Příprava nanokompozitů melon/g-C3N4-SnO2-Ag a jejich charakterizace z pohledu optoelektronických vlastností včetně zjištění fotokatalytických účinků

Abstract

This diploma thesis is focused on the synthesis and characterization of nanocomposite materials based on melon-g-C₃N₄ modified with tin (IV) oxide and silver in various weight ratios, namely melon-g-C₃N₄-SnO₂-Ag (0.5; 1; 2; and 3 wt.%), with potential application in photocatalytic processes. The main objective of this work was to prepare these materials and subsequently evaluate their photocatalytic activity in the degradation of organic pollutants, specifically Acid Orange 7 (AO7) dye and phenol. The samples prepared were subjected to comprehensive characterization, including photoluminescence spectroscopy (PL), diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), infrared and Raman spectroscopy, morphological analysis using scanning electron microscopy (SEM), and elemental analysis. Finally, cycling stability tests were performed for the best-performing nanocomposite, melon-g-C₃N₄-SnO₂-Ag (1 wt.%), and for pristine melon-g-C₃N₄. The photocatalytic activity was evaluated based on photodegradation experiments carried out under irradiation in the UVA light (360 nm) and visible light (VIS, 420 nm), respectively. SEM results confirmed the formation of nanostructured composite materials and the presence of silver. In the degradation of AO7 dye, the highest efficiency was achieved by the melon-g-C₃N₄-SnO₂-Ag (1 wt.%) composite, where approximately 75 % of the dye was removed under UVA irradiation in a total time of 150 minutes. Similarly, the highest efficiency in phenol degradation was observed for the same composite (1 wt.%), achieving about 70 % of AO7 dye removal in a total time of 150 minutes. Under combined VIS+UVA irradiation, the best performance was exhibited on the melon-g-C₃N₄-SnO₂-Ag (2 wt.%) composite, with approximately 60 % degradation in 150 minutes. For the combination of UVA+VIS, the best material was melon-g-C₃N₄-SnO₂-Ag (1 wt.%), both for phenol and AO7, with a total degradation of 50 % in 150 minutes. Under visible light only, the melon-g-C₃N₄-SnO₂-Ag (1 wt.%) composite again showed the best results for both AO7 and phenol degradation in total time of 150 minutes. The results of this study confirm that appropriate compositional tuning and the formation of heterostructures can significantly influence the optical properties and photocatalytic activity of the prepared nanocomposite materials.