Band-gap engineering of layered covalent organic frameworks via controllable exfoliation for enhanced visible-light-driven hydrogen evolution. (24th January 2020)

• Record Type: Journal Article
• Authors: Li, Lin; Zhu, Yuanzhi; Gong, Ning; Zhang, Wen; Peng, Wenchao; Li, Yang; Zhang, Fengbao; Fan, Xiaobin
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 4(2020)
• Page Start: 2689
• Page End: 2698
• Publication Date: 2020-01-24
• Subjects: Covalent organic frameworks -- Band-gap engineering -- Defect states -- Water splitting -- Visible-light-driven hydrogen evolution; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2019.11.049
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Covalent organic frameworks (COFs) has become known as a promising organic photocatalyst for hydrogen evolution reaction (HER) because of its highly designable structure at the molecular level and other advantages related to the photocatalytic reaction. Here, we report a facile approach to prepare few-layer COFs nanosheets from a typical layered COF (covalent triazine frameworks, CTFs) v ia intercalation and exfoliation with H2 SO4 and (NH4 )2 S2 O8 . Both the experiments and DFT calculations revealed the exfoliated CTFs nanosheets owned tunable optical and electronic properties because of the introduced defect states. It can not only narrow the bandgap for improved visible light absorption, but also suppress the radiative electron-hole recombination. Besides, the ultrathin structure can shorten the diffusion length of the photoexcited electrons and provide more active sites. As a result, the exfoliated nanosheets (especially the FL-CTF-2 with an apparent quantum yield of 11.14%) show much-improved performance in visible-light-driven HER compared with bulk CTFs. This work provides a new route to tail the photoelectric properties of COFs and may promote their applications in solar energy capture and conversion. Highlights: The CTFs nanosheets were prepared by controllable exfoliation. H2 SO4 and (NH4 )2 S2 O8 was used as intercalant and mild oxidant, respectively. The CTFs nanosheets have tunable bandgap due to the introduced defects. The CTFs nanosheets show much-improved performance in visible-light-driven HER.