Scanning tunneling microscopy and density functional theory have been used to investigate the details of O2 dissociation leading to the formation of oxygen adatom (Oa) pairs at terminal Ti sites. An intermediate, metastable Oa-Oa configuration with two nearest-neighbor O atoms is observed after O2 dissociation at 300 K. The nearest-neighbor Oa pairs are destabilized by Coulomb repulsion of charged Oa‘s and separate further along the Ti row into energetically more favorable second-nearest neighbor configuration. The potential energy profile calculated for O2 dissociation on Ti rows and following Oa‘s separation strongly supports the experimental observations. Furthermore, our results suggest that the itinerant electrons associated with the O vacancies (VO) are being utilized in the O2 dissociation process at the Ti row. Experimentally this is supported by the observation that not all VO‘s can be healed by O2 exposure at 300 K, as some VO‘s becoming less reactive due to supplying certain charge to Oa‘s. Further, theoretical results show that at least two oxygen vacancies per O2 molecule are required in order for the O2 dissociation at the Ti row to become viable.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry