Doctoral defence in Chemical Engineering - Árni Björn Höskuldsson

Abstract

Accelerating the ongoing transition towards renewable energy vital to lower carbon emissions. The electrification of various industrial processes, such as the production of ammonia (NH3) and nitric acid (HNO3), both of which are key ingredients in fertilizer production, would constitute an important step in that direction. Ammonia is also considered a promising future energy vector due to its high volumetric energy density. In this thesis, periodic density functional theory (DFT) calculations are used for the computational modelling of transition metal-based surfaces as potential catalysts for the electrochemical fixation of nitrogen. The first project focuses on the competition between the nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) on a tungsten electrode. When going beyond a purely thermodynamics-based framework, no additional NRR barriers are observed when the reactant and product states both bind on the same active site. The second project focuses on the scarcely studied nitrogen oxidation reaction (NOR) on a TiO2 electrode. Grand canonical DFT simulations are employed along with the inclusion of explicit solvent molecules, enabling an estimate of electrochemical barriers for a continuous range of applied potentials. The NOR on TiO2 is highly dependent on the competing oxygen evolution reaction (OER). The third and final project involves a large screening study of doped transition metal oxides in the rutile structure, with MoO2 doped with W being the most promising candidate. Nevertheless, further examination suggests that HER is likely to dominate at most reaction conditions.

About the candidate

Árni Björn Höskuldsson obtained a BSc degree in physics from the University of Iceland in 2016, and then worked as a researcher for a year in the group of Dr. Egill Skúlason. Árni finished a masters degree in theoretical physics from ETH Zürich in the summer of 2019, before enrolling as a PhD student in chemical engineering at the University of Iceland in the autumn of 2019. Alongside his studies Árni has taught physics and chemistry at MR, MH and the UoI.