Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)

O 41.26: Poster

Tuesday, March 23, 2010, 18:30–21:00, Poster B1

Reduction and Reoxidation of Thin NiO Films by CO and O₂ — •Oliver Höfert, Michael Peter Andreas Lorenz, Regine Streber, Wei Zhao, Karin Gotterbarm, Andreas Bayer, Christian Papp, and Hans-Peter Steinrück — Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen

NiO is one important material in heterogeneous catalysis. Surface defects and dislocations are considered to be the active sites; furthermore the size of particles influences the catalysts activity. We studied the reactivity of different thin NiO films on Pd(100) by in situ XPS applying synchrotron radiation at BESSY II. Due to the large lattice mismatch of 7.8% between NiO and Pd, NiO films on Pd(100) are expected to exhibit many defects such as dislocations leading to a large number of potentially active sites. To determine the reactivity of different NiO films we studied their sensitivity towards CO oxidation. Our XPS data revealed that NiO films in the submonolayer regime are indeed reduced to metallic Ni by exposure to CO at 400 K. In contrast, closed layers of NiO show a significantly lower tendency towards CO oxidation. We attribute the observed reactivity to specific sites in close vicinity of the border of uncovered Pd regions and the NiO islands. The reduction of NiO by CO is fully reversible as could be shown by subsequent reoxidation of the metallic Ni by O₂.

This work was supported by BMBF (05 ES3XBA/5) and the DFG through the Cluster of Excellence ”Engineering of Advanced Materials”.