Supercapacitors Based on Ternary Composites of Ceria-Manganese Oxide Nitrogen-Doped Graphene

A ternary composite of ceria (CeO2), manganese oxide (MnO2), and nitrogen-doped graphene (NG) is synthesized via a hydrothermal route and investigated as a promising electrode material for high-performance supercapacitors. The integration of redox-active CeO2, pseudocapacitive MnO2, and highly conductive NG results in a synergistic effect that enhances charge storage capability, structural stability, and electron/ion transport. Detailed morphological, structural, and surface analyses using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirm the formation of a well-connected, porous nanocomposite architecture with uniform elemental distribution and strong interfacial interaction. Electrochemical characterization reveals that the CeO2–MnO2–NG electrode delivers a high specific capacitance of 772 F/g at 1 A/g and retains 75.1% of its capacitance at 5 A/g, demonstrating good rate capability. This performance is attributed to the combined contributions of electric double-layer capacitance and fast faradaic redox reactions, facilitated by the composite’s interconnected structure. These findings highlight the potential of CeO2–MnO2–NG as a robust and efficient electrode material for next-generation energy storage devices.