Towards a targeted optimization of electrocatalysts by combining electrosynthesis with in-situ electron paramagnetic resonance

The increasing renewable energy production and declining interest in fossil fuel generates opportunities for the electrification of industrial processes. This electrification can be reached through different routes. A chemical production process can be replaced by an electrochemical synthesis process with direct energy supply from a renewable source without inefficient energy conversions. The economic feasibility of such a process is then determined by the activation energy of the electrochemical reaction. Electrocatalysis investigates how this energy demand (overpotential) can be reduced and what the consequences are on the selectivity. Both these parameters depend on the used electrode material at which the reaction will take place through a specific reaction mechanism. Predictions about the catalytic activity of a material are not straightforward and their development mostly goes through trial and error. Knowledge about the reaction mechanism can help to improve and speed up this development. The number of techniques that are available to study the reaction mechanism at the electrode are limited. The fact that in electrochemical reactions, electrons are transferred, often forming short-living radical intermediates, limits the possibilities for detection even more. Electron Paramagnetic Resonance (EPR) is probably the most relevant technique to gather information about the chemical nature and electronic structure of these radical intermediates. Despite the long history of the combination of electrochemistry with EPR, the use in electrocatalytic research remains underexploited up until today. The main reasons are: the availability of EPR infrastructure, the lack of specific knowledge to derive useful information from experiments and the scarcely available commercial cells and electrodes suitable for this application. This work focusses on the development of these cells and electrodes to map the limitations and diminish reservations about the combined techniques. The cells were used to investigate relevant case studies through in-situ EPR electrolysis, providing new insights in terms of reaction mechanism.

Publication year:2021

Keywords:Doctoral thesis

Accessibility:Open