Preparation and performance of rose stalk-like niobium nitride nanofibers for supercapacitor

Rose stalk-like Nb4N5 fibers were prepared by electrospinning, solvothermal method and ammonia reduction technology. The composition and morphology were characterized. The results showed that the corresponding XRD (X-ray diffractometer) pattern of the sample was indexed to tetragonal Nb4N5, and it existed as NbNxO1−x solid solution, in which Nb ions exist in the form of + 3 and + 5. The abundant valence states made Nb ions undergo reversible proton insertion/chemical adsorption in the conductive channels of the Nb4N5 nanofibers. The Nb4N5 nanofibers presented a rose stalk-like structure, and thus its specific surface area was high to 76.42 m2 g−1 with pore diameter of 13.2 nm. The specific capacitance of the Nb4N5||Nb4N5 symmetric supercapacitor device reached to 139.03 F g−1 at the current density of 10 mA g−1. When the energy density was 12.60 Wh kg−1, the power density of the supercapacitors was 2.16 kW kg−1. It was indicated that the rose stalk-like structure gave the Nb4N5 nanofibers a larger contact area which was conducive to the construction of a conductive network, and thus the electron transmission rate was improved, thereby improving the electrochemical performance of the Nb4N5 fibers electrode materials for supercapacitors.