Issue Date: February 18, 2008
Oxygen Dissociates Unevenly On Surface
Titanium dioxide catalyzes a range of reactions involving O2, including organic pollutant degradation and hydrogen production. In work that helps illuminate the surface chemistry of O2 on TiO2, a team led by physicist Igor Lyubinetsky at Pacific Northwest National Laboratory has found that when O2 dissociates and adsorbs onto a TiO2 surface, energy is distributed unequally between the individual oxygen atoms (J. Phys. Chem. C, DOI: 10.1021/jp077677u). The team used scanning tunneling microscopy to take pictures of a TiO2 surface before and after exposure to O2. O2 dissociates at vacancies on the surface, and one O atom fills a spot by forming two Ti-O bonds. Instead of landing on an adjacent site, the second O atom takes excess bond-formation energy from the first atom, converts it into kinetic energy, and skitters away to land one or two lattice spaces over. The authors speculate that such hyperthermal, mobile O atoms help account for the reactivity of TiO2-catalyzed systems.
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