Dynamics and spatial distribution of water in Nation 117 membrane investigated by NMR spin-spin relaxation

摘要

The dynamics and spatial distribution of water molecules in Nation 117 membrane has been investigated by H-1 NMR. To this end, ID and 2D spin-spin (T-2) relaxometry experiments were carried out as a function of the relative humidity ranging from 9 to 100%. The inverse Laplace transform was successfully applied to obtain the ID T-2 distributions and 2D relaxation maps. The ID T-2 distributions show two peaks at low RH and mainly one at high water content, which can be associated with the rearrangement of the exchange sites inside the polymeric channels with the amount of water. From the T-2 distribution at 70% RH three types of water were identified corresponding to different degree of molecular mobility. The 2D T-2-T-2 maps show molecular exchange between the two water populations found at low RH, while at 70% the exchange between only the two more mobile water populations takes place. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.