Self-supporting hierarchical porous NiCo2S4/RGO/CNTs nanohybrids with abundant exposed electroactive redox sites for excellent hybrid supercapacitor

Bimetallic sulfide NiCo2S4 is a highly promising electrode material for applications in novel sustainable high-performance energy storage devices, but its poor rate capability and cycling life need to be enhanced. Herein, we report a novel self-supporting hierarchical porous NiCo2S4/RGO/CNTs nanohybrids (NCSRCs) by co-modification of NiCo2S4 nanoparticles with RGO and CNTs. The synergistic effect of RGO and CNTs not only constructs a hierarchical porous conductive network that facilitates charge transport kinetic and ion diffusion kinetic, but also provides abundant induced sites for the dispersion anchoring of NiCo2S4 nanoparticles due to their high specific surface area with rich functional groups, which reduces the stacking of NiCo2S4 nanoparticles and provides abundant exposed electroactive redox sites. Therefore, the electrochemical performance test results demonstrate that the NCSRCs electrodes exhibit significantly enhanced charge storage performance, showing a high specific capacity of 257.1 mAh g−1 at 0.3 A g−1 and good rate capability. In addition, the optimal NCSRC-24//N-RGO aqueous hybrid supercapacitor delivered a high specific energy of 33.67 Wh kg−1 and ultra-long durability with 82.44% capacity retention after 22,000 cycles. These results provide a facile approach to design and synthesize novel NCSRCs nanohybrids with superior properties for high-safety, sustainable and efficient aqueous energy storage devices.