"Investigating Contributions from Vehicular and Grotthuss Transport on Hydroxide Ion Conductivity in Anion Exchange Membranes (AEMs)"

This event is sponsored by FAMU-FSU Engineering Department of Chemical & Biomedical Engineering.

Anion exchange membranes (AEMs) used in alkaline fuel cells rely on the selective transport of hydroxide ions through the membrane to produce electricity. The low conductivity of hydroxide ions in AEMs has prevented their widespread use and improving AEM conductivity is of significant fundamental and industrial relevance. The target for conductivity in AEMs set by the Department of Energy is typically ≥ 100 mS/cm at operating conditions. An understanding of the hydroxide transport mechanisms through the polymer can help in the design of membranes with improved performance. In prior work, we leveraged atomistic molecular dynamics (MD) simulations to capture correlations in hydroxide transport across four polyethylene AEMs with different functional groups. While the trends in conductivity were consistent with experiments, there was a significant difference in the magnitude between experiments and simulations. We ascribed this to the inability of our model to capture the reactive Grotthuss transport (proton hopping) mechanism which is dominant in these systems. In our current work, to account for Grotthuss transport, we use the heuristic reaction protocol REACTER that allows us to model reactions within the framework of classical simulations. We find that the simulated hydroxide conductivity is in better agreement with experimental values after the inclusion of Grotthuss transport. We extend our analysis across different AEM chemistries, including polyethylene, polysulfone, and polynorbornene, and find that the balance between vehicular and Grotthuss transport strongly depends on the polymer’s microstructure and water uptake.

Dr. Janani Sampath

Assistant Professor

Department of Chemical Engineering

University of Florida

Speaker Bio: Janani Sampath joined the Chemical Engineering department at the University of Florida as an Assistant Professor in 2021. Prior to this, she was a postdoctoral researcher at the University of Washington and the Pacific Northwest National Laboratory, where her research involved elucidating driving forces behind biomolecular self-assembly using atomistic molecular dynamics simulations and enhanced sampling methods. She received her Ph.D. in Chemical Engineering from the Ohio State University in 2018, where she studied mechanical and interfacial structure -property relationships in ion containing polymers using coarse-grained models. She was a Research Engineer in Unilever R&D between 2010–2013, where she synthesized and characterized ultrafiltration membranes for water purification. She obtained a B.E. in Chemical Engineering from R.V. College of Engineering, India, in 2010. She is a recent recipient of the Ralph E. Powe Junior Faculty Award and the ACS PRF Doctoral New Investigator Award.