We
report a greener, effortless, and scalable approach involving
the synthesis of a self-grown nanomaterial on a flexible conductive
substrate along with the synthesis of activated carbon derived from
biomass waste. Contrary to the popular idea of using a variety of
additives for the synthesis of nanomaterials, such as surface-activating
agents, 3d metal-oxide nanoplates were synthesized on a highly hydrophobic
carbon cloth substrate using no foreign elements except the metal
precursors. The activated carbon was derived from biomass waste in
that it was synthesized using withered cherry flower petals. The two
as-synthesized materials were combined to fabricate an asymmetric
supercapacitor, the design of which is presented as a greener and
sustainable way to obtain an alternative energy storage unit. The
three-dimensional nanoplate architecture from the positive electrode
combined with the densely populated meso-/microporous structures of
the negative electrode delivered an energy density of 106.3 μWh
cm–2 for a power density of 657 μW cm–2, which is maintained at 57.5 μWh cm–2 even at a high power density of 5283.4 μW cm–2. Furthermore, a highly stable rate performance was achieved with
high capacity retention even after charging–discharging for
over 6000 cycles. The fabricated device exhibits highly satisfactory
results in practice and hence presents itself as a highly capable
candidate for a green energy solution.
Herein,
we present a hierarchical structure consisting of an expanded
interlayer, which comprises MoS2 dispersed onto and diffused
into nitrogen-doped carbon nanotubes (MoS2-CNTPPys), as an electrode material for a symmetric supercapacitor device.
Structural characterizations revealed the presence of expanded interlayer
spacing as evidenced by the downshifting of the X-ray diffraction
(XRD) peaks representing the (002) plane and an increased interlayer
distance of ∼0.82 nm. Further transmission electron microscopy
(TEM) measurements showed that the MoS2 nanosheets not
only covered the surface of the CNTPPy but also penetrated
the CNTPPy to form a core–shell structure. The MoS2-CNTPPy electrode delivers a high specific capacitance
of 275 F g–1 at 1 A g–1 in aqueous
1 M H2SO4, which is 2.5 times higher than pristine
CNTPPy. The MoS2-CNTPPy symmetrical
supercapacitor (SSC) devices yield a high specific capacitance of
37.4 F g–1 with a pristine poly(vinyl alcohol) (PVA)/H2SO4 electrolyte. Surprisingly, the addition of
Na2MoO4 to PVA/H2SO4 as
a redox electrolyte further increases the specific capacitance of
MoS2-CNTPPy SSC to three times (95.14 F g–1) that of the PVA/H2SO4 electrolyte,
with outstanding capacity retention (95.6% over 5000 cycles). Overall,
the excellent performance of the hierarchical MoS2-CNTPPy electrode, coupled with the PVA/H2SO4/Na2MoO4 redox polymer gel electrolyte, is
expected to be a potent combination for energy storage device applications.
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