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Title: Hydroxide Solvation and Transport in Anion Exchange Membranes

Understanding hydroxide solvation and transport in anion exchange membranes (AEMs) can provide important insight into the design principles of these new membranes. To accurately model hydroxide solvation and transport, we developed a new multiscale reactive molecular dynamics model for hydroxide in aqueous solution, which was then subsequently modified for an AEM material. With this model, we investigated the hydroxide solvation structure and transport mechanism in the membrane. We found that a relatively even separation of the rigid side chains produces a continuous overlapping region for hydroxide transport that is made up of the first hydration shell of the tethered cationic groups. Our results show that hydroxide has a significant preference for this overlapping region, transporting through it and between the AEM side chains with substantial contributions from both vehicular (standard diffusion) and Grotthuss (proton hopping) mechanisms. Comparison of the AEM with common proton exchange membranes (PEMs) showed that the excess charge is less delocalized in the AEM than the PEMs, which is correlated with a higher free energy barrier for proton transfer reactions. The vehicular mechanism also contributes considerably more than the Grotthuss mechanism for hydroxide transport in the AEM, while our previous studies of PEM systems showed a largermore » contribution from the Grotthuss mechanism than the vehicular mechanism for proton transport. The activation energy barrier for hydroxide diffusion in the AEM is greater than that for proton diffusion in PEMs, implying a more significant enhancement of ion transport in the AEM at elevated temperatures.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [2]
  1. Univ. of Chicago, IL (United States); Wuhan Univ. (China)
  2. Univ. of Chicago, IL (United States)
  3. Northern Arizona Univ., Flagstaff, AZ (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 138; Journal Issue: 3
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
Multidisciplinary University Research Initiatives (MURI); National Natural Science Foundation of China (NNSFC)
Country of Publication:
United States