Synthesis, characterization, and application of ternary CuO/ZrO₂@S-doped g-C₃N₄ hybrid nanocomposites

Graphitic carbon nitride (g-C₃N₄) is utilized across various fields, including catalysis, hydrogen production, and biosensing, due to its basic surface sites. However, g-C₃N₄ often shows limited efficiency in such applications, mainly due to challenges related to absorption and low conductivity. This study aimed to synthesize S-doped g-C₃N₄/CuO/ZrO₂-based semiconducting ternary nanocomposites (NCs) for catalytic applications using a chemical precipitation method. A straightforward gas-templating technique was applied to achieve one-step nano-structuring of S-doped g-C₃N₄ at 550 °C. The interactions between cubical CuO structures, monoclinic ZrO₂, and flower-like S-doped g-C₃N₄ morphologies were investigated using a range of analytical techniques, including X-ray diffraction (XRD), high-resolution X-ray photoelectron spectroscopy (HR-XPS), high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA), differential thermal analysis (DTA), Brunauer-Emmett-Teller (BET) surface area analysis, and photoluminescence (PL) studies. The superior performance of CuO/ZrO₂@₂S-doped g-C₃N₄ (30%) nanocomposite is attributed to its smaller crystalline size, optimized band gap energy, and large surface area. These features collectively enhance electron-hole pair separation efficiency and increase the number of active sites for adsorption and reaction. Such improvements not only enhance sensitivity but also boost sensor efficiency through better charge carrier generation, selective detection capabilities, and facilitated charge transfer. These enhancements also contribute to reducing recombination losses and accelerating signal generation and g-C₃N₄ transport. These synthesized ternary NCs were applied to bisphenol A (BPA) detection. The electrocatalytic behaviour of the modified carbon paste electrode (CPE) was assessed by measuring BPA via cyclic voltammetry (CV) under ideal conditions (pH 5). The CuO/ZrO₂@S-doped g-C₃N₄ (30%)/CPE system demonstrated high electrocatalytic performance, achieving reproducibility with a 1.7 μM detection limit and 2.1 μM limit of quantification. Overall, this research highlights the potential of synthetic ternary NCs as versatile materials for environmental remediation applications.