Hydrogen is considered essential for the transition towards carbon neutrality. Currently, however, most hydrogen is derived from fossil fuels, because this is cheaper than producing hydrogen renewably through electrolysis. This cost gap currently impedes the adoption of renewable hydrogen and significant cost reductions are necessary to make it competitive. Crucially, the cost of cell stack components accounts for about half of the total cost of electrolysis systems. An effective way to lower the stack costs, is to improve the electrolyser’s productivity by increasing the operating current density. Increasing the current density, however, accelerates the formation of gas bubbles on the electrode surface, which reduce the efficiency. The objective of this project is, therefore, to investigate how the cell design and operating conditions affect the gas bubble removal in alkaline water electrolysers at high current densities. Through a combination of electrochemical techniques and in-situ X-ray tomography, a relation can be established between gas bubble removal and the interelectrode distance, flow fields and electrodes, enabling the optimisation of these parameters. Several operational parameters, including flow rate, cell compression, temperature, and pressure, will also be studied to gain insight into how they affect the bubble removal. This will also make it possible to link each cell design with the optimal operating conditions, in order to maximise the energy efficiency.