Extraction of Hydrogen from Water Vapor by Hydrogen Pump Using Ceramic Protonic Conductor

Abstract A blanket tritium recovery system that uses an electrochemical hydrogen pump with a protonic conductor membrane is proposed. One of the advantages of this system is the potential for processing the blanket sweep gas without fractionation of hydrogen isotopes and water vapor. In this work, hydrogen in a water molecule is extracted by a hydrogen pump using a Perovskite-type ceramic such as SrCe0.95Yb0.05O3-α. The threshold, which corresponds to the energy of H2O decomposition, for hydrogen extraction from the water molecule is 500 to 600 mV at 873 K. The threshold becomes smaller with increases of the partial pressure of the water vapor. In the case of pumping of the H2-H2O mixture gas, transportation of H2 precedes H2O decomposition below the threshold (H2O decomposition voltage), and the threshold becomes larger. In order to process the blanket sweep gas without fractionation of hydrogen isotope and water vapor, comparatively high applied voltage is required.