The effect of Co particle size on the Fischer-Tropsch synthesis (FTS) activity of carbon nanotube (CNT)-supported Co catalysts was investigated. Microemulsion (using water-to-surfactant molar ratios of 2 to12) and impregnation techniques were used to prepare catalysts with different Co particle sizes. Kinetic studies were performed to understand the effect of Co particle size on catalytic activity. Size-dependent kinetic parameters were developed using a thermodynamic method, to evaluate the structural sensitivity of the CNT-supported Co catalysts. The size-independent FTS reaction rate constant and size-independent adsorption parameter increased with increasing reac-tion temperature. The Polani parameter also depended on catalyst particle size, because of changes in the catalyst surface coverage. 相似文献
A comprehensive study was performed for the design of ABX3 perovskites, (A = Li, K, Na, B = Ge, Sn, Pb, X = F, Cl, Br, I) and organic hole transfer materials, HTMs (Fu-2a, Fu-2b, Fu-2c, and Dm-Q) for efficient perovskite solar cells (PSCs) through quantum chemistry calculations. Photovoltaic characteristics of the investigated perovskites are strongly affected by the halide anions. The results reveal that reducing the exciton binding energy of perovskites enhances the rate of the formation/dissociation of holes and electrons so F-based perovskites are superior from this viewpoint. Additionally, the electron and hole injection processes are more favorable in the case of the F-based perovskites in comparison with other studied perovskites. Moreover, spectroscopic properties of the perovskites demonstrate that KSnCl3, NaSnCl3, and F-based perovskites exhibit a greater ability of the light-harvesting and incident photon to current conversion efficiency. Ultimately, based on diverse analyses, F-based perovskites, KSnCl3 and NaSnCl3 are the preferred candidates to be applied in the PSCs due to an excellent incident photon to current conversion efficiency, light-harvesting efficiency, short circuit current, and solar cell final efficiency. 相似文献
The mechanism (regio- and stereoselectivity) of 1,3-dipolar cycloaddition (1,3-DC) of 2-ethylthio-4-phenyl-1-azetin 1 with benzonitrile oxide 2a, 2-aminobenzonitrile oxide 2b and 2-azidobenzonitrile oxide 2c has been investigated by density functional theory-based reactivity indices and activation energy calculations at B3LYP/6-31G(d,p) level of theory in the gas and solvent phase. Thermodynamic and kinetic parameters of the possible ortho/meta regioisomeric and endo/exo stereoisomeric pathways have been determined. In order to rationalize complete endo selective fashion provided by these 1,3-DC cycloadditions, a natural steric analysis between NLMOs i,j for TS1ox and TS1on and also a second-order interaction energy, E2, analysis between the donor–acceptor orbitals in these TSs were carried out. In all cases, the ortho pathways are more favorable compared to the meta alternatives and it is found that the endo pathway is preferred. Our results show that these cycloadditions follow an asynchronous one-step mechanism with a nonpolar character. Theoretical data are in good agreement with the experimental results. 相似文献
This paper demonstrates the application of composite multi-walled carbon nanotube (MWNT) polyvinylchloride (MWNT-PVC) based on 1,5-diphenylcarbazide as chromium ionophore in potentiometric measurement. The sensor shows a good Nernstian slope of 19.52 ± 0.40 mV/decade in a wide linear range concentration of 6.3 × 10−8 to 1.0 × 10−2 M for Cr(NO3)3. The detection limit of this electrode was found to be 3.2 × 10−8 M of Cr(NO3)3 and is applicable in a pH range of 3.0-6.8. It has a short response time of about 10 s. This chromium electrode has a good selectivity over 16 various metal ions. The practical analytical utility of this electrode was demonstrated by measurement of Cr(III) in drinking water and mineral water samples without any serious preliminary pre-treatment and chromium in multivitamin. 相似文献
A PVC-based membrane of 4-dimethylaminoazobenzene reveals a Nernstian potentiometric response (with slope of 19.5+/-0.6 mV/decade and a correlation coefficient of 0.999) for Cr(III) over a wide concentration range (1.66 x 10(-6)-1.0 x10(-2) mol dm(-3)). The potential of this electrode is independent of pH in the range of 3.0-5.5. It has a fast response time of about 10 s and was used for a period of 3 months with good reproducibility. The detection limits of this membrane electrode was 8 x 10(-7) M. the proposed electrode has been used as an indicator electrode in the potentiometric titration of Cr(III) with EDTA. This sensor exhibits a very good selectivities for Cr(III) over a wide variety of metal ions. 相似文献
A new generation of glutathione peroxidase enzyme mimic based on organotellurium was introduced. The catalytic cycles of these mimics, tellura and tellenol, were clarified by density functional theory and solvent-assisted proton exchange procedure as an indirect proton exchange chain. From the kinetic viewpoint, the oxidation of tellura (ΔG≠ = 23.55 kcal mol−1) was considered as the rate-determining step using a single-step process. Various behaviors of tellenol were examined in the reduction of tellurenylsulfide based on methanethiol nucleophilicity. On the basis of the turnover frequency calculations, during the catalytic cycles of tellura and tellenol, the rate of the catalytic cycle of tellura is faster than that of tellenol. A decrease in the electron density and an increase in the Laplacian from the reactant to the transition states are evidence of the bond rupture, whereas an opposite change is evidence of the bond formation. Finally, different analyses of the electron location function and localized orbital locator within the quantum theory of atoms in molecules were applied and discussed. The covalent nature of the intramolecular interactions suggests that the Te⋯N interaction is stronger than that of Te⋯H. Finally, based on different analyses, tellura can be considered the more reactive GPx mimic than tellenol. 相似文献
Research on Chemical Intermediates - Kinetic and thermodynamic aspects of the cross-coupling reaction of quinoline N-oxides by various boronic esters in the gas and solvent phases were... 相似文献
The origin of the experimentally known preference for [6,6] bonds in cycloaddition reactions involving C60 has been computationally explored. To this end, we examined the reactions of 1,3-dienes with fullerene (C60) in the context of an approach to open a large orifice on the fullerene framework by using the activation model of reactivity in combination with the energy analysis method. In this study, the effect of the alkali metal of Li+, Na+, and K+ as an encapsulated element was investigated on the kinetic and thermodynamic behaviors of the Diels–Alder (DA) process. Our calculations indicated that encapsulated Na+ and K+ cations are located close to the center of the C60 molecule; however, encapsulated Li+ is displaced from the center, which leads to a higher reactivity for Li+@C60 in DA cycloaddition reaction in the gas phase. Also, benzene as a non-polar solvent affects the DA reactions greater than water as a polar solvent. Different analyses show that solvent changes the catalysis reaction performance, in which a greater efficiency was obtained for K+ in the solvent in comparison with other alkali ions because of a facilitated mechanism of electron transfer.