Preparation and electrochemical properties of carboxylated graphene-supported NiO nanosheets for supercapacitors

Nickel oxide (NiO) with the advantages of inexpensive, non-toxic, environmentally friendly and high theoretical specific capacitance, is a potential electrode material for supercapacitors. In this work, the synthesized NiO exhibited a stacked state of nanosheets with wavy patterns and a high specific surface area. Additionally, the carboxylated graphene/nickel oxide (CG/NiO) composite electrodes were prepared through the electrostatic self-assembly technique. The CG/NiO composite electrode was systematically characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller measurements. More excitingly, the BET surface area of the CG/NiO composite electrode is 138.14 m2/g, which is three times higher than that of the pure NiO. The high surface area and unique mesoporous structure of composite electrodes facilitated rapid ion transport and sufficient redox reactions. As a result, the CG/NiO composite electrode displayed a high specific capacity of 175.5 C g−1 at 1 A/g and satisfying cycling stability (55.4 % retention after 5000 cycles at 5 A/g).