Water-Vapor Electrolysis Cell with Phosphoric Acid Electrolyte 670851
An oxygen-producing water electrolysis cell with phosphoric acid electrolyte can operate on the water vapor in recirculated cabin air and accomplish concurrent dehumidification. The development of the concept over the past 3 years involved research to define the components of electrode overvoltage and design analysis to provide a small, lightweight unit to compensate for the electrolysis power. Theoretical equations based on electrochemistry, fluid dynamics, and heat and mass transfer correlate with the observed steady state operation obtained in extended testing of experimental cells for over 1000 hr. Data on electrode life, gas purity, and voltage characteristics combined with size, weight, and power estimates indicate that the new concept would be competitive with other methods of oxygen generation for advanced space missions. The recent satisfactory performance of a prototype module in an extended test of over 1000 hr is reviewed.