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Science  13 Mar 2009:
Vol. 323, Issue 5920, pp. 1407
DOI: 10.1126/science.323.5920.1407c

In surface-catalyzed reactions, there are often myriad steps between the first contact of the reagents with the surface and the ultimate desorption of the final products. Characterization of these intermediate stages can help to unravel the reaction mechanism and thereby aid development of improved catalysts. Although scanning tunneling microscopy (STM) has been used to follow a number of reactions of adsorbed species on metal surfaces, there are few examples of such studies on metal oxides. Matthiesen et al. studied the oxidation by O2 of adsorbed hydrogen atoms on a (110) surface of titanium dioxide using time-lapsed STM images and density functional theory calculations. The data provide evidence for several intermediate species—HO2, H2O2, and H3O2—on the way to the formation of water. The coadsorption of water helps to promote hydrogen diffusion and thus allow these reactions to proceed at low temperatures (200 K). — PDS

ACS Nano 3, 10.1021/nn8008245 (2009).

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