كليدواژه :
ZnO , CuO Nanocomposite , Ammonia solution , Photocatalyst
چكيده فارسي :
Photocatalysis provides an effective treatment approach toward disposal of residual dyes from wastewater stream. This, is important to address the increasing challenges of industrialization growth and environmental issues. Through the past decades, photocatalysis has attracted attentions and among all the various solutions for unraveling the environmental issue, photocatalysis under sunlight illumination by utilizing semiconductor materials is highly suggested and diverse types of semiconductors have been developed up to now. Nanostructured heterogeneous photocatalysts process represent attractive strategies to convert directly solar energy to chemical energy. Zinc oxide nanoparticles are one such valuable metal oxide nanoparticles due to its unique characteristics such as room temperature photoluminescence, high photosensitivity, wide bandgap, catalytic efficiency, and nontoxic nature. Moreover, ZnO crystalizes in various morphologies which provides a variety of functional behaviors to become widely used in multiple applications. Several efficient synthesis methods such as hydrothermal, solvothermal, sol-gel, and co-precipitation are used in the preparation of ZnO. However, the wide band gap of ZnO (Eg = 3.4 eV) results in a narrow photo response to only ultraviolet (UV) light, restricting exploitation of the complete range of solar energy which is a limiting characteristic in this semiconductor. To overcome this problem, coupling ZnO with a p-type semiconductor has been adopted. This leads to formation of the p-n junction between n-type and p-type semiconductors which inhibits a fast recombination rate of electrons and holes and therefore, better photocatalysis efficiency. Copper oxide is a good candidate as a p-type semiconductor with a favorable band gap of 1.2 eV. Coupling ZnO with CuO restricts the high recombination rate of photogenerated electrons and holes of ZnO. In the present study, in order to have control over the sizes and shapes of the photocatalyst, different concentrations of ammonia solution were added to the synthesized solution. The aim of this work was to examine the structural variations of ZnO/CuO nanocomposites and how it influences the photocatalytic performance of the powders under the alteration of the pH value in alkaline range. The morphological properties ZnO/CuO nanocomposite were studied using the x-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM) equipped with energy dispersive x-ray (EDS). To evaluate the specific surface areas (SSA) and pore structure of the ZnO/CuO nanocomposite, Brunauer-Emmett-Teller (BET) method was utilized. The photocatalytic performance of the as-prepared powders was evaluated by monitoring the photodegradation of methylene blue (MB) under the irradiation of the visible light. Finally, on account of the diversity in morphologies of the nanocomposites provides different active facets for exposure to the light and therefore different degradation efficiency.
