context: Electrospun NiO with different nanostructures has also been widely studied in SCs. For instance, by electrospinning a PVP/nickel nitrate/citric acid polymer solution followed by a subsequent annealing process to remove PVP, NiO hollow nanofibers comprised of NiO sheets with a diameter of 17 nm were prepared. The resultant NiO nanofibers exhibited a higher pseudocapacitance (336 F g−1 at 5 mA cm−2) than the solid NiO nanofibers fabricated without citric acid (136 F g−1). In another reference, by using electrospun PAA as a sacrificial template, NiO hollow nanofibers consisting of NiO nanoparticles with diameters varying from 10 to 30 nm were synthesized through a direct ion-exchange process in oversaturated Ni(NO3)2 solution, followed by air annealing. The NiO nanofibers with a porous structure and empty space can accommodate large volume changes and exhibited a high specific capacitance of 700 F g−1 at 2 A g−1, as well as a remarkable rate capability (80% capacitance retention with the current density increasing from 1 to 5 A g−1). In addition, electrospun nickel acetate/PVP-derived NiO nanofibers were applied as cathode materials for ASCs (AC as the anode). The device delivered a specific capacitance of 141 F g−1 with an energy density of 43.75 W h kg−1 and power density of 7.5 kW kg−1.
answer: nickel acetate/PVP-derived NiO nanofibers