The preparation of hierarchical tubular structures comprised of NiO nanosheets with enhanced supercapacitive performance

Hierarchically tubular structures comprised NiO nanosheets were successfully prepared through a mild solution route based on the template of polymeric nanotubes (PNT) followed by a thermal annealing treatment. The microstructure and chemical composition of NiO nanosheets nanotubes are investigated by SEM, TEM, HRTEM, SAED and XRD. The Brunauer-Emmett-Teller (BET) specific surface area of this sample is calculated to be 98 m² g ^-1 and the majority of pores have a size in the range of 2-10 nm. The thermal behavior of Ni-precursor@PNT was studied by TGA and the weight fraction of NiO nanosheets nanotubes obtained by calcination is measured to be 57.0%. The specific capacitance of the unique NiO nanosheets nanotubes is 588 F g ^-1 at the end of 1000 cycles when the charge-discharge current density is 3 A g^-1, leading to only 5.2% capacity loss. In addition, the NiO nanotubes coating by relatively sparse and thin nanosheets possess better electrochemical properties. The specific capacitance is 960 F g ^-1 at the end of 1000 cycles when the charge-discharge current density is 10 A g^-1, leading to only 1.2% capacity loss. Broadly, the as-obtained NiO nanosheets nanotubes reveal relatively high capacitance and remarkable cycling stability in virtue of the hollow, porous, flaky and tubular nanostructures.