An eSSENCE-CECAM seminar

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Monday 27 February 2017, at 15.15: The Ångström Laboratory, Å4003
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“Physics and chemistry: The definitive structure
of Liquid Water, and Reduction of Carbon Dioxide”

Professor Lars G.M. Pettersson
FYSIKUM, AlbaNova, Stockholm University

Abstract:

Under this heading I will summarize our recent work in two important fields:
1. understanding normal liquid water and 2. how to turn CO2 into useful chemicals in a green electrochemical process. Both represent significant modelling challenges.

In the case of liquid water, I will present our benchmark paper in which the definitive oxygen-oxygen pair-distribution function, derived from many x-ray diffraction measurements, was presented [doi: 10.1063/1.4790861]. I will also briefly comment on a new picture that is evolving for liquid water, namely as a substance consisting of two normal liquids, one high-density (HDL) and one low-density (LDL) form, with its intriguing anomalous properties arising from fluctuations between them.

Global warming through emission of carbon dioxide from human activities is a current challenge. Copper is rather unique in its ability to catalyze the reduction of CO2 into ethylene, but unfortunately only in small amounts. However, by reducing copper oxide electrochemically, it has been found that a nanostructured catalyst with a much larger selectivity for ethylene is obtained. I will present our work to under- stand the origin of this selectivity which is based on the influence of subsurface oxygen species.

WELCOME!

Kersti Hermansson
Olle Eriksson

eSSENCE-SeRC-CECAM lecture

Sweden recently became a member of the European CECAM organisation
(www.cecam.org). We invite you to the first joint Uppsala-Stockholm
eSSENCE-SeRC-CECAM lecture.

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Thursday 26 January 2017, at 15.15: The Ångström Laboratory, Å4004
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Friday 27 January 2017, at 11.00:
Theor. Chem. & Biology, Roslagstullsbacken 15, Alba Nova (KTH)
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Professor Konstantin Neyman, University of Barcelona
Modelling catalytic nanomaterials
– as simple as possible, but not simpler

The speaker is a Faculty of Science and Technology Visiting Professor of Uppsala University for Winter 2016-17. He is also an ICREA Research Professor at the Department of Materials Science and Physical Chemistry of the University of Barcelona. He is an international authority in computational materials science, and nanostructured materials in particular.

Abstract:
In heterogeneous catalysts, active metal components are present as nano-aggregates of thousands of atoms. Due to their sizes, these nano-aggregates remain inaccessible to first-principles quantum-mechanical calculations. However, such species can be represented rather realistically by computationally tractable smaller metal nanoparticles (NPs) whose surface sites marginally change the reactivity with increasing particle size [1]. I will illustrate this for Pd catalysts [2, 3] as well as for the building of active sites on Pt/ceria catalysts [4-6]. I will show that employment of common slab models, which neglect the nanoscopic effects in these and similar systems, can lead to severe misrepresentation of the surface reactivity.

Dedicated NP models, as proposed by us, expose a variety of active sites, the structure and geometric flexibility of which notably better match those of the sites present in technical catalysts.

Reference:

1.  S.M. Kozlov, K.M. Neyman, Top. Catal. 56 (2013) 86

2.  K.M. Neyman, S. Schauermann, Angew. Chem. Int. Ed. 49 (2010) 4743

3.  H.A. Aleksandrov, …, K.M. Neyman, Angew. Chem. Int. Ed. 53 (2014) 13371

4.  G.N. Vayssilov, …, K.M. Neyman, J. Libuda, Nature Mater. 10 (2011) 310

5.  A. Bruix, …, K.M. Neyman, et al., Angew. Chem. Int. Ed. 53 (2014) 10525

6.  Y. Lykhach, …, V. Matolín, K.M. Neyman, J. Libuda, “Counting electrons on
supported nanopartic­les.” Nature Mater. 15 (2016) 284