Gas-Phase Fluorination of g-CN for Enhanced Photocatalytic Hydrogen Evolution.

Graphitic carbon nitride (g-CN) has attracted much attention because of its potential for application in solar energy conservation. However, the photocatalytic activity of g-CN is limited by the rapidly photogenerated carrier recombination and insufficient solar adsorption. Herein, fluorinated g-CN (F-g-CN) nanosheets are synthesized through the reaction with F/N 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 H evolution under visible irradiation is 11.6 times higher than that of pristine g-CN because of the enlarged specific area, enhanced light harvesting and accelerated photogenerated charge separation after fluorination. These results show that direct treatment with F gas is a feasible and promising strategy for modulating the texture and configuration of g-CN-based semiconductors to drastically enhance the photocatalytic H evolution process.