The electrochemical sensing of nitric oxide (NO) molecules by metal‐organic framework (MOF) catalysts has been impeded, to a large extent, owing to their poor electrical conductivity and weak NO ...adsorption. In this work, incomplete in situ conversion of V2CTx (T = terminal atoms) MXene to MOF is adopted, forming MOF@MXene heterostructures, which outperform MXene and MOF monocomponents toward electrochemical NO sensing. Density functional theory (DFT) calculation results indicate metal‐like electronic characters for the heterostructure benefiting from the dominating contribution of the V 3d orbitals of the metallic MXene. Moreover, plane‐averaged charge density difference shows substantial charge redistribution occurs at the heterointerfaces, producing a built‐in field, which facilitates charge transfer. Besides, molecular mechanics‐based simulated annealing calculation reveals greatly enhanced adsorption energies of NO molecules on the heterointerfaces than that on separate MOFs and MXenes. Hence, the facilitated charge transfer and preferential NO adsorption are responsible for the dramatically promoted performance toward NO sensing. The prudent design of MOF@MXene heterostructure may spur advanced electrocatalysts for electrochemical sensing.
Incomplete conversion of MXene to metal‐organic framework (MOF) leads to the formation of MOF@MXene heterostructure, which exhibits metal‐like electronic structures contributed by the metallic MXene counterparts. Their heterointerface induces preferential NO adsorption and substantial electrons transfer from MXene inner surface to MOF species, which engage for greatly promoted electrochemical performance toward NO sensing.
Voltage stability is a key issue to achieve the uninterrupted operation of wind farms equipped with doubly fed induction generators (DFIGs) during grid faults. This paper investigates the application ...of a static synchronous compensator (STATCOM) to assist with the uninterrupted operation of a wind turbine driving a DFIG, which is connected to a power network, during grid faults. The control schemes of the DFIG rotor- and grid-side converters and the STATCOM are suitably designed and coordinated. The system is implemented in real-time on a real time digital simulator. Results show that the STATCOM improves the transient voltage stability and therefore helps the wind turbine generator system to remain in service during grid faults.
Nitrogen‐enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area ...(SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane‐derived conductive microporous covalent triazine‐based frameworks (TCNQ‐CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m2 g−1). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g−1, considerable energy density of 42.8 Wh kg−1, and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high‐performance electrode material for electrochemical energy‐storage systems.
Superstores: A new class of conductive microporous covalent triazine‐based frameworks (TCNQ‐CTFs) has been developed as the electrode material for supercapacitors. With both large surface area and abundant nitrogen, TCNQ‐CTF‐800 had a higher specific capacitance and comparative energy density than state‐of‐the‐art nitrogen‐containing frameworks and carbon materials, which holds great potential for applications in energy storage.
Reported herein is asymmetric 3+2 annulation of arylnitrones with different classes of alkynes catalyzed by chiral rhodium(III) complexes, with the nitrone acting as an electrophilic directing group. ...Three classes of chiral indenes/indenones have been effectively constructed, depending on the nature of the substrates. The coupling system features mild reaction conditions, excellent enantioselectivity, and high atom‐economy. In particular, the coupling of N‐benzylnitrones and different classes of sterically hindered alkynes afforded C−C or C−N atropochiral pentatomic biaryls with a C‐centered point‐chirality in excellent enantio‐ and diastereoselectivity (45 examples, average 95.6 % ee). These chiral center and axis are disposed in a distal fashion and they are constructed via two distinct migratory insertions that are stereo‐determining and are under catalyst control.
Rhodium‐catalyzed C−H activation of nitrones and coupling with different classes of sterically hindered alkynes afforded C−C or C−N atropochiral and C‐centered point‐chiral indenes in excellent enantio‐ and diastereoselectivity. The chiral center and axis are disposed in a distal fashion, and they are constructed via two uncorrelated stereo‐determining steps.
Facile synthesis of elaborate nanostructured transition metal compounds with tunable components remains challenging because multiple synthetic procedures or complex manipulation are normally ...involved. Herein, an acid‐etching strategy is applied to Co, in which the composition and morphology of the resultant materials are tunable. Specifically, a novel two‐tiered Co(CO3)0.5(OH)·0.11H2O nanosheet is formed, part of which decomposes to produce hierarchical Co(CO3)0.5(OH)·0.11H2O/Co3O4 nanocomposite by tuning the etching condition. The composite shows bifunctional electrocatalytic capability towards the oxygen evolution and hydrogen evolution reactions (OER and HER). Moreover, the phosphorous dopant is introduced to boost the catalytic activity, especially in the HER. Density functional theory calculations reveal that the phosphorous dopant can dramatically push the binding energy to the ideal value, thus improving the HER performance. Computed results indicate that partial orbitals of the P atom are above the Fermi level and the P atom enhances the charge density of the neighboring Co atom, which optimizes the H* binding. In addition, an efficient overall water splitting configuration is performed with the integration of the P‐doped Co compound catalysts. The acid‐etching methodology inspires more novel nanostructured and multicomponent metal compounds for prominent electrocatalysis.
