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, largely spurred by some developments with radiation grafted AEM materials out of the laboratories of Robert Slade and John Varcoe, there has been significant attention from within the energy conversion/storage communities [1-3].  In additional to the interest in the use of AEM materials for fuel cells [1-3], the community has given additional consideration to their use for 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]. Many of the interest in these materials is a result of the opportunities that may be presented by a stable, anion-conducting polymer electrolyte materials. 

In this talk we will highlight our collaborative, simulation-focused efforts to develop and understand high performance AEM materials for electrochemical applications. Among other things, we will discuss our efforts to develop, validate, and apply simulation methodologies that can provide new and fundamental insights into the nature of the membrane(s) cationic stability, anionic conductivity, and the uncertainty in our respective models that range from atomistic to continuum scales.  These multiscale modeling approaches include everything from atomistic MD simulations using reactive (ReaxFF) and polarizable force fields, to coarse-grained molecular dynamics simulations with developed using uncertainty quantification (UQ) based methodologies and continuum level modeling approaches. 

For our initial efforts that we will discuss in this talk, we utilize relatively simple backbone materials such as Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO).  These backbone materials are effectively used as a model material system.  This enables us to develop and validate simulation methods that can predict and resolve the proper 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 concurrently be (i) processed, synthesized, and characterized in our labs, and (ii) subjected to unique processing methods/conditions that includes both casting and electro-spinning processes. 

This last capability is salient because the focus of the model and simulation development efforts are on the application to multi-scale systems. The ability to concurrently process the materials using different methods (i.e., cast, electro-spun, and co-spun with an inert matrix material) and under different conditions can drastically influence the material’s morphologies, structures, ordering, and properties. 

 

Acknowledgments:

KNG, JPM, and DC gratefully acknowledge the support of the U.S. Department of the Army, Army Materiel Command, and U.S. Army Research Development and Engineering Command.  This work was completed, in part, through the U.S. Army Research Laboratory’s Enterprise for the Multiscale Research of Materials (EMRM).  This work was completed in conjunction with an Army Research Laboratory EMRM’s Multiscale Modeling of Electronic Materials (MSME) Collaborative Research Alliance (CRA).  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, Fuel Cells, 5(2), 187 (2005).

2.    T.N. Danks, R.C.T. Slade, and J.R. Varcoe, J. Mater. Chem., 12, 3371 (2002).

3.    J.R. Varcoe et. al., Energy Environ. Sci., 7,3135 (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, 220’th ECS Meeting, Abs. No. 1501 (2011).

6.    J. M. Spurgeon, M. G. Walter, J. Zhou, P. A. Kohl and N. S. Lewis, Energy Environ. Sci., 4, 1772 (2011).