Facile fabrication of g-C3N4/CdS heterojunctions with enhanced visible-light photocatalytic degradation performances

The construction of heterojunction used to improve the photocatalytic performance of photocatalyst has attracted much attention in recent years. In this study, we aim to investigate the synergistic effect of g-C3N4 and CdS on photocatalytic degradation of organic dye pollutants. Several g-C3N4/CdS heterojunctions with different g-C3N4 contents were successfully synthesised via a simple hydrothermal reaction. Experimental measurements on photocatalytic degradation of methylene blue (MB), rhodamine B (RhB) and MB/RhB mixtures were conducted. The photodegradation results indicate that the prepared g-C3N4/CdS composites all demonstrate remarkable visible-light photocatalytic properties, and this performance is due to the formation of the g-C3N4/CdS heterojunction structures. Compared with pure g-C3N4 and CdS, the g-C3N4/CdS heterojunctions not only effectively enhance the absorption of visible light but also significantly inhibit the recombination of photogenerated carriers. Thus, this condition prolongs the lifetime of active species and markedly improves their photodegradation activities. Especially, the 0.04GCS exhibits the best photocatalytic degradation performance on MB, and its degradation rate constant is up to 0.0301 min−1 within the irradiation time of 90 min, which is 9 and 3 times higher than that of the pure g-C3N4 and CdS, respectively. In the meantime, the 0.12GCS also shows excellent photodegradation activity on RhB, and its degradation efficiency is nearly 2.32 and 2.97 times that of the pure g-C3N4 and CdS. The different degradation behaviours of the composite photocatalysts on MB/RhB mixed pollutant were investigated. The possible reaction mechanism of the photocatalytic degradation on organic dyes by the g-C3N4/CdS heterojunctions was also explored.