Design and synthesis of NiCo2O4–reduced graphene oxide composites for high performance supercapacitors

Abstract

In the present work, we used charge-bearing nanosheets as building blocks to construct a binary composite composed of NiCo 2 O 4 and reduced graphene oxide (RGO). Co-Ni hydroxides intercalated by p-aminobenzoate (PABA) ion and graphite oxide (GO) were exfoliated into positively charged hydroxide nanosheets and negatively charged graphene oxide nanosheets in water, respectively, and then these oppositely charged nanosheets were assembled to form heterostructured nanohybrids through electrostatic interactions. The subsequent thermal treatment led to the transformation of the hydroxide nanosheets into spinel NiCo 2 O 4 and also to the reduction of graphene oxide. The asobtained NiCo 2 O 4 -RGO composite exhibits an initial specific capacitance of 835 F g À1 at a specific current of 1 A g À1 and 615 F g À1 at 20 A g À1 . More interestingly, the specific capacitance of the composite increases with cycling numbers, reaches 1050 F g À1 at 450 cycles and remains at 908 F g À1 (higher than the initial value) after 4000 cycles. The high specific capacitance, remarkable rate capability and excellent cycling ability of the composites mean that they show promise for application in supercapacitors. Comparison with the capacitive behavior of pure NiCo 2 O 4 and NiCo 2 O 4 mechanically mixed with RGO displays the importance of the self-assembly of the nanosheets in making a wide range of graphene-based composite materials for applications in electrochemical energy storage.

Effect of surfactant on the morphology and capacitive performance of porous NiCo2O4

“…It displayed a specific capacitance of 580 Fg −1 at a current density of 500 mAg −1 . Besides, in the literature [20][21][22], the reported NiCo 2 O 4 -RGO composite, porous NiCo 2 O 4 , and hierarchical porous NiCo 2 O 4 nanowires exhibited a specific capacitance of 835, 658, and 743 Fg −1 at 1 A g −1 , respectively. It should be pointed out that the reported specific capacitance is still discontented.…”

The specific capacitance of sol–gel synthesised spinel MnCo2O4 in an alkaline electrolyte

“…Among metal oxides, Co oxides are normally reported to 30 have high redox activity and good reversibility, but specific capaci-31 tance is relatively low [4]. Some Co-based oxides or Co hydroxides 32 have been reported to exhibit high specific capacitance [5][6][7]. How-33 ever, carbon nanotube or nanofiber seems to be one important 34 reason in improving their specific capacitance.…”

Bio-inspired synthesis of NaCl-type CoxNi1−xO (0 ≤ x < 1) nanorods on reduced graphene oxide sheets and screening for asymmetric electrochemical capacitors

“…[21][22][23] Recently, Wang et al 24 used positively charged Co-Ni layered double hydroxide nanosheets intercalated by p-aminobenzoate ions and negatively charged graphene oxide (GO) sheets as building blocks to construct their composite via electrostatic interactions. The subsequent thermal treatment led to the transformation of the layered double hydroxide nanosheets into spinel NiCo 2 O 4 nanosheets followed by the reduction of graphene oxide to finally form the NiCo 2 O 4 /RGO composite.…”