Highly enhanced visible-light photocatalytic NOₓ purification and conversion pathway on self-structurally modified g-C₃N₄ nanosheets

The unmodified graphitic carbon nitride (g-C₃N₄) suffers from low photocatalytic activity because of the unfavourable structure. In the present work, we reported a simple self-structural modification strategy to optimize the microstructure of g-C₃N₄ and obtained graphene-like g-C₃N₄ nanosheets with porous structure. In contrast to traditional thermal pyrolysis preparation of g-C₃N₄, the present thermal condensation was improved via pyrolysis of thiourea in an alumina crucible without a cover, followed by secondary heat treatment. The popcorn-like formation and layer-by-layer thermal exfoliation of graphene-like porous g-C₃N₄ was proposed to explain the formation mechanism. The photocatalytic removal performance of both NO and NO₂ with the graphene-like porous g-C₃N₄ for was significantly enhanced by self-structural modification. Trapping experiments and in-situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) measurement were conducted to detect the active species during photocatalysis and the conversion pathway of g-C₃N₄ photocatalysis for NOₓ purification was revealed. The photocatalytic activity of graphene-like porous g-C₃N₄ was highly enhanced due to the improved charge separation and increased oxidation capacity of the ·O₂⁻ radicals and holes. This work could not only provide a novel self-structural modification for design of highly efficient photocatalysts, but also offer new insights into the mechanistic understanding of g-C₃N₄ photocatalysis. Copyright © 2018 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.