Effect of water stoichiometry on deuterium isotope separation by anion exchange membrane water electrolysis

Abstract

Water electrolysis (WE) is a key technology for a decarbonized society and is essential for hydrogen isotope separation for a future fusion reactor. In this study, deuterium (D) separation was performed by anion exchange membrane WE (AEMWE) and compared with our previous results from proton exchange membrane WE (PEMWE). WE allows D to become concentrated in solution and diluted in hydrogen gas compared with the D concentration in feed water. The separation effect increases with decreasing water stoichiometric ratio, λ, of the water feed to electrolysis volume. Owing to little water drainage from the cathode, AEMWE can be performed at λ ≈ 1.05, while λ ≈ 4.0 is the lowest for PEMWE. When the feed rate is reduced (λ < 2), D in the product water becomes more concentrated, which corresponds to a sharp rise in cell voltage owing to the water shortage at the cathode.