Electrochemical performance of hydrothermally synthesized Co-doped NiO electrodes: effect of propylene carbonate additive and doping concentration

Abstract

Transition metal oxides have received substantial attention because of their versatile applications in photocatalysis, electronics, and energy storage systems such as batteries and pseudocapacitors. Owing to their variable oxidation states, they are known as redox-active materials, which give rise to battery-type and pseudocapacitor-type electrodes for energy storage devices. In this work, 10%, 20%, and 30% cobalt-doped nickel oxide and 30% cobalt-doped nickel oxide mixed with propylene carbonate (PC) were synthesized via the hydrothermal method to produce electrode materials for a supercapacitor. The electrode materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy--energy-dispersive X-ray spectroscopy (FESEM--EDX), and Brunauer--Emmett--Teller (BET) analyses. The obtained XRD and EDX spectra confirmed crystallinity and elemental composition. The BET surface area of 30% cobalt-doped nickel oxide mixed with PC was estimated to be 17.67 m2 g-1, which is larger than that of 30% cobalt-doped nickel oxide, with a surface area of 11.05 m2 g-1. The electrode fabricated with 30% cobalt-doped nickel oxide showed better performance, and its electrochemical performance was further enhanced with the PC additive. The specific capacitance of the 30% cobalt-doped nickel oxide with PC additive reached 551 F g-1 at 0.1 A g-1 and 661 F g-1 at 5 mV s-1. The obtained results suggest that new-generation electrochemical electrodes can be optimized by adding PC during synthesis.