2 research outputs found
Cost-Effective Asymmetric Supercapacitors Based on Nickel Cobalt Oxide Nanoarrays and Biowaste-Derived Porous Carbon Electrodes
Two nanostructured
electrode materials are fabricated and used
to construct cost-effective asymmetric supercapacitors (ASCs). Hierarchical
nickel cobalt oxide nanoarrays (NCO-NA) consisting of nanosheets (NCO-NS)
or nanowires (NCO-NW) are uniformly grown on Ni foam by a simple,
effective, and generally applicable method, while biowaste-derived
hierarchical porous carbon (Bio-HPC) with an interconnected microstructure
is fabricated by pretreatment with potassium hydroxide and followed
by direct pyrolysis. Considering the mass of NiCo<sub>2</sub>O<sub>4</sub>, the maximum specific capacitance of the hierarchical NCO-NS
and NCO-NW electrodes are 2300 and 2333 F g<sup>–1</sup>, respectively,
and the specific capacitance of the Bio-HPC electrode is 253.9 F g<sup>–1</sup> at a scan rate of 5 mV s<sup>–1</sup>. NCO-NA,
Bio-HPC, a piece of polypropylene membrane, and 30 wt % KOH solution
are assembled into a high-performance, low-cost ASC with the capability
of rapidly storing electrical energy. The NCO-NW//Bio-HPC ASC exhibits
a higher energy density compared with NCO-NS//Bio-HPC ASC, while the
latter shows better cycling performance (the capacitance still remains
91.12% after 2000 cycles)
Donor–Acceptor Covalent Organic Frameworks Films with Ultralow Band Gaps to Enhanced Third-Order Nonlinear Optical Properties
Covalent organic frameworks (COFs)
have attracted much attention
in porous materials because of their structural tunability and stability.
However, the problems of low transmittance and large light scattering
due to the difficulty of powder phase processing have severely limited
their practical applications in third-order nonlinear optics (NLO).
Herein, we report the first successful synthesis of a series of donor–acceptor
(D–A) COFs films (thickness of ∼100 nm) with uniform
transparency and narrow optical band gap by the solvothermal and solid–liquid
interface methods for third-order NLO applications. Most importantly,
the designed PT–PA film exhibits excellent NLO performance,
including a normalized transmission value of ∼2.55 at the beam
focus, a modulation depth (As) of 139%,
and a high nonlinear absorption coefficient (β) of 1.83 ×
106 cm GW–1 at the pulse energy of 1
μJ, which is superior to most recently reported third-order
NLO materials. The excellent third-order NLO properties are mainly
attributed to the homogeneous transparency of the COFs films and the
extended-ordered conjugated structure and narrow optical band gap
of the COFs films, which enhance the charge transfer in their structures
and thus yield excellent third-order NLO behavior. This work provides
an option for the development of high-performance NLO optical devices
and opens a new path for the future development of COFs films in the
optical fields