A comparative study on the electrocatalytic efficiency of coupled (CuO-Co3O4) vs. mixed (CuCo2O4) metal oxides: Probed by hydrazine oxidation and sensitive determination

This work reports the synthesis of copper- and cobalt-based coupled and mixed metal oxides (CuO-Co₃O₄ and CuCo₂O₄, respectively) utilizing a simple hydrothermal and calcination approach. CuO-Co₃O₄, CuCo₂O₄, and the control samples were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray, and X-ray photoelectron spectroscopy. TEM and FE-SEM analyses of CuO-Co₃O₄ reveal the presence of two distinct morphologies: rod- and sphere-shaped particles (CuO and Co₃O₄, respectively). Further, CuO-Co₃O₄ was efficiently utilized as an electrocatalyst for the selective oxidation of hydrazine (Hyz). CuO-Co₃O₄ shows a high redox response compared to CuO, Co₃O₄, CuCo₂O₄, and the physical mixture of CuO and Co₃O₄ (CuO/Co₃O₄). This enhanced performance is attributed to the synergistic interaction between the metal ions caused by their close proximity and the increased exposure of surface active sites. CuO-Co₃O₄ shows a broad linear range (1–3500 µM), a low detection limit (0.29 µM), and high sensitivity (0.5756 µA µM^-1 cm^-2) for the Hyz determination. Kinetic parameters, for instance the diffusion coefficient and catalytic rate constant for Hyz oxidation were obtained using chronoamperometry. Additionally, CuO-Co₃O₄ was effectively utilized to analyze Hyz in real samples with acceptable recovery rates.