Confined growth of NiCo2S4 on 2D/2D porous carbon self-repairing g-C3N4/rGO heterostructure for enhanced performance of asymmetric supercapacitors

Abstract

In this work, porous carbon self-repairing g-C3N4 (pCCN) nanosheets were synthesised using a solvothermal technique followed by calcination and acid treatment. A facile hydrothermal process is employed for the confined growth of NiCo2S4 on porous carbon self-repairing g-C3N4/rGO heterostructure (pCRNCS) as hybrid material for supercapacitor electrodes. The improved electronic conductivity and activity of carbon self-repairing g-C3N4 (CCN) than g-C3N4 owing to the creation of extended delocalized π-electrons by the substitutional or interstitial C atoms in the structure and because of acid treatment, the larger planes of CCN are broken down into smaller segments, increasing the edge nitrogen and oxygen functional groups. The introduction of porous CCN led to the strong electrostatic interaction with GO and CCN which aided in the suppression of agglomeration of graphene sheets. The as-synthesised pCRNCS electrode showed remarkably high specific capacitance (1938 F/g at current density of 2 A/g). The excellent electrochemical activity is due to the 2D/2D heterostructure assembly of high surface area rGO and extended highly reactive region and defects in pCCN which facilitated the nucleation and confined growth of NiCo2S4 in the framework. The constructed pCRNCS//AC ASC exhibited remarkable electrochemical properties, including a specific capacitance of 211 F/g at 1 A/g, an exceptional capacitance retention of 93.6% after 6000 cycles, and the maximum energy density of 66 Wh/kg at a power density of 751 W/kg. The excellent capacitive behaviour of porous carbon self-repairing g-C3N4/rGO@NiCo2S4 assure the development of high-performance energy storage device.