Unveiling the effect of rGO and GCN on charge transport mechanisms in CuS/rGO/GCN composites with enhanced dielectric functionality

This study highlights the enhanced electrical and dielectric performance of copper sulfide (CuS)-based composites synthesized by incorporating electron-rich reduced graphene oxide (rGO) and semiconducting graphitic carbon nitride (GCN). These composites were synthesized via a hydrothermal method and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), UV–Visible and photoluminescence (PL) spectroscopy, to elucidate their structural, morphological, and optical properties. Among the hierarchical samples, CuS, CuS/rGO, CuS/GCN, and CuS/rGO/GCN composites, CuS/rGO demonstrated significantly improved DC and AC conductivity, attributed to the presence of abundant free charge carriers and the conductive 2D framework of rGO. AC conductivity followed Jonscher's universal power law, with the frequency exponent (S) ranging from 0.64 to 0.92. Notably, the CuS/rGO/GCN ternary composite exhibited superior dielectric and charge transport properties, driven by the synergistic interplay among CuS, rGO, and GCN. The dielectric constant (ε′) of the CuS/rGO/GCN composite showed highest value of 2921—approximately tenfold higher than that of pristine CuS (ε′ = 192.9). The dielectric relaxation behaviour was modelled using the Havriliak–Negami model, revealing a non-Debye type relaxation mechanism with absorption coefficient (α) less than 1 (0.58–0.86). The improved dielectric properties are attributed to strong interfacial and space charge polarization effects. Charge transfer mechanism in the composites was also studied using Impedance spectroscopy (IS), evaluated via Nyquist plots and corresponding equivalent circuit modelling. These findings demonstrate that CuS-based hybrid composites, particularly CuS/rGO/GCN composites, are promising materials for high-performance capacitive and energy storage applications due to their high dielectric constant and efficient charge transport characteristics.