Abstract
Graphitic carbon nitride (g-C3N4) has attracted much attention because of its potential for application in solar energy conservation. However, the photocatalytic activity of g-C3N4 is limited by the rapidly photogenerated carrier recombination and insufficient solar adsorption. Herein, fluorinated g-C3N4 (F-g-CN) nanosheets are synthesized through the reaction with F2/N2 mixed gas directly. The structural characterizations and theoretical calculations reveal that fluorination introduces N vacancy defects, structural distortion and covalent C-F bonds in the interstitial space simultaneously, which lead to mesopore formation, vacancy generation and electronic structure modification. Therefore, the photocatalytic activity of F-g-CN for H2 evolution under visible irradiation is 11.6 times higher than that of pristine g-C3N4 because of the enlarged specific area, enhanced light harvesting and accelerated photogenerated charge separation after fluorination. These results show that direct treatment with F2 gas is a feasible and promising strategy for modulating the texture and configuration of g-C3N4-based semiconductors to drastically enhance the photocatalytic H2 evolution process.
Highlights
IntroductionA great many strategies have been explored to improve its photocatalytic performance, including morphology design, elemental doping, heterojunction construction, nanocomposite hybridization and photosensitizer decoration [9,10,11]
The fluorination temperature is a crucial parameter in controlling the morphology and the fluorine content of g-C3 N4 ; g-C3 N4 was fluorinated at 120, 150 and 180 ◦ C, labeled as fluorinated g-C3N4 (F-g-CN)-120, F-g-CN-150 and F-g-CN-180, respectively, to investigate the photocatalytic activity
Based on the first-principle density functional theory (DFT) calculations, detachment of bridged N atoms in tri-s-triazine from the g-C3 N4 framework occurred during fluorination, resulting in N vacancy defects and covalent C-F bonds at the edge of the fragment
Summary
A great many strategies have been explored to improve its photocatalytic performance, including morphology design, elemental doping, heterojunction construction, nanocomposite hybridization and photosensitizer decoration [9,10,11]. Among these various strategies, it has been acknowledged that the introduction of non-metal heteroatoms is an effective method for enhancing the photocatalytic activity of semiconductors by expanding the absorption range of the solar spectrum, as highlighted in the pioneering study by Asahi et al [12]. F-doped, nanostructured carbons have attracted tremendous interest and obtained https://doi.org/10.3390/
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