As the pace of technological advances accelerates, the role of electrical energy storage has become increasingly important. Among various storage solutions, supercapacitors are garnering significant attention. Their unique attributes, including high power density, rapid charge/discharge capabilities, and extended lifecycle, position them as a promising alternative to conventional batteries. This study investigates the synthesis of a nickel oxide (NiO) and nickel oxide/graphene oxide (NiO/GO) composite using a single-step hydrothermal method, to evaluate their potential as supercapacitor electrode materials. The synthesized NiO, graphene oxide (GO), and NiO/GO composite were comprehensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy to analyze their crystal structures and chemical bonding. The XRD analysis confirmed the formation of an NiO phase with a rhombohedral crystal structure, and no change after GO incorporation. SEM analysis revealed the formation of spherical NiO particles and porous morphology of the NiO/GO composite, which also exhibited a spherical shape. The GO displayed a randomly arranged wrinkled sheet-like structure. Electrochemical analysis of the NiO/GO composite exhibited a remarkable specific capacitance of 893 F g-1 at a current density of 1 A g-1, surpassing that of NiO and GO alone, demonstrating NiO/GO has promising performance for supercapacitor applications. The charge transfer resistance, derived from the Nyquist plot, suggests that the reduction in charge transfer resistance contributed significantly to the improved capacitance. Additional stability studies of over 5,000 cycles at 5 A g-1 revealed an 85 % initial capacitance retention, confirming the advantages of GO inclusion to improve material retention for superior long-term performance. The asymmetric supercapacitor (ASC) assembled using an electrode with the configuration NiO/GO//activated carbon (AC) showed a specific capacitance of 77.8 F g-1 obtained at a current density of 0.5 A g-1.

Abstract
1. Introduction
2. Experimental Procedure
    2.1. Synthesis of NiO, GO, and NiO/GO
    2.2. Characterizations
3. Results and Discussion
    3.1. Physicochemical characterizations
    3.2. Electrochemical analyses
4. Electrochemical Study of Asymmetric Supercapacitor
5. Conclusion
Acknowledgement
References
Author Information

• Shital Bachankar(Department of Intelligent Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)
• Aditi Kumbhar(Department of Intelligent Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)
• Shaupik Mullani(Department of Intelligent Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)
• Jaehyung Park(Department of Intelligent Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)
• Taeksoo Ji(Department of Intelligent Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea, Department of Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea) Corresponding author
• Dhanaji Malavekar(Optoelectronics Convergence Research Center and Department of Materials Science and Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)
• Chihoon Kim(Department of Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Republic of Korea)