Boosting exciton dissociation and molecular oxygen activation by in-plane grafting nitrogen-doped carbon nanosheets to graphitic carbon nitride for enhanced photocatalytic performance

Shanshan Dong; Chao Liu; Yinguang Chen

doi:10.1016/j.jcis.2019.06.021

Boosting exciton dissociation and molecular oxygen activation by in-plane grafting nitrogen-doped carbon nanosheets to graphitic carbon nitride for enhanced photocatalytic performance

J Colloid Interface Sci. 2019 Oct 1:553:59-70. doi: 10.1016/j.jcis.2019.06.021. Epub 2019 Jun 7.

Authors

Shanshan Dong¹, Chao Liu¹, Yinguang Chen²

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.
² State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China. Electronic address: yinguangchen@tongji.edu.cn.

PMID: 31185384
DOI: 10.1016/j.jcis.2019.06.021

Abstract

The metal-free graphitic carbon nitride (g-C₃N₄) polymer is a promising photocatalyst for energy production and environmental protection. However, attempts to intrinsically improve its low activity in photooxidation are rarely effective for the poor molecular oxygen (O₂) activation. Here we report a synthesis of directionally nitrogen-doped in-plane metal-free heterostructure, through coplanar grafting nitrogen-doped carbon nanosheets (NDCN) to g-C₃N₄. The in-plane grafted NDCN not only promoted exciton dissociation and charge transfer but also enhanced activating O₂ to reactive oxygen species, including superoxide radicals (O₂^-) and H₂O₂. The optimal C₃N₄-NDCN coplanar heterojunction (C₃N₄-NDCN-3) photocatalytically degraded 96.3% of sulfamethoxazole (SMX) under visible light irradiation at a low light intensity of 14.5 mW cm^-2 in 4 h, whose SMX degradation rate was 37.7-fold higher than that of pure g-C₃N₄. Furthermore, C₃N₄-NDCN-3 exhibited 95.3% removal of SMX under sunlight irradiation (59.8 mW cm^-2) in 1 h, higher than the 58.0% of pristine g-C₃N₄. First-principles calculations and material characterizations demonstrated that the coplanar NDCN served as electron sink and catalytic center for hot-electron involved O₂ activation. The improved charge carrier separation and O₂ activation promoted generation of photoexcited hole and superoxide for photocatalytic degradation of SMX. The design strategy in this work inspires a new approach for high-performance polymer photocatalysts in solar energy storage and environmental remediation.

Keywords: Carbon nitride; Exciton dissociation; Molecular oxygen activation; Nitrogen-doped in-plane heterostructure; Reactive oxygen species.