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排序方式: 共有220条查询结果,搜索用时 23 毫秒
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2.
《International Journal of Hydrogen Energy》2020,45(4):2729-2744
The development of efficient metal doped semiconductors for solar energy harvesting to produce hydrogen has attracted significant attention. Herein, the H2 generation over Ag-doped TiO2 photocatalyst, synthesized using a simple and cost-effective method based on chemical reduction, was reported. The Ag/TiO2 exhibited an absorption peak in the visible region and the reduction of the bandgap to 2.5 eV due to surface plasmonic resonance (SPR). X-ray photoelectron spectroscopy revealed the presence of oxygen vacancies and 11% of Ag in Ti–Ag–O phase. The effect of reaction time and photocatalyst loading in the absence and presence of sacrificial reagents (alcohols and sulfur) on water splitting was studied and compared the activity of Ag/TiO2 with that of bare TiO2. The H2 production rate of 23.5 mmol g−1 h−1 (with an apparent quantum yield of 19%), over 1.5Ag/TiO2, was the highest ever reported so far. The observed higher activity could mainly be attributed to the existence of oxygen vacancies and the Ti–Ag–O phase. The photocatalyst was stable for three consecutive cycles in both the presence and absence of sacrificial reagents. This study offers new insights into the rational design of metal-support hybrid structures for hydrogen production through photocatalytic water splitting. 相似文献
3.
The electronic band structure and carrier density of strained armchair graphene nanoribbons (AGNRs) with widths of n =3 m and n =3 m +1 were examined using tight-binding approximation. The current-voltage (I-V) model of uniaxial strained n =3 m AGNRs incorporating quantum confinement effects is also presented in this paper. The derivation originates from energy dispersion throughout the entire Brillouin zone of uniaxial strained AGNRs based on a tight-binding approximation. Our results reveal the modification of the energy bandgap, carrier density, and drain current upon strain. Unlike the two-dimensional graphene, whose bandgap remains near to zero even when a large strain is applied, the bandgap and carrier density of AGNRs are shown to be sensitive to the magnitude of uniaxial strain. Discrepancies between the classical calculation and quantum calculation were also measured. It has been found that as much as 19% of the drive current loss is due to the quantum confinement. These analytical models which agree well with the experimental and numerical results provide physical insights into the characterizations of uniaxial strained AGNRs. 相似文献
4.
《Ceramics International》2017,43(8):6437-6445
Nitrogen - rich graphitic carbon nitride (Ng-C3N4) with improved photocatalytic activity was engineered using a facile post-annealing treatment of pristine g-C3N4 in N2 atmosphere. The thermal annealing did not modify the crystal structure, vibrational modes, or morphology of the N-rich g-C3N4 (Ng-C3N4). However, it decreased the crystallinity by broadening the dominant X-ray diffraction (XRD) peak and increased the surface area and mesoporous nature because of the formation of carbon vacancies. Diffuse reflectance spectroscopy indicated that the bandgap of the annealed Ng-C3N4 decreased from 2.82 to 2.77 eV compared to pristine g-C3N4. The increase of nitrogen content in the annealed Ng-C3N4 was quantified by X-ray photoelectron spectroscopy (XPS), which was also used to examine the formation of carbon vacancies. Photocurrent and electrochemical impedance spectroscopy measurements showed that the annealed Ng-C3N4 had higher light absorption capacity than the pristine g-C3N4. The photocatalytic performance of the samples was investigated for the degradation of crystal violet (CV) under ultra-violet light irradiation. The annealed Ng-C3N4 sample exhibited superior photodegradation of CV over pristine g-C3N4. 相似文献
5.
Ashith V.K. Gowrish K. Rao Smitha R. Sahana N. Moger 《Ceramics International》2018,44(15):17623-17629
The TiO2 films were obtained from successive ion layer adsorption and reaction (SILAR) method. A micro-controller based SILAR unit was used to precisely monitor and control the deposition parameters. The films were uniform and free from physical defects such as pores and cracks. A maximum thickness of about 700?nm was achieved. The films were found to be polycrystalline without any texture or preferred orientations. The crystallite size of the films was found to increase with thickness while the micro strain and stress were found to reduce with the thickness. Post-deposition annealing was also found to produce the similar results. The films were found to possess an indirect bandgap of about 3?eV. Various technically important parameters such as root-mean-square micro strain, Urbach energy, chemical composition, carrier concentration, electrical resistivity etc. were determined. The effects of deposition parameters on the properties of the films is discussed in detail. 相似文献
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7.
Gadolinium (Gd) doped cadmium oxide (CdO) thin films are grown at low temperature (100 °C) using pulsed laser deposition technique. The effect of oxygen partial pressures on structural, optical, and electrical properties is studied. X-ray diffraction studies reveal that these films are polycrystalline in nature with preferred orientation along (1 1 1) direction. Atomic force microscopy studies show that these films are very smooth with maximum root mean square roughness of 0.77 nm. These films are highly transparent and transparency of the films increases with increase in oxygen partial pressure. We observe an increase in optical bandgap of CdO films by Gd doping. The maximum optical band gap of 3.4 eV is observed for films grown at 1 × 10−5 mbar. The electrical resistivity of the films first decreases and then increases with increase in oxygen partial pressure. The lowest electrical resistivity of 2.71 × 10−5 Ω cm and highest mobility of 258 cm2/Vs is observed. These low temperature processed highly conducting, transparent, and wide bandgap semiconducting films could be used for flexible optoelectronic applications. 相似文献
8.
Ternary ZnCdO alloy semiconductor nanostructures were grown using electrochemical deposition. Crystalline nanostructures/nanorods with cadmium concentration ranging from 4 to 16 at% in the initial solution were electrodeposited on tin doped indium oxide (ITO) conducting glass substrates at a constant cathodic potential −0.9 V and subsequently annealed in air at 300 °C. X-ray diffraction measurements showed that the nanostructures were of wurtzite structure and possessed a compressive stress along the c-axis direction. The elemental composition of nanostructures was confirmed by energy dispersive spectroscopy (EDS). ZnO nanostructures were found to be highly transparent and had an average transmittance of 85% in the visible range of the spectrum. After the incorporation of Cd content into ZnO the average transmittance decreased and the bandgap tuning was also achieved. 相似文献
9.
G. J. Letal D. A. Thompson B. J. Robinson J. G. Simmons 《Materials Science and Engineering: B》2001,80(1-3):232-235
Bandgap engineering is used extensively in the telecommunications field. Quantum well intermixing (QWI) is a post-growth method of bandgap engineering that has been studied for the integration of photonic devices (Marsh et al., J. Vac. Sci. Technol. A16 (1998) 810). A novel method of QWI has been discovered that uses layers of indium phosphide grown by helium-plasma-assisted gas source molecular beam epitaxy, subsequently referred to as He*-InP, in combination with thermally induced QWI. The He*-InP has been shown to contain large numbers of defects that can act as fast non-radiative recombination centres. These can be used with the thermally induced QWI to produce regions with a larger bandgap and containing the fast, non-radiative defect centres. This novel intermixing process has been used to fabricate integrated distributed feedback lasers and electro-absorption modulators. 相似文献
10.
本文提出了一种采用0.25μm CMOS工艺的高性能的带隙基准参考源。该电路结构简单,性能较好。用模拟软件进行仿真,在tt模型下,其温度系数为9.6 ppm/℃,电源抑制比(PSRR)为-56 dB,电压拉偏特性为384 ppm/V。而在其它模型下,也有较低的温度系数和较高的电源抑制比。 相似文献