Bindung, Aktivierung und Dissoziation von Sauerstoff an dotierten Oxiden

Abstract

Ladungstransfer in Gegenwart von Dotanden ist auch für die Adsorption und Aktivierung kleiner Moleküle wie O2 relevant. Rastertunnelmikrokopie und DFT‐Rechnungen lieferten Hinweise auf die Bildung stark gebundener Superoxo‐Spezies auf chemisch inerten, Mo‐dotierten CaO‐Filmen (siehe Bild). Diese Sauerstoff‐Oberflächenspezies zeigt eine hohe Tendenz zur Dissoziation. Dotanden könnten auch bei der Aktivierung von Kohlenwasserstoffen an inerten Oxiden wichtig sein.

Controlling the charge state of single Mo dopants in a CaO film

“…6 In addition, Mo dopants were found to promote the dissociation of O 2 on the CaO surface, a process of pivotal importance for many oxidation reactions. 7 These examples underline the impact of doping in heterogeneous catalysis and should motivate concerted research activities on how to tailor the physical and chemical properties of wide-gap oxides by means of doping. 8 The nature of dopants in oxide materials has been comprehensively studied by theoretical means, [9][10][11][12] while experimental verification of the derived concepts is still in its infancy.…”

Phonon-Mediated Electron Transport through CaO Thin Films

“…The films contained traces of Mo that entered the oxide via atom diffusion from the metal substrate during annealing. The Mo ions are respon sible for a strong electron-donor character of the material, which controls its reactivity towards electronegative adsor bates, such as oxygen and gold [16]. Because of the insulating character of CaO, low-bias STM images could be exclusively obtained on ultrathin layers, while bias values outside the oxide gap are required to stabilize the tip on thicker films (>10 ML).…”

“…In the latter regime, electron transport likely proceeds via ballistic or hopping motion through the oxide CB and not via tunnel ing through the gap region. The operation window for STM is further restricted by a gradual upshift of the CB edge from 2.5 to 4 V when increasing the film thickness to 25 ML [16]. The shift relates to an interface dipole that arises from an electron exchange between Mo donors in the CaO matrix and the metal support.…”

Bharat Ratna: C. N. R. Rao / Alwin Mittasch Special Prize: P. Jacobs / Honorary Doctorate: J. Sauer

“…Sauer’s research interests are centered on the quantum chemistry of large chemical systems and its applications to solid catalysts and adsorbents, heterogeneous catalysis, and oxide clusters. He has reported in Chemistry—A European Journal on the thermal activation of methane,3a and in Angewandte Chemie on oxygen activation 3b. Sauer is on the International Advisory Board of ChemCatChem .…”