Enhanced rate capability of nanostructured three-dimensional graphene/Ni 3 S 2 composite for supercapacitor electrode

Abstract Three-dimensional graphene/Ni 3 S 2 (3DG/Ni 3 S 2 ) composite electrodes were produced by a facile two-step synthesis route involving chemical vapor deposition (CVD) growth of graphene foam and in situ hydrothermal synthesis of Ni 3 S 2 . The porous structure of the prepared 3DG is ideal for use as a scaffold for fabricating monolithic composite electrodes. The relative content of Ni 3 S 2 initially increased and then decreased with increasing hydrothermal reaction time. The basal surface of the electrode was completely covered after 6 h of hydrothermal reaction. The size of the Ni 3 S 2 microspheres also increased with increasing hydrothermal reaction time. The composite electrodes exhibited good specific capacitance (11.529 F cm −2 at 2 mA cm −2 , i.e., 2611.9 F g −1 at 5 mV s −1 ) and cyclability (retention of 88.97% capacitance after 1000 charge/discharge cycles at 20 mA cm −2 ). These results are attributed to the fact that the uniform distribution of the Ni 3 S 2 microspheres increased the specific surface area of the electrode and facilitated electron transfer and ion diffusion. The 3D multiplexed and highly conductive pathways provided by the defect-free graphene foam also ensured rapid charge transfer and conduction to improve the rate capability of the supercapacitors.