title: A highly efficient g-C3N4/SiO2heterojunction: the role of SiO2in the enhancement of visible light photocatalytic activity.
abstract: SiO2, an insulator, hardly has any photocatalytic acitivity due to its intrinsic property, and it is generally used as a hard template to increase the surface area of catalysts. However, in this work, we found that the surface state of the insulator SiO2can promote the migration of photogenerated charge carriers, leading to the enhancement of the photooxidation ability of graphitic carbon nitride (g-C3N4). A one-pot calcination method was employed to prepare g-C3N4/SiO2composites using melamine and SiO2as precursors. The composites present considerably high photocatalytic degradation activities for 2,4-dichlorophenol (2,4-DCP) and rhodamine B (RhB) under visible light (λ > 420 nm) irradiation, which are about 1.53 and 4.18 times as high as those of bulk g-C3N4, respectively. The enhancement of the photocatalytic activity is due to the fact that the introduction of the insulator SiO2in g-C3N4/SiO2composites can greatly improve the specific surface area of the composites; more importantly, the impurity energy level of SiO2can help accelerate the separation and transfer of electron-hole pairs of g-C3N4. Electron paramagnetic resonance (EPR) spectroscopy and trapping experiments with different radical scavengers show that the main active species of g-C3N4are superoxide radicals, while holes also play a role in photodegradation. For g-C3N4/SiO2-5, besides superoxide radicals and holes, the effect of hydroxyl radicals was greatly improved. Finally, a possible mechanism for the photogenerated charge carrier migration of the g-C3N4/SiO2photocatalyst was proposed.
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hao
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Xiuxiu
authors.initials: X
authors.lastname: Niu
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Changshun
authors.initials: C
authors.lastname: Nie
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Simeng
authors.initials: S
authors.lastname: Hao
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Zou
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Jiangman
authors.initials: J
authors.lastname: Ge
authors.affiliation: National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China. chendaimei@cugb.edu.cn.
authors.forename: Daimei
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China. yaowq@tsinghua.edu.cn.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Yao