Giant Dielectric Constant and Fast Adsorption–Sunlight Photocatalytic Properties of Al-Doped CuO–ZnO Heterostructures

In this study, Al-doped CuO–ZnO composite revealed a huge dielectric constant and fast adsorption–photocatalytic properties for industrial Congo red, Reactive yellow 145 and methyl green pollutants. Nanocrystalline ZnO, CuO and Al-doped CuO–ZnO composite was synthesized via sol–gel method. The X-ray diffraction analysis verified that the composite structure has hexagonal ZnO and monoclinic CuO phases. The morphological study of Al-doped CuO–ZnO composite displayed different types of particles having hexagonal, sheet and very fine shapes. Optically, Al-doped CuO–ZnO composite has a high visible light absorption ability compared to its individual components. For energy storage, Al-doped CuO–ZnO composite showed a semi-stable giant dielectric constant with value of 7.6215 × 10⁴ at 42 Hz. Furthermore, Al-doped CuO–ZnO composite exhibited a remarkable adsorption of Congo red, Reactive yellow 145 and methyl green dyes in addition to fast photocatalytic characteristics under sunlight. Herein, 75 mg of Al-doped CuO–ZnO composite exhibits adsorption capacity of 54, 49 and 45% for 100 mL solution contains 20 mg/L Congo red, reactive yellow 145 and methyl green, respectively. As well, the photocatalytic measurements under sunlight confirmed the full removal of all dyes after 20–25 min.