Ultrathin Dielectric Triggered Charge Injection Dynamics for High-Performance Metal Organic Framework/MXene Supercapacitors.

A MOF-MXene-BN three-component heterostructure exhibits impressive pseudocapacitive behavior with fast charge injection facilitated by an ultrathin dielectric h-BN. To address the MOF's low electronic conductivity, a 2D NiCo-MOF is grown on MXene nanosheets, enhancing conductivity and providing abundant redox-active sites. BN (boron nitride) serves a dual purpose, preventing restacking and facilitating charge injection toward NiCo-MOF. Synergistic contributions of 2D materials and a heterostructure with favorable charge injection dynamics among MOF, MXene, and BN contribute to enhanced electrochemical performance. Charge transfer mechanisms are elucidated using distribution of relaxation time technique to analyze complex EIS data and to differentiate electrode kinetics based on their respective relaxation time constants. An asymmetric supercapacitor, MOF-MXene-BN//activated carbon, achieves a specific capacity of 798 C/g, an energy density of 81 Wh/kg at 365 W/kg, and 81% capacitance retention over 5,000 cycles.

The rapid construction and biological evaluation of densely substituted pyrrolo[1,2-a]indoles via a BF3·OEt2-assisted cascade approach.

Lewis-acid cascade reactions promoted by BF3·OEt2 are reported for the synthesis of highly substituted pyrrolo[1,2-a]indoles and congeners of benzofuro[2,3-b]indoles. These reactions are highly regio- and diastereoselective towards generating up to five contiguous stereogenic centers, including two vicinal quaternary centers. Furthermore, an established cascade approach and the mechanism proposed herein are well supported by quantum chemistry calculations. In addition, a self-dimerization intermediate was trapped and isolated to establish a strategy for potential access to both pyrrolo and benzo indole derivatives, leaving sufficient freedom for broadening. Furthermore, in-silico molecular docking and all atomistic molecular dynamic (MD) simulation analysis suggests that the synthesized pyrrolo[1,2-a]indole derivatives stably bind at the active site of the mycobacterial secreted tyrosine phosphatase B (MptpB) enzyme, an emerging anti-mycobacterial drug target. Deep learning-based affinity predictions and MMPBGBSA-based energy calculations of the docked poses are presented herein.

Magnetically Triggered Interplay of Capacitive and Diffusion Contributions for Boosted Supercapacitor Performance.

The chemistry involved in supercapacitors in terms of their mechanistic contributions leading to improved specific capacity will aid in easy commercialization. The main contributory factors in a supercapacitor are either capacitive (non-diffusion controlled) or ion-diffusion behavior, which results in enhanced charge-discharge characteristics of a supercapacitor reflected in its power density, whereas ion-diffusion behavior will lead to the enhanced energy density of a supercapacitor. In this context, the present article attempts to understand the use of external magnetic fields, leading to the interplay between capacitive and ion-diffusion behavior in a high-performance supercapacitor. The model system chosen in the present study, nickel cobalt copper carbonate hydroxide (NiCoCuCH), can effectively address the interplay between capacitive and ion diffusion contributions by varying total magnetic effects involving magnetic dilution. The magneto-enhancement of the electrodes nickel cobalt copper carbonate hydroxide (NiCoCuCH) and aluminum-doped nickel cobalt copper carbonate hydroxide (Al-NiCoCuCH) was demonstrated under the magnetic field from 0 to 250 mT. Both NiCoCuCH and Al-NiCoCuCH show dominant non-diffusion-controlled (capacitive) and diffusion-controlled behavior as a function of the applied external magnetic field. Under the influence of the external magnetic field, ferromagnetic coupling between metal-oxygen-metal centers via oxygen 2p orbitals enhances, leading to a facile redox pathway. To further control the charge-discharge behavior of the electrode via the interplay between diffusive and capacitive, a non-magnetic ion, Al3+, was doped into the bare metal carbonate hydroxide crystal lattice. The Al3+ ion not only alters the crystal symmetry but also restricts the alignment of the magnetic domains in the electrode, leading to a sluggish redox pathway, effectively increasing the capacitive contribution, and leading to improved charge-discharge characteristics at the expense of energy density. We have constructed an asymmetric device with the best-performing (110 mT) NiCoCuCH electrode as a positive electrode and activated carbon as a negative electrode. The NiCoCuCH/AC ASC device at 110 mT has the largest specific capacity (1100 C g-1 at 2 A g-1) at 110 mT, leading to a high energy density (250 W h kg-1) and a power density (1.7 kW kg-1) of the electrode.

Spectator-metal-ion-guided redox-dominant cobalt oxyhydroxide as a high-performance supercapacitor.

The ability of spectator metal ions such as vanadium to enhance the electrochemical performance of supercapacitors has been explained. Vanadium-incorporated CoO(OH) combined with NiMn-layered double hydroxide (LDH) yields a specific capacitance of 1700 F g-1 at 1 A g-1 with 96% retention after 5000 cycles. The assembled asymmetric supercapacitor exhibits an energy density of 45.93 W h Kg-1 and a power density of 752 W kg-1@1 A g-1.