Mechanism study on TiO2 inducing O2- and OH radicals in O3/H2O2 system for high-efficiency NO oxidation

To achieve high NO oxidation efficiency, excessive O 3 must be used, which would lead to the high cost and escape of ozone. Herein, we adopted low cost and environmental-friendly TiO 2 as the catalyst of low concentration O 3 and H 2 O 2 system for high-efficiency NO x oxidation. The Ti sites on TiO 2 were the deprotonation sites of H 2 O 2 and H 2 O into Ti-OOH and Ti-OH species, respectively. We found that the surface of rutile phase TiO 2 had a low concentration Ti-OOH component but a large amount of Ti-OH after contacting with H 2 O 2 solution, thus lots of ·OH and a few O 2 − radicals formed with introducing O 3 molecules. H 2 O 2 solution induced the formation of a large amount of Ti-OOH and Ti-OH species on the anatase phase TiO 2 surface, thus lots of O 2 − generated in the O 3 /H 2 O 2 system. O 2 − and O H radicals could efficiently oxidize NO, in which O 2 − radicals could oxidize NO to NO 3 − in one step with high selectively. Therefore, anatase TiO 2 had better performance in NO x oxidation than rutile phase TiO 2 . The effect of temperature and SO 2 concentration on NO oxidation was also investigated, the results showed that TiO 2 -A/O 3 /H 2 O 2 system promoted NO oxidation at a low temperature and a low concentration of SO 2 .