A novel high-performance supercapacitor based on the innovated ternary CeO2@CoWO4/N-doped graphene nanocomposites

The present work used multiple steps method to fabrication the three component CeO₂@CoWO₄/N-doped graphene (CCNG) as active material for supercapacitor application for the first time. For this purpose, firstly CoWO₄ nanostructure was synthesized via hydrothermal route, after that CeO₂ nanoparticles were sonochemicaly grown on CoWO₄ nanostructures followed by thermal treatment and overall, CCNG nanocomposites were synthesized through the hydrothermal approach in presence of urea as nitrogen source. As-designed materials were physico-chemically characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and Brunauer-Emmett-Teller (BET) tests. The electrochemical capacitive of as-fabricated nanostructures were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) technologies in 3.0 M KOH solution as electrolyte. Also, molar ratio of Ce²⁺: Co²⁺ was optimized and CeO₂@CoWO₄ with molar ratio 1:2 was selected as the best electrode with specific capacitance of 489.27 F g^-1 at constant current density of 3 A g^-1. Likewise, the mass ratio of N-doped graphene to active materials was optimized and, CCNG-2 nanocomposites illustrated the highest specific capacitance of 698.18 F g⁻¹ at 3 A g⁻¹, which was greater than that of bare CoWO₄ (295.64 F g⁻¹) and CeO₂ (293.45 F g^-1) at this condition. Furthermore, CCNG-2 nanocomposites exhibited superior cycling stability 91.8 % capacity retention after 1000 cycles at sweeping scan rate of 50 mV s^-1, while CeO₂@CoWO₄ possessed 73.2 % capacity retention at 1000th cycles. These interesting results revealed that the CCNG-2 nanocomposites are capable as a active material for usage in high-performance electrochemical supercapacitors.