In-situ Construction of Sulfur-doped g-C3N4/defective g-C3N4 Isotype Step-scheme Heterojunction for Boosting Photocatalytic H2 Evolution

The rational construction of a high-efficiency stepscheme heterojunctions is an effective strategy to accelerate the photocatalytic H2. Unfortunately, the variant energy-level matching between two different semiconductor confers limited the photocatalytic performance. Herein, a newfangled graphitic-carbon nitride(g-C3N4)based isotype step-scheme heterojunction, which consists of sulfurdoped and defective active sites in one microstructural unit, is successfully developed by in-situ polymerizing N,N-dimethylformamide(DMF) and urea, accompanied by sulfur(S) powder.Therein, the polymerization between the amino groups of DMF and the amide group of urea endows the formation of rich defects. The propulsive integration of S-dopants contributes to the excellent fluffiness and dispersibility of lamellar g-C3N4. Moreover, the developed heterojunction exhibits a significantly enlarged surface area, thus leading to the more exposed catalytically active sites. Most importantly, the simultaneous introduction of S-doping and defects in the units of g-C3N4also results in a significant improvement in the separation, transfer and recombination efficiency of photo-excited electron-hole pairs. Therefore, the resulting isotype step-scheme heterojunction possesses a superior photocatalytic H2evolution activity in comparison with pristine g-C3N4. The newly afforded metal-free isotype step-scheme heterojunction in this work will supply a new insight into coupling strategies of heteroatoms doping and defect engineering for various photocatalytic systems.