A g-C3N4–CdS composite catalyst with high visible-light-driven catalytic activity and photostability for methylene blue degradation

Graphical abstract: - Highlights: • g-C3N4–CdS heterostructure exhibits a higher visible-light photocatalytic activity than g-C3N4 or CdS. • The large surface area and the synergistic effect result in the enhanced activity of g-C3N4–CdS. • g-C3N4–CdS photocatalyst effectively inhibits the photocorrosion of CdS. - Abstract: A straightforward strategy is designed to fabricate g-C3N4–CdS composite catalyst with high visible-light-driven photocatalytic activity and photostability via the precipitation method. The microscopic observation shows that CdS nanoparticles are randomly distributed on the surface of graphitic carbon nitride (g-C3N4), and X-ray diffraction (XRD) measurements and Fourier transform infrared (FT-IR) spectra further confirm that g-C3N4 and CdS coexist in the photocatalysts. The results of photocatalytic experiments demonstrate that the g-C3N4–CdS composite exhibits significantly enhanced photocatalytic activity for the photocatalytic degradation of methylene blue (MB) compared with g-C3N4 or CdS alone under visible-light irradiation. It is found that the photocatalytic degradation process follows the pseudo-first-order kinetic model and Langmuir–Hinshelwood model, indicative of an adsorption controlled reaction mechanism. The enhanced photocatalytic activity of the g-C3N4–CdS composite can be attributed to the large surface area and the synergistic effects between g-C3N4 and CdS, which can readily reduce the recombination probability of photogenerated electron-hole pairs and enhance the charge separation efficiency, leading to the higher photocatalytic performance and effectively inhibited photocorrosion. The results also show that among the catalysts with differing CdS content, the g-C3N4–CdS composite with a g-C3N4/CdS mass ratio of 1:3 exhibits the highest photodegradation efficiency (90.45%) after irradiation for 180 min