Graphene/transition metal oxide composites offer ideal supercapacitor electrode properties by combining dual capacitance mechanisms. Plasma technology is an efficient method for preparing composite materials. By adjusting the discharge parameters, the plasma characteristics within the discharge space can be modified, thereby altering the microstructure and chemical composition of the composite materials, ultimately significantly improving the energy storage efficiency of electrode materials. In this study, reduced graphene oxide/nickel oxide (rGO/NiO) composites were synthesized in a single step using an argon dielectric barrier discharge (DBD) plasma system excited by a nanosecond pulsed power supply. The effects of discharge parameters specifically applied voltage (3–8 kV) and repetition frequency (3–9 kHz) on the material's properties were systematically investigated. Material characterization revealed that both higher voltage and frequency promoted the reduction of GO and the formation of NiO. X‐ray photoelectron spectroscopy showed that the NiO content increased from 3.02% at 3 kV to 12.09% at 8 kV, and further to 13.09% at 9 kHz, accompanied by a significant decline in oxygen‐containing groups. Raman spectroscopy indicated an elevation in the I D / I G ratio, reaching a maximum of 1.18 at 9 kHz, which signifies enhanced defect density and active sites. Scanning electron microscopy (SEM) images displayed pronounced delamination and uniform dispersion of NiO nanoparticles on rGO sheets under optimal conditions. Electrochemically, the composite prepared at 9 kHz exhibited the best performance, achieving a specific capacitance of 97.87 F g −1 at 1 A g −1 , along with the smallest charge transfer resistance and most favorable ion diffusion kinetics as confirmed by electrochemical impedance spectroscopy. These results underscore that modulating voltage and frequency in DBD plasma effectively tailor the composition and morphology of rGO/NiO composites, leading to significantly improved energy storage capability. This work provides a rapid, low‐temperature, and controllable plasma approach for fabricating high‐performance supercapacitor electrode materials.
Wang et al. (Wed,) studied this question.