Hierarchically-formed nickel sulfide heterostructure via SILAR on hydrothermally grown cobalt oxide scaffolds: Role of number of over-coating and evolution of electrochemical performance in supercapacitor electrodes

Abstract The heterostructure of nickel sulfides on cobalt oxide (h-NS@CO) is realized via one-pot hydrothermal growth of Co3O4 (CO) on Ni foam (NF), followed by NS overcoating through successive ionic layer adsorption and reaction (SILAR) process. According to the number of SILAR-overcoating from 10 to 30 cycles, electrochemical performance on super-capacitors is systematically studied and moreover, a fivefold increment in the specific capacitance is achieved at the condition of 20 overcoating cycles of Ni3S2 (h-NS20) on Co3O4 (1901 F.g−1), as compared to pristine Co3O4 (375 F.g−1) at a current density of 1 A.g−1. The GCD cyclic stability study reveals that h-NS20@CO retains 91.8% capacitance even after 10,000 cycles, surpassing pristine CO based SSCs. Furthermore, h-NS20@CO-based SSCs exhibit specific capacitance of 344 F.g−1 at 1 A.g−1, along with 97% of capacitance retention after 4000 cycles. In parallel, the remarkable improvement in electrochemical performance is attributed to synergetic effects associated with heterostructure of NS20 on cobalt oxide scaffold and their mechanisms are experimentally assessed via number of layer dependency. More impressively, a wirelessly controllable LED assembly, powered by h-NS20@CO-based SSCs, is successfully implemented and its demonstration of LED operation self-manifests a potential capability for the portably accessible energy storage device.