29.03.2016
Research news
Dissertation news

Dissertation: 1.4.2016 Computational studies of gold-adsorbate complexes on modified oxides (Nevalaita)

Time:

1.4.2016 12:00 — 15:00


Location: Ylistonrinne, FYS1
M.Sc. Janne Nevalaita defends his doctoral dissertation in Physics ”Computational Studies of Gold-Adsorbate Complexes on Modifield Oxides”. Opponent Associate Professor Anders Hellman (Chalmers University of Technology, Ruotsi) and custos Adjunct Professor Karoliina Honkala (University of Jyväskylä).

Janne Nevalaita. K-S FotoM.Sc. Janne Nevalaita defends his doctoral dissertation in Physics ”Computational Studies of Gold-Adsorbate Complexes on Modifield Oxides”. Opponent Associate Professor Anders Hellman (Chalmers University of Technology, Ruotsi) and custos Adjunct Professor Karoliina Honkala (University of Jyväskylä).

Abstract

In this thesis, the adsorption of Au atoms and clusters on modified oxide surfaces is studied using density functional theory (DFT) calculations. The support effects are considered by direct analysis of the adsorbed Au and using other coadsorbates as reactivity probes. Doping the CaO(001) surface by replacing a cation with a high valence dopant such as Mo makes adsorption of electronegative species such as Au, O and oxygen molecule more exothermic. The stronger binding is accompanied with a charge transfer from the dopant to the adsorbate. A modified Born-Haber (BH) cycle was devised to estimate the effect of different physical processes on the adsorption energy on the doped oxide. The adsorption energy was split into three parts with an iono-covalent energy describing the local interactions, a redox energy accounting for the charge transfer, and a Coulomb energy for the electrostatics between a charged adsorbate and dopant. While the Coulomb energy decays with increasing adsorbate-dopant distance, the redox energy remains more exothermic due to a much shorter distance between the negative anions and the positive dopant. Water is stabilized by electrostatic interaction with anionic Au on MgO/Ag(001); however, no stabilization occurs on bulk MgO when the Au adatom is neutral. The adsorption of water dissociation products H and OH on top of an Au adatom is more exothermic with increasing film thickness. Isophorone physisorbs on the MgO/Ag(001) surface with energetic preference towards the MgO steps, which is due to stabilizing electrostatic interaction between the step cations and a polar O=C bond in the molecule.

The dissertation is published in the series Department of Physics, University of Jyväskylä Research Reports number 5/2016, Jyväskylä 2016, ISSN:0075-465X, ISBN: 978-951-39-6537-2. Pdf-version ISBN on 978-951-39-6538-9. E-publication: http://urn.fi/URN:ISBN:978-951-39-6538-9. It is available at the University Library’s Publications Unit, +358 (0)40 805 3825, myynti@library.jyu.fi.

Further information:

Janne Nevalaita, puh. +358 40 196 6284, janne.nevalaita@jyu.fi
Communications Officer Anitta Kananen, tiedotus@jyu.fi, puh. +358 40 805 4142

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Janne Nevalaita

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janne.nevalaita@jyu.fi