Equilibrium potential across cation exchange membrane in HI–I2–H2O solution

The equilibrium potential across Nafion 117 in a HIx solution (HI–I2–H2O mixture) was measured for an electro-membrane process (electro-electrodialysis, EED) in the thermochemical water-splitting iodine–sulfur process. The experimental results were correlated with a theoretical formula derived on the basis of the electrochemical reaction, the Donnan equilibrium and the Nernst–Planck equation. The obtained empirical formula could reproduce the experimental equilibrium potential within ±0.03 V. Also, the obtained regression parameter agreed well with that calculated from the vapor liquid equilibrium data of a HIx solution reported by Hodotsuka et al. (2008) [3].