Studies in heterogeneous catalysis and x-ray spectroscopy of water
Title: Studies in heterogeneous catalysis and x-ray spectroscopy of water
SNIC Project: SNIC 2021/3-34
Project Type: SNIC Large Compute
Principal Investigator: Lars G.M. Pettersson <lgm@fysik.su.se>
Affiliation: Stockholms universitet
Duration: 2022-01-01 – 2023-01-01
Classification: 10304 10407 10302
Homepage: http://xsolasgroup.fysik.su.se/
Keywords:

Abstract

The research of the group is focused on fundamental problems in heterogeneous and electrochemical catalysis and the determination of the structure and origin of the anomalous properties of liquid water. We 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 homogeneous ice nucleation. The PI has been awarded an ERC Advanced Grant to develop theoretical techniques to improve simulations of the liquid and explore consequences of a two-state picture in terms of chemistry and consequences for aquatic life. These techniques will be used to investigate structure models from newly developed force-field descriptions of water where we are actively developing the SCME-GAP force-field model. In a picture of water as locally fluctuating between more compact high-density and more open, tetrahedral conformations the question arises how gases dissolve in the liquid. Does O2 preferentially associate with the low-density regions and will this require special means for fish to extract it from the liquid? We work together with experimental colleagues in Japan on computing XES and RIXS of O2 and water and in fibrous structures modeling the interface between water and gills of fish. In heterogeneous catalysis we exploit new opportunities created by the ultrashort pulses from free-electron x-ray laser sources which enable following chemical reactions in real time. We compute structures, barriers and spectra to assist in the analysis of the experiments which have included CO desorption and oxidation on Ru(0001), as well as hydrogenation of CO on the way to synthetic fuels. We will continue by studying associative desorption of C+O as CO, N2 dissociation and the Haber-Bosch process to make ammonia as well as CO2 reduction both heterogeneously and electrocatalytically. We use microkinetic modelling including effects of adsorbate-adsorbate interactions computed at the DFT level to analyze the experimental data. This is combined with a genetic algorithm to fully explore the reaction space and evaluate the reliability of the directly computed DFT values, as well as indicate aspects that are missing from our models (e.g., missing side reactions, unexpected surface features in the experiment etc). We have a SSF funded project focusing on electrochemical generation of hydrogen from waste products, such as glycerol (from biodiesel production) and black liquor (from pulp production). Here our task is to computationally screen for good electrode materials towards both hydrogen production and value-added products that can be used as starting point for further chemical refining. Some such materials have now been synthesized and we will assist in characterizing reaction mechanisms on promising candidates.