Sulfur-vacancies promoted performance of hierarchical NiCo2S4 nanotubes through electrospinning for supercapacitors

In this work, one-dimensional (1D) NiCo 2 S 4 nanotubes with sulfur vacancies (Vc-NiCo 2 S 4 ) were designed effectively via the electrostatic spinning and chemical bath deposition (CBD) process. As-spun polyacrylonitrile (PAN) nanofibers containing surfactant were taken as hard templates. Through the in-situ growth and etching process, NiCo 2 S 4 nanotubes covered with a large number of nanosheets were generated. Sulfur vacancies were introduced by the following chemical reduction. The influence of defects was systematically discussed through structure analyses and electrochemical properties. As-obtained Vc-NiCo 2 S 4 not only maintains the original hierarchical nanotube characteristic, but also boost the electrochemical behaviors. Due to the defect treatment, Vc-NiCo 2 S 4 nanotubes have a higher specific capacity (1046 F g −1 at a current density of 1 A g −1 ) and enhanced rate capability. A symmetrical supercapacitor (SSCs) device assembled by Vc-NiCo 2 S 4 nanotubes displays a high energy density of 31.8 Wh kg −1 at the power density of 260 W kg −1 . These results indicate that the construction of 1D hierarchical nanotubes and sulfur vacancies could provide effective strategy to promote the performance of supercapacitors. Graphical abstract 1D NiCo 2 S 4 hierarchical nanotubes were prepared by employing PAN nanofibers as sacrificial templates. The Vc-NiCo 2 S 4 nanotubes after NaBH 4 reduction maintain the original morphology and optimize the electrochemical activities. Vc-NiCo 2 S 4 with sulfur vacancies exhibits enhanced electrochemical performance.