Probing the nature of active species in TiO2 photocatalysis by Spin trapping ESR experiments

The aim of this work is to probe the production of OH radicals by spin trapping ESR experiments with DMPO over different TiO2 nanoparticles, with relevant differences in the nature of the surface hydroxyl populations. The production rate of DMPO-OH adduct varies greatly, with an anatase TiO2 sample (N100 Satchleben) producing virtually no DMPO-OH, whereas TiO2 Merck shows the highest production. Surface fluorination increases significantly the DMPO-OH production on P25 and N100, while only a minor enhancement is observed on Merck TiO2. The DMPO-OH production correlates with phenol degradation rates. The possible relationships between the DMPO-OH production and the surface features of the different TiO2 will be addressed.