Studies in heterogeneous catalysis and x-ray spectroscopy of water
Title: Studies in heterogeneous catalysis and x-ray spectroscopy of water
SNIC Project: SNIC 2014/8-23
Project Type: SNAC Large
Principal Investigator: Lars G.M. Pettersson <lgm@fysik.su.se>
Affiliation: Stockholm University
Duration: 2014-07-01 – 2015-07-01
Classification: 10304 10407 10302
Homepage: http://www.physto.se/~xes/
Keywords:

Abstract

The research of the group is focused on fundamental problems in heterogeneous catalysis and the determination of the structure and origin of the anomalous properties of liquid water. We challenged the textbook picture of normal liquid water in our Science paper in 2004 and have developed a new picture of ambient water based on fluctuations between two types of local structures connected to the anomalous properties of water. These become enhanced upon supercooling where thermodynamic response functions seem to diverge at a temperature of 228 K, i.e. below the temperature of homogenous nucleation. This has never before been accessible but new data from the free-electron Linac Coherent Light Source (LCLS) x-ray laser show a continuous development towards a tetrahedral liquid down to 227 K. We perform MD simulations in the supercooled regime to analyze the data. We simulate evaporative cooling of water droplets to establish the experimental temperature calibration. We perform extensive PIMD simulations of isotope effects in water to analyze x-ray emission spectra of water and investigate the dynamics observed in femtosecond vibrational pump-probe experiments. We furthermore investigate how thermodynamic response functions of water evolve with temperature and length of the simulations. In heterogeneous catalysis we exploit new opportunities created by the ultrashort pulses from the LCLS which enable following chemical reactions in real time. We compute structures, barriers and spectra to assist in the analysis of the experiments which include CO desorption and oxidation on Ru(0001) as well as hydrogenation of CO on the way to synthetic fuels. The studies of oxygen dissociation and oxide formation at Pt electrodes, as well as water and water dissociation products, aim to develop a deep understanding of fuel cell processes.