Cyano/Hydroxyl Groups Co-Functionalized g-C 3 N 4 for Photocatalytic NO Removal: A Synergistic Strategy towards Inhibition of Toxic Intermediate NO 2.

Photocatalytic NO removal is usually accompanied by the generation of NO₂, an intermediate with a higher toxicity than NO. Therefore, it is critically important to develop new photocatalysts capable of NO selective conversion. Herein, we report on the synergistic roles of cyano and hydroxyl functional groups in photocatalytic NO removal. According to the results, the NO₂ production efficiencies on cyano/hydroxyl-group-modified g-C₃N₄ (DCN-O-R) was limited to 4.8%, which was lower than that of cyano-group-modified g-C₃N₄ (DCN, 38.6%) and pure g-C₃N₄ (CN, 50.0%). Meanwhile, the photocatalytic NO conversion efficiency over DCN-O-R was higher than that of DCN and g-C₃N₄. It was found that the insertion of cyano groups favorably changes the energy band of g-C₃N₄ towards the generation of •O₂⁻. NO can only be oxidized to NO₂ by the photogenerated holes. When NO₂ is adsorbed on the surface of hydroxyl groups, it can be further oxidized to the product NO₃⁻ by •O₂⁻. The synergistic effect of bifunctional groups regulates the conversion pathway from NO→NO₂ to NO→NO₂→NO₃⁻. This work provides a strategy to abate toxic intermediates during the NO removal process, underlining the importance of surface/interface molecular engineering in regulating catalytic reaction pathways. [ABSTRACT FROM AUTHOR]