Visible light responsive MWCNT decorated g-C3N4/Bi2S3 photocatalyst for malachite green dye degradation

A highly efficient ternary nanocomposite consisting of multiwalled carbon nanotubes (MWCNTs), graphitic carbon nitride (g-C3N4), and bismuth sulfide (Bi2S3) is developed via a simple one-step hydrothermal route. The structural, morphological, and optical properties of the developed nanocomposites are systematically analyzed using x-ray diffraction, x-ray photoelectron spectroscopy, electron microscopy, UV-vis diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller analysis. The ternary nanocomposite g-C3N4/Bi2S3/MWCNT-6 wt. % exhibits two times higher photocatalytic performance (99.6%) than g-C3N4/Bi2S3 and g-C3N4/MWCNT binary heterostructures under visible light irradiation within 50 min. The enhanced photocatalytic activity is attributed to the strong absorption of visible light and enhanced charge carriers separation efficiency, high surface area, and synergistic effect of g-C3N4, Bi2S3, and MWCNTs. A reaction mechanism for enhanced photocatalytic performance has also been proposed. The effect of different scavengers is performed to determine the role of the main reactive species responsible for dye degradation, which reveals that electrons are the main reactive species responsible for dye degradation. Moreover, the g-C3N4/Bi2S3/MWCNT ternary photocatalyst maintained excellent stability even after several cycles. Thus, the study offers a promising, stable, highly efficient, and visible-light-driven photocatalyst for dye wastewater purification.