Needle-like Co<sub>3</sub>O<sub>4</sub> Anchored on
the Graphene with Enhanced Electrochemical Performance for Aqueous
Supercapacitors
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Abstract
We
synthesized the needle-like cobalt oxide/graphene composites with
different mass ratios, which are composed of cobalt oxide (Co<sub>3</sub>O<sub>4</sub> or CoO) needle homogeneously anchored on graphene
nanosheets as the template, by a facile hydrothermal method. Without
the graphene as the template, the cobalt precursor tends to group
into urchin-like spheres formed by many fine needles. When used as
electrode materials of aqueous supercapacitor, the composites of the
needle-like Co<sub>3</sub>O<sub>4</sub>/graphene (the mass ratio of
graphene oxide(GO) and Co(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O is 1:5) exhibit a high specific capacitance of 157.7 F g<sup>–1</sup> at a current density of 0.1 A g<sup>–1</sup> in 2 mol L<sup>–1</sup> KOH aqueous solution as well as good
rate capability. Meanwhile, the capacitance retention keeps about
70% of the initial value after 4000 cycles at a current density of
0.2 A g<sup>–1</sup>. The enhancement of excellent electrochemical
performances may be attributed to the synergistic effect of graphene
and cobalt oxide components in the unique multiscale structure of
the composites
