Water dissociates into oxygen and hydrogen at high temperatures. The problem with exploiting this reaction is that very low concentrations of hydrogen and oxygen are generated even at relatively high temperatures (e.g., only 0.1 and 0.042 percent for hydrogen and oxygen, respectively, at 1600 deg C), because the equilibrium constant for this reaction is small. However, significant amounts of hydrogen or oxygen can be generated at moderate temperatures if the equilibrium is shifted toward dissociation by using a mixed-conducting (i.e., conducts both electrons and ions) membrane to remove either oxygen or hydrogen. We have studied hydrogen production via water splitting at moderate temperatures (500-900 deg C) with novel mixed-conducting membranes.
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