Production of Oxygen from Water by Electrolysis


Oxygen is produced from water by electrolysis aboard the Russian Mir Space Station. The Russians use a dedicated water processor to reclaim water from urine as a feed to the electrolysis cells.

 

 

As can be seen from the plots of enthalpy and Gibbs Free Energy vs. Temperature shown below, the reaction is both endothermic and endergonic. Electrical energy must be consumed for the reaction to proceed. The thermodynamics shown below indicate the minimum energy requirements for the production of oxygen (assuming an efficiency of 100%).

 

The Oxygen Generation Assembly (OGA) baselined for ISSA consists of 18 electrolysis cells constructed using ion exchange membranes and a conducting polymer termed a Solid Polymer Electrolyte. Oxygen is produced at ambient pressure and vented to the cabin. Hydrogen is produced at slightly elevated pressure as a potential supply source for a carbon dioxide reduction system (Sabatier Reactor).



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Author: Tugrul Sezen
sezen@nas.nasa.gov

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