Doctoral defence: Heigo Ers "Adsorption and Structuring Processes at Single Crystal Electrode – Ionic Liquid Interface – Insights from Simulations and in situ Studies"

On 16 August at 14:15, Heigo Ers will defend his thesis "Adsorption and Structuring Processes at Single Crystal Electrode – Ionic Liquid Interface – Insights from Simulations and in situ Studies".

Supervisors:
Piret Pikma, University of Tartu
Vladislav Ivaništšev, University of Tartu
professor Enn Lust, University of Tartu

Oponent:
professor Alexei Kornyshev, Imperial College London, United Kingdom

Summary:
The drive towards smaller and more efficient energy storage devices and electronic components has pushed the scientific community to come up with new ideas and solutions. Novel concentrated electrolytes are being tested for supercapacitors, while the formation of molecular wires and switches at solid surfaces is actively studied. These applications rely on adsorption or charge storage processes at the electrode and electrolyte boundary. Therefore, understanding and characterising the interfacial properties is crucial to achieving the miniaturisation and energy storage goals.

Ionic liquids have gained significant attention as potential electrolytes in energy storage due to their low vapour pressure and high electrochemical stability. Because of the high concentration of ions, their interfacial properties differ notably from other aqueous or organic electrolytes. Although the properties of electrode-ionic liquid interface continue to be under study, the adsorption of organic additives from ionic liquid mixtures has been largely overlooked.

In this work, the adsorption and structuring of ions and molecules at the electrode-ionic liquid interface are studied. The molecular dynamics simulations focused on the influence of applied potential, temperature, and electrode material on ionic liquid’s interfacial capacitance and structure. The simulations related the capacitance peaks and plateaus to the ionic liquid’s reorganisation and showed that temperature affects the capacitance foremost near the potential of zero charge. The adsorption studies of bipyridine from ionic liquid at Bi(111), Sb(111), and Cd(0001) surfaces combined various techniques to provide a comprehensive description of the process. Conducted measurements showed the formation of dense bipyridine adlayers at all studied surfaces, while identifying significant differences in self-assembled adsorbed bipyridine structures. The results highlight the complex nature of the adsorption and organisation processes.