Mechanistic elucidation of PVP-functionalized GO in modulating SnS2-g-C3N4 heterojunctions for rhodamine B degradation under visible light

This study presents a groundbreaking PGOGSn10 nanocomposite, fabricated through the strategic incorporation of PVP-functionalized GO into a SnS₂/g-C₃N₄ heterostructure, to significantly amplify its photocatalytic role for Rhodamine B (RhB) mineralization. While SnS₂/g-C₃N₄ (GSn10) systems are limited by relatively quick charge recombination and insufficient surface-active sites, the PVP-GO matrix (PGO) serves as a multifunctional mediator, boosting interfacial electron migration via π-π conjugation, preventing agglomeration, suppressing carrier recombination, and providing a suitable surface-area scaffold for dye adsorption and ROS generation. Advanced characterization analysis, including XRD, XPS, and HRTEM, validated the successful hybridization of PGO with GSn10 (PGOGSn10), revealing a 2D/3D hierarchical architecture with lattice-resolved SnS₂ (111) planes anchored onto ultrathin g-C₃N₄ nanosheets. FTIR confirmed chemical bonding between PVP's carbonyl groups and GO's oxygen functionalities, while XPS deconvolution spectra highlighted interfacial C–N–Sn bridging bonds critical for charge delocalization. Optical studies (DRS, PL) reflected a narrowed bandgap (2.4 eV) and 75 % reduction in PL intensity for PGOGSn10 versus SnS₂/g-C₃N₄, corroborated by EIS showing a 2.5-fold decrease in charge-transfer resistance. The optimized PGOGSn10 achieved 97.6 % RhB mineralization within 90 min (rate constant k = 0.029 min⁻¹), outperforming SnS₂/g-C₃N₄ composite (k = 0.016 min⁻¹) and pristine g-C₃N₄ (k = 0.0034 min⁻¹). Radical trapping experiments and terephthalic acid (TA) fluorescence assays quantified •OH and •O₂⁻ as the dominant ROS. Operational optimizations identified pH 7 as ideal (zeta potential = −32 mV for electrostatic RhB adsorption) and 0.1 g/L dose (Langmuir-Hinshelwood kinetics). Remarkably, PGOGSn10 retained 85 % efficacy after 5 reuse times.