Urea-modified carbon quantum dots as electron mediator decorated g-C3N4/WO3 with enhanced visible-light photocatalytic activity and mechanism insight

A novel urea modified carbon quantum dots (NCDs) decorated g-C3N4/WO3 Z-scheme heterojunction was prepared through in situ calcination and physical deposition way in the article. The analysis data of UV-vis spectroscopy demonstrated that the introduction of NCDs and the construction of g-C3N4/WO3 Z-scheme heterojunction can significantly improve the visible-light utilization. The enhanced photocurrent response and the reduced fluorescence intensity indicated the recombination of photogenerated electron-hole pairs in g-C3N4/WO3/NCDs composites is significantly inhibited. In addition, the results of cyclic experiment and the XRD diffraction peak of g-C3N4/WO3/NCDs before and after the experiment declared that g-C3N4/WO3/NCDs possess strong structural stability. Obviously, the excellent photocatalytic performance of g-C3N4/WO3/NCDs can be ascribed to the above three experimental processes. Experimental analysis of free radical capture confirmed that superoxide ion radicals (center dot O-2(-)) was the main active component in photocatalytic degradation, and the possible degradation mechanism of g-C3N4/WO3/NCDs was proposed.