(118d) A Multiscale Approach Toward the Design and Understanding of Stable and Conductive Anion Exchange Membrane Materials

Improved anion exchange membrane (AEM) materials are needed to develop next generation electrochemical devices including fuel cells. In recent years, there has been significant attention within the energy conversion/storage communities [1-3].  In addition to the interest in the use of AEM materials for fuel cells [1-3], there is consideration for their use in areas including chemical processing and energy storage [3-6], electrolysis and solar-to-fuel production [3,6], desalination and dialysis [3], and purification and separation processes [3]. The interest in these materials is a result of the opportunities that may be presented by a stable, anion-conducting polymer electrolyte membrane. 

In this talk we will highlight our collaborative, simulation-focused, efforts to develop and understand high performance AEM materials for electrochemical applications. We discuss our approach to implementing a multi-scale description of the AEM with surrounding solvent and ions.  The multi-scale description enables calculation of mesoscopic and microscopic ionic and solvent mobility coupled with ion solvation, binding, and transport within the membrane. Our multiscale modeling approach includes atomistic molecular dynamics simulations using reactive (ReaxFF) and polarizable (APPLE&P) force fields, coarse-grained molecular simulations using UQ-driven parameterization algorithms, and full cell continuum level modeling. 

For our initial efforts, we utilize backbone materials such as Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO).  The PPO backbone is  used as a model material system that enables us to develop and validate simulation methods to predict and resolve structure-property relationships; a key step before moving to more complex materials. Further, the simpler PPO-type backbone materials provide a key advantage at this stage in that they can currently be (i) processed, synthesized, and characterized in our labs, and (ii) subjected to unique processing methods/conditions that includes both casting and electro-spinning fabrication.  This last capability is salient because our multi-scale modeling and simulation efforts focus on bridging various time- and length-scales. The ability to process the materials using different methods can drastically influence the material’s morphologies, structures, ordering, and properties, which provide a robust platform for validation of the developed simulation models and their predictive capabilities.

Acknowledgments:

KNG and JPM gratefully acknowledge the support of the U.S. Department of the Army, Army Materiel Command, and U.S. Army Research Development and Engineering Command (RDECOM).  This work was completed, in part, through the U.S. Army Research Laboratory (ARL) Enterprise for the Multiscale Research of Materials (EMRM).  This work was completed in conjunction with an ARL EMRM’s Multiscale Modeling of Electronic Materials (MSME) Collaborative Research Alliance (CRA), which is led out of the University of Utah.  VM, LCJ, JL, DB, JBH, ZL, AvD, WZ, and RMK gratefully acknowledge the financial support of the MSME CRA. 

References:

[1.]    J.R. Varcoe and R.C.T. Slade, “ Prospects for Alkaline Anion-Exchange Membranes in Low Temperature Fuel Cells.” Fuel Cells, 5(2) pp. 187 (2005).

[2.]    T.N. Danks, R.C.T. Slade, and J.R. Varcoe “Comparison of PVDF- and FEP-based radiation grafted alkaline anion-exchange membranes for use in low temperature portable DMFCs.” J. Mater. Chem., 12pp. 3371 (2002).

[3.]    J.R. Varcoe et al, “Anion-exchange membranes in electrochemical energy systems.” Energy Environ. Sci., 7pp. 3135 (2014).

[4.]    W.E. Mustain, J. A. Vega, and N.S. Spinner “Electrochemical Reactor for CO₂ Conversion Utilization and Associated Carbonate Electrocatalyst.” U.S. Patent Applications 13/289,508, US20120193222 A1 (2012).

[5.]    N. Spinner and W.E. Mustain, “Electrochemical Conversion of CO₂ and CH₄ to CH₃OH at Room Temperature through a Carbonate Anion Pathway.” 220’th ECS Meeting, No. 1501 (2011).

[6]      J. M. Spurgeon, M. G. Walter, J. Zhou, P. A. Kohl and N. S. Lewis, “Electrical conductivity, ionic conductivity, optical absorption, and gas separation properties of ionically conductive polymer membranes embedded with Si microwire arrays.” Energy Environ. Sci., 4, 1772 (2011).