Efficient and low-cost transition metal single-atom catalysts (TMSACs) for hydrogen evolution reaction (HER) have been recognized as research hotspots recently with advances in delivering good catalytic activity without noble metals. However, the high-cost complex preparation of TMSACs and insufficient stability limited their practical applications. Herein, a simple top-down pyrolysis approach to obtain P-modified Co SACs loaded on the crosslinked defect-rich carbon nanosheets was introduced for alkaline hydrogen evolution, where Co atoms are locally confined before pyrolysis to prevent aggregation.
View Article and Find Full Text PDFA density functional theory study of copper-mediated dehydroacylation of 4-phenyl-2-butanone to the corresponding olefin reveals a flexible N-H transfer process and a metal-independent C-C cleavage mechanism. When '-methylpicolinohydrazonamide (MPHA) acts as the activating reagent, N-H cleavage can easily take place stepwise proton transfer/electron transfer (PT/ET) and the rate-determining step is C-C homolysis with a total free energy barrier of 22.6 kcal mol, which is consistent with experimental observation of no kinetic isotope effects (KIE) at β-H.
View Article and Find Full Text PDFA density functional theory study of Cu-catalyzed desaturation of δ-valerolactone into α,β-unsaturated counterparts reveals an unexpected binuclear di-tert-butyl peroxide (DTBP) homolysis with spin-crossover and a radical α-C-H bond activation mechanism. The rate-determining step in the reaction catalyzed by CuIOAc-CyPPh2 is the homolysis of the O-O bond in DTBP with a total free energy barrier of 26.9 kcal mol-1, which is consistent with the observed first-order dependences on LCuI-PR3 and DTBP, as well as the pseudo-zeroth-order with lactone.
View Article and Find Full Text PDFTwo-line atomic fluorescence (TLAF) is a promising technique for two-dimensional (2D) flame thermometry. However, it suffers either from a low signal-to-noise ratio (SNR) when excited in the linear regime or a quenching effect and nonlinear behavior in the nonlinear regime. This work aims to develop a new TLAF modality, which can overcome the aforementioned limitations based on a specifically designed laser source that can generate long pulses (∼400) with a moderate energy of ∼0.
View Article and Find Full Text PDFNonlinear excitation regime two-line atomic fluorescence (NTLAF) is a promising two-dimensional (2D) thermometry technique for turbulent sooty flames. However, the complexity of calibrating three system parameters and expensive instruments restricts the application of the current NTLAF technique. Here we propose a simple and cheap NTLAF measurement approach based on a one-parameter model and tunable diode laser absorption spectroscopy (TDLAS) calibration.
View Article and Find Full Text PDFThe wavelength modulation spectroscopy (WMS) technique has been demonstrated as a powerful and indispensable tool for quantitative and real-time measurements on the combustion process of various industrial devices. However, the varying pressure occurred in the aero-engine combustor significantly affects the accuracy and efficiency of the WMS technique. To address this issue, this work reports a novel method named WMS pressure correction model, which can enable fast signal processing in the measurements at varying pressure.
View Article and Find Full Text PDFThe partial oxidation of starch was achieved in the presence of oxygen with Na4Co(H2O)6V10O28·18H2O (abbreviated as CoV10) as catalyst. The oxidation degree of starch was determined by FT-IR, XRD and SEM measurements, which indicated that the aerobic oxidation of starch was promoted by oxidative catalyst CoV10. The application of CoV10 could give a high oxidation degree (DO) of 1.
View Article and Find Full Text PDFGuang Pu Xue Yu Guang Pu Fen Xi
August 2013
In order to develop a new sort of thermally sensitive phosphor coating, the emission spectrum thermally sensitivity of Mg4FGeO6 : Mn induced by laser was studied. The spectrum measurement system with heating function was set up, and the emission spectrum of Mg4FGeO6 : Mn at various temperatures were measured. Absorption spectrum was measured, and the mechanism of formation of the structure of double peak was analyzed with the perturbation theory of crystal lattice.
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