Promoting the photocatalytic NO oxidation activity of hierarchical porous g-C₃N₄ by introduction of nitrogen vacancies and charge channels

Sluggishcharge kinetics and moderate adsorption–desorption ability of gas molecules aremajor limitations for photocatalytic NOx elimination of bulk g-C₃N₄. A hierarchical porous g-C₃N₄ photocatalystmodified with N vacancies and charge channels (KCNN) was prepared by thermalpolymerisation in KCl medium followed by quenching to increase thephotocatalytic efficiency. The optimized KCNN sample exhibits highly enhancedphotocatalytic NO removal rate (70.5%), which is superior to those of bulk g-C₃N₄ (38.1%),porous g-C₃N₄ (54.5%) and K-doped g-C₃N₄ (58.6%),respectively. X-ray photoelectron spectroscopy and electron paramagneticresonance data reveal the successful formation of N vacancy in g-C₃N₄ framework.The enhanced activity of KCNN is ascribed to the enlarged surface area,expanded light absorption, low charge recombination efficiency and strongoxidation capability, respectively. In situ DRIFTS and density functionaltheory results suggest that the introduction of N vacancies and K⁺ ionsenable control over NO adsorption and activation, leading to the implementationof a preferred pathway (NO → NO⁺ → NO₃⁻) and reduction in the emission of toxicintermediates. This work presents a potential idea for improving the chargetransfer of layered materials and optimising thediffusion/adsorption/activation of gas molecules for photocatalytic NOoxidation. Copyright © 2023 Elsevier B.V. All rights reserved.