Crystal Growth, Optical Properties, and Photocatalytic Performances of ZnO-CuAl₂O₄ Hybrid Compounds: Theoretical and Experimental Studies

In this study, a two-step synthesis of the ZnO-CuAl₂O₄ nanocomposite with houseleek-like grains structures is developed for the first time. The proposed preparation procedure is led to an increase in bandgap energy (E_g) of the synthesized nanocomposite in comparison with the synthesized ZnO nanoparticles. Theoretically, based on a relation between E_g and the number of surface atoms, the increase in Eg value has been ascribed to the morphology of the synthesized samples. Experimentally, the photocatalytic performance of the synthesized composites, and pristine ZnO and CuAl₂O₄ are evaluated by comparing the degradation of methyl orange (MO) solution as a model of azo dye pollutants under UV irradiation. ZnO content and solution pH are selected as variables. Experimental results are showed that acidic pH (≈4) leads to the highest photodegradation performance due to the anionic nature of the MO solution. On the other hand, CuAl₂O₄-25%ZnO attained the highest degradation efficiency and high adsorption behavior of the composite is the main reason for this achievement.