Gas-Phase Fluorination of g-C₃N₄ for Enhanced Photocatalytic Hydrogen Evolution

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.