Hierarchical Ni–Co double hydroxide nanosheets on reduced graphene oxide self-assembled on Ni foam for high-energy hybrid supercapacitors

Abstract

This work presents a novel method for the self-assembly of reduced graphene oxide (rGO) on nickel foam (NF) and the subsequent electrodeposition of hierarchical Ni-Co double hydroxide (NiCo-DH) nanosheets (NS) on rGO as a supercapacitor electrode. The self-assembly of rGO on NF is achieved by the direct reduction of graphene oxide at 50 °C. NF is not only used as the support of rGO but also the reducing agent for the reduction of GO. As the battery-type electrode material for supercapacitor, NiCo-DH supported on rGO modified NF (Ni-Co DHNS@rGO-NF) displays an ultrahigh areal capacity of 5.820 C cm−2 at 20 mA cm−2, a 100% coulombic efficiency and a 78% capacity retention after 2000 cycles at 100 mA cm−2. An hybrid supercapacitor (HSC) is also assembled based on Ni-Co DHNS@rGO-NF as the positive electrode and active carbon (AC) as the negative electrode. The ASC exhibits a prominent energy density of 45.83 Wh kg−1 at a high power density of 396.15 W kg−1. The excellent electrochemical performance is attributed to the large surface area of the hierarchical NiCo-DH nanosheets array and the synergistic effect between Ni-Co DHNS and rGO.