Atomic-scale Modelling of Electro-catalytic Surfaces and Dynamic Electrochemical Interfaces

This dissertation addresses numerical calculations on the atomic scale to study catalytic surfaces for electrochemistry. The first half of the thesis deals with calculations on the properties of catalytic surfaces, using well known methodology, whereas the second half of the thesis deals with the development of new methodology to explicitly include the electrolyte in the atomic scale calculations.

Chapter 3 presents calculations on contracted and reconstructed platinum surfaces, which are relevant for development of catalysts for proton exchange membrane fuel cells. Correlation of the results with experimental observations show that there is a natural limit to how far the reactivity of the catalysts can can be fine-tuned, exclusively using the strain effect, that is imposed by alloying with lanthanides.

In chapter 4, calculations are presented for several newly discovered catalysts for the hydrogen evolution reaction. The results show that molybdenum carbides and borides have reactive surfaces, which is not in consistency with their high catalytic activity. A possible active facet is suggested for the molybdenum boride.

It is likely, however, that other unexplored active sites, surface terminations or phases are responsible for the observed catalytic activities. For nickel di-phosphide, which is another recently discovered catalyst for the hydrogen evolution reaction, it was possible to determine several facets and active sites, which have advantageous catalytic properties.

Chapter 5 presents the new methodology to calculate the structure of the electrolyte in the electrochemical interface. The strength of this methodology is that it makes fewer assumptions on the physics of the interface, while it takes a fundamental statistical mechanics approach. Large datasets of states for the electrolyte in contact with the surfaces of gold (111) and platinum (111) were calculated.

Analysis methods were developed for determining the structure of the electrolyte as averages, which depend on pH and the electrode potential of the metal. The methodology remains under development, and it is expected that it will contribute with new insight to how pH and ionic chemical potentials affect the structure of the interface, to the benefit of future fundamental research in electrochemistry.