Interfacial defect modulation in hydrothermal CeO2/graphene nanocomposites for next-generation supercapacitors

Abstract

This study aims to examine the supercapacitor performance of CeO₂/graphene nanocomposites synthesized via hydrothermal techniques. X-Ray Diffraction (XRD) results confirmed the successful synthesis of the nanocomposite, with distinct peaks corresponding to the crystalline structure of CeO₂. Transmission Electron Microscopy (TEM) analysis confirmed the uniform distribution of graphene sheets within the CeO₂ matrix, indicating efficient integration of the materials at the nanoscale. The existence of distinctive D (∼1350 cm⁻¹) and G (∼1585 cm⁻¹) bands, as well as the F_2g mode of cubic CeO₂ (∼450 cm⁻¹), further validated the successful production of defect-rich graphene using Raman spectroscopy, giving direct spectroscopic validation beyond PXRD analysis. UV-visible spectroscopy revealed characteristic absorption peaks at 323 and 385 nm for pure CeO₂, which shifted to 329 and 375 nm in the composite, indicating modification of defect states at the CeO₂-graphene interface. A significant reduction in optical band gap from 3.21 eV (CeO₂) to 2.75 eV (CeO₂/Graphene) was observed, indicating a modified electrical structure at the interface between graphene and CeO₂. The electrochemical performance of CeO₂ and CeO₂/Graphene was evaluated using CV, GCD, and EIS. CeO₂/Graphene exhibited higher specific capacitance (231 F g⁻¹) than CeO₂ (142 F g⁻¹) in CV, and showed improved cycling stability with a peak capacitance of 285 F g⁻¹ in GCD. EIS revealed reduced charge transfer resistance for CeO₂/Graphene, enhancing electrochemical performance. These findings highlight the superior charge storage, energy density (5.7 Wh kg⁻¹), and power density of CeO₂/Graphene, making it a promising material for supercapacitors and energy storage applications.