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
In this thesis we have discussed several parameters that affect the electrochemical conversion of enviromentaly harmful molecules such as nitrates and carbon dioxide to more valuable and less... Show moreIn this thesis we have discussed several parameters that affect the electrochemical conversion of enviromentaly harmful molecules such as nitrates and carbon dioxide to more valuable and less deleterious compounds, in order to cast light onto the mechanism of the reaction to achieve an efficient and selective system.The thesis is divided in two main parts, the reduction of nitrates(chapter 2) and the mechanistic study of CO2 conversion to different products such as ethanol(chapter 3), ethylene(chapters 4 and 5) and propylene carbonate (chapter 6). Show less