Construction of MoS2/graphite/C3N4 Ternary Photocatalytic System Through Communicating Electron

Abstract

A MoS2/graphite/C3N4 ternary photocatalytic material (MGC catalyst) was successfully synthesized, characterized, and applied to the photodegradation of Methylene Blue (MB). In addition, the photocatalytic mechanism of MGC was illustrated through modern characterization technology and density functional theory (DFT) computation. The findings of characterization (XRD, SEM-EDX, UV-Vis, XPS) confirmed that MGC was a composite photocatalyst of C3N4-graphite-MoS2 ternary structure, and displayed excellent visible light absorption performance. MGC photocatalyst exhibited the highest degradation efficiencies of MB than that of C3N4 and MoS2 catalyst, and it effectively improved the removal of pollutant. Also, the first-order reaction model suitably described the photocatalytic reaction process. The recycling experiments proved that MGC catalyst possessed remarkable photocatalytic stability in the degradation activities of MB, and the morphology maintained stable after three times of reusing. The ternary composite structure of MGC was conducive to the generation and transfer of the photo-generated electrons and photo-generated holes. Besides, MGC photocatalyst obtained the lowest photoluminescence spectrum intensity, which might decrease the combination probability of photo-induced electrons and holes. Electron spin resonance (ESR) analysis verified that the active radicals of •OH and •O2- measured in photocatalytic reaction probably played an essential part in the degradation of MB. Furthermore, through calculating the band structure, density of states (DOS), and work function, it was illustrated that the two opposite potential barriers forming between graphite, MoS2 and C3N interface effectively accelerated the division of photo-induced electrons and photo-induced holes in MoS2 and C3N4. Then, the recombination probability of photo-induced electrons and holes was reduced, and hence that greatly improved the photocatalytic efficiency of MB.