Tuning the strength of built-in electric field in 2D/2D g-C3N4/SnS2 and g-C3N4/ZrS2 S-scheme heterojunctions by nonmetal doping
Bicheng Zhu, Haiyan Tan, Jiajie Fan, Bei Cheng, Jiaguo Yu, Wingkei Ho
Abstract
Single photocatalysts usually exhibit unsatisfactory performance due to the serious recombination of photogenerated electron‒hole pairs. Combining two photocatalysts to construct S-scheme heterojunction could solve this problem. In S-scheme mechanism, the interfacial built-in electric field (IEF) provides a vital driving force for efficient charge separation. Modifying the IEF is a feasible strategy to further improve the photocatalytic activity. Herein, a novel idea of tuning the strength of IEF in 2D/2D graphitic carbon nitride (g-C3N4)/MS2 (M = Sn, Zr) S-scheme heterojunctions by nonmetal doping was developed by employing density functional theory calculation. Three nonmetal elements (O, P, and S) were severally introduced into g-C3N4/MS2 composites. Charge density difference suggested that O and S doping led to increased interfacial electron transfer, while P doping had minimal influence. As expected, the calculated field strength of O- and S-doped g-C3N4/MS2 composites was significantly larger than that of pristine and P-doped g-C3N4/MS2 composites. Therefore, O and S doping endowed g-C3N4/MS2 S-scheme heterojunctions with enhanced IEF and more thorough charge transfer. Correspondingly, the experimentally synthesized O-C3N4/SnS2 composite exhibited better photocatalytic H2-production activity than g-C3N4/SnS2 composite. This work proposed an original idea of employing proper nonmetal doping to magnify the advantage of S-scheme heterojunction in accelerating charge separation.