Characterization of the degradation of carbon supported tin and bismuth gas-diffusion electrodes applied in alkaline CO2 electrolysis

The continuously rising CO2 concentration in the atmosphere and the associated climate change resulting in a steady increase in the planets temperature requires immediate counteraction and mitigation of CO2 emissions. Possible CO2 mitigation concepts are carbon capture and storage or in the best-case carbon utilization. Renewable energy can be used to power CO2 electrolysis devices in which CO2 is used as feed stock and converted to value-added products (CO, CH4, C2H4, HCOOH / HCOO-, …) guiding the route to a circular carbon economy. Therefore, traditional synthesis routes for carbonaceous species might be substituted by environmental friendlier CO2 electrolysis. Consequently, the role of CO2 can be changed from a harmful species to a valuable resource. This thesis focuses on the tin catalyzed electrochemical conversion of CO2 to formate which is principally close to be economically feasible due to the already achieved performance targets (activity, selectivity) for this half-cell reaction. Nevertheless, long-term operation and full cell setups are rarely reported since most of the scientists focus on the development of suitable catalysts for a specific target product. Consequently, the degradation of CO2 converting electrodes is an underrepresented topic in literature. Therefore, this thesis provides an elaborated fundamental electrochemical impedance spectroscopic (EIS) study which can be used to identify degradation mechanisms during operation of an CO2 electrolysis cell