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Abstract |
Gas conversion by plasma (ionized gas) is gaining interest as a potential candidate to contribute to the electrification of the chemical industry. Several approaches are considered, and this work mainly focuses on plasma catalysis. In plasma catalysis, a catalytic material is combined with a plasma with the aim of improving the performance of the process. However, several aspects of plasma catalysis are poorly understood, with many complex underlying mechanisms hindering a straightforward understanding, optimization, and implementation of this technology. This work takes a multidisciplinary approach to address current challenges in plasma catalysis. On the one hand, electrical diagnostics of dielectric barrier discharges are employed to understand the discharge properties and correlate them to other observations. On the other hand, electron microscopy is leveraged to gain insights into the microscopic structure of the relevant materials in this research. By combining these techniques, the effect of the catalytic material on the plasma discharge is illustrated. The microscopic properties of the catalytic material clearly influence the plasma discharge characteristics. Moreover, these discharge characteristics can dominate the overall performance of the plasma-catalytic process. Furthermore, erosion of the exposed electrode in the dielectric barrier discharge is found to contaminate the material inside the plasma reactor. This behavior is found to be persistent across several gases and plasma reactors, although the discharge characteristics again play a crucial role in the formation of these erosion products. To further investigate the effects of (conductive) materials on the plasma discharge, a diffuse dielectric barrier discharge is studied as it is exposed to a conductive layer. This conductive layer is found to significantly influence the electrical properties of the system, thus affecting the discharge characteristics. Further, the results indicate that the material can additionally affect the plasma through other processes, such as enhanced electron emission, enabling a discharge at lower voltages. Finally, a plasma setup is presented that enables the investigation of a material with a scanning electron microscope while it is exposed to a plasma. This system is characterized and the effect of the plasma on materials is studied. As the plasma operates with a constant electric field, the sample is continuously bombarded with ions and sputtering can be observed. In addition, oxidation of the sample is observed when exposed to an oxygen containing plasma, highlighting the potential of this system in the field of plasma catalysis and beyond. |
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