Humans on Mars

Project description

Human space exploration is strongly constrained by the availability of in-situ resources. These resources are essential for reducing transportation costs and establishing permanent human outposts, e.g. on the Moon or on Mars. Among these resources, oxygen is a critical requirement, needing to be produced in substantial quantities - primarily for space transportation systems and life support - while minimising energy consumption. Alkaline water electrolysis is a promising method for splitting water into oxygen and hydrogen, utilising either electric energy or directly solar power. However, during this process, the nubleation, growth, and detachment of bubbles at the electrode-electrolyte interface create the "bubble effect", which impacts performance. Bubbles reduce the active surface area for electro-catalytic reactions while simultaneously enhancing mass transport by collecting gas molecules from the supersaturated solution.

In this project "bubble trouble", part of the "Humans on Mars" initiative, we aim to explore electrodes with surfaces of varying complexity - ranging from flat to nanostructured - made from nickel and iron. Our goal is to better understand the interactions between structural and thermodynamic parameters (such as geometry and surface tension) and operational parameters (including temperature, pressure, and electrode potential) during bubble formation, growth, and detachment. This will be achieved through a fusion of materials science and engineering, advanced time-resolved electro-analytical techniques, and multi-phase, multi-scale fluid-dynamic modelling. The final goal is to optimise the process in low gravity conditions.

In the early stages of the project, we are simulating bubble formation and detachment right at our labs. Utilising microelectrodes - mere cross-sections of a 25um-diameter platinum wire - we are exploring this process in a controlled, observable manner. An example of this in motion, where a bubble periodically grows and detaches, is shown in a video.

While the bubble growth and detachment is followed by a camera, we acquire time-resolved impedance spectra through dynamic multifrequency analysis. This data provides deep insights into the system's electrochemical properties, uncovering invaluable information on the rate of surface reaction and charge transfer resistance, the resistance of the solution, and the impact of diffusion and convection on the concentration of hydrogen and ions.