Eco-friendly g-C₃N₄@Ag₂S photocatalyst for synergistic degradation of mixed azo dyes under visible light

Graphitic carbon nitride (g-C₃N₄) and silver sulfide (Ag₂S) have drawn much interest as a potentially effective photocatalyst for breaking down the organic dye because of their exceptional optical and electrical characteristics. In this work, a g-C₃N₄@Ag₂S hybrid nanocomposite was successfully synthesized via a co-precipitation method to improve the degradation efficiency of organic pollutants under visible light. The structural, morphological, and optical properties of the synthesized nanocomposite were thoroughly analysed using XRD, FTIR, SEM, HRTEM, UV-Vis, BET, and XPS techniques. The XRD pattern confirmed the formation of a mixed hexagonal-monoclinic crystal structure, indicating the successful integration of Ag₂S nanoparticles onto the g-C₃N₄ matrix with a crystallite size of ∼20 nm. UV-Vis DRS analysis showed a red-shift in the absorption edge, and the estimated optical band gap of the composite was 1.5 eV, indicating enhanced visible light harvesting. The combination of g-C₃N₄ and Ag₂S resulted in a strong synergistic effect, significantly enhancing the photocatalytic activity due to improved light absorption, effective generation of reactive oxygen species (ROS), and efficient separation of photogenerated charge carriers. Photocatalytic experiments demonstrated remarkable degradation efficiencies of 99.07 % for Methyl Orange (MO) and 97.93 % for Methylene Blue (MB) under visible light irradiation within 150 min. Furthermore, the composite exhibited outstanding performance in the simultaneous degradation of mixed dye systems, achieving 97 % degradation of MO and 96 % of MB, indicating its potential for treating complex wastewater mixtures. Furthermore, the reusability of the g-C₃N₄@Ag₂S catalyst was 94 % for MO and 92 % for MB after five cycles. These findings demonstrate the efficiency, stability, and practical applicability of the g-C₃N₄@Ag₂S nanocomposite as a promising photocatalyst for environmental remediation.