Construction of a flower-shaped g-C3N4/ZnIn2S4 composite with heterogeneous structural defects for highly efficient photocatalytic degradation of pollutants

Abstract

To improve the photocatalytic performance of carbon nitride (g-C₃N₄), a flower-shaped COCN/ZIS composite was synthesized by growing ZnIn₂S₄ (ZIS) onto structurally defective g-C₃N₄ (COCN) nanosheets. The experimental results indicate that the prepared photocatalyst has excellent photocatalytic performance for the degradation of methylene blue (MB), with an apparent rate constant of 0.0661 min⁻¹, which is approximately 6.89, 6.06 and 7.39 times greater than that of g-C₃N₄ (0.0096 min⁻¹), COCN (0.01091 min⁻¹) and ZIS (0.00895 min⁻¹), separately. The improvement in the photocatalytic performance of COCN/ZIS can be attributed to the defect structure of COCN and the well-matched relationship between COCN and ZIS, both of which result in valid photoinduced charge separation and migration. This has also been confirmed by the synergy coefficient (3.33). Furthermore, the total organic carbon content (TOC) removal rates of MB and wastewater by the 60-COCN/ZIS composite were 85.96 % and 75.32 %, respectively, suggesting that the resultant catalyst has potential application in the photodegradation treatment of MB. Finally, the capture experiments and electron paramagnetic resonance analysis show that ·OH, ·O₂^– and h⁺ species are generated during the process, among which ·OH plays a great part in the photodegradation of MB by the COCN/ZIS compound.