In situ growth of Ni-Co-S nanosheet arrays on rGO decorated Ni foam toward high-performance supercapacitors

Abstract

Ni–Co–S nanosheet arrays were successfully anchored on graphene covered Ni foam (Ni–Co–S–rGO/NF-1) by consecutive electrochemical methods and high-performance positive electrode material for supercapacitors was obtained. • Ni–Co–S nanosheet arrays were grown on reduced graphene oxide covered Ni foam (rGO/NF). • Synchronous electroreduction and electrodeposition of graphene oxide resulted in rGO/NF. • Combination of cyclic voltammetry and potentiostatic techniques was adopted for Ni–Co–S arrays. • The as-prepared electrode revealed excellent rate performance and higher specific capacity. Electrodes for supercapacitors (SCs) with excellent capacity and rate performance have always been in high demand. Herein, Ni–Co–S nanosheet arrays were successfully anchored on reduced graphene oxide (rGO) covered Ni foam (denoted as Ni–Co–S–rGO/NF–1) by consecutive electrochemical methods and high-performance positive electrode material for SCs was obtained. It was worth mentioning that there were two innovations in this preparation: the first one was that synchronous electroreduction and electrodeposition of graphene oxide (GO) resulted in rGO tightly wrapped Ni foam (denoted as rGO/NF), which enhanced the electroconductibility of the substrate and achieved outstanding rate performance; the second one was that a two-step combination approach composed of cyclic voltammetry (CV) technique and potentiostatic technique was adopted to deposit Ni–Co–S nanosheet arrays, which ensured both higher specific capacity and relatively robust growth of Ni–Co–S on rGO/NF. On account of a synergistic effect of the Ni–Co–S and rGO as well as the unique thin sheet-like nanostructure, the as-prepared electrode revealed excellent supercapacitor properties, including higher specific capacity of 976 C g −1 at current density of 1 A g −1 , impressive rate capability with 86.4 % retention at 60 A g −1 , and long-term stability of 82.2 % capacity retention after 10,000 cycles. An asymmetric supercapacitor fabricated by the Ni–Co–S–rGO/NF–1 and activated carbon exhibited a maximum energy density of 27 Wh kg −1 at the power density of 801 W kg −1 , and a power density of 8115 W kg −1 at the energy density of 11.0 Wh kg −1 . The excellent performance of the Ni–Co–S–rGO/NF–1 electrode suggests that it could be the hopeful electrode materials for energy storage devices.