Synthesis of reduced graphene oxide decorated with cuprite nanoparticles for energy-storage devices: Dielectric properties and electrical conductivity

Abstract

This work reports a single‐step hydrothermal synthesis of reduced graphene oxide (rGO) uniformly decorated with cuprite (Cu₂O) nanoparticles. Unlike conventional multi-step methods, this approach enables in-situ reduction and nanoparticle anchoring in a single step, ensuring strong interfacial contact and uniform Cu₂O NP dispersion (7–43 nm) across the rGO sheets. By adjusting the Cu₂O loading up to 0.05 g, the indirect bandgap narrows from 1.97 eV (pure rGO) to 0.12 eV, and the direct bandgap from 4.0 eV to 2.6 eV. At 1 kHz, the real permittivity (ε′) rises from ∼145 (rGO) to >230 (rGO/0.05 g Cu₂O), indicating ≈60 % increase in energy‐storage capability. AC conductivity increases by nearly two orders of magnitude compared to bare rGO, reflecting enhanced carrier mobility and defect‐state hopping induced by Cu₂O. XRD, Raman, XPS, and TEM all confirm effective GO reduction and crystalline Cu₂O formation with strong interfacial contact. These tunable improvements demonstrate that Cu₂O/rGO nanocomposites are promising for flexible electronics, high‐performance supercapacitors, and optoelectronic applications.