Revealing the critical roles of silver species on TNT film for photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation: From mechanism study to scaled-up test

Ag nanoparticles are commonly employed as co-catalysts to promote photocatalytic reactions. In addition to their apparent roles as electron traps and catalytic active sites, nanoparticulate Ag can also generate hot electrons under visible light irradiation, which endows visible light photocatalytic activity to its supporting material. On the other hand, Ag0 can be easily converted to Ag2O, however, few studies focus on its formation and roles during the photocatalytic process. In this work, we have successfully fabricated and optimized the preparation procedures of titania nanotube (TNT) and Ag species deposited TNT to get the optimum photochemical activities of Ag modified TNT. Specifically, the roles of Ag species on TNT film have been investigated by photoelectrochemical (PEC) measurements and photocatalytic decomposition of volatile organic pollutants under UV or visible light irradiation. Toluene (30 ppm) can be effectively decomposed (∼83.3%) and mineralized (∼70.7%) by Ag species modified TNT in 3 h under UV–visible light irradiation, while the degradation and mineralization ratios are only about 60.0% and 33.3% under visible light irradiation. The results demonstrate that appropriate Ag/Ag2O ratio on TNT film are crucial for improving PEC and photocatalytic performance, and the interconversion between Ag and Ag2O influences the photochemical stability of Ag/TNT film. The scaled-up tests (∼1.0 m3 reactor) on the degradation of low concentration of toluene and formaldehyde prove that the optimized Ag/TNT film can be considered as a promising photocatalyst for indoor air purification.