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排序方式: 共有181条查询结果,搜索用时 31 毫秒
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Saroj Kumari Aadesh P. Singh Sonal Dinesh Deva Rohit Shrivastav Sahab Dass Vibha R. Satsangi 《International Journal of Hydrogen Energy》2010
Nanoporous hematite (α-Fe2O3) thin films doped with Ti4+ deposited by spray-pyrolysis were successfully used in photoelectrochemical splitting of water for solar hydrogen production. X-ray diffraction, field emission scanning electron microscopy, UV–visible absorption and photoelectrochemical studies have been performed on the undoped and Ti4+ doped hematite thin films. Morphology of α-Fe2O3 thin films was observed to be nanoporous, with increased porosity (pore size ∼12 to 20 nm) on increasing doping concentration. A significant decrease in the bandgap energy from 1.95 to 1.27 eV was found due to doping. α-Fe2O3 film doped with 0.02 M Ti4+ ions exhibited best solar to hydrogen conversion efficiency (photoconversion efficiency) of 1.38% at 0.5 V/SCE. Highest photocurrent densities of 0.34 mA/cm2 at zero bias and 1.98 mA/cm2 at 0.5 V/SCE were obtained by incorporating 0.02 M Ti4+ in α-Fe2O3, which are significantly larger than earlier reported values. Donor density (30.8 × 1020 cm−3) and flatband potential (−1.01 V/SCE) obtained were also maximum for this sample. Hydrogen collected in 1 hr at Pt electrode with the best photoelectrode was 2.44 mL with 150 mW/cm2 visible light source. 相似文献
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Anupam Srivastav Pawan Kumar Anuradha Verma York R. Smith Vibha Rani Satsangi Rohit Shrivastav Umesh V. Waghmare Sahab Dass 《International Journal of Hydrogen Energy》2018,43(33):15815-15822
Though bismuth vanadate (BiVO4) is extensively used as a photoactive material, its performance in harnessing solar energy is limited by ineffective separation of photo-excited charge carriers. We demonstrate here a concept of n-n+ homojunction of BiVO4/BiV1-xMnxO4-y, which improves its charge separation efficiency. Using first-principles theoretical calculations, we determine the effect of Mn substitution on oxygen vacancy formation energies and associated changes in the electronic structure of BiVO4. Showing that Mn substitution pushes the Fermi level of BiVO4 towards its conduction band, we predict that the associated enhanced bending of bands at the homojunction (BiVO4/BiV1-xMnxO4-y) facilitates efficient separation of charge carriers. With Mott-Schottky experiments, we verify the increased band bending at the n-n+ homojunction, and show that the maximum photocurrent density measured in a sample with n-n+ homojunction is ten times higher than that obtained of the pristine sample. Secondly, Mn substitution in BiVO4 also reduces the oxygen vacancy formation energy, promoting higher concentration of O-vacancies, further enhancing the photoelectrochemical response. 相似文献
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Urolithiasis is a common diagnostic and therapeutic problem in small-animal veterinary practice. The traditional diagnostic approach usually consists of clinical, radiological and ultrasonographic examination of the patient. The main diagnostic material is still urine sediment, ignoring the fact that presence of crystalluria is not always of pathological significance. In order to establish the most effective therapeutic and preventative strategies, especially in the case of multicomponent stone, it is crucial to define the exact elemental composition of the given stone including crystallization nidus chemical contents. In the course of the research, the usefulness of scanning electron microscopy combined with X-ray-dispersive spectrometry in analysis of canine mixed and compound stones was investigated. The obtained results indicated that the tested method allows one to trace the dynamics of the crystallization process, including crystallization nucleus detection, and concurrently and quantitatively assess the elemental composition of the given urinary concrement. Moreover, the conducted research showed epidemiological data of urolithiasis occurrence in a population of dogs coming from the southern part of Poland. 相似文献
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Babita Kumari Shailja Sharma Nirupama Singh Anuradha Verma Vibha R. Satsangi Sahab Dass Rohit Shrivastav 《International Journal of Hydrogen Energy》2014
ZnO thin films, showing nano-ridges at the surface and the top layer embedded with metal (Ag/Au) nanoparticles (MNP), were obtained by sol-gel synthesis, using zinc acetate dihydrate [(CH3.COO)2Zn.2H2O] as precursor. The method involved prior synthesis of Ag and Au nanoparticles via biological reduction of AgNO3 and HAuCl4, respectively, using algae Spirulina platensis. The XRD analysis indicated dominant evolution of wurtzite ZnO phase. Low-angle shift in peaks, seen with nanoparticles embedded films, indicated partial diffusion of metals into ZnO lattice. Band gap energy was least affected and lied in the expected range. AFM and SEM analysis revealed the surface topography and morphology, while EDX analysis confirmed the elemental stoichiometry and existence of Ag/Au nanoparticles in samples. Significant gain in photoelectrochemical current using MNP embedded films is largely accountable to the improvement in electrical conductance and the role played by metal nanoparticles in charge-carrier separation, collection and transport. 相似文献
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Orth Ulrich; Robins Richard W.; Trzesniewski Kali H.; Maes Jürgen; Schmitt Manfred 《Canadian Metallurgical Quarterly》2009,118(3):472
Data from two large longitudinal studies were used to analyze reciprocal relations between self-esteem and depressive symptoms across the adult life span. Study 1 included 1,685 participants aged 18 to 96 years assessed 4 times over a 9-year period. Study 2 included 2,479 participants aged 18 to 88 years assessed 3 times over a 4-year period. In both studies, cross-lagged regression analyses indicated that low self-esteem predicted subsequent depressive symptoms, but depressive symptoms did not predict subsequent levels of self-esteem. This pattern of results replicated across all age groups, for both affective–cognitive and somatic symptoms of depression, and after controlling for content overlap between the self-esteem and depression scales. The results suggest that low self-esteem operates as a risk factor for depressive symptoms at all phases of the adult life span. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Aadesh P. Singh Saroj Kumari Rohit Shrivastav Sahab Dass Vibha R. Satsangi 《International Journal of Hydrogen Energy》2008
This paper describes the photoelectrochemical studies on nanostructured iron doped titanium dioxide (TiO2) thin films prepared by sol-gel spin coating method. Thin films were characterized by X-ray diffraction, Raman spectroscopy, spectral absorbance, atomic force microscopy and photoelectrochemical (PEC) measurements. XRD study shows that the films were polycrystalline with the photoactive anatase phase of TiO2. Doping of Fe in TiO2 resulted in a shift of absorption edge towards the visible region of solar spectrum. The observed bandgap energy decreased from 3.3 to 2.89 eV on increasing the doping concentration upto 0.2 at.% Fe. 0.2 at.% Fe doped TiO2 exhibited the highest photocurrent density, ∼0.92 mA/cm2 at zero external bias. Flatband potential and donor density determined from the Mott–Schottky plots were found to vary with doping concentration from −0.54 to −0.92 V/SCE and 1.7 × 1019 to 4.3 × 1019 cm−3, respectively. 相似文献