A morphology‐ and component‐tunable synthesis is applied to the acid‐etching of Co. The resultant hierarchical multicomponent nanocomposite exhibits bifunctional electrocatalytic activity for water electrolysis, which can be further improved by the implementation of phosphorous doping. An efficient full water splitting configuration is performed with the P‐doped Co species as the bifunctional electrocatalyst.
This paper proposes a least-square (LS) support vector machine (SVM)-based model for short-term solar power prediction (SPP). The input of the model includes historical data of atmospheric ...transmissivity in a novel two-dimensional (2D) form and other meteorological variables, including sky cover, relative humidity, and wind speed. The output of the model is the predicted atmospheric transmissivity, which then is converted to solar power according to the latitude of the site and the time of the day. Computer simulations are carried out to validate the proposed model by using the data obtained from the National Solar Radiation Database (NSRDB). Results show that the proposed model not only significantly outperforms a reference autoregressive (AR) model but also achieves better results than a radial basis function neural network (RBFNN)-based model in terms of prediction accuracy. The superiority of using transmissivity over sigmoid functions for data normalization is testified. Simulation studies also show that the use of additional meteorological variables, especially sky cover, improves the accuracy of SPP.
► A support vector machine model is proposed for short-term solar power prediction. ► The model input includes historical data of multiple meteorological variables. ► The proposed model outperforms autoregressive model and RBFNN model. ► The model has been validated by computer simulations using real-world data.
Adsorption and dissociation processes of gas molecules on bulk materials and nanomaterials are essential for catalytic conversion of carbon dioxide (CO2). In this work, we systematically investigated ...the CO2 adsorption and dissociation on low index surfaces of different transition metals by Density Functional Theory (DFT) calculations. A comparison study demonstrates that the open surfaces (Fe(100), Ni(100), Ni(110), Rh(100), and Ir(100)) have stronger interactions with CO2 molecules than the close-packed surfaces. The order of energy barriers for CO2 dissociation is Fe(110), Ir(100) < Ru(0001), Rh(100), Co(0001), Ni(100) < Os(0001), Ni(111) < Ir(111), Rh(111), Ni(110) < Fe(100), Pt(111) < Cu(100), Pd(111) < Cu(111). The interaction order between the dissociative CO*, O* species and the surfaces is Fe(100) > Fe(110) > Ru(0001) > Os(0001) > Ir(100), Rh(100) > Ni(110) > Co(0001) > Rh(111), Ir(111) > Ni(100), Ni(111) > Cu(100) > Pt(111) > Cu(111), Pd(111). In addition, we found that the change trend of adsorption energy is consistent with that of charge transfer amounts from the low index surfaces to CO2. The Brønsted–Evans–Polanyi relation showed that the electronic effects of Ni(111) and Ni(110), Cu(111) and Cu(100) and the geometric effects of Fe(110) and Fe(100), Ir(111) and Ir(100) have great influence on the CO2 dissociation, which is closely related to cleavage of C–O in transition states. Our results may provide an insight into the design of highly efficient nanocatalysts for CO2-involved reactions.
Multiple sclerosis is characterized by inflammatory activity that results in destruction of the myelin sheaths that enwrap axons. The currently available medications for multiple sclerosis are ...predominantly immune-modulating and do not directly promote repair. White matter regeneration, or remyelination, is a new and exciting potential approach to treating multiple sclerosis, as remyelination repairs the damaged regions of the central nervous system. A wealth of new strategies in animal models that promote remyelination, including the repopulation of oligodendrocytes that produce myelin, has led to several clinical trials to test new reparative therapies. In this Review, we highlight the biology of, and obstacles to, remyelination. We address new strategies to improve remyelination in preclinical models, highlight the therapies that are currently undergoing clinical trials and discuss the challenges of objectively measuring remyelination in trials of repair in multiple sclerosis.
A novel interface neurocontroller (INC) is proposed for the coordinated reactive power control between a large wind farm equipped with doubly fed induction generators (DFIGs) and a static synchronous ...compensator (STATCOM). The heuristic dynamic programming (HDP) technique and radial basis function neural networks (RBFNNs) are used to design this INC. It effectively reduces the level of voltage sags as well as the over-currents in the DFIG rotor circuit during grid faults, and therefore, significantly enhances the fault ride-through capability of the wind farm. The INC also acts as a coordinated external damping controller for the wind farm and the STATCOM, and therefore, improves power oscillation damping of the system after grid faults. Simulation studies are carried out in PSCAD/EMTDC and the results are presented to verify the proposed INC.
This paper proposes a model to find the equilibria in the short-term electricity market with large-scale wind power penetration. The behavior of each strategic player is modeled through a two-stage ...mathematical problem with equilibrium constraints (MPEC), where the upper-level problem maximizes the profit of the strategic player and the lower-level problem describes the clearing processes of the day-ahead and real-time markets while considering the network constraints. The joint solution of all the MPECs constitutes an equilibrium problem with equilibrium constraints (EPEC). The uncertain wind power production and demand are represented by a set of plausible scenarios. By using the duality theory and Karush-Kuhn-Tucker condition, each MPEC is transferred into a mixed-integer linear programing problem. The Nash equilibria of the electricity market are obtained by solving the EPEC using Game theory and the diagonalization algorithm. Case studies are performed to show the effectiveness of the proposed model.
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