Electrocatalytic and Cold Plasma Technologies for Advancing Sustainable Chemistry

The continuous rise in atmospheric CO2 concentration has resulted in global warming, which is perhaps the most pressing issue of the 21st century. All environmental spheres are impacted, and significant changes in industrial production are necessary. The electrification of the chemical industry is crucial in this regard. This thesis focuses on two technologies for sustainable development: electrochemical reduction of oxalic acid catalyzed by titanium nanotubes and plasma-assisted CO2 splitting. The first part of the thesis will study the morphology and activity of titanium nanotubes by changing anodization time and potential, aging of the electrolyte solution, and type of pretreatment (thermal, electrochemical, or no pretreatment). The text discusses the effect of rapid breakdown anodization on nanostructure and its relation to data obtained from FESEM, AFM, and ECSA. Higher performances were measured by longer and rougher nanotubes suggesting a synergic effect. A Faradaic efficiency to glycolic acid (86 %) and oxalic conversion (48 %) at −0.8 V vs. RHE was obtained, superior to the existing literature on TiO2-only electrodes at room temperature. Moreover, the chemical nature of the active sites and its relationship with nanostructure was investigated by CV and XPS, showing that oxygen vacancies are crucial to catalyze the reaction. The second part of the thesis focuses on improving a DBD reactor for CO2 splitting using cold plasma. It compares the performances (conversion, SEI, and energy efficiency) of a classic DBD reactor with a smooth electrode to an innovative reactor with an internal electrode of two different porosities (0.2 μm and 0.5μm). The data indicate that porosity has a beneficial effect, likely due to a higher plasma density within the pores and a tip effect that increases the local electric field. Additionally, this study will demonstrate the impact of a boehmite layer deposited on porous electrodes through dip coating. Compared to a packed configuration, the results demonstrate higher conversion and energy efficiency, while avoiding a reduction in residence time. This could also be a turning point to reduce the costs. The data were collected using both pure CO2 and CO2 diluted.