RESUMEN
With the increasing demand for renewable energy and clean energy, photocatalysis is considered an economical and feasible source of energy. In this work, we select two-dimensional (2D) materials of X2CT2 (X = Cr, Hf, Mo, Sc, Ti, Zr; T = Cl, F, O, OH), Mxene, and MS2 (M = Mo, W) to form 20 systems of 2D van der Waals (vdW) heterostructures. We establish five screening steps, and the 2D Mo2CF2/WS2 vdW heterostructures meet all the screening conditions. Mo2CF2/WS2 is a type II semiconductor with a band gap of 1.58 eV, proper band edge position and high solar-to-hydrogen efficiency (17.15%) and power conversion efficiency (23.4%). An excellent electron-hole recombination time of 21.2 ps and electron (hole) migration time of 149 (265) fs are obtained in the 2D Mo2CF2/WS2 vdW heterostructure. In addition, the calculation results of Gibbs free energy show that a hydrogen reduction reaction and water oxidation reaction can proceed smoothly under the driving of photogenerated holes.
RESUMEN
A strong metal-support interaction (SMSI) type catalyst has been synthesized and applied to a molten hydroxide direct carbon fuel cell (MHDCFC) to enhance the reaction activity of the anode carbon fuel through the interaction between the metal Ni and the support CeO2. Two catalysts have been prepared by a direct precipitation method (denoted NiO@CeO2) and a hydrothermal method (denoted NiO-CeO2), which are reduced by H2 to obtain Ni@CeO2 and Ni-CeO2, respectively. X-ray photoelectron spectroscopy (XPS), Raman, and temperature-programmed hydrogen reduction (H2-TPR) analysis results show that there are obvious oxygen vacancies and a Ni-O-Ce interface structure in NiO-CeO2 and Ni-CeO2, which is induced by the interaction between Ni and CeO2. The calculation results of current density and power density show that the performance of the MHDCFC is significantly improved in the presence of Ni-CeO2. The function fitting curves of the logarithm of the reaction rate constant (ln k) and the reciprocal of the temperature (1/T) show that the slope of the curve is decreased significantly after the addition of Ni-CeO2. In combination with density functional theory (DFT), the anode carbon reaction path is simulated in the MHDCFC, and the calculation results show that the reaction energy for the anodic carbon to generate carbon dioxide is decreased by 1.03 eV in the presence of Ni-CeO2.
RESUMEN
A novel [4+1] spiroannulation of o- & p-bromophenols with α,ß-unsaturated imines has been developed for the direct synthesis of a new family of azaspirocyclic molecules. Notably, several other halophenols (X=Cl, I) were also applicable for this transformation. Moreover, a catalytic asymmetric version of the reaction was realized with 1-bromo-2-naphthols by using a chiral ScIII /Py-Box catalyst. Mechanistic studies revealed that this domino reaction proceeded through electrophile-triggered dearomatization of phenol derivatives at their halogenated positions and followed by halogen-displacement with N-nucleophiles via a radical-based SRN 1 mechanism.
RESUMEN
Conventional approaches on using hydroxylamine derivatives as single nitrogen sources, for the construction of n-membered (n > 3) N-heterocycles, rely upon two chemical operations by involving sequential nucleophilic and electrophilic C-N bond formations. Here, we report a highly efficient cascade of alkyne insertion/C-H activation/amination for the rapid preparation of a myriad of tricyclic indoles, in a single-step transformation, by using bifunctional secondary hydroxylamines. It is noteworthy that judicious selection of applicable amino agents, for enabling the prior oxidative addition of aryl iodide to initial Pd(0) species and subsequent two C-N bonds formation, was the key to the success of this reaction. Control experiments indicated that a five-membered palladacyclic intermediate played a crucial role in promoting the final aminative ring closure.
