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

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 degrees 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. (C) 2018 Elsevier B.V. All rights reserved.