Polyvinylpyrrolidone and freeze drying-assisted growth of an α-Ni(OH) 2 /reduced graphene oxide hybrid structure as a superior electrode material for supercapacitors

Herein, α-Ni(OH) 2 ultrathin sheets on reduced graphene oxide layers were synthesized via a simple single-step precipitation process. The structure, morphology, and chemical composition of the as-synthesized α-Ni(OH) 2 /rGO hybrid structure are well characterized using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. A 30 wt% α-Ni(OH) 2 /rGO denoted as NG2 achieved a superb supercapacitor performance, displaying specific capacitance (capacity) of 1050 F g −1 (580 C g −1 ) at 1 A g −1 current density. The assembled supercapacitor delivered specific energy of 60 W h kg −1 at a specific power of 1.1 kW kg −1 . Still, it retained a high specific power of 3.9 kW kg −1 at 43 W h kg −1 , demonstrating a retention percentage of 88% after 4000 repetitive charge/discharge cycles.