MoO3/g-C3N4 heterostructure for degradation of organic pollutants under visible light irradiation: High efficiency, general degradation and Z-scheme degradation mechanism

The development of semiconductor photocatalyst with simple and controllable components, high catalytic efficiency and cycle stability, and diversified degradation goals is an important condition for achieving large-scale commercial applications for environmental remediation. The achievement of these important performance indicators requires the precise modulation of the components and the clarification of the photocatalysis process and charge transfer mechanisms. In this work, we have fabricated a heterostructured photocatalyst composed of graphite carbon nitride (g-C3N4) nanosheets and MoO3 nanoparticles through a simple mixing and annealing process. The compound exhibits effective visible light photocatalytic activity for both rhodamine (RhB) and methyl orange (MO). In the evaluation of RhB catalytic performance, the optimized heterojunction photocatalyst achieves extremely high visible light photocatalytic performance with a small amount of catalyst (0.1 g/L). It is characterized by nearly 100% degradation rate within 24 min. The kinetic constant k is 0.11 min−1, and the cycle stability is 100% after four cycles. Direct Z-scheme charge transfer is established based on the measurement of energy level positions, free radical scavenging experiment and electrochemical analysis. Electrons accumulate in the g-C3N4 conduction band while holes remain in the MoO3 valence band, maintaining a high redox potential and promoting effective carrier separation. Superoxide radicals and holes play a prominent role in photocatalytic degradation, and the role of hydroxyl radicals cannot be ignored.