Construction of C@WS2/g-C3N4 Z-scheme photocatalyst with C film as an effective electron mediator and its enhanced degradation of 2,4-dichlorophenol under visible light

A novel Z-scheme heterojunction C@WS2/g-C3N4 composite was prepared with carbon as a bridge for improving the photocatalytic property. The results of composition and structure studies demonstrate that the introduced carbon was deposited on the surface of WS2 with a film form in the ternary composites. The analysis of optical and photo-electrochemical properties reveals that the carbon film played as an electron-mediator in the ternary composites and could improve the separation and transportation of photogenerated charge. Meanwhile, it could change the pathway of photogenerated electrons between WS2 and g-C3N4, thereby constructing a Z-scheme heterojunction for maintaining the redox ability of photogenerated charge. The ternary 2%-C@WS2/g-C3N4 composite exhibited an excellent photodegradation rate towards 2,4-dichlorophenol (2,4-DCP) under visible light irradiation, which was 3.15 and 3.06 times of the pure g-C3N4 and binary WS2/g-C3N4 composite, respectively. Besides, the degradation pathway of 2,4-DCP and photocatalytic degradation mechanisms were investigated and discussed in detail. The generated ·O2--, ·OH and h+ by ternary composites could promote the dechlorination reaction of 2,4-DCP effectively and decompose it into smaller organic molecules. This work extends the design of g-C3N4-based 2D/2D heterojunction or Z-scheme photocatalysts to remediate the environment.