Influence of synthesis time on the photocatalytic activity of Mg-doped g-C3N4

Abstract

In this study, magnesium-doped graphite carbon nitride (Mg-doped g-C₃N₄) materials were successfully synthesised via a simple chemical method, with synthesis durations ranging from 3 to 18 hours, followed by thermal treatment at 90°C. The crystal structure and chemical states of the materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), while the optical properties were evaluated through UV-Vis absorption and photoluminescence (PL) spectra. The photocatalytic performance was investigated through the degradation of an organic Rhodamine B (RhB) solution under illumination with a Xenon lamp and natural sunlight. The results revealed that all Mg-doped samples exhibited superior photocatalytic activity compared with pristine g-C3N4. This enhancement is attributed to the presence of Mg²⁺ cations acting as electron “trapping centers”, which suppress the recombination of photogenerated electron-hole pairs. Moreover, the incorporation of Mg into the heptazine framework increases the specific surface area, thereby promoting the overall photocatalytic efficiency of the materials.