Ni‐Mn Co‐Doped <scp> CeO ₂ </scp> /Carbon Nanofiber Nanocomposite Grown Hydrothermally: A High Surface Area Electrode Material for Improved Electrochemical Performance

ABSTRACT This study reports the synthesis and evaluation of a Ni 0.03 Mn 0.03 Ce 0.94 O 2 nanocomposite supported on carbon nanofibers (CNFs) for use as a functional electrode for energy storage devices. The composite was produced via one‐pot hydrothermal approach at 200°C. Nickel and manganese were co‐doped into the CeO 2 lattice to improve its electrochemical properties by introducing oxygen vacancies, enhancing electrical conductivity, and promoting redox activity. Structural analysis using XRD confirmed the polycrystalline fluorite structure of CeO 2 . SEM and TEM revealed the uniform dispersion of nano‐flakes and cluster‐like structures on the CNFs along with atomic composition of each element. BET analysis showed that the composite has a large surface area of 280.35 m 2 g −1 with a porous structure, which helps in fast ion diffusion and better electrolyte accessibility. Optical studies indicated a reduced band gap of 2.7 ± 0.2 eV, supporting the presence of defect states. Electrochemical measurements were analyzed in 1 M H 2 SO 4 with 0.1 M Na 2 SO 4 as an additive electrolyte. The composite exhibited the high specific capacitance of 613 Fg −1 at a current density of 1 Ag −1 . The corresponding energy density and power density were calculated to be 196.5 Whkg −1 and 1441 Wkg −1 , respectively. The electrode also showed good cycling stability, retaining 89% of its initial capacitance after 5000 charge–discharge cycles. The co‐doping of Ni and Mn in CeO 2 /CNF leads to significantly improved capacitance, energy density, and remarkable durability over extended cycles. Such characteristics make it a potential material for next‐generation supercapacitor electrodes.