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

Abstract

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.