A Ag nanoparticle functionalized Sg-C3N4/Bi2O3 2D nanohybrid: a promising visible light harnessing photocatalyst towards degradation of rhodamine B and tetracycline

Abstract

In the present work, S doped graphitic carbon nitride (Sg-C₃N₄) 2D nanosheets were synthesized by performing a thermal polymerization reaction of thiourea at 500 °C. After that the surface of Sg-C₃N₄ was functionalized with Bi₂O₃/Ag composite nanoparticles via a chemical precipitation method followed by heat treatment at 330 °C. The prepared Sg-C₃N₄/Bi₂O₃/Ag ternary nanocomposites were used as a visible light active photocatalyst for catalytic degradation of rhodamine B (RhB) dye and tetracycline hydrochloride, under natural solar light. The prepared ternary nanocomposites were characterized by using UV-Vis DRS, FT-IR, FESEM, EDX, TEM, XRD, photoluminescence (PL), electrochemical impedance spectroscopy and XPS analytical techniques. The XRD, UV-Vis DRS and FT-IR studies clearly revealed the formation of ternary phases in the composites. From the TEM and EDX studies it was clearly observed that spherical Ag nanoparticles (5–10 nm) and irregular Bi₂O₃ particles (60–120 nm) were decorated on the surface of 2D S doped g-C₃N₄ nanosheets. XPS studies also confirmed the formation of the ternary nanocomposite system. The results from the photocatalytic degradation of RhB dye revealed that 95% of the RhB dye was decolorized within 90 min of contact time by Sg-C₃N₄/Bi₂O₃/Ag ternary nanocomposites under natural solar light. Among the different prepared photocatalysts, Sg-C₃N₄/Bi₂O₃/Ag (15%) was found to be the most efficient photocatalyst towards the decolourization of RhB dye. This result is ascribed to the optimum loading of Ag, formation of a hetero-junction between the ternary phases, more light harvesting capacity and the lowest recombination rate of charge carriers. Apart from the coloured RhB dye, the photocatalytic degradation of the non-coloured tetracycline hydrochloride (TCH) compound was also studied to understand the photosensitization effect on the degradation process. Again scavenger studies were also performed in order to understand the mechanism of photodegradation. It was observed that along with the electron and hole pairs generated by light photons, hydroxide radicals play an important role in the degradation mechanism. The reusability study indicates that the photocatalysts prepared were highly stable at room temperature and can be recycled and reused for up to four successful cycles without a major loss in their performance.