Synergetic assembly of a molybdenum disulfide/carbon quantum dot heterojunction with enhanced light absorption and electron transfer di-functional properties for photocatalysis

Cocatalysts play important roles in enhanced efficiency of heterojunctions that their selection and synthesis are essential. Carbon quantum dots (CQDs), as one of important cocatalysts, often suffer from complicated synthesis, low functionality, and low photocatalytic efficiency issues that need to be solved effectively. In this study, we constructed a new molybdenum disulfide/N,S-doped carbon quantum dots (MoS2/N,S-CQDs) heterojunction with enhanced light absorption and electrons transfer di-functional properties via a facile one-pot hydrothermal method. The MoS2/N,S-CQDs simultaneously degraded 99.8% of methylene blue (MB) and 95.1% of malachite green (MG) in an actual water system (Tianjin Lake) under simulated sunlight irradiation for 120 min. The heterojunction showed obvious efficiencies under both infrared light (degraded 83.8% of MG after 120 min) and visible light (90.1% MG after 120 min) irradiation. According to energy level and density functional theory (DFT) analyses, the electrons in MoS2/N,S-CQDs were demonstrated that transferred from N,S-CQDs to MoS2 interfaces, and the light-absorption range of the composites was effectively extended to near-infrared ranges owing to excellent up-conversion fluorescence property of the N,S-CQDs. We believe that the facile synthetic technique and effective multifunctional properties of composite have the potential for further research on CQDs-based heterojunctions and their industrial applications.