Sustainable energy from wind and solar is most readily available near the sea. Seawater electrolysis would thus be a highly promising method for intermittently storing surplus electricity from... Show moreSustainable energy from wind and solar is most readily available near the sea. Seawater electrolysis would thus be a highly promising method for intermittently storing surplus electricity from these sources, in the form of hydrogen. Unfortunately, the direct use of seawater in electrolysers brings with it a selectivity problem, caused by the chloride salts in such water. Instead of forming oxygen at the anode, which is environmentally harmless and thus the desired product, the formation of toxic chlorine becomes possible in seawater, and this reaction has to be avoided. This thesis is focussed on how the anodic evolution of oxygen and chlorine compete, and how selectivity between these two reactions may be optimized for the benefit of seawater electrolysis, and electrocatalysis in general. Show less
With the energy transition toward a renewable energy supply and a CO2-neutral economy, electrification of the energy system is rising in importance, which leads to the challenge of long-term... Show moreWith the energy transition toward a renewable energy supply and a CO2-neutral economy, electrification of the energy system is rising in importance, which leads to the challenge of long-term storage of renewable electricity. A promising option is the electrochemical conversion of biomass or carbon dioxide in chemicals as energy carrier. In this research, catalysis of the electrochemical CO2 reduction was studied to obtain liquid fuels. In this fundamental study we discovered that so-called disproportionation reactions may occur simultaneously with the CO2 reduction reaction influencing the product spectrum. Moreover, we focused on metalloprotoporphyrins immobilized on a graphite surface. We found that the selectivity can be steered toward formic acid with rhodium, tin or indium metal centers. Apart from intrinsic catalyst parameters, we studied the influence of parameters related to the immobilization and the composition of the electrolyte. We showed that the substrate and its pretreatment as well as encapsulation of the catalyst in polymers can have a signifcant influence on the electrocatalysis of CO2 reduction. The results obtained in this thesis provide insight in the energy efficiency, reaction rate and selectivity of the CO2 reduction reaction, and play an important role for the development of an industrially viable process. Show less