Nitrogen defect structure and NO+ intermediate promoted photocatalytic NO removal on H2 treated g-C3N4

[Display omitted] •The photocatalytic performance of g-C3N4 is tuned via effect of N-Defects.•Experimental and theoretical calculations were highly combined.•The effects of nitrogen defects on the electronic structure were investigated.•The NO+ reaction intermediate was formed on the N defects sites.•The pivotal roles of N-defects in g-C3N4 on reaction mechanism were revealed. By heating g-C3N4 powder in the hydrogen atmosphere, nitrogen defects were introduced into the framework of g-C3N4 where the nitrogen atoms in g-C3N4 were reacted and partially removed with hydrogen. The effects of nitrogen defects on the electronic structure, optical properties, generation of reactive oxygen species and photocatalytic NO oxidation of g-C3N4 were investigated by combining experimental characterization and DFT theoretical calculations. The N defect is located at N2C sites and can be tuned by the H2 treating temperature. The obtained N defective g-C3N4 products possessed narrower bandgap adjusted by surface N defects and were able to promote the separation of photoexcited charge carries and produce reactive oxygen species more efficiently than pristine g-C3N4. The NO+ reaction intermediate was formed on the N defects sites and enabled an accelerated photocatalytic reaction that contributed to enhanced photocatalytic NO removal. The NO removal ratio on N defects g-C3N4 obtained at 600 °C (CH-H-600) was 2.6 times that of pristine g-C3N4 under visible light irradiation. The present work could provide new insights into the understanding of the role of N-defects in g-C3N4 and application of photocatalytic technology for efficient air purification.