Catalyst Surface Species Imaged | December 15, 2008 Issue - Vol. 86 Issue 50 | Chemical & Engineering News
Volume 86 Issue 50 | p. 30 | Concentrates
Issue Date: December 15, 2008

Catalyst Surface Species Imaged

Researchers have imaged two intermediates proposed to play key roles in oxygen and water interactions on catalyst surfaces
Department: Science & Technology
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Surface Shot
O2 (aqua) reacts with surface OH groups (blue and yellow) on TiO2 (red and blue, left) to form a previously undetected HO2 species (aqua and yellow, center). HO2 dissociates to an adsorbed O atom and an OH group bound to a Ti atom.
Credit: Adapted from J. Phys. Chem. C
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Surface Shot
O2 (aqua) reacts with surface OH groups (blue and yellow) on TiO2 (red and blue, left) to form a previously undetected HO2 species (aqua and yellow, center). HO2 dissociates to an adsorbed O atom and an OH group bound to a Ti atom.
Credit: Adapted from J. Phys. Chem. C

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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