Today, the energy sector is highly dependent on heterogeneous catalysis because a future solution to end our dependency on natural sources lies in generating hydrogen by splitting water. Several... Show moreToday, the energy sector is highly dependent on heterogeneous catalysis because a future solution to end our dependency on natural sources lies in generating hydrogen by splitting water. Several transition metals, such as Pt, are known to be good catalyst materials for water splitting reactions. They play a key role in understanding the fundamental aspects of the elementary interactions occurring on the surfaces of catalysts. These surfaces, however, are generally very complex and contain a wide distribution of structurally and chemically different sites with different activities. One of the key issues in optimizing the activity of the catalysts is to distinguish and specify the active sites on the surface. In this thesis we use highly corrugated Pt surfaces and UHV techniques (TPD, LEED, and STM) to explore the effects of surface defects on adsorption and desorption of water and related adsorbates. We elucidate to what extent the substrate type influences the structure of interfacial water both in the monolayer and thin film regime. Our studies also show that step geometry is the determining factor in low temperature oxygen dissociation. Show less
In this study we focused on the simulation of the interaction of water and its dissociation products hydrogen, oxygen and OH with platinum surfaces that contain a periodic arrangement of single... Show moreIn this study we focused on the simulation of the interaction of water and its dissociation products hydrogen, oxygen and OH with platinum surfaces that contain a periodic arrangement of single-atom-high steps. We simulate these interactions using the framework of density functional theory and employ high-performance computing resources such as the Cartesius supercomputer of SURFsara. We find that the two possible types of step edges exhibit increased binding strengths compared to the flat parts of the interface. This binding strength is a key factor in the chemical reactivity of these surfaces. Furthermore, we investigate the structure of higher coverages of water molecules around the step edges, where we observe surprising changes, namely the appearance of four, five and seven-membered rings, compared to the six-membered rings that are usually observed on the flat surfaces. Our predictions for these structures are confirmed using high-resolution scanning tunneling microscopy data. Our results are among the first simulations of high-coverage water adsorption on regularly stepped platinum surfaces, which will help advance our understanding of solvation effects at the step edges, which are relevant for the fields of solvation science, electrochemistry and surface science. Show less
