Sulfonated polyaniline-encapsulated graphene@graphitic carbon nitride nanocomposites for significantly enhanced photocatalytic degradation of phenol: a mechanistic study

The discharge of organic pollutants such as phenols and their derivatives in industrial effluents is a major threat to potable water, leading to a global requirement of cost-effective novel materials for decontamination to get high-quality water. In view of these concerns, sulfonated polyaniline, (s-PANI)@graphitic carbon nitride (g-C3N4) and its nanocomposites with graphene (GN) were synthesized via in situ oxidative polymerization of aniline in the presence of g-C3N4 and GN. The weight ratio of GN varied as 1, 3, and 5% of the weight of g-C3N4. The resulting s-PANI@g-C3N4 and s-PANI@g-C3N4/GN(1-5%) composites were characterized in terms of structural, optical, morphological, and surface chemical state changes through X-ray diffraction (XRD), UV-visible diffuse absorbance spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared nanocomposites were analyzed for their ability to degrade phenol moieties by high-performance liquid chromatography (HPLC). The results revealed enhanced photocatalytic degradation with GN-based sulfonated s-PANI@g-C3N4/GN(1-5%). The nanocomposite with 1% GN loading showed the highest photocatalytic activity in comparison with nanocomposites containing 3% and 5% GN. The enhancement of photocatalytic activity could be attributed to the involvement of the sp2 carbon atoms, the interaction of the OC carbon atoms, and the high migration efficiency of charge carriers. However, higher amounts of GN (3 to 5%) caused a negative shielding effect by impeding charge recombination, thereby resulting in reduced photocatalytic activities of these composites. The proposed methodology can be a potential route for the elimination of phenolic compounds in the treatment of natural water reservoirs