Photocatalytic oxidation mechanism of isoprene over titanium oxide by UV-Vis lights

Isoprene is an important precursor of tropospheric ozone due to its high ozone formation potential and widespread biogenic sources. However, its control technology has not received sufficient attention. Here we investigate the photo-catalytical oxidation performance and mechanism of isoprene over a TiO2 (P25) catalyst. The mean conversion is (46.1 +/- 3.7)% with a corresponding CO2 selectivity of (84.3 +/- 0.3)% in humidified air when irradiated by UV-Vis lights (350-760 nm) in a flow system, with a reactor volume space velocity of 2647 h-1 for 670 ppb isoprene. Relative humidity has little influence on the activity. Electron holes dominantly initiate the oxidation of isoprene, leading to the formation of center dot C5H8, followed by organic peroxides, and other intermediates in the presence of O2 and H2O as supported by results from radical -trapping experiments, as well as in situ surface and gas -phase product analysis. Our results suggest that the P25 is a promising catalyst for removing ambient isoprene.