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