Visible light-driven degradation of Brilliant Green and Indigo Carmine organic contaminants using SnS2/GCN/rGO and CuS/GCN/rGO ternary composites – A comparative study

Abstract

This study introduces novel SnS₂/GCN/rGO and CuS/GCN/rGO ternary composites for the visible-light-driven degradation of organic contaminants, specifically targeting the dyes Brilliant Green (BG) and Indigo Carmine (IC). X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS), UV–visible, Photoluminescence (PL), and impedance spectroscopy were used to characterize the synthesized samples to extract the characteristic features of the catalysts. The chemical compositions of synthesized samples were confirmed using X-ray photoelectron spectroscopy (XPS). The ternary composite SnS₂/GCN/rGO revealed the degradation of BG by 98.0 % and IC by 80.9 %. CuS/GCN/rGO composite has shown degradation efficiencies of 92.7 % for BG and 78.5 % for IC. Unlike previous approaches, this work provides a comparative analysis of SnS₂ and CuS-based ternary systems, emphasizing their distinct photocatalytic mechanisms Z-scheme in SnS₂/GCN/rGO and direct electron transfer in CuS/GCN/rGO. By integrating GCN and rGO, this study addresses the typical limitations of metal sulfides, such as rapid charge recombination, enhanced electron mobility, and overall degradation efficiency under visible light. The confirmation of degradation species is made using chemical oxygen demand (COD) measurements. These results were supported by the reduction in the photoluminescence intensity and lower charge transfer resistance by impedance spectra suggesting an enhanced degradation rate for the ternary composites.