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Hydrothermal Growth of Hierarchical Ni3S2 and Co3S4 on a Reduced Graphene Oxide Hydrogel@Ni Foam: A High-Energy-Density Aqueous Asymmetric Supercapacitor
journal contribution
posted on 2015-01-21, 00:00 authored by Debasis Ghosh, Chapal Kumar DasNi
foam@reduced graphene oxide (rGO) hydrogel–Ni3S2 and Ni foam@rGO hydrogel–Co3S4 composites have been successfully synthesized with the aid of a
two-step hydrothermal protocol, where the rGO hydrogel is sandwiched
between the metal sulfide and Ni foam substrate. Sonochemical deposition
of exfoliated rGO on Ni foam with subsequent hydrothermal treatment
results in the formation of a rGO-hydrogel-coated Ni foam. Then second-time
hydrothermal treatment of the dried Ni@rGO substrate with corresponding
metal nitrate and sodium sulfide results in individual uniform growth
of porous Ni3S2 nanorods and a Co3S4 self-assembled nanosheet on a Ni@rGO substrate. Both
Ni@rGO–Ni3S2 and Ni@rGO–Co3S4 have been electrochemically characterized in
a 6 M KOH electrolyte, exhibiting high specific capacitance values
of 987.8 and 1369 F/g, respectively, at 1.5 A/g accompanied by the
respective outstanding cycle stability of 97.9% and 96.6% at 12 A/g
over 3000 charge–discharge cycles. An advanced aqueous asymmetric
(AAS) supercapacitor has been fabricated by exploiting the as-prepared
Ni@rGO–Co3S4 as a positive electrode
and Ni@rGO–Ni3S2 as a negative electrode.
The as-fabricated AAS has shown promising energy densities of 55.16
and 24.84 Wh/kg at high power densities of 975 and 13000 W/kg, respectively,
along with an excellent cycle stability of 96.2% specific capacitance
retention over 3000 charge–discharge cycles at 12 A/g. The
enhanced specific capacitance, stupendous cycle stability, elevated
energy density, and a power density as an AAS of these electrode materials
indicate that it could be a potential candidate in the field of supercapacitors.