Supported Au nanoparticles on crystalline carbon nitride for boosted photocatalytic NO oxidation

Photocatalytic oxidation of nitrogen oxide (NO) through molecular oxygen activation offers an appealing solution for addressing air environmental crisis. However, the low activity and selectivity of the oxygen reduction reaction, as well as the NO2 emission from the photolysis of monodentate NO3-, severely restrict the NO photooxidation efficiency. Herein, a photocatalyst tailored for NO oxidation is prepared by depositing gold (Au) nanoparticles onto a crystalline carbon nitride (CCN) support by a facile wet-chemical reduction method. In-situ and quasi in-situ characterizations demonstrate that the Au active sites could facilitate the one-electron activation of oxygen, forming superoxide radical intermediates. The adsorption configuration of NO3- products transitions from a weak monodentate binding mode to a stronger bidentate mode to mitigate the risk of unfavorable photolysis. As a result, an apparent NO removal ratio of 92.8 % within the first 5 min of irradiation at 400 nm wavelength light is achieved over the as-synthesized Au/CCN photocatalyst. The decay rate of k1 over Au/CCN (-0.001 min-1) surpasses the CCN (-0.008 min-1) within 150 min irradiation of the light, indicating higher stability and efficiency of the Au/CCN photocatalyst than that of CCN. This strategy shows the importance of the rational design of the active sites to enhance molecule oxygen activation and reaction intermediates production to solve air pollution remediation due to NOx.