Enhanced photodegradation ability and mechanism study of g-C3N4 by dual modified with sulfur-containing quantum dots doping after oxidization

Abstract A series of dual modified g-C3N4 (CN) composites were synthesized by integrating oxidation and doping quantum dots. Oxidation made the valance band and conduction band of the modified CN shifted to the opposite direction, resulting in higher redox activity. Meanwhile, the oxidized CN (O-CN) is more conducive to the deposition of SCNQDs due to electrostatic interaction. The introduction of sulfur-containing carbon nitride quantum dots (SCNQDs) can improve the light trapping ability and the separation efficiency of photogenerated charge-carriers. Moreover, quantum confinement effect of SCNQDs contributes to the upshift of valance band to enhance the reduction ability of composite (CN/SCNQDs), even though the band gap was not changed. The synergistic effect of dual modification made the composite (10:1-O-CN/SCNQDs) own the highest photodegradation rate of 1.43 mg/ (h·100 mg catalyst), which was 4.5, 2.0 and 1.9 times of CN, CN/SCNQDs and O-CN, respectively. Photodegradation mechanism of the composite was inferred that holes and superoxide radical played primary roles, whereas hydroxyl radical showed neglect effect. This work may provide some beneficial ideas for constructing high-performance co-modified organic photocatalysts.