Construction of Novel Z-Scheme N-CQDs/Sn3O4 Heterojunction for Excellent Photocatalytic Degradation of Organic Pollutant

Abstract

The construction of heterojunction can improve the transfer and separation efficiency of photogenerated electron-hole pairs, which is conducive to the photocatalytic removal of pollutant. In this work, a novel Z-scheme N-CQDs (Nitrogen-doped carbon quantum dots)/Sn3O4 heterojunction was synthesized by a facile hydrothermal method. N-CQDs were evenly dispersed on the surface of Sn3O4, which is helpful for the formation of heterostructured interface between N-CQDs and Sn3O4. As-prepared N-CQDs/Sn3O4 heterojunctions exhibited superior visible light photocatalytic activity to pure Sn3O4 for the degradation of methyl orange (MO). Especially, the 1.25% N-CQDs/Sn3O4 sample displayed the optimal photocatalytic activity with a 78% removal efficiency of MO under visible light illumination for 80 min. The improvement of photocatalytic behavior could be mainly attributed to the formation of Z-scheme heterostructure between N-CQDs and Sn3O4 interfaces, which not only increases the photoinduced charges separation efficiency but also reserves the high energy electrons and high energy holes, as well as the higher specific surface area. Active species trapping experiments demonstrated that superoxide radical and holes are important active species during the photocatalytic degradation process. This work provides a novel insight into the design and synthesis of Sn3O4-based heterojunction for removal of organic pollutants.