Fundamental study of water electrolysis for life support system in space

To establish supporting technologies, JAXA (Japan Aerospace eXploration Agency) is researching systems that will be indispensable for manned space activities beyond low earth orbit, including “Water Recycling Technology” and “Air Recycle Technology”. In this paper, SPE (solid polymer electrolyte) water electrolysis is investigated for the recycling technology. Although water is usually supplied into anode side on the earth, cathode feed type and static one is employed under the special environment. The performance of the cathode one could match our target by flushing the gas bubbles sticking on the electrode, while the static one shows the gas-free electrolysis process without any mechanical pumping system. The in situ observation during aqueous water electrolysis shows active bubble motions depending on the solution components. Gas bubbles spontaneously jumps and detach from the electrode in KOH electrolysis, while they easily coalesce and stick in H2SO4 one. The transient behavior is strongly controlled by wettability under microgravity where the buoyancy force can be neglected.