NiCo2S4 nanosphere anchored on N, S co-doped activated carbon for high-performance asymmetric supercapacitors

Throughout the evolution of supercapacitors, binary transition metal sulfides have been extensively researched for their potential as electrode materials. Here, NSAC-NiCo2S4 composites are prepared by in-situ growing NiCo2S4 nanosphere on N, S co-doped activated carbon (NSAC) using a simple solvothermal way. The optimized NSAC-NiCo2S4 composite inherits the NSAC's huge specific surface area, hierarchical porous structure, and high electronic conductivity, along with the excellent capacitive performance of NiCo2S4. This combination effectively reduces contact resistance and enhances the transfer rate. Calculations based on the density functional theory further indicate that synergistic interactions between NiCo2S4 and NSAC in the composite lower the OH- adsorption energy and release more active electrons. This enhancement facilitates the electrochemical reaction kinetics in supercapacitors. The as-fabricated NSAC-NiCo2S4-2 electrode possesses a remarkable specific capacitance (762 F g- 1 ) at 1 A g- 1 and exhibits a minimal charge transfer resistance (0.28 Omega). Furthermore, an asymmetric supercapacitor (positive electrode: NSAC-NiCo2S4-2; negative electrode: NSAC), achieves an impressive energy density of 36.6 Wh kg- 1 at a power density of 400.0 W kg- 1 . It also exhibits exceptional cycling stability, maintaining 86.2 % of its capacity after 10,000 cycles. These excellent results further highlight the great potential of the obtained NSAC-NiCo2S4 composites for use in energy reserve systems.