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101.
K.B. Ibrahim W.-N. Su M.-C. Tsai A.W. Kahsay S.A. Chala M.K. Birhanu J.-F. Lee B.J. Hwang 《Materials Today Chemistry》2022
Developing oxygen evolution reaction (OER) electrocatalyst based on earth-abundant materials holds great promise for ascertaining water-splitting to surmount its deprived kinetics. In this regard, NiFe-LDH (layered double hydroxide) receives considerable attention owing to their layered structure. However, they still suffer from poor electronic conductivity and structural stability. We combined NiFe-LDH nanosheets with Magnéli phase Ti4O7 into a heterostructured composite. A series of analyses reveal that decorating Ti4O7 facilitates charge transfer to enhance the conductivity of NiFe-LDH-Ti4O7. During electrochemical measurement, Ni2+ is transformed to metastable Ni3+ (Ni (OH)→ NiOOH) before the OER onset potential. Thus, the presence of Ni3+ as the main active sites could improve the chemisorption of OH? to facilitate OER. As a result, the NiFe-LDH-Ti4O7 catalyst delivers as low as onset potential (1.43 V). Combining the holey structure (NiFe-LDH and Ti4O7) and the defect engineering generated on NiFe-LDH-Ti4O7 as a synergistic effect improves the OER performance. The inclusion of Ti4O7 in the composite leads to more vacancy sites, as evidenced by the extended X-ray absorption fine structure (EXAFS) analysis. The obtained defective structure with a low coordination environment would improve the electronic conductivity and facilitate the adsorption process of H2O onto metal cations, thereby increasing the intrinsic catalytic activity of NiOOH. The strong coupling of NiFe-LDH and Ti4O7 also increases the stability, and the heterostructured composite helps maintain the structural robustness of the LDH. 相似文献
102.
The paper discusses local porosity theory and its relation with other geometric characterization methods for porous media such as correlation functions and contact distributions. Special emphasis is placed on the charcterization of geometric observables through Hadwigers theorem in stochastic geometry. The four basic Minkowski functionals are introduced into local porosity theory, and for the first time a relationship is established between the Euler characteristic and the local percolation probabilities. Local porosity distributions and local percolation probabilities provide a scale dependent characterization of the microstructure of porous media that can be used in an effective medium approach to predict transport. 相似文献
103.
104.
LI Qian-rong PAN Zhen YIN Hao WANG Wei 《高等学校化学研究》2007,23(4):421-425
4β-Azido-4-demethyl-4'-O-demethyl-epipodophyllotoxin reacted with phenyliodonium diacetate in MeOH at room temperature to synthesize a novel podophyllotoxin derivative containing a cyclohexadienone group with the original configurations of C2 and C4,which are required for the antitumor activities.The component and structure of the pro-duct were confirmed using elemental analysis,high-resolution mass spectrum,1H and 13C NMR spectra,and infrared spectrum.Furthermore,the fragmentation routes of the product were fully assigned with electron-impact time-of-flight mass spectrometry(EI-TOF MS),which can also be used for the structural elucidation based on the molecular ion at m/z 455(16%)and three novel characteristic fragment ions at m/z 183(37%),425(7%),and 199(5%).The cyclohexadienone product is sensitive to acidic media.When it is treated with a trace of acid,another novel derivative containing an orthoquinone moiety is formed,which links with the metabolism of the cancer inhibitors. 相似文献
105.
A new kind of polytriazoleimide containing bisphenyl-l,2,3-triazole(BPT) was synthesized by copper-catalyzed 1,3-dipolar cycloaddition of azides and alkynes(CuAAC) and polycondensation.The thermal stability and degradation mechanism of the polytriazoleimide were investigated.The results show that the structure of BPT in polytriazoleimide transforms to phenylindole after thermal treatment,accompanying the release of N2. 相似文献
106.
Roumen Anguelov Evgenija D. Popova 《Journal of Computational and Applied Mathematics》2010,235(2):358-365
This paper brings together two methods producing numerical solutions with a statement of their quality — the nonstandard finite difference method and the method of validated computing. It deals with the construction and the analysis of reliable numerical discretizations of dynamical systems by employing these two techniques. An epidemiological model is used as a model example for their combined application. 相似文献
107.
Symbiodinolide is a polyol macrolide isolated from the marine dinoflagellate Symbiodinium sp. in 2007. The C14-C24 fragment of symbiodinolide possessing the 17R/18R/21R absolute configuration, which was obtained as one of the degraded products of symbiodinolide, was synthesized stereoselectively from cis-2-butene-1,4-diol. The detailed comparison of the synthetic product with the degraded product in the spectroscopic data confirmed that the stereostructure of the C14-C24 fragment was 17R, 18R, and 21R. 相似文献
108.
109.
Study of structural properties of (Ba0.5Sr0.5)PbO3 has been carried out in a wide temperature range from 10 to 1223 K using the X-ray powder diffraction technique. Two temperature-induced structural phase transitions at 948 and 1198 K have been found. For polycrystallines the XPS and electrical resistivity measurements have been performed. 相似文献
110.
The ultrafast dynamics of excited electronic states in a series of quasi-one-dimensional halogen-bridged platinum-complexes was investigated by using femtosecond luminescence spectroscopy. In Pt-Br system, the wave-packet oscillation of the local vibration of self-trapped excitons (STEs) was observed. The time evolutions of luminescence intensity in Pt-Br and Pt-Cl were successfully described by using a model based on a wave-packet motion on the interaction mode coordinate. In Pt-I, very fast decay was observed, suggesting the existence of efficient non-radiative decay channel directing to structural change. 相似文献