Waste silk fiber derived nitrogen doped reduced graphene oxide anchored nickel doped cobalt vanadate for supercapacitor applications

Abstract

The present study uses Kibisu waste silk fiber as a carbon source to synthesize nitrogen-doped reduced graphene oxide (NRGO). NRGO is anchored with nickel-doped cobalt vanadate (Ni@Co₃V₂O₈:Ni@CoV) and forms a stable Ni@CoV/NRGO nanocomposite. A simple solvothermal approach using deep eutectic solvents has been developed for the generation of Ni@CoV/NRGO nanocomposite. X-ray diffraction studies (XRD), Raman spectroscopic, microscopic, energy dispersive spectroscopic (EDS) and X-ray photoelectron spectroscopic (XPS) studies confirm the doping of Ni to CoV, nitrogen to the RGO matrix, and the formation of nanocomposite. Ni@CoV/NRGO showed a significant increase in the specific capacitance (Csp: 434 F g⁻¹) compared to NRGO (275 F g⁻¹) and Ni@CoV (59 F g⁻¹) at a scan rate of 2 mV s⁻¹ using the cyclic voltammetry (CV) technique. Enhanced electrochemical performance in Ni@CoV/NRGO could be credited to the combination of faradaic (from Ni@CoV) and electrical double layer capacitance (NRGO) which exhibited pseudocapacitor behavior. In addition, variable oxidation states, and increased conductivity in Ni@CoV/NRGO are responsible for increased electrochemical performance. Even after 5000 cycles, Ni@CoV/NRGO showed good stability and retained 65 %. Asymmetric device (ASD) was fabricated using Ni@CoV/NRGO and activated carbon as the positive and negative electrodes, respectively. ASD showed a Csp of 146 F g⁻¹ at a 2 mV s⁻¹ scan rate. These findings point to Ni@CoV/NRGO as a suitable candidate for high-performance supercapacitors with a balanced energy density and power density.