Enhanced proton conduction of imidazole localized in one-dimensional Ni-metal-organic framework nanofibers.

Metal-organic frameworks (MOFs) show possibilities to be potential candidates for proton exchange membranes (PEMs). However, the poor flexibility and processability of MOFs due to their crystalline nature limit their applications significantly. An efficient approach to overcome this limitation is to combine MOFs with polymers. In this work, novel lightweight and flexible Ni-MOFs/polyacrylonitrile nanofibers were fabricated by electrospinning. The nanofibers consisted of one-dimensional proton conduction channels for imidazole and show enhanced proton conductivity. A proton conductivity of 6.04 × 10-5 Scm-1 was achieved at 363 K and 90% RH. Furthermore, the proton transport dynamics of the fibers were investigated using the AC impedance technique.

Nickel nanoparticles embedded in porous carbon nanofibers and its electrochemical properties.

Flexible porous carbon nanofibers containing nickel nanoparticles were synthesized by direct carbonization of electrospun Ni-MOFs/polyacrylonitrile fibers. The as-synthesized composite nanofibers were employed as binder-free electrodes, and exhibit high specific capacitance (up 672 F g-1 at current density of 2 A g-1) and superior rate capability (57% capacitance retention from current density of 2-10 A g-1), which may be attributed to their binder-free nature, unique one-dimensional (1D) structure and highly dispersed electrochemically active nickel nanoparticles. Furthermore, a symmetric supercapacitor was assembled using the fiber electrodes in 6 M KOH, and the energy density of 17.8 Wh kg-1 was achieved in a potential window of 1.5 V. This self-standing fiber with abundant mesopores and macropores is expected to become a promising electrode material for high-performance supercapacitors.

Formation of nickel-cobalt sulphide@graphene composites with enhanced electrochemical capacitive properties.

Here, nickel-cobalt sulphide particles embedded in graphene layers (porous Ni-Co-S@G), were successfully prepared by one-step annealing of metallocene/metal-organic framework (MOF) hybrids involving simultaneous carbonization and sulfidation. Benefiting from the porous structure, highly conductive graphene layers and large loading of super-capacitive Ni-Co-S, the obtained Ni-Co-S@G composites exhibited excellent electrochemical performance with a specific capacitance of 1463 F g-1 at a current density of 1 A g-1. A flexible solid-state asymmetric supercapacitor (ASC), assembled with Ni-Co-S@G and active carbon, demonstrated a high energy density of 51.0 W h kg-1 at a power density of 650.3 W kg-1. It is noteworthy that the ASC offered robust flexibility and excellent performance that was maintained when the devices were bent at various angles. The results indicate that the as-prepared materials could potentially be applied in high-performance electrochemical capacitors.

Development of high sensitivity 4H-SiC detectors for fission neutron pulse shape measurements.

4H-silicon carbide (4H-SiC) detectors are well suited for measurements of fission neutron pulse shape for their compact size, excellent radiation resistance, and hydrogen free composition. The aim of this study is to improve the 4H-SiC detector's sensitivity to fission neutron pulses. 4H-SiC detectors with varied epilayer thicknesses are fabricated and then tested in the pulsed neutron field of the Chinese Fast Burst Reactor II (CFBR II). The sensitivity of the 4H-SiC detector to the CFBR II neutron pulse is increased by 139.8%, with the enlargement of epilayer thickness from 20 µm to 120 µm. By employing the proton-recoil method, the sensitivity of the 4H-SiC detector to the CFBR II neutron pulse is further increased by 11.6%. With enhanced sensitivity to fission neutron pulses, 4H-SiC detectors are promising devices for high intensity neutron pulse measurements.