Abstract: The gas-solid heterogeneous photocatalytic oxidation using TiO₂/UVwas conducted, and it was found that the degradation efficiency of NO_x in air was very high, reaching 97% in the ranges of experimental concentration. Some factors affecting NOphotocatalytic destruction were investigated. The adsorption of NO_x on TiO₂ thin film surface in the dark, photocatalytic reaction kinetics and mechanism were studied, and some important conclusions were drawn. The product of NO_x photocatalysis was detected to be HNO₃ by FTIR. The greater part of HNO₃ was adsorbed on TiO₂ surface, causing catalyst deactivation, but when the catalyst was washed by water, its activity was regenerated as usual. In the end, NO_x photocatalytic oxidation experiments were performed under sunlight irradiation, and NO_x photocatalytic degradation yields remained high. The results showed that this process has potential applications to the elimination of NO_x from the air.

Key words: NO_x, Photocatalysis, TiO₂, Gas-phase reaction, Kinetics and mechanism