The facile synthesis of hierarchical NiCoO₂ nanotubes comprised ultrathin nanosheets for supercapacitors

Hierarchical NiCoO₂ nanosheets nanotubes are successfully prepared by a mild solution method based on the template of polymeric nanotubes (PNT) followed by a thermal annealing treatment. The microstructure and chemical composition of NiCoO₂ nanosheets nanotubes are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analyzer, X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). When evaluated as an electrode material for supercapacitors, the results of electrochemical test show that the unique NiCoO₂ nanosheets nanotubes exhibit relatively high specific capacitance of 1468, 1352, 1233, 1178, 1020 and 672 F g^-1 at the discharge current densities of 2, 4, 8, 10, 20 and 40 A g^-1, respectively. They also reveal an excellent cycling stability of 99.2% retention after 3000 cycles at 10 A g^-1. The smart nanostructures of the NiCoO₂ nanosheets nanotubes make a prominent contribution to the excellent electrochemical performance.