RSA CE&C 2015-2021

70 In the Alkaliboost project, we are studying this ohmic resistance ‘mystery’ to find its origin. For this, we combine advanced electrochemical techniques such as electrochemical impedance spectroscopy with optical techniques, which allows us to study bubble behavior. We use 3D-printed electrolyzers, enabling us to study different cell configurations, and have a larger pressurized cell capable of operating up to 90 °C (see photo), enabling us to work under industrially relevant conditions and at a relevant scale.We combine this with advancedmodeling techniques of multi-phase flows to enhance our physical understanding of the processes occurring in the electrolyzer. The results of the Alkaliboost project suggest that gas bubbles play a key role. As expected, their presence in the electrolyte increases the ohmic resistance, but this effect seems less than expected. What seems especially relevant is the ability of the bubbles to stick to the separator or even form inside the separator as a result of supersaturation. This suggests that the hydrophilicity of the separator is of key importance and that increased hydrophilicity is the key to reducing ohmic resistance. The Alkaliboost project is clearly of a multidisciplinary nature in electrochemical engineering, making it very suitable for collaboration within EIRES. This starts with colleagues from the field of electrochemistry, ranging from fundamental electrochemistry to electrocatalysis and porous electrodes. There are then specialists from related chemical engineering fields, such as materials science, thermodynamics, fluid dynamics, multi-phase flow, chemical reactor engineering and membranes. It even extends to the optimal integration of the electrochemical stack in the overall process. A good example of this is research that we have recently carried out on the interplay between the rectifier and the electrolyzer. Figure 1: Alkaliboost setup: the ability to study alkaline electrolysis up to 90 °C and 50 bar.