Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Heterogeneous catalysis I

O 15.2: Vortrag

Montag, 26. März 2012, 16:15–16:30, MA 042

Oxygen dissociation on pristine and doped CaO films — •Yi Cui, Niklas Nilius, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany

Dissociation of O2 is often the initial step for oxidation reactions on supported metal catalysts. As the dissociation cross section is low on the surface of many wide-gap oxides, we have tried to improve the performance by inserting impurity ions that act as electron donors. For this purpose, Mo-doped CaO films have been prepared and analyzed with respect to their O2 adsorption behavior, using scanning tunneling microscopy. Whereas at room temperature, both the pristine and doped films spontaneously dissociate oxygen, intact O2 molecules are detected on pristine CaO upon exposure at 100 K. These molecules can be split in a controlled manner by electron injection from the STM tip. On the doped films, on the other hand, oxygen dissociation takes place at any temperature, suggesting that a spontaneous electron transfer from the Mo dopants into the anti-bonding oxygen orbitals triggers the decay of the molecule.