Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 34: Elektronische Struktur IV
O 34.6: Vortrag
Donnerstag, 27. März 2003, 16:15–16:30, M\"UL/ELCH
Point Defects at the MoO3(010) Surface: DFT Cluster Model Studies — •Renata Tokarz-Sobieraj1, Malgorzata Witko1, and Klaus Hermann2 — 1Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30239 Krakow, Poland — 2Fritz-Haber-Institute der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
Molybdenum oxide (VI), is a functional component of catalysts in many chemical processes. In selective oxidation reactions oxygen vacancies are formed, which may act as new active sites at the surface, undergo re-oxidation or give rise to more extended defects. As a consequence, MoO3 may become reduced to MonO3n−1, and finally to MoO2. Local electronic structures of MoO3 and MoO2 oxides were studied by DFT method using StoBe code. Defected (010) surface of MoO3 was described by a formation of single and double surface O vacancies.
Formation of O vacancies is found to be a local process, which leads to the reduction of nearby Mo centers and electronic structure that seems to be an intermediate between that of MoO3 and MoO2. The creation of O vacancies is facilitated by hydrogen presence. Total and partial densities of states obtained for clean and defected MoO3(010) as well as for clean MoO2(011) give a clear picture of the reduction mechanism. Appearance of a new peak in the gap between the valence and conduction bands that results from the occupation of metal d orbital and may be associated with the color center is shown.