Influence of flow and pressure distribution inside a gas diffusion electrode on the performance of a flow-by CO2 electrolyzer

Over the last few years, the scientific community has paid lots of interest in the electrochemical CO2 reduction (ECR) as a possible solution for earth's global warming and the transitioning to a CO2 neutral industry. The majority of the researchers focus on improving the catalyst material, leading to higher current densities at lower cell potentials and increased selectivities. However, so far, little attention has been given to the investigation and optimization of the ECR reactor design and process parameters, which are equally, if not more, important in order to up-scale the process towards an industrial level. In this work the ECR towards formate on tin nano-particles in a flow-by electrolyzer is discussed. Special attention is given to the lay-out of both the reactor and the overall process. Additionally, the influence of the differential pressure across the gas diffusion electrode (GDE) on the reactor performance is investigated. It was found that by controlling the differential pressure, the perspiration, or leaking of electrolyte through the GDE, could be controlled and minimized. Results show that by controlling the differential pressure at 0 mbar, perspiration is minimal and that an optimal CO2 diffusion can be achieved, leading to an overall FE of 76% over 6 h at 100 mA/cm(2). Furthermore, due to the electro-wetting effect of the GDE, it was impossible to operate the reactor without perspiration, thereby avoiding the risk of salt crystallization in the reactor. Overall this study strengthens the idea that flow-by electrolyzers are promising reactors for the industrialization of electrochemical CO2 conversion and that pressure regulation is essential to obtain optimal process conditions.