Three-dimensional activated reduced graphene oxide nanocup/nickel aluminum layered double hydroxides composite with super high electrochemical and capacitance performances

Abstract

The paper reported a three-dimensional activated reduced graphene oxide nanocup/nickel aluminum layered double hydroxides composite (3D-ARGON/NiAl-LDH) with super high electrochemical and capacitance performances. Graphene oxide was reduced by hydrazine in ammonia medium to form three-dimensional reduced graphene oxide nanocup using polystyrene colloidal particle as sacrificial template. The nanocup was then activated by the alkali corrosion and thermal annealing. The 3D-ARGON/NiAl-LDH was finally fabricated by the hydrothermal synthesis via in situ growth of ultrathin NiAl-LDH nanoflakes on the 3D-ARGON in an ethanol medium. The study demonstrated that the composite offers special 3D architecture with a macropore on the rim of a cup and large mesoporous structure on the wall of a cup, which will greatly boost the electron transfer and mass transport during the faradaic redox reaction, and displays excellent electrochemical and capactance performances, including high specific capacitance and rate capability, good charge/discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2712.7Fg−1 at the current density of 1Ag−1, which is more than 7-fold that of pure NiAl-LDH, 3-fold that of common reduced graphene oxide/NiAl-LDH and 1.8-fold that of two-dimensional activated reduced graphene oxide/NiAl-LDH. The specific capacitance can remain 1174Fg−1 when the current density increases up to 50Ag−1. After 5000 cycles at the current density of 30Ag−1, the capacitance can keep at least 98.9%. This study provides a promising approach for the design and synthesis of graphene-based materials with largely enhanced supercapacitor behaviors, which can be potentially applied in energy storage/conversion devices.