Issue Date: December 15, 2008
Catalyst Surface Species Imaged
Researchers at Pacific Northwest National Laboratory have imaged two never-before-seen chemical intermediates that have been proposed to play key roles in the interconversion of oxygen and water on catalyst surfaces (J. Phys. Chem. C, DOI: 10.1021/jp807030n). The study broadens understanding of surface reaction mechanisms in photocatalyzed H2O splitting and other reactions of H2O and O2 on solids. Igor Lyubinetsky, Yingge Du, and coworkers prepared partially hydroxylated titania—a model photocatalyst—by exposing the crystal to H2O, which dissociates at crystal defect sites. The group then treated the prepared surface with O2. On the basis of scanning tunneling microscopy images recorded before and after O2 exposure, along with calculations that aid in interpreting the images, the researchers report the first observation of adsorbed hydroperoxyl, HO2, which they say forms directly upon reaction of O2 with a single OH group that bridges two titanium atoms in the row beneath. HO2 can then dissociate to form an adsorbed O atom and the other elusive species: a Ti-bound OH group.
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