To obtain deuterium in a gas state from a mixed gas of hydrogen and deuterium at a low cost. A first electrode 11 is an electrode made of a metal allowing hydrogen (H component and D component) to permeate therethrough (hydrogen permeable metal), and the hydrogen permeable metal is Pd, for example. H ions and D ions having permeated through the first electrode 11 flow to the side of a second electrode 12 in a proton conduction layer 20. When the first electrode 11 is used as an anode and the second electrode 12 as a cathode, H ions and D ions flow in the proton conduction layer 20 from the left to the right in the drawing. In that case, hydrogen component in an input gas is more likely to flow into an atmosphere on the cathode side than deuterium component, and an H/D composition ratio accordingly becomes higher in a product gas than in the input gas. In an exhaust gas extracted after H and D components in the input gas are thus consumed, D component has been enriched.

To obtain deuterium in a gas state from a mixed gas of hydrogen and deuterium at a low cost. A first electrode 11 is an electrode made of a metal allowing hydrogen (H component and D component) to permeate therethrough (hydrogen permeable metal), and the hydrogen permeable metal is Pd, for example. H ions and D ions having permeated through the first electrode 11 flow to the side of a second electrode 12 in a proton conduction layer 20. When the first electrode 11 is used as an anode and the second electrode 12 as a cathode, H ions and D ions flow in the proton conduction layer 20 from the left to the right in the drawing. In that case, hydrogen component in an input gas is more likely to flow into an atmosphere on the cathode side than deuterium component, and an H/D composition ratio accordingly becomes higher in a product gas than in the input gas. In an exhaust gas extracted after H and D components in the input gas are thus consumed, D component has been enriched.