Příprava nano g-C3N4 dvoustupňovým tepelným procesem a studium fotokatalýzy na methylenové modři, Kongo červeni a malachitové zeleni v UV/VIS, včetně studia nanokompozitu z pohledu některých fyzikálně-chemických charakteristik

Abstract

This bachelor thesis focuses on the preparation of nanostructured graphitic carbon nitride (g-C3N4) and the study of its photocatalytic potential. The main objective is to synthesize the material via an efficient two-step thermal process. The first step involves the polymerization of the melamine precursor at 500 °C for 2 hours, followed by 520 °C for 4 hours, resulting in bulkg-C3N4. In the second stage, thermal exfoliation of the prepared bulk material is carried out at 500 °C for 3 hours, leading to successful delamination into ultrathin nanolayers with a yield of 20,16 %. The prepared samples are characterized using XRD, SEM, DRS, FI-IR, PL, and Raman spectroscopy. The thesis examines in detail the photocatalysts efficiency in the degradation of methylene blue, Congo red, malachite green, and crystal violet under UV and visible radiation. The results confirm successful delamination into ultrathin layers and an increase in the bandgap energy to 2,77 eV due to the quantum confinement effect. The nanostructured form exhibits significantly higher activity and faster kinetics compared to the original bulk material. The fastest degradation is observed for malachite green, where an 81 % efficiency is achieved under visible light after just 30 minutes. Under UVA radiation, exfoliated g-C3N4 achieves complete elimination of Congo Red (100 %) after 180 minutes, as well as high efficiency for methylene blue (91 %) and crystal violet (82 %). The findings present g-C3N4 as a promising, metal-independent, and environmentally friendly material for advanced technologies for the treatment of wastewater containing organic pollutants.