Development of proton exchange membranes for HI concentration in thermochemical water-splitting IS process

Tanaka, Nobuyuki 

A thermochemical water-splitting iodine-sulfur process enables us to provide the Carbon-free hydrogen (H) at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and more. The cation exchange membranes (CEMs) for the HI mediated electro electrodialysis (EED) were developed using a radiation grafted polymerization method in order to improve the process efficiency of the IS process. High proton (H) conductivity and selectivity are required for the performance of CEMs to reduce the consumption energy for EED. The H conductivity of the radiation grafted CEMs were successfully improved by controlling the grafting amount, comparing with that of Nafion. Moreover, the H selectivity and water transport of the developed CEMs was improved by introducing the crosslinker. Currently, the further improvement of the membrane performance is underway by using the ion-track grafting technic.